Optimize redrawing so that the mouse is more responsive, from Marc Espie.

[micropolis] / src / tcl / tclutil.c

/* 
 * tclUtil.c --
 *
 *      This file contains utility procedures that are used by many Tcl
 *      commands.
 *
 * Copyright 1987-1991 Regents of the University of California
 * Permission to use, copy, modify, and distribute this
 * software and its documentation for any purpose and without
 * fee is hereby granted, provided that the above copyright
 * notice appear in all copies.  The University of California
 * makes no representations about the suitability of this
 * software for any purpose.  It is provided "as is" without
 * express or implied warranty.
 */

#ifndef lint
static char rcsid[] = "$Header: /user6/ouster/tcl/RCS/tclUtil.c,v 1.63 92/07/02 08:50:54 ouster Exp $ SPRITE (Berkeley)";
#endif

#include "tclint.h"

/*
 * The following values are used in the flags returned by Tcl_ScanElement
 * and used by Tcl_ConvertElement.  The value TCL_DONT_USE_BRACES is also
 * defined in tcl.h;  make sure its value doesn't overlap with any of the
 * values below.
 *
 * TCL_DONT_USE_BRACES -        1 means the string mustn't be enclosed in
 *                              braces (e.g. it contains unmatched braces,
 *                              or ends in a backslash character, or user
 *                              just doesn't want braces);  handle all
 *                              special characters by adding backslashes.
 * USE_BRACES -                 1 means the string contains a special
 *                              character that can be handled simply by
 *                              enclosing the entire argument in braces.
 * BRACES_UNMATCHED -           1 means that braces aren't properly matched
 *                              in the argument.
 */

#define USE_BRACES              2
#define BRACES_UNMATCHED        4

/*
 * The variable below is set to NULL before invoking regexp functions
 * and checked after those functions.  If an error occurred then regerror
 * will set the variable to point to a (static) error message.  This
 * mechanism unfortunately does not support multi-threading, but then
 * neither does the rest of the regexp facilities.
 */

char *tclRegexpError = NULL;

/*
 * Function prototypes for local procedures in this file:
 */

static void             SetupAppendBuffer _ANSI_ARGS_((Interp *iPtr,
                            int newSpace));
\f
/*
 *----------------------------------------------------------------------
 *
 * TclFindElement --
 *
 *      Given a pointer into a Tcl list, locate the first (or next)
 *      element in the list.
 *
 * Results:
 *      The return value is normally TCL_OK, which means that the
 *      element was successfully located.  If TCL_ERROR is returned
 *      it means that list didn't have proper list structure;
 *      interp->result contains a more detailed error message.
 *
 *      If TCL_OK is returned, then *elementPtr will be set to point
 *      to the first element of list, and *nextPtr will be set to point
 *      to the character just after any white space following the last
 *      character that's part of the element.  If this is the last argument
 *      in the list, then *nextPtr will point to the NULL character at the
 *      end of list.  If sizePtr is non-NULL, *sizePtr is filled in with
 *      the number of characters in the element.  If the element is in
 *      braces, then *elementPtr will point to the character after the
 *      opening brace and *sizePtr will not include either of the braces.
 *      If there isn't an element in the list, *sizePtr will be zero, and
 *      both *elementPtr and *termPtr will refer to the null character at
 *      the end of list.  Note:  this procedure does NOT collapse backslash
 *      sequences.
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

int
TclFindElement(interp, list, elementPtr, nextPtr, sizePtr, bracePtr)
    Tcl_Interp *interp;         /* Interpreter to use for error reporting. */
    register char *list;        /* String containing Tcl list with zero
                                 * or more elements (possibly in braces). */
    char **elementPtr;          /* Fill in with location of first significant
                                 * character in first element of list. */
    char **nextPtr;             /* Fill in with location of character just
                                 * after all white space following end of
                                 * argument (i.e. next argument or end of
                                 * list). */
    int *sizePtr;               /* If non-zero, fill in with size of
                                 * element. */
    int *bracePtr;              /* If non-zero fill in with non-zero/zero
                                 * to indicate that arg was/wasn't
                                 * in braces. */
{
    register char *p;
    int openBraces = 0;
    int inQuotes = 0;
    int size;

    /*
     * Skim off leading white space and check for an opening brace or
     * quote.   Note:  use of "isascii" below and elsewhere in this
     * procedure is a temporary workaround (7/27/90) because Mx uses characters
     * with the high-order bit set for some things.  This should probably
     * be changed back eventually, or all of Tcl should call isascii.
     */

    while (isascii(*list) && isspace(*list)) {
        list++;
    }
    if (*list == '{') {
        openBraces = 1;
        list++;
    } else if (*list == '"') {
        inQuotes = 1;
        list++;
    }
    if (bracePtr != 0) {
        *bracePtr = openBraces;
    }
    p = list;

