Rewrite documentation of IO subsystem.

4 files changed, 260 insertions, 337 deletions

diff --git a/generic/tcl.h b/generic/tcl.h
index 571a9b9..c1187c6 100644
--- a/generic/tcl.h
+++ b/generic/tcl.h
@@ -1653,7 +1653,7 @@ typedef struct Tcl_FSVersion_ *Tcl_FSVersion;
  * struct Tcl_Filesystem:
  *
  * One such structure exists for each type (kind) of filesystem. It collects
- * together in one place all the functions that are part of the specific
+ * together the functions that form the interface for a particulr the
  * filesystem. Tcl always accesses the filesystem through one of these
  * structures.
  *
@@ -1668,147 +1668,119 @@ typedef struct Tcl_Filesystem {
 				 * compatibility can be assured. */
     Tcl_FSVersion version;	/* Version of the filesystem type. */
     Tcl_FSPathInFilesystemProc *pathInFilesystemProc;
-				/* Function to check whether a path is in this
+				/* Determines whether the pathname is in this
 				 * filesystem. This is the most important
 				 * filesystem function. */
     Tcl_FSDupInternalRepProc *dupInternalRepProc;
-				/* Function to duplicate internal fs rep. May
-				 * be NULL (but then fs is less efficient). */
+				/* Duplicates the internal handle of the node.
+				 * If it is NULL, the filesystem is less
+				 * performant. */
     Tcl_FSFreeInternalRepProc *freeInternalRepProc;
-				/* Function to free internal fs rep. Must be
-				 * implemented if internal representations
-				 * need freeing, otherwise it can be NULL. */
+				/* Frees the internal handle of the node.  NULL
+				 * only if there is no need to free resources
+				 * used for the internal handle. */
     Tcl_FSInternalToNormalizedProc *internalToNormalizedProc;
-				/* Function to convert internal representation
-				 * to a normalized path. Only required if the
-				 * fs creates pure path objects with no
-				 * string/path representation. */
+				/* Converts the internal handle to a normalized
+				 * path.  NULL if the filesystem creates nodes
+				 * having no pathname. */
     Tcl_FSCreateInternalRepProc *createInternalRepProc;
-				/* Function to create a filesystem-specific
-				 * internal representation. May be NULL if
-				 * paths have no internal representation, or
-				 * if the Tcl_FSPathInFilesystemProc for this
-				 * filesystem always immediately creates an
-				 * internal representation for paths it
-				 * accepts. */
+				/* Creates an internal handle for a pathname.
+				 * May be NULL if pathnames have no internal
+				 * handle or if pathInFilesystemProc always
+				 * immediately creates an internal
+				 * representation for pathnames in the
+				 * filesystem. */
     Tcl_FSNormalizePathProc *normalizePathProc;
-				/* Function to normalize a path.  Should be
-				 * implemented for all filesystems which can
-				 * have multiple string representations for
-				 * the same path object. */
+				/* Normalizes a path.  Should be implemented if
+				 * the filesystems supports multiple paths to
+				 * the same node. */
     Tcl_FSFilesystemPathTypeProc *filesystemPathTypeProc;
-				/* Function to determine the type of a path in
-				 * this filesystem. May be NULL. */
+				/* Determines the type of a path in this
+				 * filesystem. May be NULL. */
     Tcl_FSFilesystemSeparatorProc *filesystemSeparatorProc;
-				/* Function to return the separator
-				 * character(s) for this filesystem. Must be
-				 * implemented. */
-    Tcl_FSStatProc *statProc;	/* Function to process a 'Tcl_FSStat()' call.
-				 * Must be implemented for any reasonable
-				 * filesystem. */
-    Tcl_FSAccessProc *accessProc;
-				/* Function to process a 'Tcl_FSAccess()'
-				 * call. Must be implemented for any
+				/* Produces the separator character(s) for this
+				 * filesystem. Must not be NULL. */
+    Tcl_FSStatProc *statProc;	/* Called by 'Tcl_FSStat()'.  Provided by any
 				 * reasonable filesystem. */
+    Tcl_FSAccessProc *accessProc;
+				/* Called by 'Tcl_FSAccess()'.  Implemented by
+				 * any reasonable filesystem. */
     Tcl_FSOpenFileChannelProc *openFileChannelProc;
-				/* Function to process a
-				 * 'Tcl_FSOpenFileChannel()' call. Must be
-				 * implemented for any reasonable
-				 * filesystem. */
+				/* Called by 'Tcl_FSOpenFileChannel()'.
+				 * Provided by any reasonable filesystem. */
     Tcl_FSMatchInDirectoryProc *matchInDirectoryProc;
-				/* Function to process a
-				 * 'Tcl_FSMatchInDirectory()'.  If not
-				 * implemented, then glob and recursive copy
-				 * functionality will be lacking in the
-				 * filesystem. */
-    Tcl_FSUtimeProc *utimeProc;	/* Function to process a 'Tcl_FSUtime()' call.
-				 * Required to allow setting (not reading) of
-				 * times with 'file mtime', 'file atime' and
-				 * the open-r/open-w/fcopy implementation of
-				 * 'file copy'. */
-    Tcl_FSLinkProc *linkProc;	/* Function to process a 'Tcl_FSLink()' call.
-				 * Should be implemented only if the
-				 * filesystem supports links (reading or
-				 * creating). */
+				/* Called by 'Tcl_FSMatchInDirectory()'.  NULL
+				 * if the filesystem does not support glob or
+				 * recursive copy. */
+    Tcl_FSUtimeProc *utimeProc;	/* Called by 'Tcl_FSUtime()', by 'file
+				 *  mtime' to set (not read) times, 'file
+				 *  atime', and the open-r/open-w/fcopy variant
+				 *  of 'file copy'. */
+    Tcl_FSLinkProc *linkProc;	/* Called by 'Tcl_FSLink()'. NULL if reading or
+				 *  creating links is not supported. */
     Tcl_FSListVolumesProc *listVolumesProc;
-				/* Function to list any filesystem volumes
-				 * added by this filesystem. Should be
-				 * implemented only if the filesystem adds
-				 * volumes at the head of the filesystem. */
+				/* Lists filesystem volumes added by this
+				 * filesystem. NULL if the filesystem does not
