/*
 * tclPathObj.c --
 *
 *	This file contains the implementation of Tcl's "path" object type used
 *	to represent and manipulate a general (virtual) filesystem entity in
 *	an efficient manner.
 *
 * Copyright (c) 2003 Vince Darley.
 *
 * See the file "license.terms" for information on usage and redistribution of
 * this file, and for a DISCLAIMER OF ALL WARRANTIES.
 */

#include "tclInt.h"
#include "tclFileSystem.h"

/*
 * Prototypes for functions defined later in this file.
 */

static Tcl_Obj *	AppendPath(Tcl_Obj *head, Tcl_Obj *tail);
static void		DupFsPathInternalRep(Tcl_Obj *srcPtr,
			    Tcl_Obj *copyPtr);
static void		FreeFsPathInternalRep(Tcl_Obj *pathPtr);
static void		UpdateStringOfFsPath(Tcl_Obj *pathPtr);
static int		SetFsPathFromAny(Tcl_Interp *interp, Tcl_Obj *pathPtr);
static int		FindSplitPos(const char *path, int separator);
static int		IsSeparatorOrNull(int ch);
static Tcl_Obj *	GetExtension(Tcl_Obj *pathPtr);
static int		MakePathFromNormalized(Tcl_Interp *interp,
			    Tcl_Obj *pathPtr);

/*
 * Define the 'path' object type, which Tcl uses to represent file paths
 * internally.
 */

static Tcl_ObjType tclFsPathType = {
    "path",				/* name */
    FreeFsPathInternalRep,		/* freeIntRepProc */
    DupFsPathInternalRep,		/* dupIntRepProc */
    UpdateStringOfFsPath,		/* updateStringProc */
    SetFsPathFromAny			/* setFromAnyProc */
};

/*
 * struct FsPath --
 *
 * Internal representation of a Tcl_Obj of "path" type. This can be used to
 * represent relative or absolute paths, and has certain optimisations when
 * used to represent paths which are already normalized and absolute.
 *
 * Note that both 'translatedPathPtr' and 'normPathPtr' can be a circular
 * reference to the container Tcl_Obj of this FsPath.
 *
 * There are two cases, with the first being the most common:
 *
 * (i) flags == 0, => Ordinary path.
 *
 * translatedPathPtr contains the translated path (which may be a circular
 * reference to the object itself). If it is NULL then the path is pure
 * normalized (and the normPathPtr will be a circular reference). cwdPtr is
 * null for an absolute path, and non-null for a relative path (unless the cwd
 * has never been set, in which case the cwdPtr may also be null for a
 * relative path).
 *
 * (ii) flags != 0, => Special path, see TclNewFSPathObj
 *
 * Now, this is a path like 'file join $dir $tail' where, cwdPtr is the $dir
 * and normPathPtr is the $tail.
 *
 */

typedef struct FsPath {
    Tcl_Obj *translatedPathPtr; /* Name without any ~user sequences. If this
				 * is NULL, then this is a pure normalized,
				 * absolute path object, in which the parent
				 * Tcl_Obj's string rep is already both
				 * translated and normalized. */
    Tcl_Obj *normPathPtr;	/* Normalized absolute path, without ., .. or
				 * ~user sequences. If the Tcl_Obj containing
				 * this FsPath is already normalized, this may
				 * be a circular reference back to the
				 * container. If that is NOT the case, we have
				 * a refCount on the object. */
    Tcl_Obj *cwdPtr;		/* If null, path is absolute, else this points
				 * to the cwd object used for this path. We
				 * have a refCount on the object. */
    int flags;			/* Flags to describe interpretation - see
				 * below. */
    ClientData nativePathPtr;	/* Native representation of this path, which
				 * is filesystem dependent. */
    int filesystemEpoch;	/* Used to ensure the path representation was
				 * generated during the correct filesystem
				 * epoch. The epoch changes when
				 * filesystem-mounts are changed. */
    Tcl_Filesystem *fsPtr;	/* The Tcl_Filesystem that claims this path */
} FsPath;

/*
 * Flag values for FsPath->flags.
 */

#define TCLPATH_APPENDED 1
#define TCLPATH_NEEDNORM 4

/*
 * Define some macros to give us convenient access to path-object specific
 * fields.
 */

#define PATHOBJ(pathPtr) ((FsPath *) (pathPtr)->internalRep.twoPtrValue.ptr1)
#define SETPATHOBJ(pathPtr,fsPathPtr) \
	((pathPtr)->internalRep.twoPtrValue.ptr1 = (void *) (fsPathPtr))
#define PATHFLAGS(pathPtr) (PATHOBJ(pathPtr)->flags)

/*
 *---------------------------------------------------------------------------
 *
 * TclFSNormalizeAbsolutePath --
 *
 *	Takes an absolute path specification and computes a 'normalized' path
 *	from it.
 *
 *	A normalized path is one which has all '../', './' removed. Also it is
 *	one which is in the 'standard' format for the native platform. On
 *	Unix, this means the path must be free of symbolic links/aliases, and
 *	on Windows it means we want the long form, with that long form's
 *	case-dependence (which gives us a unique, case-dependent path).
 *
 *	The behaviour of this function if passed a non-absolute path is NOT
 *	defined.
 *
 *	pathPtr may have a refCount of zero, or may be a shared object.
 *
 * Results:
 *	The result is returned in a Tcl_Obj with a refCount of 1, which is
 *	therefore owned by the caller. It must be freed (with
 *	Tcl_DecrRefCount) by the caller when no longer needed.
 *
 * Side effects:
 *	None (beyond the memory allocation for the result).
 *
 * Special note:
 *	This code was originally based on code from Matt Newman and
 *	Jean-Claude Wippler, but has since been totally rewritten by Vince
 *	Darley to deal with symbolic links.
 *
 *---------------------------------------------------------------------------
 */

Tcl_Obj *
TclFSNormalizeAbsolutePath(
    Tcl_Interp *interp,		/* Interpreter to use */
    Tcl_Obj *pathPtr)		/* Absolute path to normalize */
{
    const char *dirSep, *oldDirSep;
    int first = 1;		/* Set to zero once we've passed the first
				 * directory separator - we can't use '..' to
				 * remove the volume in a path. */
    Tcl_Obj *retVal = NULL;
    dirSep = TclGetString(pathPtr);

    if (tclPlatform == TCL_PLATFORM_WINDOWS) {
	if (   (dirSep[0] == '/' || dirSep[0] == '\\')
	    && (dirSep[1] == '/' || dirSep[1] == '\\')
	    && (dirSep[2] == '?')
	    && (dirSep[3] == '/' || dirSep[3] == '\\')) {
	    /* NT extended path */
	    dirSep += 4;

	    if (   (dirSep[0] == 'U' || dirSep[0] == 'u')
		&& (dirSep[1] == 'N' || dirSep[1] == 'n')
		&& (dirSep[2] == 'C' || dirSep[2] == 'c')
		&& (dirSep[3] == '/' || dirSep[3] == '\\')) {
		/* NT extended UNC path */
		dirSep += 4;
	    }
	}
	if (dirSep[0] != 0 && dirSep[1] == ':' &&
		(dirSep[2] == '/' || dirSep[2] == '\\')) {
	    /* Do nothing */
	} else if ((dirSep[0] == '/' || dirSep[0] == '\\')
		&& (dirSep[1] == '/' || dirSep[1] == '\\')) {
	    /*
	     * UNC style path, where we must skip over the first separator,
	     * since the first two segments are actually inseparable.
	     */

	    dirSep += 2;
	    dirSep += FindSplitPos(dirSep, '/');
	    if (*dirSep != 0) {
		dirSep++;
	    }
	}
    }

    /*
     * Scan forward from one directory separator to the next, checking for
     * '..' and '.' sequences which must be handled specially. In particular
     * handling of '..' can be complicated if the directory before is a link,
     * since we will have to expand the link to be able to back up one level.
     */

    while (*dirSep != 0) {
	oldDirSep = dirSep;
	if (!first) {
	    dirSep++;
	}
	dirSep += FindSplitPos(dirSep, '/');
	if (dirSep[0] == 0 || dirSep[1] == 0) {
	    if (retVal != NULL) {
		Tcl_AppendToObj(retVal, oldDirSep, dirSep - oldDirSep);
	    }
	    break;
	}
	if (dirSep[1] == '.') {
	    if (retVal != NULL) {
		Tcl_AppendToObj(retVal, oldDirSep, dirSep - oldDirSep);
		oldDirSep = dirSep;
	    }
	again:
	    if (IsSeparatorOrNull(dirSep[2])) {
		/*
		 * Need to skip '.' in the path.
		 */
		int curLen;

		if (retVal == NULL) {
		    const char *path = TclGetString(pathPtr);
		    retVal = Tcl_NewStringObj(path, dirSep - path);
		    Tcl_IncrRefCount(retVal);
		}
		(void) Tcl_GetStringFromObj(retVal, &curLen);
		if (curLen == 0) {
		    Tcl_AppendToObj(retVal, dirSep, 1);
		}
		dirSep += 2;
		oldDirSep = dirSep;
		if (dirSep[0] != 0 && dirSep[1] == '.') {
		    goto again;
		}
		continue;
	    }
	    if (dirSep[2] == '.' && IsSeparatorOrNull(dirSep[3])) {
		Tcl_Obj *link;
		int curLen;
		char *linkStr;

		/*
		 * Have '..' so need to skip previous directory.
		 */

		if (retVal == NULL) {
		    const char *path = TclGetString(pathPtr);

		    retVal = Tcl_NewStringObj(path, dirSep - path);
		    Tcl_IncrRefCount(retVal);
		}
		(void) Tcl_GetStringFromObj(retVal, &curLen);
		if (curLen == 0) {
		    Tcl_AppendToObj(retVal, dirSep, 1);
		}
		if (!first || (tclPlatform == TCL_PLATFORM_UNIX)) {
		    link = Tcl_FSLink(retVal, NULL, 0);

		    /* Safety check in case driver caused sharing */
		    if (Tcl_IsShared(retVal)) {
			TclDecrRefCount(retVal);
			retVal = Tcl_DuplicateObj(retVal);
			Tcl_IncrRefCount(retVal);
		    }

		    if (link != NULL) {
			/*
			 * Got a link. Need to check if the link is relative
			 * or absolute, for those platforms where relative
			 * links exist.
			 */

			if (tclPlatform != TCL_PLATFORM_WINDOWS &&
				Tcl_FSGetPathType(link) == TCL_PATH_RELATIVE) {
			    /*
			     * We need to follow this link which is relative
			     * to retVal's directory. This means concatenating
			     * the link onto the directory of the path so far.
			     */

			    const char *path =
				    Tcl_GetStringFromObj(retVal, &curLen);

			    while (--curLen >= 0) {
				if (IsSeparatorOrNull(path[curLen])) {
				    break;
				}
			    }