    /*
     * Find the end of the element (either a space or a close brace or
     * the end of the string).
     */

    while (1) {
        switch (*p) {

            /*
             * Open brace: don't treat specially unless the element is
             * in braces.  In this case, keep a nesting count.
             */

            case '{':
                if (openBraces != 0) {
                    openBraces++;
                }
                break;

            /*
             * Close brace: if element is in braces, keep nesting
             * count and quit when the last close brace is seen.
             */

            case '}':
                if (openBraces == 1) {
                    char *p2;

                    size = p - list;
                    p++;
                    if ((isascii(*p) && isspace(*p)) || (*p == 0)) {
                        goto done;
                    }
                    for (p2 = p; (*p2 != 0) && (!isspace(*p2)) && (p2 < p+20);
                            p2++) {
                        /* null body */
                    }
                    Tcl_ResetResult(interp);
                    sprintf(interp->result,
                            "list element in braces followed by \"%.*s\" instead of space",
                            p2-p, p);
                    return TCL_ERROR;
                } else if (openBraces != 0) {
                    openBraces--;
                }
                break;

            /*
             * Backslash:  skip over everything up to the end of the
             * backslash sequence.
             */

            case '\\': {
                int size;

                (void) Tcl_Backslash(p, &size);
                p += size - 1;
                break;
            }

            /*
             * Space: ignore if element is in braces or quotes;  otherwise
             * terminate element.
             */

            case ' ':
            case '\f':
            case '\n':
            case '\r':
            case '\t':
            case '\v':
                if ((openBraces == 0) && !inQuotes) {
                    size = p - list;
                    goto done;
                }
                break;

            /*
             * Double-quote:  if element is in quotes then terminate it.
             */

            case '"':
                if (inQuotes) {
                    char *p2;

                    size = p-list;
                    p++;
                    if ((isascii(*p) && isspace(*p)) || (*p == 0)) {
                        goto done;
                    }
                    for (p2 = p; (*p2 != 0) && (!isspace(*p2)) && (p2 < p+20);
                            p2++) {
                        /* null body */
                    }
                    Tcl_ResetResult(interp);
                    sprintf(interp->result,
                            "list element in quotes followed by \"%.*s\" %s",
                            p2-p, p, "instead of space");
                    return TCL_ERROR;
                }
                break;

            /*
             * End of list:  terminate element.
             */

            case 0:
                if (openBraces != 0) {
                    Tcl_SetResult(interp, "unmatched open brace in list",
                            TCL_STATIC);
                    return TCL_ERROR;
                } else if (inQuotes) {
                    Tcl_SetResult(interp, "unmatched open quote in list",
                            TCL_STATIC);
                    return TCL_ERROR;
                }
                size = p - list;
                goto done;

        }
        p++;
    }

    done:
    while (isascii(*p) && isspace(*p)) {
        p++;
    }
    *elementPtr = list;
    *nextPtr = p;
    if (sizePtr != 0) {
        *sizePtr = size;
    }
    return TCL_OK;
}
\f
/*
 *----------------------------------------------------------------------
 *
 * TclCopyAndCollapse --
 *
 *      Copy a string and eliminate any backslashes that aren't in braces.
 *
 * Results:
 *      There is no return value.  Count chars. get copied from src
 *      to dst.  Along the way, if backslash sequences are found outside
 *      braces, the backslashes are eliminated in the copy.
 *      After scanning count chars. from source, a null character is
 *      placed at the end of dst.
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

void
TclCopyAndCollapse(count, src, dst)
    int count;                  /* Total number of characters to copy
                                 * from src. */
    register char *src;         /* Copy from here... */
    register char *dst;         /* ... to here. */
{
    register char c;
    int numRead;