+				 * use volumes. */
     Tcl_FSFileAttrStringsProc *fileAttrStringsProc;
-				/* Function to list all attributes strings
-				 * which are valid for this filesystem. If not
-				 * implemented the filesystem will not support
-				 * the 'file attributes' command. This allows
-				 * arbitrary additional information to be
-				 * attached to files in the filesystem. */
+				/* List all valid attributes strings.  NULL if
+				 * the filesystem does not support the 'file
+				 * attributes' command.  Can be used to attach
+				 * arbitrary additional data to files in a
+				 * filesystem. */
     Tcl_FSFileAttrsGetProc *fileAttrsGetProc;
-				/* Function to process a
-				 * 'Tcl_FSFileAttrsGet()' call, used by 'file
-				 * attributes'. */
+				/* Called by 'Tcl_FSFileAttrsGet()' and by 
+				 * 'file attributes'. */
     Tcl_FSFileAttrsSetProc *fileAttrsSetProc;
-				/* Function to process a
-				 * 'Tcl_FSFileAttrsSet()' call, used by 'file
-				 * attributes'.  */
+				/* Called by 'Tcl_FSFileAttrsSet()' and by
+				 * 'file attributes'.  */
     Tcl_FSCreateDirectoryProc *createDirectoryProc;
-				/* Function to process a
-				 * 'Tcl_FSCreateDirectory()' call. Should be
-				 * implemented unless the FS is read-only. */
+				/* Called by 'Tcl_FSCreateDirectory()'.  May be
+				 * NULL if the filesystem is read-only. */
     Tcl_FSRemoveDirectoryProc *removeDirectoryProc;
-				/* Function to process a
-				 * 'Tcl_FSRemoveDirectory()' call. Should be
-				 * implemented unless the FS is read-only. */
+				/* Called by 'Tcl_FSRemoveDirectory()'.  May be
+				 * NULL if the filesystem is read-only. */
     Tcl_FSDeleteFileProc *deleteFileProc;
-				/* Function to process a 'Tcl_FSDeleteFile()'
-				 * call. Should be implemented unless the FS
-				 * is read-only. */
+				/* Called by 'Tcl_FSDeleteFile()' May be NULL
+				 * if the filesystem is is read-only. */
     Tcl_FSCopyFileProc *copyFileProc;
-				/* Function to process a 'Tcl_FSCopyFile()'
-				 * call. If not implemented Tcl will fall back
-				 * on open-r, open-w and fcopy as a copying
-				 * mechanism, for copying actions initiated in
-				 * Tcl (not C). */
+				/* Called by 'Tcl_FSCopyFile()'.  If NULL, for
+				 * a copy operation at the script level (not
+				 * C) Tcl uses open-r, open-w and fcopy. */
     Tcl_FSRenameFileProc *renameFileProc;
-				/* Function to process a 'Tcl_FSRenameFile()'
-				 * call. If not implemented, Tcl will fall
-				 * back on a copy and delete mechanism, for
-				 * rename actions initiated in Tcl (not C). */
+				/* Called by 'Tcl_FSRenameFile()'. If NULL, for
+				 * a rename operation at the script level (not
+				 * C) Tcl performs a copy operation followed
+				 * by a delete operation. */
     Tcl_FSCopyDirectoryProc *copyDirectoryProc;
-				/* Function to process a
-				 * 'Tcl_FSCopyDirectory()' call. If not
-				 * implemented, Tcl will fall back on a
-				 * recursive create-dir, file copy mechanism,
-				 * for copying actions initiated in Tcl (not
-				 * C). */
-    Tcl_FSLstatProc *lstatProc;	/* Function to process a 'Tcl_FSLstat()' call.
-				 * If not implemented, Tcl will attempt to use
-				 * the 'statProc' defined above instead. */
+				/* Called by 'Tcl_FSCopyDirectory()'. If NULL,
+				 * for a copy operation at the script level
+				 * (not C) Tcl recursively creates directories
+				 * and copies files. */
+    Tcl_FSLstatProc *lstatProc;	/* Called by 'Tcl_FSLstat()'. If NULL, Tcl
+				 * attempts to use 'statProc' instead. */
     Tcl_FSLoadFileProc *loadFileProc;
-				/* Function to process a 'Tcl_FSLoadFile()'
-				 * call. If not implemented, Tcl will fall
-				 * back on a copy to native-temp followed by a
-				 * Tcl_FSLoadFile on that temporary copy. */
+				/* Called by 'Tcl_FSLoadFile()'. If NULL, Tcl
+				 * performs a copy to a temporary file in the
+				 * native filesystem and then calls
+				 * Tcl_FSLoadFile() on that temporary copy. */
     Tcl_FSGetCwdProc *getCwdProc;
-				/* Function to process a 'Tcl_FSGetCwd()'
-				 * call. Most filesystems need not implement
-				 * this. It will usually only be called once,
-				 * if 'getcwd' is called before 'chdir'. May
-				 * be NULL. */
-    Tcl_FSChdirProc *chdirProc;	/* Function to process a 'Tcl_FSChdir()' call.
-				 * If filesystems do not implement this, it
-				 * will be emulated by a series of directory
-				 * access checks. Otherwise, virtual
-				 * filesystems which do implement it need only
-				 * respond with a positive return result if
-				 * the dirName is a valid directory in their
-				 * filesystem. They need not remember the
-				 * result, since that will be automatically
-				 * remembered for use by GetCwd. Real
-				 * filesystems should carry out the correct
-				 * action (i.e. call the correct system
-				 * 'chdir' api). If not implemented, then 'cd'
-				 * and 'pwd' will fail inside the
-				 * filesystem. */
+				/* Called by 'Tcl_FSGetCwd()'.  Normally NULL.
+				 * Usually only called once:  If 'getcwd' is
+				 * called before 'chdir' is ever called. */
+    Tcl_FSChdirProc *chdirProc;	/* Called by 'Tcl_FSChdir()'.  For a virtual
+				 * filesystem, chdirProc just returns zero
+				 * (success) if the pathname is a valid
+				 * directory, and some other value otherwise.
+				 * For A real filesystem, chdirProc performs
+				 * the correct action, e.g.  calls the system
+				 * 'chdir' function. If not implemented, then
+				 * 'cd' and 'pwd' fail for a pathname in this
+				 * filesystem. On success Tcl stores the
+				 * pathname for use by GetCwd.  If NULL, Tcl
+				 * performs records the pathname as the new
+				 * current directory if it passes a series of
+				 * directory access checks. */
 } Tcl_Filesystem;
 
