/*
 *  This file defines the string_tokenize interface
 * Time-stamp:      "2005-04-25 18:47:21 bkorb"
 *
 *  string_tokenize copyright 2005 Bruce Korb
 *
 *  string_tokenize is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public
 *  License as published by the Free Software Foundation; either
 *  version 2.1 of the License, or (at your option) any later version.
 *
 *  string_tokenize is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public
 *  License along with string_tokenize; if not, write to:
 *             The Free Software Foundation, Inc.,
 *             51 Franklin Street, Fifth Floor,
 *             Boston, MA  02110-1301, USA.
 */
#include <ctype.h>
#include <errno.h>
#include <stdlib.h>

#define cc_t   const unsigned char
#define ch_t   unsigned char

/* = = = START-STATIC-FORWARD = = = */
/* static forward declarations maintained by :mkfwd */
static void
copy_cooked( ch_t** ppDest, cc_t** ppSrc );

static void
copy_raw( ch_t** ppDest, cc_t** ppSrc );
/* = = = END-STATIC-FORWARD = = = */

static void
copy_cooked( ch_t** ppDest, cc_t** ppSrc )
{
    ch_t* pDest = (ch_t*)*ppDest;
    const ch_t* pSrc  = (const ch_t*)(*ppSrc + 1);

    for (;;) {
        ch_t ch = *(pSrc++);
        switch (ch) {
        case NUL:   *ppSrc = NULL; return;
        case '"':   goto done;
        case '\\':
            pSrc += ao_string_cook_escape_char( (char*)pSrc, (char*)&ch, 0x7F );
            if (ch == 0x7F)
                break;
            /* FALLTHROUGH */

        default:
            *(pDest++) = ch;
        }
    }

 done:
    *ppDest = (ch_t*)pDest; /* next spot for storing character */
    *ppSrc  = (ch_t*)pSrc;  /* char following closing quote    */
}


static void
copy_raw( ch_t** ppDest, cc_t** ppSrc )
{
    ch_t* pDest = *ppDest;
    cc_t* pSrc  = *ppSrc + 1;

    for (;;) {
        ch_t ch = *(pSrc++);
        switch (ch) {
        case NUL:   *ppSrc = NULL; return;
        case '\'':  goto done;
        case '\\':
            /*
             *  *Four* escapes are handled:  newline removal, escape char
             *  quoting and apostrophe quoting
             */
            switch (*pSrc) {
            case NUL:   *ppSrc = NULL; return;
            case '\r':
                if (*(++pSrc) == '\n')
                    ++pSrc;
                continue;

            case '\n':
                ++pSrc;
                continue;

            case '\'':
                ch = '\'';
                /* FALLTHROUGH */

            case '\\':
                ++pSrc;
                break;
            }
            /* FALLTHROUGH */

        default:
            *(pDest++) = ch;
        }
    }

 done:
    *ppDest = pDest; /* next spot for storing character */
    *ppSrc  = pSrc;  /* char following closing quote    */
}


/*=export_func ao_string_tokenize
 *
 * what: tokenize an input string
 *
 * arg:  + const char* + string + string to be tokenized +
 *
 * ret_type:  token_list_t*
 * ret_desc:  pointer to a structure that lists each token
 *
 * doc:
 *
 * This function will convert one input string into a list of strings.
 * The list of strings is derived by separating the input based on
 * white space separation.  However, if the input contains either single
 * or double quote characters, then the text after that character up to
 * a matching quote will become the string in the list.
 *
 *  The returned pointer should be deallocated with @code{free(3C)} when
 *  are done using the data.  The data are placed in a single block of
 *  allocated memory.  Do not deallocate individual token/strings.
 *
 *  The structure pointed to will contain at least these two fields:
 *  @table @samp
 *  @item tkn_ct
 *  The number of tokens found in the input string.
 *  @item tok_list
 *  An array of @code{tkn_ct + 1} pointers to substring tokens, with
 *  the last pointer set to NULL.
 *  @end table
 *
 * There are two types of quoted strings: single quoted (@code{'}) and
 * double quoted (@code{"}).  Singly quoted strings are fairly raw in that
 * escape characters (@code{\\}) are simply another character, except when
 * preceding the following characters:
 * @example
 * @code{\\}  double backslashes reduce to one
 * @code{'}   incorporates the single quote into the string
 * @code{\n}  suppresses both the backslash and newline character
 * @end example
 *
 * Double quote strings are formed according to the rules of string
 * constants in ANSI-C programs.
 *
 * example:
 * @example
 *    #include <stdlib.h>
 *    int ix;
 *    token_list_t* ptl = ao_string_tokenize( some_string )
 *    for (ix = 0; ix < ptl->tkn_ct; ix++)
 *       do_something_with_tkn( ptl->tkn_list[ix] );
 *    free( ptl );
 * @end example
 * Note that everything is freed with the one call to @code{free(3C)}.
 *
 * err:
 *  NULL is returned and @code{errno} will be set to indicate the problem:
 *  @itemize @bullet
 *  @item
 *  @code{EINVAL} - There was an unterminated quoted string.
 *  @item
 *  @code{ENOENT} - The input string was empty.
 *  @item
 *  @code{ENOMEM} - There is not enough memory.
 *  @end itemize
=*/
token_list_t*
ao_string_tokenize( const char* str )
{
    int max_token_ct = 1; /* allow for trailing NUL on string */
    token_list_t* res;