    for (c = *src; count > 0; src++, c = *src, count--) {
        if (c == '\\') {
            *dst = Tcl_Backslash(src, &numRead);
            if (*dst != 0) {
                dst++;
            }
            src += numRead-1;
            count -= numRead-1;
        } else {
            *dst = c;
            dst++;
        }
    }
    *dst = 0;
}
\f
/*
 *----------------------------------------------------------------------
 *
 * Tcl_SplitList --
 *
 *      Splits a list up into its constituent fields.
 *
 * Results
 *      The return value is normally TCL_OK, which means that
 *      the list was successfully split up.  If TCL_ERROR is
 *      returned, it means that "list" didn't have proper list
 *      structure;  interp->result will contain a more detailed
 *      error message.
 *
 *      *argvPtr will be filled in with the address of an array
 *      whose elements point to the elements of list, in order.
 *      *argcPtr will get filled in with the number of valid elements
 *      in the array.  A single block of memory is dynamically allocated
 *      to hold both the argv array and a copy of the list (with
 *      backslashes and braces removed in the standard way).
 *      The caller must eventually free this memory by calling free()
 *      on *argvPtr.  Note:  *argvPtr and *argcPtr are only modified
 *      if the procedure returns normally.
 *
 * Side effects:
 *      Memory is allocated.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_SplitList(interp, list, argcPtr, argvPtr)
    Tcl_Interp *interp;         /* Interpreter to use for error reporting. */
    char *list;                 /* Pointer to string with list structure. */
    int *argcPtr;               /* Pointer to location to fill in with
                                 * the number of elements in the list. */
    char ***argvPtr;            /* Pointer to place to store pointer to array
                                 * of pointers to list elements. */
{
    char **argv;
    register char *p;
    int size, i, result, elSize, brace;
    char *element;

    /*
     * Figure out how much space to allocate.  There must be enough
     * space for both the array of pointers and also for a copy of
     * the list.  To estimate the number of pointers needed, count
     * the number of space characters in the list.
     */

    for (size = 1, p = list; *p != 0; p++) {
        if (isspace(*p)) {
            size++;
        }
    }
    size++;                     /* Leave space for final NULL pointer. */
    argv = (char **) ckalloc((unsigned)
            ((size * sizeof(char *)) + (p - list) + 1));
    for (i = 0, p = ((char *) argv) + size*sizeof(char *);
            *list != 0; i++) {
        result = TclFindElement(interp, list, &element, &list, &elSize, &brace);
        if (result != TCL_OK) {
            ckfree((char *) argv);
            return result;
        }
        if (*element == 0) {
            break;
        }
        if (i >= size) {
            ckfree((char *) argv);
            Tcl_SetResult(interp, "internal error in Tcl_SplitList",
                    TCL_STATIC);
            return TCL_ERROR;
        }
        argv[i] = p;
        if (brace) {
            strncpy(p, element, elSize);
            p += elSize;
            *p = 0;
            p++;
        } else {
            TclCopyAndCollapse(elSize, element, p);
            p += elSize+1;
        }
    }

    argv[i] = NULL;
    *argvPtr = argv;
    *argcPtr = i;
    return TCL_OK;
}
\f
/*
 *----------------------------------------------------------------------
 *
 * Tcl_ScanElement --
 *
 *      This procedure is a companion procedure to Tcl_ConvertElement.
 *      It scans a string to see what needs to be done to it (e.g.
 *      add backslashes or enclosing braces) to make the string into
 *      a valid Tcl list element.
 *
 * Results:
 *      The return value is an overestimate of the number of characters
 *      that will be needed by Tcl_ConvertElement to produce a valid
 *      list element from string.  The word at *flagPtr is filled in
 *      with a value needed by Tcl_ConvertElement when doing the actual
 *      conversion.
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_ScanElement(string, flagPtr)
    char *string;               /* String to convert to Tcl list element. */
    int *flagPtr;               /* Where to store information to guide
                                 * Tcl_ConvertElement. */
{
    int flags, nestingLevel;
    register char *p;

    /*
     * This procedure and Tcl_ConvertElement together do two things:
     *
     * 1. They produce a proper list, one that will yield back the
     * argument strings when evaluated or when disassembled with
     * Tcl_SplitList.  This is the most important thing.
     * 
     * 2. They try to produce legible output, which means minimizing the
     * use of backslashes (using braces instead).  However, there are
     * some situations where backslashes must be used (e.g. an element
     * like "{abc": the leading brace will have to be backslashed.  For
     * each element, one of three things must be done:
     *
     * (a) Use the element as-is (it doesn't contain anything special
     * characters).  This is the most desirable option.
     *
     * (b) Enclose the element in braces, but leave the contents alone.
     * This happens if the element contains embedded space, or if it
     * contains characters with special interpretation ($, [, ;, or \),
     * or if it starts with a brace or double-quote, or if there are
     * no characters in the element.
     *
     * (c) Don't enclose the element in braces, but add backslashes to
     * prevent special interpretation of special characters.  This is a
     * last resort used when the argument would normally fall under case
     * (b) but contains unmatched braces.  It also occurs if the last
     * character of the argument is a backslash.
     *
     * The procedure figures out how many bytes will be needed to store
     * the result (actually, it overestimates).  It also collects information
     * about the element in the form of a flags word.
     */

    nestingLevel = 0;
    flags = 0;
    p = string;
    if ((*p == '{') || (*p == '"') || (*p == 0)) {
        flags |= USE_BRACES;
    }
    for ( ; *p != 0; p++) {
        switch (*p) {
            case '{':
                nestingLevel++;
                break;
            case '}':
                nestingLevel--;
                if (nestingLevel < 0) {
                    flags |= TCL_DONT_USE_BRACES|BRACES_UNMATCHED;
                }
                break;
            case '[':
            case '$':
            case ';':
            case ' ':
            case '\f':
            case '\n':
            case '\r':
            case '\t':
            case '\v':
                flags |= USE_BRACES;
                break;
            case '\\':
                if (p[1] == 0) {
                    flags = TCL_DONT_USE_BRACES;
                } else {
                    int size;