 /*
@@ -2069,29 +2041,28 @@ typedef struct Tcl_EncodingType {
  *				reset to an initial state. If the source
  *				buffer contains the entire input stream to be
  *				converted, this flag should be set.
- * TCL_ENCODING_STOPONERROR -	If set, then the converter will return
- *				immediately upon encountering an invalid byte
- *				sequence or a source character that has no
- *				mapping in the target encoding. If clear, then
- *				the converter will skip the problem,
- *				substituting one or more "close" characters in
- *				the destination buffer and then continue to
+ * TCL_ENCODING_STOPONERROR -	If set, the converter returns immediately upon
+ *				encountering an invalid byte sequence or a
+ *				source character that has no mapping in the
+ *				target encoding. If clear, the converter
+ *				substitues the problematic character(s) with
+ *				one or more "close" characters in the
+ *				destination buffer and then continues to
  *				convert the source.
- * TCL_ENCODING_NO_TERMINATE - 	If set, Tcl_ExternalToUtf will not append a
- *				terminating NUL byte.  Knowing that it will
- *				not need space to do so, it will fill all
- *				dstLen bytes with encoded UTF-8 content, as
- *				other circumstances permit.  If clear, the
- *				default behavior is to reserve a byte in
- *				the dst space for NUL termination, and to
- *				append the NUL byte.
+ * TCL_ENCODING_NO_TERMINATE - 	If set, Tcl_ExternalToUtf does not append a
+ *				terminating NUL byte.  Since it does not need
+ *				an extra byte for a terminating NUL, it fills
+ *				all dstLen bytes with encoded UTF-8 content if
+ *				needed.  If clear, a byte is reserved in the
+ *				dst space for NUL termination, and a
+ *				terminating NUL is appended.
  * TCL_ENCODING_CHAR_LIMIT -	If set and dstCharsPtr is not NULL, then
- *				Tcl_ExternalToUtf takes the initial value
- *				of *dstCharsPtr is taken as a limit of the
- *				maximum number of chars to produce in the
- *				encoded UTF-8 content.  Otherwise, the
- *				number of chars produced is controlled only
- *				by other limiting factors.
+ *				Tcl_ExternalToUtf takes the initial value of
+ *				*dstCharsPtr as a limit of the maximum number
+ *				of chars to produce in the encoded UTF-8
+ *				content.  Otherwise, the number of chars
+ *				produced is controlled only by other limiting
+ *				factors.
  */
 