			    /*
			     * We want the trailing slash.
			     */

			    Tcl_SetObjLength(retVal, curLen+1);
			    Tcl_AppendObjToObj(retVal, link);
			    TclDecrRefCount(link);
			    linkStr = Tcl_GetStringFromObj(retVal, &curLen);
			} else {
			    /*
			     * Absolute link.
			     */

			    TclDecrRefCount(retVal);
			    if (Tcl_IsShared(link)) {
				retVal = Tcl_DuplicateObj(link);
				TclDecrRefCount(link);
			    } else {
				retVal = link;
			    }
			    linkStr = Tcl_GetStringFromObj(retVal, &curLen);

			    /*
			     * Convert to forward-slashes on windows.
			     */

			    if (tclPlatform == TCL_PLATFORM_WINDOWS) {
				int i;

				for (i = 0; i < curLen; i++) {
				    if (linkStr[i] == '\\') {
					linkStr[i] = '/';
				    }
				}
			    }
			}
		    } else {
			linkStr = Tcl_GetStringFromObj(retVal, &curLen);
		    }

		    /*
		     * Either way, we now remove the last path element.
		     * (but not the first character of the path)
		     */

		    while (--curLen >= 0) {
			if (IsSeparatorOrNull(linkStr[curLen])) {
			    if (curLen) {
				Tcl_SetObjLength(retVal, curLen);
			    } else {
				Tcl_SetObjLength(retVal, 1);
			    }
			    break;
			}
		    }
		}
		dirSep += 3;
		oldDirSep = dirSep;

		if ((curLen == 0) && (dirSep[0] != 0)) {
		    Tcl_SetObjLength(retVal, 0);
		}

		if (dirSep[0] != 0 && dirSep[1] == '.') {
		    goto again;
		}
		continue;
	    }
	}
	first = 0;
	if (retVal != NULL) {
	    Tcl_AppendToObj(retVal, oldDirSep, dirSep - oldDirSep);
	}
    }

    /*
     * If we didn't make any changes, just use the input path.
     */

    if (retVal == NULL) {
	retVal = pathPtr;
	Tcl_IncrRefCount(retVal);

	if (Tcl_IsShared(retVal)) {
	    /*
	     * Unfortunately, the platform-specific normalization code which
	     * will be called below has no way of dealing with the case where
	     * an object is shared. It is expecting to modify an object in
	     * place. So, we must duplicate this here to ensure an object with
	     * a single ref-count.
	     *
	     * If that changes in the future (e.g. the normalize proc is given
	     * one object and is able to return a different one), then we
	     * could remove this code.
	     */

	    TclDecrRefCount(retVal);
	    retVal = Tcl_DuplicateObj(pathPtr);
	    Tcl_IncrRefCount(retVal);
	}
    }

    /*
     * Ensure a windows drive like C:/ has a trailing separator
     */

    if (tclPlatform == TCL_PLATFORM_WINDOWS) {
	int len;
	const char *path = Tcl_GetStringFromObj(retVal, &len);

	if (len == 2 && path[0] != 0 && path[1] == ':') {
	    if (Tcl_IsShared(retVal)) {
		TclDecrRefCount(retVal);
		retVal = Tcl_DuplicateObj(retVal);
		Tcl_IncrRefCount(retVal);
	    }
	    Tcl_AppendToObj(retVal, "/", 1);
	}
    }

    /*
     * Now we have an absolute path, with no '..', '.' sequences, but it still
     * may not be in 'unique' form, depending on the platform. For instance,
     * Unix is case-sensitive, so the path is ok. Windows is case-insensitive,
     * and also has the weird 'longname/shortname' thing (e.g. C:/Program
     * Files/ and C:/Progra~1/ are equivalent).
     *
     * Virtual file systems which may be registered may have other criteria
     * for normalizing a path.
     */

    TclFSNormalizeToUniquePath(interp, retVal, 0);

    /*
     * Since we know it is a normalized path, we can actually convert this
     * object into an FsPath for greater efficiency
     */

    MakePathFromNormalized(interp, retVal);

    /*
     * This has a refCount of 1 for the caller, unlike many Tcl_Obj APIs.
     */

    return retVal;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_FSGetPathType --
 *
 *	Determines whether a given path is relative to the current directory,
 *	relative to the current volume, or absolute.
 *
 * Results:
 *	Returns one of TCL_PATH_ABSOLUTE, TCL_PATH_RELATIVE, or
 *	TCL_PATH_VOLUME_RELATIVE.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

Tcl_PathType
Tcl_FSGetPathType(
    Tcl_Obj *pathPtr)
{
    return TclFSGetPathType(pathPtr, NULL, NULL);
}

/*
 *----------------------------------------------------------------------
 *
 * TclFSGetPathType --
 *
 *	Determines whether a given path is relative to the current directory,
 *	relative to the current volume, or absolute. If the caller wishes to
 *	know which filesystem claimed the path (in the case for which the path
 *	is absolute), then a reference to a filesystem pointer can be passed
 *	in (but passing NULL is acceptable).
 *
 * Results:
 *	Returns one of TCL_PATH_ABSOLUTE, TCL_PATH_RELATIVE, or
 *	TCL_PATH_VOLUME_RELATIVE. The filesystem reference will be set if and
 *	only if it is non-NULL and the function's return value is
 *	TCL_PATH_ABSOLUTE.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

Tcl_PathType
TclFSGetPathType(
    Tcl_Obj *pathPtr,
    Tcl_Filesystem **filesystemPtrPtr,
    int *driveNameLengthPtr)
{
    FsPath *fsPathPtr;

    if (Tcl_FSConvertToPathType(NULL, pathPtr) != TCL_OK) {
	return TclGetPathType(pathPtr, filesystemPtrPtr, driveNameLengthPtr,
		NULL);
    }

    fsPathPtr = PATHOBJ(pathPtr);
    if (fsPathPtr->cwdPtr == NULL) {
	return TclGetPathType(pathPtr, filesystemPtrPtr, driveNameLengthPtr,
		NULL);
    }

    if (PATHFLAGS(pathPtr) == 0) {
	/* The path is not absolute... */
#ifdef __WIN32__
	/* ... on Windows we must make another call to determine whether
	 * it's relative or volumerelative [Bug 2571597]. */
	return TclGetPathType(pathPtr, filesystemPtrPtr, driveNameLengthPtr,
		NULL);
#else
	/* On other systems, quickly deduce !absolute -> relative */
	return TCL_PATH_RELATIVE;
#endif
    }
    return TclFSGetPathType(fsPathPtr->cwdPtr, filesystemPtrPtr,
	    driveNameLengthPtr);
}

/*
 *---------------------------------------------------------------------------
 *
 * TclPathPart
 *
 *	This function calculates the requested part of the given path, which
 *	can be:
 *
 *	- the directory above ('file dirname')
 *	- the tail            ('file tail')
 *	- the extension       ('file extension')
 *	- the root            ('file root')
 *
 *	The 'portion' parameter dictates which of these to calculate. There
 *	are a number of special cases both to be more efficient, and because
 *	the behaviour when given a path with only a single element is defined
 *	to require the expansion of that single element, where possible.
 *
 *	Should look into integrating 'FileBasename' in tclFCmd.c into this
 *	function.
 *
 * Results:
 *	NULL if an error occurred, otherwise a Tcl_Obj owned by the caller
 *	(i.e. most likely with refCount 1).
 *
 * Side effects:
 *	None.
 *
 *---------------------------------------------------------------------------
 */

Tcl_Obj *
TclPathPart(
    Tcl_Interp *interp,		/* Used for error reporting */
    Tcl_Obj *pathPtr,		/* Path to take dirname of */
    Tcl_PathPart portion)	/* Requested portion of name */
{
    if (pathPtr->typePtr == &tclFsPathType) {
	FsPath *fsPathPtr = PATHOBJ(pathPtr);

	if (PATHFLAGS(pathPtr) != 0) {
	    switch (portion) {
	    case TCL_PATH_DIRNAME: {
		/*
		 * Check if the joined-on bit has any directory delimiters in
		 * it. If so, the 'dirname' would be a joining of the main
		 * part with the dirname of the joined-on bit. We could handle
		 * that special case here, but we don't, and instead just use
		 * the standardPath code.
		 */

		int numBytes;
		const char *rest =
			Tcl_GetStringFromObj(fsPathPtr->normPathPtr, &numBytes);

		if (strchr(rest, '/') != NULL) {
		    goto standardPath;
		}
		/*
		 * If the joined-on bit is empty, then [file dirname] is
		 * documented to return all but the last non-empty element
		 * of the path, so we need to split apart the main part to
		 * get the right answer.  We could do that here, but it's
		 * simpler to fall back to the standardPath code.
		 * [Bug 2710920]
		 */
		if (numBytes == 0) {
		    goto standardPath;
		}
		if (tclPlatform == TCL_PLATFORM_WINDOWS
			&& strchr(rest, '\\') != NULL) {
		    goto standardPath;
		}

		/*
		 * The joined-on path is simple, so we can just return here.
		 */

		Tcl_IncrRefCount(fsPathPtr->cwdPtr);
		return fsPathPtr->cwdPtr;
	    }
	    case TCL_PATH_TAIL: {
		/*
		 * Check if the joined-on bit has any directory delimiters in
		 * it. If so, the 'tail' would be only the part following the
		 * last delimiter. We could handle that special case here, but
		 * we don't, and instead just use the standardPath code.
		 */

		int numBytes;
		const char *rest =
			Tcl_GetStringFromObj(fsPathPtr->normPathPtr, &numBytes);

		if (strchr(rest, '/') != NULL) {
		    goto standardPath;
		}
		/*
		 * If the joined-on bit is empty, then [file tail] is
		 * documented to return the last non-empty element
		 * of the path, so we need to split off the last element
		 * of the main part to get the right answer.  We could do
		 * that here, but it's simpler to fall back to the
		 * standardPath code.  [Bug 2710920]
		 */
		if (numBytes == 0) {
		    goto standardPath;
		}
		if (tclPlatform == TCL_PLATFORM_WINDOWS
			&& strchr(rest, '\\') != NULL) {
		    goto standardPath;
		}
		Tcl_IncrRefCount(fsPathPtr->normPathPtr);
		return fsPathPtr->normPathPtr;
	    }
	    case TCL_PATH_EXTENSION:
		return GetExtension(fsPathPtr->normPathPtr);
	    case TCL_PATH_ROOT: {
		const char *fileName, *extension;
		int length;

		fileName = Tcl_GetStringFromObj(fsPathPtr->normPathPtr,
			&length);
		extension = TclGetExtension(fileName);
		if (extension == NULL) {
		    /*
		     * There is no extension so the root is the same as the
		     * path we were given.
		     */