                    (void) Tcl_Backslash(p, &size);
                    p += size-1;
                    flags |= USE_BRACES;
                }
                break;
        }
    }
    if (nestingLevel != 0) {
        flags = TCL_DONT_USE_BRACES | BRACES_UNMATCHED;
    }
    *flagPtr = flags;

    /*
     * Allow enough space to backslash every character plus leave
     * two spaces for braces.
     */

    return 2*(p-string) + 2;
}
\f
/*
 *----------------------------------------------------------------------
 *
 * Tcl_ConvertElement --
 *
 *      This is a companion procedure to Tcl_ScanElement.  Given the
 *      information produced by Tcl_ScanElement, this procedure converts
 *      a string to a list element equal to that string.
 *
 * Results:
 *      Information is copied to *dst in the form of a list element
 *      identical to src (i.e. if Tcl_SplitList is applied to dst it
 *      will produce a string identical to src).  The return value is
 *      a count of the number of characters copied (not including the
 *      terminating NULL character).
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_ConvertElement(src, dst, flags)
    register char *src;         /* Source information for list element. */
    char *dst;                  /* Place to put list-ified element. */
    int flags;                  /* Flags produced by Tcl_ScanElement. */
{
    register char *p = dst;

    /*
     * See the comment block at the beginning of the Tcl_ScanElement
     * code for details of how this works.
     */

    if ((flags & USE_BRACES) && !(flags & TCL_DONT_USE_BRACES)) {
        *p = '{';
        p++;
        for ( ; *src != 0; src++, p++) {
            *p = *src;
        }
        *p = '}';
        p++;
    } else if (*src == 0) {
        /*
         * If string is empty but can't use braces, then use special
         * backslash sequence that maps to empty string.
         */

        p[0] = '\\';
        p[1] = '0';
        p += 2;
    } else {
        for (; *src != 0 ; src++) {
            switch (*src) {
                case ']':
                case '[':
                case '$':
                case ';':
                case ' ':
                case '\\':
                case '"':
                    *p = '\\';
                    p++;
                    break;
                case '{':
                case '}':
                    if (flags & BRACES_UNMATCHED) {
                        *p = '\\';
                        p++;
                    }
                    break;
                case '\f':
                    *p = '\\';
                    p++;
                    *p = 'f';
                    p++;
                    continue;
                case '\n':
                    *p = '\\';
                    p++;
                    *p = 'n';
                    p++;
                    continue;
                case '\r':
                    *p = '\\';
                    p++;
                    *p = 'r';
                    p++;
                    continue;
                case '\t':
                    *p = '\\';
                    p++;
                    *p = 't';
                    p++;
                    continue;
                case '\v':
                    *p = '\\';
                    p++;
                    *p = 'v';
                    p++;
                    continue;
            }
            *p = *src;
            p++;
        }
    }
    *p = '\0';
    return p-dst;
}
\f
/*
 *----------------------------------------------------------------------
 *
 * Tcl_Merge --
 *
 *      Given a collection of strings, merge them together into a
 *      single string that has proper Tcl list structured (i.e.
 *      Tcl_SplitList may be used to retrieve strings equal to the
 *      original elements, and Tcl_Eval will parse the string back
 *      into its original elements).
 *
 * Results:
 *      The return value is the address of a dynamically-allocated
 *      string containing the merged list.
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

char *
Tcl_Merge(argc, argv)
    int argc;                   /* How many strings to merge. */
    char **argv;                /* Array of string values. */
{
#   define LOCAL_SIZE 20
    int localFlags[LOCAL_SIZE], *flagPtr;
    int numChars;
    char *result;
    register char *dst;
    int i;

    /*
     * Pass 1: estimate space, gather flags.
     */

    if (argc <= LOCAL_SIZE) {
        flagPtr = localFlags;
    } else {
        flagPtr = (int *) ckalloc((unsigned) argc*sizeof(int));
    }
    numChars = 1;
    for (i = 0; i < argc; i++) {
        numChars += Tcl_ScanElement(argv[i], &flagPtr[i]) + 1;
    }