    if (str == NULL)  goto bogus_str;

    /*
     *  Trim leading white space.  Use "ENOENT" and a NULL return to indicate
     *  an empty string was passed.
     */
    while (isspace( *str ))  str++;
    if (*str == NUL) {
    bogus_str:
        errno = ENOENT;
        return NULL;
    }

    /*
     *  Take an approximate count of tokens.  If no quoted strings are used,
     *  it will be accurate.  If quoted strings are used, it will be a little
     *  high and we'll squander the space for a few extra pointers.
     */
    {
        cc_t* pz = (cc_t*)str;

        do {
            max_token_ct++;
            while (! isspace( *++pz ))
                if (*pz == NUL) goto found_nul;
            while (isspace( *pz ))  pz++;
        } while (*pz != NUL);

    found_nul:
        ;
    }

    res = malloc( sizeof(*res) + strlen(str) + (max_token_ct * sizeof(ch_t*)) );
    if (res == NULL) {
        errno = ENOMEM;
        return res;
    }

    /*
     *  Now copy each token into the output buffer.
     */
    {
        ch_t* pzDest = (ch_t*)(res->tkn_list + (max_token_ct + 1));
        res->tkn_ct  = 0;

        do  {
            res->tkn_list[ res->tkn_ct++ ] = pzDest;
            for (;;) {
                char ch = *str;
                if (isspace( ch )) {
                found_white_space:
                    while (isspace( *++str ))  ;
                    break;
                }

                switch (ch) {
                case '"':
                    copy_cooked( &pzDest, (cc_t**)&str );
                    if (str == NULL) {
                        free(res);
                        errno = EINVAL;
                        return NULL;
                    }
                    if (isspace( *str ))
                        goto found_white_space;
                    break;

                case '\'':
                    copy_raw( &pzDest, (cc_t**)&str );
                    if (str == NULL) {
                        free(res);
                        errno = EINVAL;
                        return NULL;
                    }
                    if (isspace( *str ))
                        goto found_white_space;
                    break;

                case NUL:
                    goto copy_done;

                default:
                    str++;
                    *(pzDest++) = ch;
                }
            } copy_done:;

            /*
             * NUL terminate the last token and see if we have any more tokens.
             */
            *(pzDest++) = NUL;
        } while (*str != NUL);

        res->tkn_list[ res->tkn_ct ] = NULL;
    }

    return res;
}

#ifdef TEST
#include <stdio.h>
#include <string.h>

int
main( int argc, char** argv )
{
    if (argc == 1) {
        printf("USAGE:  %s arg [ ... ]\n", *argv);
        return 1;
    }
    while (--argc > 0) {
        char* arg = *(++argv);
        token_list_t* p = ao_string_tokenize( arg );
        if (p == NULL) {
            printf( "Parsing string ``%s'' failed:\n\terrno %d (%s)\n",
                    arg, errno, strerror( errno ));
        } else {
            int ix = 0;
            printf( "Parsed string ``%s''\ninto %d tokens:\n", arg, p->tkn_ct );
            do {
                printf( " %3d:  ``%s''\n", ix+1, p->tkn_list[ix] );
            } while (++ix < p->tkn_ct);
            free(p);
        }
    }
    return 0;
}
#endif

/*
 * Local Variables:
 * mode: C
 * c-file-style: "stroustrup"
 * tab-width: 4
 * indent-tabs-mode: nil
 * End:
 * end of autoopts/tokenize.c */
