tok_subst

SFL
Version 2.11

`tok_subst`

#include "sfltok.h"
char *
tok_subst (const char *string, SYMTAB *symbols)

Synopsis

Performs symbol substitution into the specified string. Returns a newly-allocated string containing the result, or NULL if there was not enough memory. The symbol table holds the set of symbols that may be inserted. Undefined symbols are inserted as an empty value. Symbols are specified in the string using this syntax: $(name), where 'name' is case-sensitive. This version does not allow embedded symbols.

Source Code - (sfltok.c)

{
    char
        *sym_start,
        *sym_end,
        *sym_name,                      /*  Symbol name to look for          */
        *copied_to,                     /*  Up to where we copied so far     */
        *cur_result,                    /*  Current result buffer            */
        *new_result;                    /*  After adding next symbol         */
    int
        sym_length;                     /*  Length of symbol name            */
    SYMBOL
        *symbol;                        /*  Symbol in symbol table           */

    ASSERT (string);
    ASSERT (symbols);

    /*  Parse from left to right, looking for $(...) patterns                */
    cur_result = mem_strdup ("");       /*  Result buffer is empty           */
    sym_start  = strchr (string, '$');
    copied_to  = (char *) string;
    while (sym_start)
      {
        sym_end = strchr (++sym_start, ')');
        if (*sym_start == '('
        &&   sym_end
        &&  *sym_end   == ')')
          {
            /*  First, copy string up to sym_start                           */
            size_t cur_len = strlen (cur_result);
            ASSERT ((sym_start - copied_to) >= 0);

            new_result = mem_alloc (cur_len + (sym_start - copied_to));
            if (new_result == NULL)
              {
                mem_free (cur_result);
                return (NULL);
              }

            strncpy (new_result, cur_result, (cur_len + 1));
            strncat (new_result, copied_to, sym_start - 1 - copied_to);
            mem_free (cur_result);
            cur_result = new_result;
            copied_to  = sym_end + 1;

            /*  Now translate and insert symbol                              */
            sym_length = sym_end - sym_start - 1;
            sym_name   = mem_alloc (sym_length + 1);
            if (sym_name == NULL)
              {
                mem_free (cur_result);
                return (NULL);
              }

            memcpy (sym_name, sym_start + 1, sym_length);
            sym_name [sym_length] = 0;
            symbol = sym lookup symbol (symbols, sym_name);
            mem_free (sym_name);
            if (symbol)
              {
                xstrcpy_debug ();
                new_result = xstrcpy (NULL, cur_result, symbol-> value, NULL);
                mem_free (cur_result);
                cur_result = new_result;
              }
          }
        else
            sym_end = sym_start + 1;

        sym_start = strchr (sym_end, '$');
      }
    /*  Copy anything remaining in the string                                */
    xstrcpy_debug ();
    new_result = xstrcpy (NULL, cur_result, copied_to, NULL);
    mem_free (cur_result);
    return (new_result);
}

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