    /*
     * Pass two: copy into the result area.
     */

    result = (char *) ckalloc((unsigned) numChars);
    dst = result;
    for (i = 0; i < argc; i++) {
        numChars = Tcl_ConvertElement(argv[i], dst, flagPtr[i]);
        dst += numChars;
        *dst = ' ';
        dst++;
    }
    if (dst == result) {
        *dst = 0;
    } else {
        dst[-1] = 0;
    }

    if (flagPtr != localFlags) {
        ckfree((char *) flagPtr);
    }
    return result;
}
\f
/*
 *----------------------------------------------------------------------
 *
 * Tcl_Concat --
 *
 *      Concatenate a set of strings into a single large string.
 *
 * Results:
 *      The return value is dynamically-allocated string containing
 *      a concatenation of all the strings in argv, with spaces between
 *      the original argv elements.
 *
 * Side effects:
 *      Memory is allocated for the result;  the caller is responsible
 *      for freeing the memory.
 *
 *----------------------------------------------------------------------
 */

char *
Tcl_Concat(argc, argv)
    int argc;                   /* Number of strings to concatenate. */
    char **argv;                /* Array of strings to concatenate. */
{
    int totalSize, i;
    register char *p;
    char *result;

    for (totalSize = 1, i = 0; i < argc; i++) {
        totalSize += strlen(argv[i]) + 1;
    }
    result = (char *) ckalloc((unsigned) totalSize);
    if (argc == 0) {
        *result = '\0';
        return result;
    }
    for (p = result, i = 0; i < argc; i++) {
        char *element;
        int length;

        /*
         * Clip white space off the front and back of the string
         * to generate a neater result, and ignore any empty
         * elements.
         */

        element = argv[i];
        while (isspace(*element)) {
            element++;
        }
        for (length = strlen(element);
                (length > 0) && (isspace(element[length-1]));
                length--) {
            /* Null loop body. */
        }
        if (length == 0) {
            continue;
        }
        (void) strncpy(p, element, length);
        p += length;
        *p = ' ';
        p++;
    }
    if (p != result) {
        p[-1] = 0;
    } else {
        *p = 0;
    }
    return result;
}
\f
/*
 *----------------------------------------------------------------------
 *
 * Tcl_StringMatch --
 *
 *      See if a particular string matches a particular pattern.
 *
 * Results:
 *      The return value is 1 if string matches pattern, and
 *      0 otherwise.  The matching operation permits the following
 *      special characters in the pattern: *?\[] (see the manual
 *      entry for details on what these mean).
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_StringMatch(string, pattern)
    register char *string;      /* String. */
    register char *pattern;     /* Pattern, which may contain
                                 * special characters. */
{
    char c2;

    while (1) {
        /* See if we're at the end of both the pattern and the string.
         * If so, we succeeded.  If we're at the end of the pattern
         * but not at the end of the string, we failed.
         */
        
        if (*pattern == 0) {
            if (*string == 0) {
                return 1;
            } else {
                return 0;
            }
        }
        if ((*string == 0) && (*pattern != '*')) {
            return 0;
        }

        /* Check for a "*" as the next pattern character.  It matches
         * any substring.  We handle this by calling ourselves
         * recursively for each postfix of string, until either we
         * match or we reach the end of the string.
         */
        
        if (*pattern == '*') {
            pattern += 1;
            if (*pattern == 0) {
                return 1;
            }
            while (1) {
                if (Tcl_StringMatch(string, pattern)) {
                    return 1;
                }
                if (*string == 0) {
                    return 0;
                }
                string += 1;
            }
        }
    
        /* Check for a "?" as the next pattern character.  It matches
         * any single character.
         */

        if (*pattern == '?') {
            goto thisCharOK;
        }

        /* Check for a "[" as the next pattern character.  It is followed
         * by a list of characters that are acceptable, or by a range
         * (two characters separated by "-").
         */
        
        if (*pattern == '[') {
            pattern += 1;
            while (1) {
                if ((*pattern == ']') || (*pattern == 0)) {
                    return 0;
                }
                if (*pattern == *string) {
                    break;
                }
                if (pattern[1] == '-') {
                    c2 = pattern[2];
                    if (c2 == 0) {
                        return 0;
                    }
                    if ((*pattern <= *string) && (c2 >= *string)) {
                        break;
                    }
                    if ((*pattern >= *string) && (c2 <= *string)) {
                        break;
                    }
                    pattern += 2;
                }
                pattern += 1;
            }
            while ((*pattern != ']') && (*pattern != 0)) {
                pattern += 1;
            }
            goto thisCharOK;
        }
    
        /* If the next pattern character is '/', just strip off the '/'
         * so we do exact matching on the character that follows.
         */
        
        if (*pattern == '\\') {
            pattern += 1;
            if (*pattern == 0) {
                return 0;
            }
        }