		    Tcl_IncrRefCount(pathPtr);
		    return pathPtr;
		} else {
		    /*
		     * Need to return the whole path with the extension
		     * suffix removed.  Do that by joining our "head" to
		     * our "tail" with the extension suffix removed from
		     * the tail.
		     */

		    Tcl_Obj *resultPtr =
			    TclNewFSPathObj(fsPathPtr->cwdPtr, fileName,
			    (int)(length - strlen(extension)));

		    Tcl_IncrRefCount(resultPtr);
		    return resultPtr;
		}
	    }
	    default:
		/* We should never get here */
		Tcl_Panic("Bad portion to TclPathPart");
		/* For less clever compilers */
		return NULL;
	    }
	} else if (fsPathPtr->cwdPtr != NULL) {
	    /* Relative path */
	    goto standardPath;
	} else {
	    /* Absolute path */
	    goto standardPath;
	}
    } else {
	int splitElements;
	Tcl_Obj *splitPtr, *resultPtr;

    standardPath:
	resultPtr = NULL;
	if (portion == TCL_PATH_EXTENSION) {
	    return GetExtension(pathPtr);
	} else if (portion == TCL_PATH_ROOT) {
	    int length;
	    const char *fileName, *extension;

	    fileName = Tcl_GetStringFromObj(pathPtr, &length);
	    extension = TclGetExtension(fileName);
	    if (extension == NULL) {
		Tcl_IncrRefCount(pathPtr);
		return pathPtr;
	    } else {
		Tcl_Obj *root = Tcl_NewStringObj(fileName,
			(int) (length - strlen(extension)));

		Tcl_IncrRefCount(root);
		return root;
	    }
	}

	/*
	 * The behaviour we want here is slightly different to the standard
	 * Tcl_FSSplitPath in the handling of home directories;
	 * Tcl_FSSplitPath preserves the "~" while this code computes the
	 * actual full path name, if we had just a single component.
	 */

	splitPtr = Tcl_FSSplitPath(pathPtr, &splitElements);
	Tcl_IncrRefCount(splitPtr);
	if (splitElements == 1  &&  TclGetString(pathPtr)[0] == '~') {
	    Tcl_Obj *norm;

	    TclDecrRefCount(splitPtr);
	    norm = Tcl_FSGetNormalizedPath(interp, pathPtr);
	    if (norm == NULL) {
		return NULL;
	    }
	    splitPtr = Tcl_FSSplitPath(norm, &splitElements);
	    Tcl_IncrRefCount(splitPtr);
	}
	if (portion == TCL_PATH_TAIL) {
	    /*
	     * Return the last component, unless it is the only component, and
	     * it is the root of an absolute path.
	     */

	    if ((splitElements > 0) && ((splitElements > 1) ||
		    (Tcl_FSGetPathType(pathPtr) == TCL_PATH_RELATIVE))) {
		Tcl_ListObjIndex(NULL, splitPtr, splitElements-1, &resultPtr);
	    } else {
		resultPtr = Tcl_NewObj();
	    }
	} else {
	    /*
	     * Return all but the last component. If there is only one
	     * component, return it if the path was non-relative, otherwise
	     * return the current directory.
	     */

	    if (splitElements > 1) {
		resultPtr = Tcl_FSJoinPath(splitPtr, splitElements - 1);
	    } else if (splitElements == 0 ||
		    (Tcl_FSGetPathType(pathPtr) == TCL_PATH_RELATIVE)) {
		TclNewLiteralStringObj(resultPtr, ".");
	    } else {
		Tcl_ListObjIndex(NULL, splitPtr, 0, &resultPtr);
	    }
	}
	Tcl_IncrRefCount(resultPtr);
	TclDecrRefCount(splitPtr);
	return resultPtr;
    }
}

/*
 * Simple helper function
 */

static Tcl_Obj *
GetExtension(
    Tcl_Obj *pathPtr)
{
    const char *tail, *extension;
    Tcl_Obj *ret;

    tail = TclGetString(pathPtr);
    extension = TclGetExtension(tail);
    if (extension == NULL) {
	ret = Tcl_NewObj();
    } else {
	ret = Tcl_NewStringObj(extension, -1);
    }
    Tcl_IncrRefCount(ret);
    return ret;
}

/*
 *---------------------------------------------------------------------------
 *
 * Tcl_FSJoinPath --
 *
 *	This function takes the given Tcl_Obj, which should be a valid list,
 *	and returns the path object given by considering the first 'elements'
 *	elements as valid path segments (each path segment may be a complete
 *	path, a partial path or just a single possible directory or file
 *	name). If any path segment is actually an absolute path, then all
 *	prior path segments are discarded.
 *
 *	If elements < 0, we use the entire list that was given.
 *
 *	It is possible that the returned object is actually an element of the
 *	given list, so the caller should be careful to store a refCount to it
 *	before freeing the list.
 *
 * Results:
 *	Returns object with refCount of zero, (or if non-zero, it has
 *	references elsewhere in Tcl). Either way, the caller must increment
 *	its refCount before use. Note that in the case where the caller has
 *	asked to join zero elements of the list, the return value will be an
 *	empty-string Tcl_Obj.
 *
 *	If the given listObj was invalid, then the calling routine has a bug,
 *	and this function will just return NULL.
 *
 * Side effects:
 *	None.
 *
 *---------------------------------------------------------------------------
 */

Tcl_Obj *
Tcl_FSJoinPath(
    Tcl_Obj *listObj,		/* Path elements to join, may have a zero
				 * reference count. */
    int elements)		/* Number of elements to use (-1 = all) */
{
    Tcl_Obj *res;
    int i;
    Tcl_Filesystem *fsPtr = NULL;

    if (elements < 0) {
	if (Tcl_ListObjLength(NULL, listObj, &elements) != TCL_OK) {
	    return NULL;
	}
    } else {
	/*
	 * Just make sure it is a valid list.
	 */

	int listTest;

	if (Tcl_ListObjLength(NULL, listObj, &listTest) != TCL_OK) {
	    return NULL;
	}

	/*
	 * Correct this if it is too large, otherwise we will waste our time
	 * joining null elements to the path.
	 */

	if (elements > listTest) {
	    elements = listTest;
	}
    }

    res = NULL;

    for (i = 0; i < elements; i++) {
	Tcl_Obj *elt, *driveName = NULL;
	int driveNameLength, strEltLen, length;
	Tcl_PathType type;
	char *strElt, *ptr;

	Tcl_ListObjIndex(NULL, listObj, i, &elt);

	/*
	 * This is a special case where we can be much more efficient, where
	 * we are joining a single relative path onto an object that is
	 * already of path type. The 'TclNewFSPathObj' call below creates an
	 * object which can be normalized more efficiently. Currently we only
	 * use the special case when we have exactly two elements, but we
	 * could expand that in the future.
	 */

	if ((i == (elements-2)) && (i == 0) && (elt->typePtr == &tclFsPathType)
		&& !(elt->bytes != NULL && (elt->bytes[0] == '\0'))) {
	    Tcl_Obj *tail;

	    Tcl_ListObjIndex(NULL, listObj, i+1, &tail);
	    type = TclGetPathType(tail, NULL, NULL, NULL);
	    if (type == TCL_PATH_RELATIVE) {
		const char *str;
		int len;

		str = Tcl_GetStringFromObj(tail, &len);
		if (len == 0) {
		    /*
		     * This happens if we try to handle the root volume '/'.
		     * There's no need to return a special path object, when
		     * the base itself is just fine!
		     */

		    if (res != NULL) {
			TclDecrRefCount(res);
		    }
		    return elt;
		}

		/*
		 * If it doesn't begin with '.' and is a unix path or it a
		 * windows path without backslashes, then we can be very
		 * efficient here. (In fact even a windows path with
		 * backslashes can be joined efficiently, but the path object
		 * would not have forward slashes only, and this would
		 * therefore contradict our 'file join' documentation).
		 */

		if (str[0] != '.' && ((tclPlatform != TCL_PLATFORM_WINDOWS)
			|| (strchr(str, '\\') == NULL))) {
		    /*
		     * Finally, on Windows, 'file join' is defined to convert
		     * all backslashes to forward slashes, so the base part
		     * cannot have backslashes either.
		     */

		    if ((tclPlatform != TCL_PLATFORM_WINDOWS)
			    || (strchr(Tcl_GetString(elt), '\\') == NULL)) {
			if (res != NULL) {
			    TclDecrRefCount(res);
			}
			return TclNewFSPathObj(elt, str, len);
		    }
		}

		/*
		 * Otherwise we don't have an easy join, and we must let the
		 * more general code below handle things.
		 */
	    } else if (tclPlatform == TCL_PLATFORM_UNIX) {
		if (res != NULL) {
		    TclDecrRefCount(res);
		}
		return tail;
	    } else {
		const char *str = TclGetString(tail);

		if (tclPlatform == TCL_PLATFORM_WINDOWS) {
		    if (strchr(str, '\\') == NULL) {
			if (res != NULL) {
			    TclDecrRefCount(res);
			}
			return tail;
		    }
		}
	    }
	}
	strElt = Tcl_GetStringFromObj(elt, &strEltLen);
	type = TclGetPathType(elt, &fsPtr, &driveNameLength, &driveName);
	if (type != TCL_PATH_RELATIVE) {
	    /*
	     * Zero out the current result.
	     */

	    if (res != NULL) {
		TclDecrRefCount(res);
	    }

	    if (driveName != NULL) {
		/*
		 * We've been given a separate drive-name object, because the
		 * prefix in 'elt' is not in a suitable format for us (e.g. it
		 * may contain irrelevant multiple separators, like
		 * C://///foo).
		 */

		res = Tcl_DuplicateObj(driveName);
		TclDecrRefCount(driveName);

		/*
		 * Do not set driveName to NULL, because we will check its
		 * value below (but we won't access the contents, since those
		 * have been cleaned-up).
		 */
	    } else {
		res = Tcl_NewStringObj(strElt, driveNameLength);
	    }
	    strElt += driveNameLength;
	} else if (driveName != NULL) {
	    Tcl_DecrRefCount(driveName);
	}

	/*
	 * Optimisation block: if this is the last element to be examined, and
	 * it is absolute or the only element, and the drive-prefix was ok (if
	 * there is one), it might be that the path is already in a suitable
	 * form to be returned. Then we can short-cut the rest of this
	 * function.
	 */

	if ((driveName == NULL) && (i == (elements - 1))
		&& (type != TCL_PATH_RELATIVE || res == NULL)) {
	    /*
	     * It's the last path segment. Perform a quick check if the path
	     * is already in a suitable form.
	     */

	    if (tclPlatform == TCL_PLATFORM_WINDOWS) {
		if (strchr(strElt, '\\') != NULL) {
		    goto noQuickReturn;
		}
	    }
	    ptr = strElt;
	    while (*ptr != '\0') {
		if (*ptr == '/' && (ptr[1] == '/' || ptr[1] == '\0')) {
		    /*
		     * We have a repeated file separator, which means the path
		     * is not in normalized form
		     */

		    goto noQuickReturn;
		}
		ptr++;
	    }
	    if (res != NULL) {
		TclDecrRefCount(res);
	    }