 #define TCL_ENCODING_START		0x01
diff --git a/generic/tclEncoding.c b/generic/tclEncoding.c
index 0ec0649..430f705 100644
--- a/generic/tclEncoding.c
+++ b/generic/tclEncoding.c
@@ -83,7 +83,7 @@ typedef struct {
 } TableEncodingData;
 
 /*
- * The following structures is the clientData for a dynamically-loaded,
+ * Each of the following structures is the clientData for a dynamically-loaded
  * escape-driven encoding that is itself comprised of other simpler encodings.
  * An example is "iso-2022-jp", which uses escape sequences to switch between
  * ascii, jis0208, jis0212, gb2312, and ksc5601. Note that "escape-driven"
@@ -117,8 +117,8 @@ typedef struct {
 				 * 0. */
     int numSubTables;		/* Length of following array. */
     EscapeSubTable subTables[1];/* Information about each EscapeSubTable used
-				 * by this encoding type. The actual size will
-				 * be as large as necessary to hold all
+				 * by this encoding type. The actual size is
+				 * as large as necessary to hold all
 				 * EscapeSubTables. */
 } EscapeEncodingData;
 
@@ -156,7 +156,7 @@ static ProcessGlobalValue encodingFileMap = {
  * A list of directories making up the "library path". Historically this
  * search path has served many uses, but the only one remaining is a base for
  * the encodingSearchPath above. If the application does not explicitly set
- * the encodingSearchPath, then it will be initialized by appending /encoding
+ * the encodingSearchPath, then it is initialized by appending /encoding
  * to each directory in this "libraryPath".
  */
 
@@ -177,7 +177,7 @@ TCL_DECLARE_MUTEX(encodingMutex)
 /*
  * The following are used to hold the default and current system encodings.
  * If NULL is passed to one of the conversion routines, the current setting of
- * the system encoding will be used to perform the conversion.
+ * the system encoding is used to perform the conversion.
  */
 
 static Tcl_Encoding defaultEncoding = NULL;
@@ -451,9 +451,8 @@ TclGetLibraryPath(void)
  *	Keeps the per-thread copy of the library path current with changes to
  *	the global copy.
  *
- *	NOTE: this routine returns void, so there's no way to report the error
- *	that searchPath is not a valid list. In that case, this routine will
- *	silently do nothing.
+ *	Since the result of this routine is void, if searchPath is not a valid
+ *	list this routine silently does nothing.
  *
  *----------------------------------------------------------------------
  */
@@ -475,17 +474,16 @@ TclSetLibraryPath(
  *
  * FillEncodingFileMap --
  *
- *	Called to bring the encoding file map in sync with the current value
+ *	Called to update the encoding file map with the current value
  *	of the encoding search path.
  *
- *	Scan the directories on the encoding search path, find the *.enc
- *	files, and store the found pathnames in a map associated with the
- *	encoding name.
+ *	Finds *.end files in the directories on the encoding search path and
+ *	stores the found pathnames in a map associated with the encoding name.
  *
- *	In particular, if $dir is on the encoding search path, and the file
- *	$dir/foo.enc is found, then store a "foo" -> $dir entry in the map.
- *	Later, any need for the "foo" encoding will quickly * be able to
- *	construct the $dir/foo.enc pathname for reading the encoding data.
+ *	If $dir is on the encoding search path and the file $dir/foo.enc is
+ *	found, stores a "foo" -> $dir entry in the map.  if the "foo" encoding
+ *	is needed later, the $dir/foo.enc name can be quickly constructed in
+ *	order to read the encoding data.
  *
  * Results:
  *	None.
@@ -584,9 +582,9 @@ TclInitEncodingSubsystem(void)
     Tcl_MutexUnlock(&encodingMutex);
 
