argv.c

linux syslinux source code

#ident "$Id: argv.c,v 1.3 2004/12/21 02:47:08 hpa Exp $"
/* ----------------------------------------------------------------------- *
 *   
 *   Copyright 2004 H. Peter Anvin - All Rights Reserved
 *
 *   Permission is hereby granted, free of charge, to any person
 *   obtaining a copy of this software and associated documentation
 *   files (the "Software"), to deal in the Software without
 *   restriction, including without limitation the rights to use,
 *   copy, modify, merge, publish, distribute, sublicense, and/or
 *   sell copies of the Software, and to permit persons to whom
 *   the Software is furnished to do so, subject to the following
 *   conditions:
 *   
 *   The above copyright notice and this permission notice shall
 *   be included in all copies or substantial portions of the Software.
 *   
 *   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 *   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 *   OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 *   NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 *   HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 *   WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 *   FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 *   OTHER DEALINGS IN THE SOFTWARE.
 *
 * ----------------------------------------------------------------------- */

/*
 * argv.c
 *
 * Parse a single C string into argc and argv (argc is return value.)
 * memptr points to available memory.
 */

#include <inttypes.h>
#include <stddef.h>
#include <stdio.h>

#define ALIGN_UP(p,t)       ((t *)(((uintptr_t)(p) + (sizeof(t)-1)) & ~(sizeof(t)-1)))

extern char _end[];	     /* Symbol created by linker */
void *__mem_end = &_end;     /* Global variable for use by malloc() */

int __parse_argv(char ***argv, const char *str)
{
  char argv0[] = "";
  char *mem = __mem_end;
  const char *p = str;
  char *q = mem;
  char *r;
  char **arg;
  int wasspace = 1;
  int argc = 1;

  /* First copy the string, turning whitespace runs into nulls */
  for ( p = str ; ; p++ ) {
    if ( *p <= ' ' ) {
      if ( !wasspace ) {
	wasspace = 1;
	*q++ = '\0';
      }
    } else {
      if ( wasspace ) {
	argc++;
	wasspace = 0;
      }
      *q++ = *p;
    }

    /* This test is AFTER we have processed the null byte;
       we treat it as a whitespace character so it terminates
       the last argument */
    if ( ! *p )
      break;
  }

  /* Now create argv */
  arg = ALIGN_UP(q,char *);
  *argv = arg;
  *arg++ = argv0;		/* argv[0] */
  
  q--;				/* Point q to final null */
  if ( mem < q )
    *arg++ = mem;		/* argv[1] */

  for ( r = mem ; r < q ; r++ ) {
    if ( *r == '\0' ) {
      *arg++ = r+1;
    }
  }

  *arg++ = NULL;		/* Null pointer at the end */
  __mem_end = arg;		/* End of memory we used */

  return argc;
}