	    /*
	     * This element is just what we want to return already - no
	     * further manipulation is requred.
	     */

	    return elt;
	}

	/*
	 * The path element was not of a suitable form to be returned as is.
	 * We need to perform a more complex operation here.
	 */

    noQuickReturn:
	if (res == NULL) {
	    res = Tcl_NewObj();
	    ptr = Tcl_GetStringFromObj(res, &length);
	} else {
	    ptr = Tcl_GetStringFromObj(res, &length);
	}

	/*
	 * Strip off any './' before a tilde, unless this is the beginning of
	 * the path.
	 */

	if (length > 0 && strEltLen > 0 && (strElt[0] == '.') &&
		(strElt[1] == '/') && (strElt[2] == '~')) {
	    strElt += 2;
	}

	/*
	 * A NULL value for fsPtr at this stage basically means we're trying
	 * to join a relative path onto something which is also relative (or
	 * empty). There's nothing particularly wrong with that.
	 */

	if (*strElt == '\0') {
	    continue;
	}

	if (fsPtr == &tclNativeFilesystem || fsPtr == NULL) {
	    TclpNativeJoinPath(res, strElt);
	} else {
	    char separator = '/';
	    int needsSep = 0;

	    if (fsPtr->filesystemSeparatorProc != NULL) {
		Tcl_Obj *sep = (*fsPtr->filesystemSeparatorProc)(res);

		if (sep != NULL) {
		    separator = TclGetString(sep)[0];
		}
		/* Safety check in case the VFS driver caused sharing */
		if (Tcl_IsShared(res)) {
		    TclDecrRefCount(res);
		    res = Tcl_DuplicateObj(res);
		    Tcl_IncrRefCount(res);
		}
	    }

	    if (length > 0 && ptr[length -1] != '/') {
		Tcl_AppendToObj(res, &separator, 1);
		Tcl_GetStringFromObj(res, &length);
	    }
	    Tcl_SetObjLength(res, length + (int) strlen(strElt));

	    ptr = TclGetString(res) + length;
	    for (; *strElt != '\0'; strElt++) {
		if (*strElt == separator) {
		    while (strElt[1] == separator) {
			strElt++;
		    }
		    if (strElt[1] != '\0') {
			if (needsSep) {
			    *ptr++ = separator;
			}
		    }
		} else {
		    *ptr++ = *strElt;
		    needsSep = 1;
		}
	    }
	    length = ptr - TclGetString(res);
	    Tcl_SetObjLength(res, length);
	}
    }
    if (res == NULL) {
	res = Tcl_NewObj();
    }
    return res;
}

/*
 *---------------------------------------------------------------------------
 *
 * Tcl_FSConvertToPathType --
 *
 *	This function tries to convert the given Tcl_Obj to a valid Tcl path
 *	type, taking account of the fact that the cwd may have changed even if
 *	this object is already supposedly of the correct type.
 *
 *	The filename may begin with "~" (to indicate current user's home
 *	directory) or "~<user>" (to indicate any user's home directory).
 *
 * Results:
 *	Standard Tcl error code.
 *
 * Side effects:
 *	The old representation may be freed, and new memory allocated.
 *
 *---------------------------------------------------------------------------
 */

int
Tcl_FSConvertToPathType(
    Tcl_Interp *interp,		/* Interpreter in which to store error message
				 * (if necessary). */
    Tcl_Obj *pathPtr)		/* Object to convert to a valid, current path
				 * type. */
{
    /*
     * While it is bad practice to examine an object's type directly, this is
     * actually the best thing to do here. The reason is that if we are
     * converting this object to FsPath type for the first time, we don't need
     * to worry whether the 'cwd' has changed. On the other hand, if this
     * object is already of FsPath type, and is a relative path, we do have to
     * worry about the cwd. If the cwd has changed, we must recompute the
     * path.
     */

    if (pathPtr->typePtr == &tclFsPathType) {
	if (TclFSEpochOk(PATHOBJ(pathPtr)->filesystemEpoch)) {
	    return TCL_OK;
	}

	if (pathPtr->bytes == NULL) {
	    UpdateStringOfFsPath(pathPtr);
	}
	FreeFsPathInternalRep(pathPtr);
    }

    return Tcl_ConvertToType(interp, pathPtr, &tclFsPathType);

    /*
     * We used to have more complex code here:
     *
     * FsPath *fsPathPtr = PATHOBJ(pathPtr);
     * if (fsPathPtr->cwdPtr == NULL || PATHFLAGS(pathPtr) != 0) {
     *     return TCL_OK;
     * } else {
     *     if (TclFSCwdPointerEquals(&fsPathPtr->cwdPtr)) {
     *         return TCL_OK;
     *     } else {
     *         if (pathPtr->bytes == NULL) {
     *             UpdateStringOfFsPath(pathPtr);
     *         }
     *         FreeFsPathInternalRep(pathPtr);
     *         return Tcl_ConvertToType(interp, pathPtr, &tclFsPathType);
     *     }
     * }
     *
     * But we no longer believe this is necessary.
     */
}

/*
 * Helper function for normalization.
 */

static int
IsSeparatorOrNull(
    int ch)
{
    if (ch == 0) {
	return 1;
    }
    switch (tclPlatform) {
    case TCL_PLATFORM_UNIX:
	return (ch == '/' ? 1 : 0);
    case TCL_PLATFORM_WINDOWS:
	return ((ch == '/' || ch == '\\') ? 1 : 0);
    }
    return 0;
}

/*
 * Helper function for SetFsPathFromAny. Returns position of first directory
 * delimiter in the path. If no separator is found, then returns the position
 * of the end of the string.
 */

static int
FindSplitPos(
    const char *path,
    int separator)
{
    int count = 0;
    switch (tclPlatform) {
    case TCL_PLATFORM_UNIX:
	while (path[count] != 0) {
	    if (path[count] == separator) {
		return count;
	    }
	    count++;
	}
	break;

    case TCL_PLATFORM_WINDOWS:
	while (path[count] != 0) {
	    if (path[count] == separator || path[count] == '\\') {
		return count;
	    }
	    count++;
	}
	break;
    }
    return count;
}

/*
 *---------------------------------------------------------------------------
 *
 * TclNewFSPathObj --
 *
 *	Creates a path object whose string representation is '[file join
 *	dirPtr addStrRep]', but does so in a way that allows for more
 *	efficient creation and caching of normalized paths, and more efficient
 *	'file dirname', 'file tail', etc.
 *
 * Assumptions:
 *	'dirPtr' must be an absolute path. 'len' may not be zero.
 *
 * Results:
 *	The new Tcl object, with refCount zero.
 *
 * Side effects:
 *	Memory is allocated. 'dirPtr' gets an additional refCount.
 *
 *---------------------------------------------------------------------------
 */

Tcl_Obj *
TclNewFSPathObj(
    Tcl_Obj *dirPtr,
    const char *addStrRep,
    int len)
{
    FsPath *fsPathPtr;
    Tcl_Obj *pathPtr;
    const char *p;
    int state = 0, count = 0;

    /* [Bug 2806250] - this is only a partial solution of the problem.
     * The PATHFLAGS != 0 representation assumes in many places that
     * the "tail" part stored in the normPathPtr field is itself a
     * relative path.  Strings that begin with "~" are not relative paths,
     * so we must prevent their storage in the normPathPtr field.
     *
     * More generally we ought to be testing "addStrRep" for any value
     * that is not a relative path, but in an unconstrained VFS world
     * that could be just about anything, and testing could be expensive.
     * Since this routine plays a big role in [glob], anything that slows
     * it down would be unwelcome.  For now, continue the risk of further
     * bugs when some Tcl_Filesystem uses otherwise relative path strings
     * as absolute path strings.  Sensible Tcl_Filesystems will avoid
     * that by mounting on path prefixes like foo:// which cannot be the
     * name of a file or directory read from a native [glob] operation.
     */
    if (addStrRep[0] == '~') {
	Tcl_Obj *tail = Tcl_NewStringObj(addStrRep, len);

	pathPtr = AppendPath(dirPtr, tail);
	Tcl_DecrRefCount(tail);
	return pathPtr;
    }

    pathPtr = Tcl_NewObj();
    fsPathPtr = (FsPath *) ckalloc(sizeof(FsPath));

    /*
     * Set up the path.
     */

    fsPathPtr->translatedPathPtr = NULL;
    fsPathPtr->normPathPtr = Tcl_NewStringObj(addStrRep, len);
    Tcl_IncrRefCount(fsPathPtr->normPathPtr);
    fsPathPtr->cwdPtr = dirPtr;
    Tcl_IncrRefCount(dirPtr);
    fsPathPtr->nativePathPtr = NULL;
    fsPathPtr->fsPtr = NULL;
    fsPathPtr->filesystemEpoch = 0;

    SETPATHOBJ(pathPtr, fsPathPtr);
    PATHFLAGS(pathPtr) = TCLPATH_APPENDED;
    pathPtr->typePtr = &tclFsPathType;
    pathPtr->bytes = NULL;
    pathPtr->length = 0;

    /*
     * Look for path components made up of only "."
     * This is overly conservative analysis to keep simple.  It may
     * mark some things as needing more aggressive normalization
     * that don't actually need it.  No harm done.
     */
    for (p = addStrRep; len > 0; p++, len--) {
       switch (state) {
       case 0: /* So far only "." since last dirsep or start */
           switch (*p) {
           case '.':
               count++;
               break;
           case '/':
           case '\\':
           case ':':
               if (count) {
                   PATHFLAGS(pathPtr) |= TCLPATH_NEEDNORM;
                   len = 0;
               }
               break;
           default:
               count = 0;
               state = 1;
           }
       case 1: /* Scanning for next dirsep */
           switch (*p) {
           case '/':
           case '\\':
           case ':':
               state = 0;
               break;
           }
       }
    }
    if (len == 0 && count) {
       PATHFLAGS(pathPtr) |= TCLPATH_NEEDNORM;
    }

    return pathPtr;
}

static Tcl_Obj *
AppendPath(
    Tcl_Obj *head,
    Tcl_Obj *tail)
{
    int numBytes;
    const char *bytes;
    Tcl_Obj *copy = Tcl_DuplicateObj(head);

    /*
     * This is likely buggy when dealing with virtual filesystem drivers
     * that use some character other than "/" as a path separator.  I know
     * of no evidence that such a foolish thing exists.  This solution was
     * chosen so that "JoinPath" operations that pass through either path
     * intrep produce the same results; that is, bugward compatibility.  If
     * we need to fix that bug here, it needs fixing in Tcl_FSJoinPath() too.
     */
    bytes = Tcl_GetStringFromObj(tail, &numBytes);
    if (numBytes == 0) {
	Tcl_AppendToObj(copy, "/", 1);
    } else {
	TclpNativeJoinPath(copy, bytes);
    }
    return copy;
}