     /*
-     * Create a few initial encodings. Note that the UTF-8 to UTF-8
-     * translation is not a no-op, because it will turn a stream of improperly
-     * formed UTF-8 into a properly formed stream.
+     * Create a few initial encodings.  UTF-8 to UTF-8 translation is not a
+     * no-op because it turns a stream of improperly formed UTF-8 into a
+     * properly formed stream.
      */
 
     type.encodingName	= NULL;
@@ -806,11 +804,7 @@ Tcl_SetDefaultEncodingDir(
  *	interp was NULL.
  *
  * Side effects:
- *	The new encoding type is entered into a table visible to all
- *	interpreters, keyed off the encoding's name. For each call to this
- *	function, there should eventually be a call to Tcl_FreeEncoding, so
- *	that the database can be cleaned up when encodings aren't needed
- *	anymore.
+ *	LoadEncodingFile is called if necessary.
  *
  *-------------------------------------------------------------------------
  */
@@ -848,15 +842,15 @@ Tcl_GetEncoding(
  *
  * Tcl_FreeEncoding --
  *
- *	This function is called to release an encoding allocated by
- *	Tcl_CreateEncoding() or Tcl_GetEncoding().
+ *	Releases an encoding allocated by Tcl_CreateEncoding() or
+ *	Tcl_GetEncoding().
  *
  * Results:
  *	None.
  *
  * Side effects:
  *	The reference count associated with the encoding is decremented and
- *	the encoding may be deleted if nothing is using it anymore.
+ *	the encoding is deleted if nothing is using it anymore.
  *
  *---------------------------------------------------------------------------
  */
@@ -875,13 +869,14 @@ Tcl_FreeEncoding(
  *
  * FreeEncoding --
  *
- *	This function is called to release an encoding by functions that
- *	already have the encodingMutex.
+ *	Decrements the reference count of an encoding.  The caller must hold
+ *	encodingMutes.
  *
  * Results:
  *	None.
  *
  * Side effects:
+ *	Releases the resource for an encoding if it is now unused.
  *	The reference count associated with the encoding is decremented and
  *	the encoding may be deleted if nothing is using it anymore.
  *
@@ -1069,23 +1064,22 @@ Tcl_SetSystemEncoding(
  *
  * Tcl_CreateEncoding --
  *
- *	This function is called to define a new encoding and the functions
- *	that are used to convert between the specified encoding and Unicode.
+ *	Defines a new encoding, along with the functions that are used to
+ *	convert to and from Unicode.
  *
  * Results:
  *	Returns a token that represents the encoding. If an encoding with the
  *	same name already existed, the old encoding token remains valid and
- *	continues to behave as it used to, and will eventually be garbage
- *	collected when the last reference to it goes away. Any subsequent
- *	calls to Tcl_GetEncoding with the specified name will retrieve the
- *	most recent encoding token.
+ *	continues to behave as it used to, and is eventually garbage collected
+ *	when the last reference to it goes away. Any subsequent calls to
+ *	Tcl_GetEncoding with the specified name retrieve the most recent
+ *	encoding token.
  *
  * Side effects:
- *	The new encoding type is entered into a table visible to all
- *	interpreters, keyed off the encoding's name. For each call to this
- *	function, there should eventually be a call to Tcl_FreeEncoding, so
- *	that the database can be cleaned up when encodings aren't needed
- *	anymore.
+ *	A new record having the name of the encoding is entered into a table of
+ *	encodings visible to all interpreters.  For each call to this function,
+ *	there should eventually be a call to Tcl_FreeEncoding, which cleans
+ *	deletes the record in the table when an encoding is no longer needed.
  *
  *---------------------------------------------------------------------------
  */
@@ -1332,10 +1326,9 @@ Tcl_ExternalToUtf(
  *
  * Tcl_UtfToExternalDString --
  *
- *	Convert a source buffer from UTF-8 into the specified encoding. If any
+ *	Convert a source buffer from UTF-8 to the specified encoding. If any
  *	of the bytes in the source buffer are invalid or cannot be represented
- *	in the target encoding, a default fallback character will be
- *	substituted.
+ *	in the target encoding, a default fallback character is substituted.
  *
  * Results:
  *	The converted bytes are stored in the DString, which is then NULL
@@ -1646,13 +1639,13 @@ OpenEncodingFileChannel(
  *	the data.
  *
  * Results:
- *	The return value is the newly loaded Encoding, or NULL if the file
- *	didn't exist of was in the incorrect format. If NULL was returned, an
- *	error message is left in interp's result object, unless interp was
- *	NULL.
+ *	The return value is the newly loaded Tcl_Encoding or NULL if the file
+ *	didn't exist or could not be processed. If NULL is returned and interp
+ *	is not NULL, an error message is left in interp's result object.
  *
  * Side effects:
- *	File read from disk.
+ *	A corresponding encoding file might be read from persistent storage, in
+ *	which case LoadTableEncoding is called.
  *
  *---------------------------------------------------------------------------
  */
@@ -1660,8 +1653,8 @@ OpenEncodingFileChannel(
 static Tcl_Encoding
 LoadEncodingFile(
     Tcl_Interp *interp,		/* Interp for error reporting, if not NULL. */
-    const char *name)		/* The name of the encoding file on disk and
-				 * also the name for new encoding. */
+    const char *name)		/* The name of both the encoding file
+				 * and the new encoding. */
 {
     Tcl_Channel chan = NULL;
     Tcl_Encoding encoding = NULL;
@@ -1715,27 +1708,27 @@ LoadEncodingFile(
  *
  * LoadTableEncoding --
  *
- *	Helper function for LoadEncodingTable(). Loads a table to that
- *	converts between Unicode and some other encoding and creates an
- *	encoding (using a TableEncoding structure) from that information.
+ *	Helper function for LoadEncodingFile().  Creates a Tcl_EncodingType
+ *	structure along with its corresponding TableEncodingData structure, and
+ *	passes it to Tcl_Createncoding.
  *
- *	File contains binary data, but begins with a marker to indicate
- *	byte-ordering, so that same binary file can be read on either endian
- *	platforms.
+ *	The file contains binary data but begins with a marker to indicate
+ *	byte-ordering so a single binary file can be read on big or
+ *	little-endian systems.
  *
  * Results:
- *	The return value is the new encoding, or NULL if the encoding could
- *	not be created (because the file contained invalid data).
+ *	Returns the new Tcl_Encoding,  or NULL if it could could
+ *	not be created because the file contained invalid data.
  *
  * Side effects:
- *	None.
+ *	See Tcl_CreateEncoding(). 
  *
  *-------------------------------------------------------------------------
  */
 