        /* There's no special character.  Just make sure that the next
         * characters of each string match.
         */
        
        if (*pattern != *string) {
            return 0;
        }

        thisCharOK: pattern += 1;
        string += 1;
    }
}
\f
/*
 *----------------------------------------------------------------------
 *
 * Tcl_SetResult --
 *
 *      Arrange for "string" to be the Tcl return value.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      interp->result is left pointing either to "string" (if "copy" is 0)
 *      or to a copy of string.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_SetResult(interp, string, freeProc)
    Tcl_Interp *interp;         /* Interpreter with which to associate the
                                 * return value. */
    char *string;               /* Value to be returned.  If NULL,
                                 * the result is set to an empty string. */
    Tcl_FreeProc *freeProc;     /* Gives information about the string:
                                 * TCL_STATIC, TCL_VOLATILE, or the address
                                 * of a Tcl_FreeProc such as free. */
{
    register Interp *iPtr = (Interp *) interp;
    int length;
    Tcl_FreeProc *oldFreeProc = iPtr->freeProc;
    char *oldResult = iPtr->result;

    iPtr->freeProc = freeProc;
    if (string == NULL) {
        iPtr->resultSpace[0] = 0;
        iPtr->result = iPtr->resultSpace;
        iPtr->freeProc = 0;
    } else if (freeProc == TCL_VOLATILE) {
        length = strlen(string);
        if (length > TCL_RESULT_SIZE) {
            iPtr->result = (char *) ckalloc((unsigned) length+1);
            iPtr->freeProc = (Tcl_FreeProc *) free;
        } else {
            iPtr->result = iPtr->resultSpace;
            iPtr->freeProc = 0;
        }
        strcpy(iPtr->result, string);
    } else {
        iPtr->result = string;
    }

    /*
     * If the old result was dynamically-allocated, free it up.  Do it
     * here, rather than at the beginning, in case the new result value
     * was part of the old result value.
     */

    if (oldFreeProc != 0) {
        (*oldFreeProc)(oldResult);
    }
}
\f
/*
 *----------------------------------------------------------------------
 *
 * Tcl_AppendResult --
 *
 *      Append a variable number of strings onto the result already
 *      present for an interpreter.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      The result in the interpreter given by the first argument
 *      is extended by the strings given by the second and following
 *      arguments (up to a terminating NULL argument).
 *
 *----------------------------------------------------------------------
 */

void
Tcl_AppendResult(Tcl_Interp *interp, ...)
{
    va_list argList;
    register Interp *iPtr;
    char *string;
    int newSpace;

    /*
     * First, scan through all the arguments to see how much space is
     * needed.
     */

    va_start(argList, interp);
    iPtr = (Interp *)interp;
    newSpace = 0;
    while (1) {
        string = va_arg(argList, char *);
        if (string == NULL) {
            break;
        }
        newSpace += strlen(string);
    }
    va_end(argList);

    /*
     * If the append buffer isn't already setup and large enough
     * to hold the new data, set it up.
     */

    if ((iPtr->result != iPtr->appendResult)
           || ((newSpace + iPtr->appendUsed) >= iPtr->appendAvl)) {
       SetupAppendBuffer(iPtr, newSpace);
    }

    /*
     * Final step:  go through all the argument strings again, copying
     * them into the buffer.
     */

    va_start(argList, interp);
    while (1) {
        string = va_arg(argList, char *);
        if (string == NULL) {
            break;
        }
        strcpy(iPtr->appendResult + iPtr->appendUsed, string);
        iPtr->appendUsed += strlen(string);
    }
    va_end(argList);
}
\f
/*
 *----------------------------------------------------------------------
 *
 * Tcl_AppendElement --
 *
 *      Convert a string to a valid Tcl list element and append it
 *      to the current result (which is ostensibly a list).
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      The result in the interpreter given by the first argument
 *      is extended with a list element converted from string.  If
 *      the original result wasn't empty, then a blank is added before
 *      the converted list element.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_AppendElement(interp, string, noSep)
    Tcl_Interp *interp;         /* Interpreter whose result is to be
                                 * extended. */
    char *string;               /* String to convert to list element and
                                 * add to result. */
    int noSep;                  /* If non-zero, then don't output a
                                 * space character before this element,
                                 * even if the element isn't the first
                                 * thing in the output buffer. */
{
    register Interp *iPtr = (Interp *) interp;
    int size, flags;
    char *dst;

    /*
     * See how much space is needed, and grow the append buffer if
     * needed to accommodate the list element.
     */

    size = Tcl_ScanElement(string, &flags) + 1;
    if ((iPtr->result != iPtr->appendResult)
           || ((size + iPtr->appendUsed) >= iPtr->appendAvl)) {
       SetupAppendBuffer(iPtr, size+iPtr->appendUsed);
    }