/*
 *---------------------------------------------------------------------------
 *
 * TclFSMakePathRelative --
 *
 *	Only for internal use.
 *
 *	Takes a path and a directory, where we _assume_ both path and
 *	directory are absolute, normalized and that the path lies inside the
 *	directory. Returns a Tcl_Obj representing filename of the path
 *	relative to the directory.
 *
 * Results:
 *	NULL on error, otherwise a valid object, typically with refCount of
 *	zero, which it is assumed the caller will increment.
 *
 * Side effects:
 *	The old representation may be freed, and new memory allocated.
 *
 *---------------------------------------------------------------------------
 */

Tcl_Obj *
TclFSMakePathRelative(
    Tcl_Interp *interp,		/* Used for error reporting if not NULL. */
    Tcl_Obj *pathPtr,		/* The path we have. */
    Tcl_Obj *cwdPtr)		/* Make it relative to this. */
{
    int cwdLen, len;
    const char *tempStr;

    if (pathPtr->typePtr == &tclFsPathType) {
	FsPath *fsPathPtr = PATHOBJ(pathPtr);

	if (PATHFLAGS(pathPtr) != 0
		&& fsPathPtr->cwdPtr == cwdPtr) {
	    pathPtr = fsPathPtr->normPathPtr;

	    /* TODO: Determine how much, if any, of this forcing
	     * the relative path tail into the "path" Tcl_ObjType
	     * with a recorded cwdPtr context has any actual value.
	     *
	     * Nothing is getting cached.  Not normPathPtr, not nativePathPtr,
	     * nor fsPtr, so storing the cwdPtr context against which such
	     * cached values might later be validated appears to be of no
	     * value.  Take that away, and all this code is just a mildly
	     * optimized equivalent of a call to SetFsPathFromAny().  That
	     * optimization may have some value, *if* these value in fact
	     * get used as "path" values before used as something else.
	     * If not, though, whatever cost we pay below to convert to
	     * one of the "path" intreps is just a waste, it seems.  The
	     * usual convention in the core is to delay ObjType conversion
	     * until it is needed and demanded, and I don't see why this
	     * section of code should be an exception to that.  Leaving it
	     * in place for the rest of the 8.5.* releases just for sake
	     * of stability.
	     */

	    /*
	     * Free old representation.
	     */

	    if (pathPtr->typePtr != NULL) {
		if (pathPtr->bytes == NULL) {
		    if (pathPtr->typePtr->updateStringProc == NULL) {
			if (interp != NULL) {
			    Tcl_ResetResult(interp);
			    Tcl_AppendResult(interp, "can't find object"
				    "string representation", NULL);
			}
			return NULL;
		    }
		    pathPtr->typePtr->updateStringProc(pathPtr);
		}
		TclFreeIntRep(pathPtr);
	    }

	    /*
	     * Now pathPtr is a string object.
	     */

	    fsPathPtr = (FsPath *) ckalloc(sizeof(FsPath));

	    /*
	     * Circular reference, by design.
	     */

	    fsPathPtr->translatedPathPtr = pathPtr;
	    fsPathPtr->normPathPtr = NULL;
	    fsPathPtr->cwdPtr = cwdPtr;
	    Tcl_IncrRefCount(cwdPtr);
	    fsPathPtr->nativePathPtr = NULL;
	    fsPathPtr->fsPtr = NULL;
	    fsPathPtr->filesystemEpoch = 0;

	    SETPATHOBJ(pathPtr, fsPathPtr);
	    PATHFLAGS(pathPtr) = 0;
	    pathPtr->typePtr = &tclFsPathType;

	    return pathPtr;
	}
    }

    /*
     * We know the cwd is a normalised object which does not end in a
     * directory delimiter, unless the cwd is the name of a volume, in which
     * case it will end in a delimiter! We handle this situation here. A
     * better test than the '!= sep' might be to simply check if 'cwd' is a
     * root volume.
     *
     * Note that if we get this wrong, we will strip off either too much or
     * too little below, leading to wrong answers returned by glob.
     */

    tempStr = Tcl_GetStringFromObj(cwdPtr, &cwdLen);

    /*
     * Should we perhaps use 'Tcl_FSPathSeparator'? But then what about the
     * Windows special case? Perhaps we should just check if cwd is a root
     * volume.
     */

    switch (tclPlatform) {
    case TCL_PLATFORM_UNIX:
	if (tempStr[cwdLen-1] != '/') {
	    cwdLen++;
	}
	break;
    case TCL_PLATFORM_WINDOWS:
	if (tempStr[cwdLen-1] != '/' && tempStr[cwdLen-1] != '\\') {
	    cwdLen++;
	}
	break;
    }
    tempStr = Tcl_GetStringFromObj(pathPtr, &len);

    return Tcl_NewStringObj(tempStr + cwdLen, len - cwdLen);
}

/*
 *---------------------------------------------------------------------------
 *
 * MakePathFromNormalized --
 *
 *	Like SetFsPathFromAny, but assumes the given object is an absolute
 *	normalized path. Only for internal use.
 *
 * Results:
 *	Standard Tcl error code.
 *
 * Side effects:
 *	The old representation may be freed, and new memory allocated.
 *
 *---------------------------------------------------------------------------
 */

static int
MakePathFromNormalized(
    Tcl_Interp *interp,		/* Used for error reporting if not NULL. */
    Tcl_Obj *pathPtr)		/* The object to convert. */
{
    FsPath *fsPathPtr;

    if (pathPtr->typePtr == &tclFsPathType) {
	return TCL_OK;
    }

    /*
     * Free old representation
     */

    if (pathPtr->typePtr != NULL) {
	if (pathPtr->bytes == NULL) {
	    if (pathPtr->typePtr->updateStringProc == NULL) {
		if (interp != NULL) {
		    Tcl_ResetResult(interp);
		    Tcl_AppendResult(interp, "can't find object"
			    "string representation", NULL);
		}
		return TCL_ERROR;
	    }
	    pathPtr->typePtr->updateStringProc(pathPtr);
	}
	TclFreeIntRep(pathPtr);
    }

    fsPathPtr = (FsPath *) ckalloc(sizeof(FsPath));

    /*
     * It's a pure normalized absolute path.
     */

    fsPathPtr->translatedPathPtr = NULL;

    /*
     * Circular reference by design.
     */

    fsPathPtr->normPathPtr = pathPtr;
    fsPathPtr->cwdPtr = NULL;
    fsPathPtr->nativePathPtr = NULL;
    fsPathPtr->fsPtr = NULL;
    /* Remember the epoch under which we decided pathPtr was normalized */
    fsPathPtr->filesystemEpoch = TclFSEpoch();

    SETPATHOBJ(pathPtr, fsPathPtr);
    PATHFLAGS(pathPtr) = 0;
    pathPtr->typePtr = &tclFsPathType;

    return TCL_OK;
}

/*
 *---------------------------------------------------------------------------
 *
 * Tcl_FSNewNativePath --
 *
 *	This function performs the something like the reverse of the usual
 *	obj->path->nativerep conversions. If some code retrieves a path in
 *	native form (from, e.g. readlink or a native dialog), and that path is
 *	to be used at the Tcl level, then calling this function is an
 *	efficient way of creating the appropriate path object type.
 *
 *	Any memory which is allocated for 'clientData' should be retained
 *	until clientData is passed to the filesystem's freeInternalRepProc
 *	when it can be freed. The built in platform-specific filesystems use
 *	'ckalloc' to allocate clientData, and ckfree to free it.
 *
 * Results:
 *	NULL or a valid path object pointer, with refCount zero.
 *
 * Side effects:
 *	New memory may be allocated.
 *
 *---------------------------------------------------------------------------
 */

Tcl_Obj *
Tcl_FSNewNativePath(
    Tcl_Filesystem *fromFilesystem,
    ClientData clientData)
{
    Tcl_Obj *pathPtr = NULL;
    FsPath *fsPathPtr;


    if (fromFilesystem->internalToNormalizedProc != NULL) {
	pathPtr = (*fromFilesystem->internalToNormalizedProc)(clientData);
    }
    if (pathPtr == NULL) {
	return NULL;
    }

    /*
     * Free old representation; shouldn't normally be any, but best to be
     * safe.
     */

    if (pathPtr->typePtr != NULL) {
	if (pathPtr->bytes == NULL) {
	    if (pathPtr->typePtr->updateStringProc == NULL) {
		return NULL;
	    }
	    pathPtr->typePtr->updateStringProc(pathPtr);
	}
	TclFreeIntRep(pathPtr);
    }

    fsPathPtr = (FsPath *) ckalloc(sizeof(FsPath));

    fsPathPtr->translatedPathPtr = NULL;

    /*
     * Circular reference, by design.
     */

    fsPathPtr->normPathPtr = pathPtr;
    fsPathPtr->cwdPtr = NULL;
    fsPathPtr->nativePathPtr = clientData;
    fsPathPtr->fsPtr = fromFilesystem;
    fsPathPtr->filesystemEpoch = TclFSEpoch();

    SETPATHOBJ(pathPtr, fsPathPtr);
    PATHFLAGS(pathPtr) = 0;
    pathPtr->typePtr = &tclFsPathType;

    return pathPtr;
}

/*
 *---------------------------------------------------------------------------
 *
 * Tcl_FSGetTranslatedPath --
 *
 *	This function attempts to extract the translated path from the given
 *	Tcl_Obj. If the translation succeeds (i.e. the object is a valid
 *	path), then it is returned. Otherwise NULL will be returned, and an
 *	error message may be left in the interpreter (if it is non-NULL)
 *
 * Results:
 *	NULL or a valid Tcl_Obj pointer.
 *
 * Side effects:
 *	Only those of 'Tcl_FSConvertToPathType'
 *
 *---------------------------------------------------------------------------
 */

Tcl_Obj *
Tcl_FSGetTranslatedPath(
    Tcl_Interp *interp,
    Tcl_Obj *pathPtr)
{
    Tcl_Obj *retObj = NULL;
    FsPath *srcFsPathPtr;

    if (Tcl_FSConvertToPathType(interp, pathPtr) != TCL_OK) {
	return NULL;
    }
    srcFsPathPtr = PATHOBJ(pathPtr);
    if (srcFsPathPtr->translatedPathPtr == NULL) {
	if (PATHFLAGS(pathPtr) != 0) {
	    /*
	     * We lack a translated path result, but we have a directory
	     * (cwdPtr) and a tail (normPathPtr), and if we join the
	     * translated version of cwdPtr to normPathPtr, we'll get the
	     * translated result we need, and can store it for future use.
	     */