 static Tcl_Encoding
 LoadTableEncoding(
-    const char *name,		/* Name for new encoding. */
+    const char *name,		/* Name of the new encoding. */
     int type,			/* Type of encoding (ENCODING_?????). */
     Tcl_Channel chan)		/* File containing new encoding. */
 {
@@ -1852,10 +1845,10 @@ LoadTableEncoding(
     }
 
     /*
-     * Invert toUnicode array to produce the fromUnicode array. Performs a
+     * Invert the toUnicode array to produce the fromUnicode array. Performs a
      * single malloc to get the memory for the array and all the pages needed
-     * by the array. While reading in the toUnicode array, we remembered what
-     * pages that would be needed for the fromUnicode array.
+     * by the array. While reading in the toUnicode array remember what
+     * pages are needed for the fromUnicode array.
      */
 
     if (symbol) {
@@ -1894,8 +1887,8 @@ LoadTableEncoding(
     if (type == ENCODING_MULTIBYTE) {
 	/*
 	 * If multibyte encodings don't have a backslash character, define
-	 * one. Otherwise, on Windows, native file names won't work because
-	 * the backslash in the file name will map to the unknown character
+	 * one. Otherwise, on Windows, native file names don't work because
+	 * the backslash in the file name maps to the unknown character
 	 * (question mark) when converting from UTF-8 to external encoding.
 	 */
 
@@ -1907,13 +1900,13 @@ LoadTableEncoding(
     }
     if (symbol) {
 	/*
-	 * Make a special symbol encoding that not only maps the symbol
-	 * characters from their Unicode code points down into page 0, but
-	 * also ensure that the characters on page 0 map to themselves. This
-	 * is so that a symbol font can be used to display a simple string
-	 * like "abcd" and have alpha, beta, chi, delta show up, rather than
-	 * have "unknown" chars show up because strictly speaking the symbol
-	 * font doesn't have glyphs for those low ASCII chars.
+	 * Make a special symbol encoding that maps each symbol character from
+	 * its Unicode code point down into page 0, and also ensure that each
+	 * characters on page 0 maps to itself so that a symbol font can be
+	 * used to display a simple string like "abcd" and have alpha, beta,
+	 * chi, delta show up, rather than have "unknown" chars show up because
+	 * strictly speaking the symbol font doesn't have glyphs for those low
+	 * ASCII chars.
 	 */
 
 	page = dataPtr->fromUnicode[0];
@@ -1960,7 +1953,7 @@ LoadTableEncoding(
     }
 
     /*
-     * Read lines from the encoding until EOF.
+     * Read lines until EOF.
      */
 
     for (TclDStringClear(&lineString);
@@ -2037,7 +2030,7 @@ LoadTableEncoding(
 
 static Tcl_Encoding
 LoadEscapeEncoding(
-    const char *name,		/* Name for new encoding. */
+    const char *name,		/* Name of the new encoding. */
     Tcl_Channel chan)		/* File containing new encoding. */
 {
     int i;
@@ -3661,14 +3654,13 @@ EscapeFromUtfProc(
  *
  * EscapeFreeProc --
  *
- *	This function is invoked when an EscapeEncodingData encoding is
- *	deleted. It deletes the memory used by the encoding.
+ *	Frees resources used by the encoding.
  *
  * Results:
  *	None.
  *
  * Side effects:
- *	Memory freed.
+ *	Memory is freed.
  *
  *---------------------------------------------------------------------------
  */
diff --git a/generic/tclFileName.c b/generic/tclFileName.c
index 3419d7c..834eef7 100644
--- a/generic/tclFileName.c
+++ b/generic/tclFileName.c
@@ -1680,9 +1680,8 @@ Tcl_GlobObjCmd(
  *
  * TclGlob --
  *
- *	This procedure prepares arguments for the DoGlob call. It sets the
- *	separator string based on the platform, performs * tilde substitution,
- *	and calls DoGlob.
+ *	Sets the separator string based on the platform, performs tilde
+ *	substitution, and calls DoGlob.
  *
  *	The interpreter's result, on entry to this function, must be a valid
  *	Tcl list (e.g. it could be empty), since we will lappend any new
diff --git a/generic/tclPathObj.c b/generic/tclPathObj.c
index f7f1c8f..660db03 100644
--- a/generic/tclPathObj.c
+++ b/generic/tclPathObj.c
@@ -47,37 +47,21 @@ static const Tcl_ObjType fsPathType = {
 /*
  * 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.
- *
- * There are two cases, with the first being the most common:
- *
- * (i) flags == 0, => Ordinary path.
- *
- * translatedPathPtr contains the translated path. If it is NULL then the path
- * is pure normalized. 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.
- *
+ * Internal representation of a Tcl_Obj of fsPathType 
  */
 
