source: MondoRescue/branches/3.3/mindi-busybox/libbb/percent_decode.c@ 3647

/* vi: set sw=4 ts=4: */
/*
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 */

//kbuild:lib-y += percent_decode.o

#include "libbb.h"

static unsigned hex_to_bin(unsigned char c)
{
    unsigned v;

    v = c - '0';
    if (v <= 9)
        return v;
    /* c | 0x20: letters to lower case, non-letters
     * to (potentially different) non-letters */
    v = (unsigned)(c | 0x20) - 'a';
    if (v <= 5)
        return v + 10;
    return ~0;
/* For testing:
void t(char c) { printf("'%c'(%u) %u\n", c, c, hex_to_bin(c)); }
int main() { t(0x10); t(0x20); t('0'); t('9'); t('A'); t('F'); t('a'); t('f');
t('0'-1); t('9'+1); t('A'-1); t('F'+1); t('a'-1); t('f'+1); return 0; }
*/
}

char* FAST_FUNC percent_decode_in_place(char *str, int strict)
{
    /* note that decoded string is always shorter than original */
    char *src = str;
    char *dst = str;
    char c;

    while ((c = *src++) != '\0') {
        unsigned v;

        if (!strict && c == '+') {
            *dst++ = ' ';
            continue;
        }
        if (c != '%') {
            *dst++ = c;
            continue;
        }
        v = hex_to_bin(src[0]);
        if (v > 15) {
 bad_hex:
            if (strict)
                return NULL;
            *dst++ = '%';
            continue;
        }
        v = (v * 16) | hex_to_bin(src[1]);
        if (v > 255)
            goto bad_hex;
        if (strict && (v == '/' || v == '\0')) {
            /* caller takes it as indication of invalid
             * (dangerous wrt exploits) chars */
            return str + 1;
        }
        *dst++ = v;
        src += 2;
    }
    *dst = '\0';
    return str;
}