	    Tcl_Obj *translatedCwdPtr = Tcl_FSGetTranslatedPath(interp,
		    srcFsPathPtr->cwdPtr);
	    if (translatedCwdPtr == NULL) {
		return NULL;
	    }

	    retObj = Tcl_FSJoinToPath(translatedCwdPtr, 1,
		    &(srcFsPathPtr->normPathPtr));
	    srcFsPathPtr->translatedPathPtr = retObj;
	    if (translatedCwdPtr->typePtr == &tclFsPathType) {
		srcFsPathPtr->filesystemEpoch
			= PATHOBJ(translatedCwdPtr)->filesystemEpoch;
	    } else {
		srcFsPathPtr->filesystemEpoch = 0;
	    }
	    Tcl_IncrRefCount(retObj);
	    Tcl_DecrRefCount(translatedCwdPtr);
	} else {
	    /*
	     * It is a pure absolute, normalized path object. This is
	     * something like being a 'pure list'. The object's string,
	     * translatedPath and normalizedPath are all identical.
	     */

	    retObj = srcFsPathPtr->normPathPtr;
	}
    } else {
	/*
	 * It is an ordinary path object.
	 */

	retObj = srcFsPathPtr->translatedPathPtr;
    }

    if (retObj != NULL) {
	Tcl_IncrRefCount(retObj);
    }
    return retObj;
}

/*
 *---------------------------------------------------------------------------
 *
 * Tcl_FSGetTranslatedStringPath --
 *
 *	This function attempts to extract the translated path from the given
 *	Tcl_Obj. If the translation succeeds (i.e. the object is a valid
 *	path), then the path is returned. Otherwise NULL will be returned, and
 *	an error message may be left in the interpreter (if it is non-NULL)
 *
 * Results:
 *	NULL or a valid string.
 *
 * Side effects:
 *	Only those of 'Tcl_FSConvertToPathType'
 *
 *---------------------------------------------------------------------------
 */

const char *
Tcl_FSGetTranslatedStringPath(
    Tcl_Interp *interp,
    Tcl_Obj *pathPtr)
{
    Tcl_Obj *transPtr = Tcl_FSGetTranslatedPath(interp, pathPtr);

    if (transPtr != NULL) {
	int len;
	const char *orig = Tcl_GetStringFromObj(transPtr, &len);
	char *result = (char *) ckalloc((unsigned) len+1);

	memcpy(result, orig, (size_t) len+1);
	TclDecrRefCount(transPtr);
	return result;
    }

    return NULL;
}

/*
 *---------------------------------------------------------------------------
 *
 * Tcl_FSGetNormalizedPath --
 *
 *	This important function attempts to extract from the given Tcl_Obj a
 *	unique normalised path representation, whose string value can be used
 *	as a unique identifier for the file.
 *
 * Results:
 *	NULL or a valid path object pointer.
 *
 * Side effects:
 *	New memory may be allocated. The Tcl 'errno' may be modified in the
 *	process of trying to examine various path possibilities.
 *
 *---------------------------------------------------------------------------
 */

Tcl_Obj *
Tcl_FSGetNormalizedPath(
    Tcl_Interp *interp,
    Tcl_Obj *pathPtr)
{
    FsPath *fsPathPtr;

    if (Tcl_FSConvertToPathType(interp, pathPtr) != TCL_OK) {
	return NULL;
    }
    fsPathPtr = PATHOBJ(pathPtr);

    if (PATHFLAGS(pathPtr) != 0) {
	/*
	 * This is a special path object which is the result of something like
	 * 'file join'
	 */

	Tcl_Obj *dir, *copy;
	int tailLen, cwdLen, pathType;

	pathType = Tcl_FSGetPathType(fsPathPtr->cwdPtr);
	dir = Tcl_FSGetNormalizedPath(interp, fsPathPtr->cwdPtr);
	if (dir == NULL) {
	    return NULL;
	}
	/* TODO: Figure out why this is needed. */
	if (pathPtr->bytes == NULL) {
	    UpdateStringOfFsPath(pathPtr);
	}

	Tcl_GetStringFromObj(fsPathPtr->normPathPtr, &tailLen);
	if (tailLen) {
	    copy = AppendPath(dir, fsPathPtr->normPathPtr);
	} else {
	    copy = Tcl_DuplicateObj(dir);
	}
	Tcl_IncrRefCount(dir);
	Tcl_IncrRefCount(copy);

	/*
	 * We now own a reference on both 'dir' and 'copy'
	 */

	(void) Tcl_GetStringFromObj(dir, &cwdLen);
	cwdLen += (Tcl_GetString(copy)[cwdLen] == '/');

	/* Normalize the combined string. */

	if (PATHFLAGS(pathPtr) & TCLPATH_NEEDNORM) {
	    /*
	     * If the "tail" part has components (like /../) that cause
	     * the combined path to need more complete normalizing,
	     * call on the more powerful routine to accomplish that so
	     * we avoid [Bug 2385549] ...
	     */

	    Tcl_Obj *newCopy = TclFSNormalizeAbsolutePath(interp, copy);
	    Tcl_DecrRefCount(copy);
	    copy = newCopy;
	} else {
	    /*
	     * ... but in most cases where we join a trouble free tail
	     * to a normalized head, we can more efficiently normalize the
	     * combined path by passing over only the unnormalized tail
	     * portion.  When this is sufficient, prior developers claim
	     * this should be much faster.  We use 'cwdLen-1' so that we are
	     * already pointing at the dir-separator that we know about.
	     * The normalization code will actually start off directly
	     * after that separator.
	     */

	    TclFSNormalizeToUniquePath(interp, copy, cwdLen-1);
	}

	/* Now we need to construct the new path object. */

	if (pathType == TCL_PATH_RELATIVE) {
	    Tcl_Obj *origDir = fsPathPtr->cwdPtr;

	    /*
	     * NOTE: here we are (dangerously?) assuming that origDir points
	     * to a Tcl_Obj with Tcl_ObjType == &tclFsPathType .  The
	     *     pathType = Tcl_FSGetPathType(fsPathPtr->cwdPtr);
	     * above that set the pathType value should have established
	     * that, but it's far less clear on what basis we know there's
	     * been no shimmering since then.
	     */

	    FsPath *origDirFsPathPtr = PATHOBJ(origDir);

	    fsPathPtr->cwdPtr = origDirFsPathPtr->cwdPtr;
	    Tcl_IncrRefCount(fsPathPtr->cwdPtr);

	    TclDecrRefCount(fsPathPtr->normPathPtr);
	    fsPathPtr->normPathPtr = copy;

	    /*
	     * That's our reference to copy used.
	     */

	    TclDecrRefCount(dir);
	    TclDecrRefCount(origDir);
	} else {
	    TclDecrRefCount(fsPathPtr->cwdPtr);
	    fsPathPtr->cwdPtr = NULL;
	    TclDecrRefCount(fsPathPtr->normPathPtr);
	    fsPathPtr->normPathPtr = copy;

	    /*
	     * That's our reference to copy used.
	     */

	    TclDecrRefCount(dir);
	}
	PATHFLAGS(pathPtr) = 0;
    }

    /*
     * Ensure cwd hasn't changed.
     */

    if (fsPathPtr->cwdPtr != NULL) {
	if (!TclFSCwdPointerEquals(&fsPathPtr->cwdPtr)) {
	    if (pathPtr->bytes == NULL) {
		UpdateStringOfFsPath(pathPtr);
	    }
	    FreeFsPathInternalRep(pathPtr);
	    if (Tcl_ConvertToType(interp, pathPtr, &tclFsPathType) != TCL_OK) {
		return NULL;
	    }
	    fsPathPtr = PATHOBJ(pathPtr);
	} else if (fsPathPtr->normPathPtr == NULL) {
	    int cwdLen;
	    Tcl_Obj *copy;

	    copy = AppendPath(fsPathPtr->cwdPtr, pathPtr);

	    (void) Tcl_GetStringFromObj(fsPathPtr->cwdPtr, &cwdLen);
	    cwdLen += (Tcl_GetString(copy)[cwdLen] == '/');

	    /*
	     * Normalize the combined string, but only starting after the end
	     * of the previously normalized 'dir'. This should be much faster!
	     */

	    TclFSNormalizeToUniquePath(interp, copy, cwdLen-1);
	    fsPathPtr->normPathPtr = copy;
	    Tcl_IncrRefCount(fsPathPtr->normPathPtr);
	}
    }
    if (fsPathPtr->normPathPtr == NULL) {
	Tcl_Obj *useThisCwd = NULL;
	int pureNormalized = 1;

	/*
	 * Since normPathPtr is NULL, but this is a valid path object, we know
	 * that the translatedPathPtr cannot be NULL.
	 */

	Tcl_Obj *absolutePath = fsPathPtr->translatedPathPtr;
	const char *path = TclGetString(absolutePath);

	Tcl_IncrRefCount(absolutePath);

	/*
	 * We have to be a little bit careful here to avoid infinite loops
	 * we're asking Tcl_FSGetPathType to return the path's type, but that
	 * call can actually result in a lot of other filesystem action, which
	 * might loop back through here.
	 */

	if (path[0] == '\0') {
	    /*
	     * Special handling for the empty string value.  This one is
	     * very weird with [file normalize {}] => {}.  (The reasoning
	     * supporting this is unknown to DGP, but he fears changing it.)
	     * Attempt here to keep the expectations of other parts of
	     * Tcl_Filesystem code about state of the FsPath fields satisfied.
	     *
	     * In particular, capture the cwd value and save so it can be
	     * stored in the cwdPtr field below.
	     */

	    useThisCwd = Tcl_FSGetCwd(interp);
	} else {
	    /*
	     * We don't ask for the type of 'pathPtr' here, because that is
	     * not correct for our purposes when we have a path like '~'. Tcl
	     * has a bit of a contradiction in that '~' paths are defined as
	     * 'absolute', but in reality can be just about anything,
	     * depending on how env(HOME) is set.
	     */

	    Tcl_PathType type = Tcl_FSGetPathType(absolutePath);

	    if (type == TCL_PATH_RELATIVE) {
		useThisCwd = Tcl_FSGetCwd(interp);

		if (useThisCwd == NULL) {
		    return NULL;
		}

		pureNormalized = 0;
		Tcl_DecrRefCount(absolutePath);
		absolutePath = Tcl_FSJoinToPath(useThisCwd, 1, &absolutePath);
		Tcl_IncrRefCount(absolutePath);

		/*
		 * We have a refCount on the cwd.
		 */
#ifdef __WIN32__
	    } else if (type == TCL_PATH_VOLUME_RELATIVE) {
		/*
		 * Only Windows has volume-relative paths.
		 */

		Tcl_DecrRefCount(absolutePath);
		absolutePath = TclWinVolumeRelativeNormalize(interp,
			path, &useThisCwd);
		if (absolutePath == NULL) {
		    return NULL;
		}
		pureNormalized = 0;
#endif /* __WIN32__ */
	    }
	}