 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. */
-    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. */
+    Tcl_Obj *translatedPathPtr; /*  If the path has been normalized (flags ==
+				 *  0), this is NULL.  Otherwise it is a path
+				 *  in which any ~user sequences have been
+				 *  translated away. */
+    Tcl_Obj *normPathPtr;	/*  If the path has been normalized (flags ==
+				 *  0), this is an absolute path without ., ..
+				 *  or ~user components.  Otherwise it is a
+				 *  path, possibly absolute, to normalize
+				 *  relative to cwdPtr. */
+    Tcl_Obj *cwdPtr;		/*  If NULL, either translatedPtr exists or
+				 *  normPathPtr exists and is absolute. */
     int flags;			/* Flags to describe interpretation - see
 				 * below. */
     ClientData nativePathPtr;	/* Native representation of this path, which
@@ -131,17 +115,17 @@ typedef struct FsPath {
  *	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.
+ *	The result is returned in a Tcl_Obj with a refCount already
+ *	incremented, which gives the caller ownership of it.  The caller must
+ *	arrange for Tcl_DecRefCount to be called when the object is 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.
+ *	Originally based on code from Matt Newman and Jean-Claude Wippler. 
+ *	Totally rewritten later by Vince Darley to handle symbolic links.
  *
  *---------------------------------------------------------------------------
  */
@@ -710,9 +694,8 @@ TclPathPart(
 	}
 
 	/*
-	 * 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
+	 * Tcl_FSSplitPath preserves the "~",  but this code computes the
 	 * actual full path name, if we had just a single component.
 	 */
 
@@ -871,7 +854,7 @@ TclJoinPath(
 	 * could expand that in the future.
 	 *
 	 * Bugfix [a47641a0]. TclNewFSPathObj requires first argument
-	 * to be an absolute path. Added a check for that elt is absolute.
+	 * to be an absolute path. Added a check to ensure that elt is absolute.
 	 */
 
 	if ((eltIr)
@@ -1508,7 +1491,7 @@ MakePathFromNormalized(
  *
  * Tcl_FSNewNativePath --
  *
- *	This function performs the something like the reverse of the usual
+ *	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
@@ -1571,16 +1554,18 @@ Tcl_FSNewNativePath(
  *
  * Tcl_FSGetTranslatedPath --
  *
- *	This function attempts to extract the translated path from the given
+ *	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)
+ *	path), then it is returned. Otherwise NULL is returned and an
+ *	error message may be left in the interpreter if it is not NULL.
  *
  * Results:
- *	NULL or a valid Tcl_Obj pointer.
+ *	A Tcl_Obj pointer or NULL.
  *
  * Side effects:
- *	Only those of 'Tcl_FSConvertToPathType'
+ *	pathPtr is converted to fsPathType if necessary.
+ *
+ *	FsPath members are modified as needed.
  *
  *---------------------------------------------------------------------------
  */
@@ -1598,7 +1583,12 @@ Tcl_FSGetTranslatedPath(
     }
     srcFsPathPtr = PATHOBJ(pathPtr);
     if (srcFsPathPtr->translatedPathPtr == NULL) {
-	if (PATHFLAGS(pathPtr) != 0) {
+	if (PATHFLAGS(pathPtr) == 0) {
+	    /*
+	     * Path is already normalized
+	     */
+	    retObj = srcFsPathPtr->normPathPtr;
+	} else {
 	    /*
 	     * We lack a translated path result, but we have a directory
 	     * (cwdPtr) and a tail (normPathPtr), and if we join the
@@ -1625,14 +1615,6 @@ Tcl_FSGetTranslatedPath(
 		srcFsPathPtr->filesystemEpoch = 0;
 	    }
 	    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 {
 	/*
@@ -1800,11 +1782,6 @@ Tcl_FSGetNormalizedPath(
 	    TclDecrRefCount(fsPathPtr->normPathPtr);
 	    fsPathPtr->normPathPtr = copy;
 