    /*
     * Convert the string into a list element and copy it to the
     * buffer that's forming.
     */

    dst = iPtr->appendResult + iPtr->appendUsed;
    if (!noSep && (iPtr->appendUsed != 0)) {
        iPtr->appendUsed++;
        *dst = ' ';
        dst++;
    }
    iPtr->appendUsed += Tcl_ConvertElement(string, dst, flags);
}
\f
/*
 *----------------------------------------------------------------------
 *
 * SetupAppendBuffer --
 *
 *      This procedure makes sure that there is an append buffer
 *      properly initialized for interp, and that it has at least
 *      enough room to accommodate newSpace new bytes of information.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

static void
SetupAppendBuffer(iPtr, newSpace)
    register Interp *iPtr;      /* Interpreter whose result is being set up. */
    int newSpace;               /* Make sure that at least this many bytes
                                 * of new information may be added. */
{
    int totalSpace;

    /*
     * Make the append buffer larger, if that's necessary, then
     * copy the current result into the append buffer and make the
     * append buffer the official Tcl result.
     */

    if (iPtr->result != iPtr->appendResult) {
        /*
         * If an oversized buffer was used recently, then free it up
         * so we go back to a smaller buffer.  This avoids tying up
         * memory forever after a large operation.
         */

        if (iPtr->appendAvl > 500) {
            ckfree(iPtr->appendResult);
            iPtr->appendResult = NULL;
            iPtr->appendAvl = 0;
        }
        iPtr->appendUsed = strlen(iPtr->result);
    }
    totalSpace = newSpace + iPtr->appendUsed;
    if (totalSpace >= iPtr->appendAvl) {
        char *new;

        if (totalSpace < 100) {
            totalSpace = 200;
        } else {
            totalSpace *= 2;
        }
        new = (char *) ckalloc((unsigned) totalSpace);
        strcpy(new, iPtr->result);
        if (iPtr->appendResult != NULL) {
            ckfree(iPtr->appendResult);
        }
        iPtr->appendResult = new;
        iPtr->appendAvl = totalSpace;
    } else if (iPtr->result != iPtr->appendResult) {
        strcpy(iPtr->appendResult, iPtr->result);
    }
    Tcl_FreeResult(iPtr);
    iPtr->result = iPtr->appendResult;
}
\f
/*
 *----------------------------------------------------------------------
 *
 * Tcl_ResetResult --
 *
 *      This procedure restores the result area for an interpreter
 *      to its default initialized state, freeing up any memory that
 *      may have been allocated for the result and clearing any
 *      error information for the interpreter.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_ResetResult(interp)
    Tcl_Interp *interp;         /* Interpreter for which to clear result. */
{
    register Interp *iPtr = (Interp *) interp;

    Tcl_FreeResult(iPtr);
    iPtr->result = iPtr->resultSpace;
    iPtr->resultSpace[0] = 0;
    iPtr->flags &=
            ~(ERR_ALREADY_LOGGED | ERR_IN_PROGRESS | ERROR_CODE_SET);
}
\f
/*
 *----------------------------------------------------------------------
 *
 * Tcl_SetErrorCode --
 *
 *      This procedure is called to record machine-readable information
 *      about an error that is about to be returned.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      The errorCode global variable is modified to hold all of the
 *      arguments to this procedure, in a list form with each argument
 *      becoming one element of the list.  A flag is set internally
 *      to remember that errorCode has been set, so the variable doesn't
 *      get set automatically when the error is returned.
 *
 *----------------------------------------------------------------------
 */
void
Tcl_SetErrorCode(Tcl_Interp *interp, ...)
{
    va_list argList;
    char *string;
    int flags;
    Interp *iPtr;

    /*
     * Scan through the arguments one at a time, appending them to
     * $errorCode as list elements.
     */

    va_start(argList, interp);
    iPtr = (Interp *)interp;
    flags = TCL_GLOBAL_ONLY | TCL_LIST_ELEMENT;
    while (1) {
        string = va_arg(argList, char *);
        if (string == NULL) {
            break;
        }
        (void) Tcl_SetVar2((Tcl_Interp *) iPtr, "errorCode",
                (char *) NULL, string, flags);
        flags |= TCL_APPEND_VALUE;
    }
    va_end(argList);
    iPtr->flags |= ERROR_CODE_SET;
}
\f
/*
 *----------------------------------------------------------------------
 *
 * TclGetListIndex --
 *
 *      Parse a list index, which may be either an integer or the
 *      value "end".
 *
 * Results:
 *      The return value is either TCL_OK or TCL_ERROR.  If it is
 *      TCL_OK, then the index corresponding to string is left in
 *      *indexPtr.  If the return value is TCL_ERROR, then string
 *      was bogus;  an error message is returned in interp->result.
 *      If a negative index is specified, it is rounded up to 0.
 *      The index value may be larger than the size of the list
 *      (this happens when "end" is specified).
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