	/*
	 * Already has refCount incremented.
	 */

	fsPathPtr->normPathPtr = TclFSNormalizeAbsolutePath(interp,
		absolutePath);

	/*
	 * Check if path is pure normalized (this can only be the case if it
	 * is an absolute path).
	 */

	if (pureNormalized) {
	    if (!strcmp(TclGetString(fsPathPtr->normPathPtr),
		    TclGetString(pathPtr))) {
		/*
		 * The path was already normalized. Get rid of the duplicate.
		 */

		TclDecrRefCount(fsPathPtr->normPathPtr);

		/*
		 * We do *not* increment the refCount for this circular
		 * reference.
		 */

		fsPathPtr->normPathPtr = pathPtr;
	    }
	}
	if (useThisCwd != NULL) {
	    /*
	     * We just need to free an object we allocated above for relative
	     * paths (this was returned by Tcl_FSJoinToPath above), and then
	     * of course store the cwd.
	     */

	    fsPathPtr->cwdPtr = useThisCwd;
	}
	TclDecrRefCount(absolutePath);
    }

    return fsPathPtr->normPathPtr;
}

/*
 *---------------------------------------------------------------------------
 *
 * Tcl_FSGetInternalRep --
 *
 *	Extract the internal representation of a given path object, in the
 *	given filesystem. If the path object belongs to a different
 *	filesystem, we return NULL.
 *
 *	If the internal representation is currently NULL, we attempt to
 *	generate it, by calling the filesystem's
 *	'Tcl_FSCreateInternalRepProc'.
 *
 * Results:
 *	NULL or a valid internal representation.
 *
 * Side effects:
 *	An attempt may be made to convert the object.
 *
 *---------------------------------------------------------------------------
 */

ClientData
Tcl_FSGetInternalRep(
    Tcl_Obj *pathPtr,
    Tcl_Filesystem *fsPtr)
{
    FsPath *srcFsPathPtr;

    if (Tcl_FSConvertToPathType(NULL, pathPtr) != TCL_OK) {
	return NULL;
    }
    srcFsPathPtr = PATHOBJ(pathPtr);

    /*
     * We will only return the native representation for the caller's
     * filesystem. Otherwise we will simply return NULL. This means that there
     * must be a unique bi-directional mapping between paths and filesystems,
     * and that this mapping will not allow 'remapped' files -- files which
     * are in one filesystem but mapped into another. Another way of putting
     * this is that 'stacked' filesystems are not allowed. We recognise that
     * this is a potentially useful feature for the future.
     *
     * Even something simple like a 'pass through' filesystem which logs all
     * activity and passes the calls onto the native system would be nice, but
     * not easily achievable with the current implementation.
     */

    if (srcFsPathPtr->fsPtr == NULL) {
	/*
	 * This only usually happens in wrappers like TclpStat which create a
	 * string object and pass it to TclpObjStat. Code which calls the
	 * Tcl_FS.. functions should always have a filesystem already set.
	 * Whether this code path is legal or not depends on whether we decide
	 * to allow external code to call the native filesystem directly. It
	 * is at least safer to allow this sub-optimal routing.
	 */

	Tcl_FSGetFileSystemForPath(pathPtr);

	/*
	 * If we fail through here, then the path is probably not a valid path
	 * in the filesystsem, and is most likely to be a use of the empty
	 * path "" via a direct call to one of the objectified interfaces
	 * (e.g. from the Tcl testsuite).
	 */

	srcFsPathPtr = PATHOBJ(pathPtr);
	if (srcFsPathPtr->fsPtr == NULL) {
	    return NULL;
	}
    }

    /*
     * There is still one possibility we should consider; if the file belongs
     * to a different filesystem, perhaps it is actually linked through to a
     * file in our own filesystem which we do care about. The way we can check
     * for this is we ask what filesystem this path belongs to.
     */

    if (fsPtr != srcFsPathPtr->fsPtr) {
	const Tcl_Filesystem *actualFs = Tcl_FSGetFileSystemForPath(pathPtr);

	if (actualFs == fsPtr) {
	    return Tcl_FSGetInternalRep(pathPtr, fsPtr);
	}
	return NULL;
    }

    if (srcFsPathPtr->nativePathPtr == NULL) {
	Tcl_FSCreateInternalRepProc *proc;
	char *nativePathPtr;

	proc = srcFsPathPtr->fsPtr->createInternalRepProc;
	if (proc == NULL) {
	    return NULL;
	}

	nativePathPtr = (*proc)(pathPtr);
	srcFsPathPtr = PATHOBJ(pathPtr);
	srcFsPathPtr->nativePathPtr = nativePathPtr;
    }

    return srcFsPathPtr->nativePathPtr;
}

/*
 *---------------------------------------------------------------------------
 *
 * TclFSEnsureEpochOk --
 *
 *	This will ensure the pathPtr is up to date and can be converted into a
 *	"path" type, and that we are able to generate a complete normalized
 *	path which is used to determine the filesystem match.
 *
 * Results:
 *	Standard Tcl return code.
 *
 * Side effects:
 *	An attempt may be made to convert the object.
 *
 *---------------------------------------------------------------------------
 */

int
TclFSEnsureEpochOk(
    Tcl_Obj *pathPtr,
    Tcl_Filesystem **fsPtrPtr)
{
    FsPath *srcFsPathPtr;

    if (pathPtr->typePtr != &tclFsPathType) {
	return TCL_OK;
    }

    srcFsPathPtr = PATHOBJ(pathPtr);

    /*
     * Check if the filesystem has changed in some way since this object's
     * internal representation was calculated.
     */

    if (!TclFSEpochOk(srcFsPathPtr->filesystemEpoch)) {
	/*
	 * We have to discard the stale representation and recalculate it.
	 */

	if (pathPtr->bytes == NULL) {
	    UpdateStringOfFsPath(pathPtr);
	}
	FreeFsPathInternalRep(pathPtr);
	if (SetFsPathFromAny(NULL, pathPtr) != TCL_OK) {
	    return TCL_ERROR;
	}
	srcFsPathPtr = PATHOBJ(pathPtr);
    }

    /*
     * Check whether the object is already assigned to a fs.
     */

    if (srcFsPathPtr->fsPtr != NULL) {
	*fsPtrPtr = srcFsPathPtr->fsPtr;
    }
    return TCL_OK;
}

/*
 *---------------------------------------------------------------------------
 *
 * TclFSSetPathDetails --
 *
 *	???
 *
 * Results:
 *	None
 *
 * Side effects:
 *	???
 *
 *---------------------------------------------------------------------------
 */

void
TclFSSetPathDetails(
    Tcl_Obj *pathPtr,
    Tcl_Filesystem *fsPtr,
    ClientData clientData)
{
    FsPath *srcFsPathPtr;

    /*
     * Make sure pathPtr is of the correct type.
     */

    if (pathPtr->typePtr != &tclFsPathType) {
	if (SetFsPathFromAny(NULL, pathPtr) != TCL_OK) {
	    return;
	}
    }

    srcFsPathPtr = PATHOBJ(pathPtr);
    srcFsPathPtr->fsPtr = fsPtr;
    srcFsPathPtr->nativePathPtr = clientData;
    srcFsPathPtr->filesystemEpoch = TclFSEpoch();
}

/*
 *---------------------------------------------------------------------------
 *
 * Tcl_FSEqualPaths --
 *
 *	This function tests whether the two paths given are equal path
 *	objects. If either or both is NULL, 0 is always returned.
 *
 * Results:
 *	1 or 0.
 *
 * Side effects:
 *	None.
 *
 *---------------------------------------------------------------------------
 */

int
Tcl_FSEqualPaths(
    Tcl_Obj *firstPtr,
    Tcl_Obj *secondPtr)
{
    char *firstStr, *secondStr;
    int firstLen, secondLen, tempErrno;

    if (firstPtr == secondPtr) {
	return 1;
    }

    if (firstPtr == NULL || secondPtr == NULL) {
	return 0;
    }
    firstStr = Tcl_GetStringFromObj(firstPtr, &firstLen);
    secondStr = Tcl_GetStringFromObj(secondPtr, &secondLen);
    if ((firstLen == secondLen) && (strcmp(firstStr, secondStr) == 0)) {
	return 1;
    }

    /*
     * Try the most thorough, correct method of comparing fully normalized
     * paths.
     */

    tempErrno = Tcl_GetErrno();
    firstPtr = Tcl_FSGetNormalizedPath(NULL, firstPtr);
    secondPtr = Tcl_FSGetNormalizedPath(NULL, secondPtr);
    Tcl_SetErrno(tempErrno);

    if (firstPtr == NULL || secondPtr == NULL) {
	return 0;
    }

    firstStr = Tcl_GetStringFromObj(firstPtr, &firstLen);
    secondStr = Tcl_GetStringFromObj(secondPtr, &secondLen);
    return (firstLen == secondLen) && (strcmp(firstStr, secondStr) == 0);
}

/*
 *---------------------------------------------------------------------------
 *
 * SetFsPathFromAny --
 *
 *	This function tries to convert the given Tcl_Obj to a valid Tcl path
 *	type.
 *
 *	The filename may begin with "~" (to indicate current user's home
 *	directory) or "~<user>" (to indicate any user's home directory).
 *
 * Results:
 *	Standard Tcl error code.
 *
 * Side effects:
 *	The old representation may be freed, and new memory allocated.
 *
 *---------------------------------------------------------------------------
 */

static int
SetFsPathFromAny(
    Tcl_Interp *interp,		/* Used for error reporting if not NULL. */
    Tcl_Obj *pathPtr)		/* The object to convert. */
{
    int len;
    FsPath *fsPathPtr;
    Tcl_Obj *transPtr;
    char *name;

    if (pathPtr->typePtr == &tclFsPathType) {
	return TCL_OK;
    }

    /*
     * First step is to translate the filename. This is similar to
     * Tcl_TranslateFilename, but shouldn't convert everything to windows
     * backslashes on that platform. The current implementation of this piece
     * is a slightly optimised version of the various Tilde/Split/Join stuff
     * to avoid multiple split/join operations.
     *
     * We remove any trailing directory separator.
     *
     * However, the split/join routines are quite complex, and one has to make
     * sure not to break anything on Unix or Win (fCmd.test, fileName.test and
     * cmdAH.test exercise most of the code).
     */

    name = Tcl_GetStringFromObj(pathPtr, &len);