-	    /*
-	     * That's our reference to copy used.
-	     */
-	    copy = NULL;
-
 	    TclDecrRefCount(dir);
 	    TclDecrRefCount(origDir);
 	} else {
@@ -1813,10 +1790,6 @@ Tcl_FSGetNormalizedPath(
 	    TclDecrRefCount(fsPathPtr->normPathPtr);
 	    fsPathPtr->normPathPtr = copy;
 
-	    /*
-	     * That's our reference to copy used.
-	     */
-	    copy = NULL;
 	    TclDecrRefCount(dir);
 	}
 	PATHFLAGS(pathPtr) = 0;
@@ -1857,7 +1830,7 @@ Tcl_FSGetNormalizedPath(
 	Tcl_Obj *useThisCwd = NULL;
 
 	/*
-	 * Since normPathPtr is NULL, but this is a valid path object, we know
+	 * Since normPathPtr is NULL but this is a valid path object, we know
 	 * that the translatedPathPtr cannot be NULL.
 	 */
 
@@ -1957,19 +1930,23 @@ Tcl_FSGetNormalizedPath(
  *
  * 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.
+ *	Produces a native representation of a given path object in the given
+ *	filesystem.
  *
- *	If the internal representation is currently NULL, we attempt to
- *	generate it, by calling the filesystem's
- *	'Tcl_FSCreateInternalRepProc'.
+ *	In the future it might be desirable to have separate versions
+ *	of this function with different signatures, for example
+ *	Tcl_FSGetNativeWinPath, Tcl_FSGetNativeUnixPath etc. Right now, since
+ *	native paths are all string based, we use just one function.
  *
  * Results:
- *	NULL or a valid internal representation.
+ *
+ *	The native handle for the path, or NULL if the path is not handled by
+ *	the given filesystem
  *
  * Side effects:
- *	An attempt may be made to convert the object.
+ *
+ *	Tcl_FSCreateInternalRepProc if needed to produce the native
+ *	handle, which is then stored in the internal representation of pathPtr.
  *
  *---------------------------------------------------------------------------
  */
@@ -1987,49 +1964,36 @@ Tcl_FSGetInternalRep(
     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.
+     * Currently there must be a unique bi-directional mapping between a path
+     * and a filesystem, and therefore there is no way to "remap" a file, i.e.,
+     * to map a file in one filesystem into another. Another way of putting
+     * this is that 'stacked' filesystems are not allowed.  It could be useful
+     * in the future to redesign the system to allow that.
      *
      * 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.
+     * not currently easily achievable.
      */
 
     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) {
+	    /*
+	     * 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).
+	     */
 	    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 the file belongs to a different filesystem, perhaps it is actually
+     * linked through to a file in the given filesystem. Check this by
+     * inspecting the filesystem associated with the given path.
      */
 
     if (fsPtr != srcFsPathPtr->fsPtr) {
@@ -2064,15 +2028,15 @@ Tcl_FSGetInternalRep(
  *
  * 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.
+ *	Ensure that the path is a valid path, and that it has a 
+ *	fsPathType internal representation that is not stale.
  *
  * Results:
- *	Standard Tcl return code.
+ *	A standard Tcl return code.
  *
  * Side effects:
- *	An attempt may be made to convert the object.
+ *	The internal representation of fsPtrPtr is converted to fsPathType if
+ *	possible.
  *
  *---------------------------------------------------------------------------
  */
@@ -2090,14 +2054,11 @@ TclFSEnsureEpochOk(
 
     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.
+	 * The filesystem has changed in some way since the internal
+	 * representation for this object was calculated. Discard the stale
+	 * representation and recalculate it.
 	 */
 
 	TclGetString(pathPtr);
@@ -2108,11 +2069,10 @@ TclFSEnsureEpochOk(
 	srcFsPathPtr = PATHOBJ(pathPtr);
     }
 
-    /*
-     * Check whether the object is already assigned to a fs.
-     */
-
     if (srcFsPathPtr->fsPtr != NULL) {
+	/*
+	 * There is already a filesystem assigned to this path.
+	 */
 	*fsPtrPtr = srcFsPathPtr->fsPtr;
     }
     return TCL_OK;
@@ -2220,11 +2180,12 @@ Tcl_FSEqualPaths(
  *
  * SetFsPathFromAny --
  *
- *	This function tries to convert the given Tcl_Obj to a valid Tcl path
- *	type.
+ *	Attempt to convert the internal representation of pathPtr to
+ *	fsPathType.
  *
- *	The filename may begin with "~" (to indicate current user's home
- *	directory) or "~<user>" (to indicate any user's home directory).
+ *	A tilde ("~") character at the beginnig of the filename indicates the
+ *	current user's home directory, and "~<user>" indicates a particular
+ *	user's directory.
  *
  * Results:
  *	Standard Tcl error code.
@@ -2308,7 +2269,7 @@ SetFsPathFromAny(
 	    Tcl_DStringFree(&dirString);
 	} else {
 	    /*
-	     * We have a user name '~user'
+	     * There is a '~user'
 	     */
 
 	    const char *expandedUser;