int
TclGetListIndex(interp, string, indexPtr)
    Tcl_Interp *interp;                 /* Interpreter for error reporting. */
    char *string;                       /* String containing list index. */
    int *indexPtr;                      /* Where to store index. */
{
    if (isdigit(*string) || (*string == '-')) {
        if (Tcl_GetInt(interp, string, indexPtr) != TCL_OK) {
            return TCL_ERROR;
        }
        if (*indexPtr < 0) {
            *indexPtr = 0;
        }
    } else if (strncmp(string, "end", strlen(string)) == 0) {
        *indexPtr = 1<<30;
    } else {
        Tcl_AppendResult(interp, "bad index \"", string,
                "\": must be integer or \"end\"", (char *) NULL);
        return TCL_ERROR;
    }
    return TCL_OK;
}
\f
/*
 *----------------------------------------------------------------------
 *
 * TclCompileRegexp --
 *
 *      Compile a regular expression into a form suitable for fast
 *      matching.  This procedure retains a small cache of pre-compiled
 *      regular expressions in the interpreter, in order to avoid
 *      compilation costs as much as possible.
 *
 * Results:
 *      The return value is a pointer to the compiled form of string,
 *      suitable for passing to regexec.  If an error occurred while
 *      compiling the pattern, then NULL is returned and an error
 *      message is left in interp->result.
 *
 * Side effects:
 *      The cache of compiled regexp's in interp will be modified to
 *      hold information for string, if such information isn't already
 *      present in the cache.
 *
 *----------------------------------------------------------------------
 */

regexp *
TclCompileRegexp(interp, string)
    Tcl_Interp *interp;                 /* For use in error reporting. */
    char *string;                       /* String for which to produce
                                         * compiled regular expression. */
{
    register Interp *iPtr = (Interp *) interp;
    int i, length;
    regexp *result;

    length = strlen(string);
    for (i = 0; i < NUM_REGEXPS; i++) {
        if ((length == iPtr->patLengths[i])
                && (strcmp(string, iPtr->patterns[i]) == 0)) {
            /*
             * Move the matched pattern to the first slot in the
             * cache and shift the other patterns down one position.
             */

            if (i != 0) {
                int j;
                char *cachedString;

                cachedString = iPtr->patterns[i];
                result = iPtr->regexps[i];
                for (j = i-1; j >= 0; j--) {
                    iPtr->patterns[j+1] = iPtr->patterns[j];
                    iPtr->patLengths[j+1] = iPtr->patLengths[j];
                    iPtr->regexps[j+1] = iPtr->regexps[j];
                }
                iPtr->patterns[0] = cachedString;
                iPtr->patLengths[0] = length;
                iPtr->regexps[0] = result;
            }
            return iPtr->regexps[0];
        }
    }

    /*
     * No match in the cache.  Compile the string and add it to the
     * cache.
     */

    tclRegexpError = NULL;
    result = regcomp(string);
    if (tclRegexpError != NULL) {
        Tcl_AppendResult(interp,
            "couldn't compile regular expression pattern: ",
            tclRegexpError, (char *) NULL);
        return NULL;
    }
    if (iPtr->patterns[NUM_REGEXPS-1] != NULL) {
        ckfree(iPtr->patterns[NUM_REGEXPS-1]);
        ckfree((char *) iPtr->regexps[NUM_REGEXPS-1]);
    }
    for (i = NUM_REGEXPS - 2; i >= 0; i--) {
        iPtr->patterns[i+1] = iPtr->patterns[i];
        iPtr->patLengths[i+1] = iPtr->patLengths[i];
        iPtr->regexps[i+1] = iPtr->regexps[i];
    }
    iPtr->patterns[0] = (char *) ckalloc((unsigned) (length+1));
    strcpy(iPtr->patterns[0], string);
    iPtr->patLengths[0] = length;
    iPtr->regexps[0] = result;
    return result;
}
\f
/*
 *----------------------------------------------------------------------
 *
 * regerror --
 *
 *      This procedure is invoked by the Henry Spencer's regexp code
 *      when an error occurs.  It saves the error message so it can
 *      be seen by the code that called Spencer's code.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      The value of "string" is saved in "tclRegexpError".
 *
 *----------------------------------------------------------------------
 */

void
regerror(string)
    char *string;                       /* Error message. */
{
    tclRegexpError = string;
}