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/**
* writes a hexadecimal representation of a binary string. does not NULL terminate destination.
*
* h and b may not overlap. period.
*
* @param h [out] destination (requires 2l space)
* @param b [in] source
* @param l [in] length of source
*/
void bin2hex (char * h, const unsigned char * b, size_t l) {
for (size_t i = 0; i < l; i++) {
int ms = b[i] >> 4;
int ls = b[i] & 0xF;
assert(ms < 16);
assert(ls < 16);
*h++ = ms < 10 ? '0'+ms : 'a'+ms-10;
*h++ = ls < 10 ? '0'+ls : 'a'+ls-10;
}
}
/**
* converts a hexadecimal string to bytes
*
* b and h may not overlap, unless they are the same address
*
* @param b [out] array of bytes to write to with capacity l
* @param h [in] array of hex to read from with 2l hex digits
* @param l [in] length of output array
*/
void hex2bin (unsigned char * b, const char * h, int l) {
for (int i = 0; i < l; i++) {
char ms = *h++;
char ls = *h++;
b[i] = (ms >= 'a' ? ms - 'a' + 10 : (ms >= 'A' ? ms - 'A' + 10 : ms - '0')) << 4;
b[i] |= (ls >= 'a' ? ls - 'a' + 10 : (ls >= 'A' ? ls - 'A' + 10 : ls - '0'));
}
}
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