    /*
     * Handle tilde substitutions, if needed.
     */

    if (name[0] == '~') {
	char *expandedUser;
	Tcl_DString temp;
	int split;
	char separator = '/';

	split = FindSplitPos(name, separator);
	if (split != len) {
	    /*
	     * We have multiple pieces '~user/foo/bar...'
	     */

	    name[split] = '\0';
	}

	/*
	 * Do some tilde substitution.
	 */

	if (name[1] == '\0') {
	    /*
	     * We have just '~'
	     */

	    const char *dir;
	    Tcl_DString dirString;

	    if (split != len) {
		name[split] = separator;
	    }

	    dir = TclGetEnv("HOME", &dirString);
	    if (dir == NULL) {
		if (interp) {
		    Tcl_ResetResult(interp);
		    Tcl_AppendResult(interp, "couldn't find HOME environment "
			    "variable to expand path", NULL);
		}
		return TCL_ERROR;
	    }
	    Tcl_DStringInit(&temp);
	    Tcl_JoinPath(1, &dir, &temp);
	    Tcl_DStringFree(&dirString);
	} else {
	    /*
	     * We have a user name '~user'
	     */

	    Tcl_DStringInit(&temp);
	    if (TclpGetUserHome(name+1, &temp) == NULL) {
		if (interp != NULL) {
		    Tcl_ResetResult(interp);
		    Tcl_AppendResult(interp, "user \"", name+1,
			    "\" doesn't exist", NULL);
		}
		Tcl_DStringFree(&temp);
		if (split != len) {
		    name[split] = separator;
		}
		return TCL_ERROR;
	    }
	    if (split != len) {
		name[split] = separator;
	    }
	}

	expandedUser = Tcl_DStringValue(&temp);
	transPtr = Tcl_NewStringObj(expandedUser, Tcl_DStringLength(&temp));

	if (split != len) {
	    /*
	     * Join up the tilde substitution with the rest.
	     */

	    if (name[split+1] == separator) {
		/*
		 * Somewhat tricky case like ~//foo/bar. Make use of
		 * Split/Join machinery to get it right. Assumes all paths
		 * beginning with ~ are part of the native filesystem.
		 */

		int objc;
		Tcl_Obj **objv;
		Tcl_Obj *parts = TclpNativeSplitPath(pathPtr, NULL);

		Tcl_ListObjGetElements(NULL, parts, &objc, &objv);

		/*
		 * Skip '~'. It's replaced by its expansion.
		 */

		objc--; objv++;
		while (objc--) {
		    TclpNativeJoinPath(transPtr, Tcl_GetString(*objv++));
		}
		TclDecrRefCount(parts);
	    } else {
		/*
		 * Simple case. "rest" is relative path. Just join it. The
		 * "rest" object will be freed when Tcl_FSJoinToPath returns
		 * (unless something else claims a refCount on it).
		 */

		Tcl_Obj *joined;
		Tcl_Obj *rest = Tcl_NewStringObj(name+split+1, -1);

		Tcl_IncrRefCount(transPtr);
		joined = Tcl_FSJoinToPath(transPtr, 1, &rest);
		TclDecrRefCount(transPtr);
		transPtr = joined;
	    }
	}
	Tcl_DStringFree(&temp);
    } else {
	/* Bug 3479689: protect 0-refcount pathPth from getting freed */
	pathPtr->refCount++;
	transPtr = Tcl_FSJoinToPath(pathPtr, 0, NULL);
	pathPtr->refCount--;
    }

    /*
     * Now we have a translated filename in 'transPtr'. This will have forward
     * slashes on Windows, and will not contain any ~user sequences.
     */

    fsPathPtr = (FsPath *) ckalloc(sizeof(FsPath));

    fsPathPtr->translatedPathPtr = transPtr;
    if (transPtr != pathPtr) {
	Tcl_IncrRefCount(fsPathPtr->translatedPathPtr);
	/* Redo translation when $env(HOME) changes */
	fsPathPtr->filesystemEpoch = TclFSEpoch();
    } else {
	fsPathPtr->filesystemEpoch = 0;
    }
    fsPathPtr->normPathPtr = NULL;
    fsPathPtr->cwdPtr = NULL;
    fsPathPtr->nativePathPtr = NULL;
    fsPathPtr->fsPtr = NULL;

    /*
     * Free old representation before installing our new one.
     */

    TclFreeIntRep(pathPtr);
    SETPATHOBJ(pathPtr, fsPathPtr);
    PATHFLAGS(pathPtr) = 0;
    pathPtr->typePtr = &tclFsPathType;
    return TCL_OK;
}

static void
FreeFsPathInternalRep(
    Tcl_Obj *pathPtr)		/* Path object with internal rep to free. */
{
    FsPath *fsPathPtr = PATHOBJ(pathPtr);

    if (fsPathPtr->translatedPathPtr != NULL) {
	if (fsPathPtr->translatedPathPtr != pathPtr) {
	    TclDecrRefCount(fsPathPtr->translatedPathPtr);
	}
    }
    if (fsPathPtr->normPathPtr != NULL) {
	if (fsPathPtr->normPathPtr != pathPtr) {
	    TclDecrRefCount(fsPathPtr->normPathPtr);
	}
	fsPathPtr->normPathPtr = NULL;
    }
    if (fsPathPtr->cwdPtr != NULL) {
	TclDecrRefCount(fsPathPtr->cwdPtr);
    }
    if (fsPathPtr->nativePathPtr != NULL && fsPathPtr->fsPtr != NULL) {
	Tcl_FSFreeInternalRepProc *freeProc =
		fsPathPtr->fsPtr->freeInternalRepProc;

	if (freeProc != NULL) {
	    (*freeProc)(fsPathPtr->nativePathPtr);
	    fsPathPtr->nativePathPtr = NULL;
	}
    }

    ckfree((char *) fsPathPtr);
    pathPtr->typePtr = NULL;
}

static void
DupFsPathInternalRep(
    Tcl_Obj *srcPtr,		/* Path obj with internal rep to copy. */
    Tcl_Obj *copyPtr)		/* Path obj with internal rep to set. */
{
    FsPath *srcFsPathPtr = PATHOBJ(srcPtr);
    FsPath *copyFsPathPtr = (FsPath *) ckalloc(sizeof(FsPath));

    SETPATHOBJ(copyPtr, copyFsPathPtr);

    if (srcFsPathPtr->translatedPathPtr == srcPtr) {
	/* Cycle in src -> make cycle in copy. */
	copyFsPathPtr->translatedPathPtr = copyPtr;
    } else {
	copyFsPathPtr->translatedPathPtr = srcFsPathPtr->translatedPathPtr;
	if (copyFsPathPtr->translatedPathPtr != NULL) {
	    Tcl_IncrRefCount(copyFsPathPtr->translatedPathPtr);
	}
    }

    if (srcFsPathPtr->normPathPtr == srcPtr) {
	/* Cycle in src -> make cycle in copy. */
	copyFsPathPtr->normPathPtr = copyPtr;
    } else {
	copyFsPathPtr->normPathPtr = srcFsPathPtr->normPathPtr;
	if (copyFsPathPtr->normPathPtr != NULL) {
	    Tcl_IncrRefCount(copyFsPathPtr->normPathPtr);
	}
    }

    copyFsPathPtr->cwdPtr = srcFsPathPtr->cwdPtr;
    if (copyFsPathPtr->cwdPtr != NULL) {
	Tcl_IncrRefCount(copyFsPathPtr->cwdPtr);
    }

    copyFsPathPtr->flags = srcFsPathPtr->flags;

    if (srcFsPathPtr->fsPtr != NULL
	    && srcFsPathPtr->nativePathPtr != NULL) {
	Tcl_FSDupInternalRepProc *dupProc =
		srcFsPathPtr->fsPtr->dupInternalRepProc;

	if (dupProc != NULL) {
	    copyFsPathPtr->nativePathPtr =
		    (*dupProc)(srcFsPathPtr->nativePathPtr);
	} else {
	    copyFsPathPtr->nativePathPtr = NULL;
	}
    } else {
	copyFsPathPtr->nativePathPtr = NULL;
    }
    copyFsPathPtr->fsPtr = srcFsPathPtr->fsPtr;
    copyFsPathPtr->filesystemEpoch = srcFsPathPtr->filesystemEpoch;

    copyPtr->typePtr = &tclFsPathType;
}

/*
 *---------------------------------------------------------------------------
 *
 * UpdateStringOfFsPath --
 *
 *	Gives an object a valid string rep.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Memory may be allocated.
 *
 *---------------------------------------------------------------------------
 */

static void
UpdateStringOfFsPath(
    register Tcl_Obj *pathPtr)	/* path obj with string rep to update. */
{
    FsPath *fsPathPtr = PATHOBJ(pathPtr);
    int cwdLen;
    Tcl_Obj *copy;

    if (PATHFLAGS(pathPtr) == 0 || fsPathPtr->cwdPtr == NULL) {
	Tcl_Panic("Called UpdateStringOfFsPath with invalid object");
    }

    copy = AppendPath(fsPathPtr->cwdPtr, fsPathPtr->normPathPtr);

    pathPtr->bytes = Tcl_GetStringFromObj(copy, &cwdLen);
    pathPtr->length = cwdLen;
    copy->bytes = tclEmptyStringRep;
    copy->length = 0;
    TclDecrRefCount(copy);
}

/*
 *---------------------------------------------------------------------------
 *
 * TclNativePathInFilesystem --
 *
 *	Any path object is acceptable to the native filesystem, by default (we
 *	will throw errors when illegal paths are actually tried to be used).
 *
 *	However, this behavior means the native filesystem must be the last
 *	filesystem in the lookup list (otherwise it will claim all files
 *	belong to it, and other filesystems will never get a look in).
 *
 * Results:
 *	TCL_OK, to indicate 'yes', -1 to indicate no.
 *
 * Side effects:
 *	None.
 *
 *---------------------------------------------------------------------------
 */

int
TclNativePathInFilesystem(
    Tcl_Obj *pathPtr,
    ClientData *clientDataPtr)
{
    /*
     * A special case is required to handle the empty path "". This is a valid
     * path (i.e. the user should be able to do 'file exists ""' without
     * throwing an error), but equally the path doesn't exist. Those are the
     * semantics of Tcl (at present anyway), so we have to abide by them here.
     */

    if (pathPtr->typePtr == &tclFsPathType) {
	if (pathPtr->bytes != NULL && pathPtr->bytes[0] == '\0') {
	    /*
	     * We reject the empty path "".
	     */

	    return -1;
	}

	/*
	 * Otherwise there is no way this path can be empty.
	 */
    } else {
	/*
	 * It is somewhat unusual to reach this code path without the object
	 * being of tclFsPathType. However, we do our best to deal with the
	 * situation.
	 */

	int len;

	(void) Tcl_GetStringFromObj(pathPtr, &len);
	if (len == 0) {
	    /*
	     * We reject the empty path "".
	     */

	    return -1;
	}
    }

    /*
     * Path is of correct type, or is of non-zero length, so we accept it.
     */

    return TCL_OK;
}

/*
 * Local Variables:
 * mode: c
 * c-basic-offset: 4
 * fill-column: 78
 * End:
 */
