LXR busybox/libbb/percent

   1/* vi: set sw=4 ts=4: */
   2/*
   3 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
   4 */
   5
   6//kbuild:lib-y += percent_decode.o
   7
   8#include "libbb.h"
   9
  10static unsigned hex_to_bin(unsigned char c)
  11{
  12        unsigned v;
  13
  14        v = c - '0';
  15        if (v <= 9)
  16                return v;
  17        /* c | 0x20: letters to lower case, non-letters
  18         * to (potentially different) non-letters */
  19        v = (unsigned)(c | 0x20) - 'a';
  20        if (v <= 5)
  21                return v + 10;
  22        return ~0;
  23/* For testing:
  24void t(char c) { printf("'%c'(%u) %u\n", c, c, hex_to_bin(c)); }
  25int main() { t(0x10); t(0x20); t('0'); t('9'); t('A'); t('F'); t('a'); t('f');
  26t('0'-1); t('9'+1); t('A'-1); t('F'+1); t('a'-1); t('f'+1); return 0; }
  27*/
  28}
  29
  30char* FAST_FUNC percent_decode_in_place(char *str, int strict)
  31{
  32        /* note that decoded string is always shorter than original */
  33        char *src = str;
  34        char *dst = str;
  35        char c;
  36
  37        while ((c = *src++) != '\0') {
  38                unsigned v;
  39
  40                if (!strict && c == '+') {
  41                        *dst++ = ' ';
  42                        continue;
  43                }
  44                if (c != '%') {
  45                        *dst++ = c;
  46                        continue;
  47                }
  48                v = hex_to_bin(src[0]);
  49                if (v > 15) {
  50 bad_hex:
  51                        if (strict)
  52                                return NULL;
  53                        *dst++ = '%';
  54                        continue;
  55                }
  56                v = (v * 16) | hex_to_bin(src[1]);
  57                if (v > 255)
  58                        goto bad_hex;
  59                if (strict && (v == '/' || v == '\0')) {
  60                        /* caller takes it as indication of invalid
  61                         * (dangerous wrt exploits) chars */
  62                        return str + 1;
  63                }
  64                *dst++ = v;
  65                src += 2;
  66        }
  67        *dst = '\0';
  68        return str;
  69}
  70