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/**
@file rexmpp_base64.c
@brief Base64 implementation
@author defanor <defanor@uberspace.net>
@date 2021
@copyright MIT license.
Implements RFC 4648.
*/
#include <stdlib.h>
#include <stddef.h>
#include "rexmpp_base64.h"
char map_range (char x, char from_start, char from_end, char to_start, char otherwise) {
if (x >= from_start && x <= from_end) {
return (to_start + x - from_start);
} else {
return otherwise;
}
}
char to_b64 (char x) {
return map_range(x, 0, 25, 'A',
map_range(x, 26, 51, 'a',
map_range(x, 52, 61, '0',
map_range(x, 62, 62, '+',
map_range(x, 63, 63, '/',
'=')))));
}
char from_b64 (char x) {
return map_range(x, 'A', 'Z', 0,
map_range(x, 'a', 'z', 26,
map_range(x, '0', '9', 52,
map_range(x, '+', '+', 62,
map_range(x, '/', '/', 63,
64)))));
}
int rexmpp_base64_to (const char *in, size_t in_len, char **out, size_t *out_len) {
if (in_len == 0) {
return -1;
}
if (in == NULL) {
return -1;
}
*out_len = (in_len + 2) / 3 * 4;
char *res = malloc(*out_len + 1);
if (res == NULL) {
return -1;
}
res[*out_len] = '\0';
*out = res;
while (res < *out + *out_len) {
char a = in[0];
char b = in_len > 1 ? in[1] : 0;
char c = in_len > 2 ? in[2] : 0;
res[0] = to_b64((a & 0xFC) >> 2);
res[1] = to_b64(((a & 0x03) << 4) | ((b & 0xF0) >> 4));
res[2] = in_len > 1 ? to_b64((((b & 0x0F) << 2) | ((c & 0xC0) >> 6))) : '=';
res[3] = in_len > 2 ? to_b64((c & 0x3F)) : '=';
in_len -= 3;
in += 3;
res += 4;
}
return 0;
}
int rexmpp_base64_from (const char *in, size_t in_len, char **out, size_t *out_len) {
if (in_len == 0) {
return -1;
}
if (in == NULL) {
return -1;
}
if (in_len % 4) {
return -1;
}
*out_len = in_len / 4 * 3;
char *res = malloc(*out_len);
if (res == NULL) {
return -1;
}
*out = res;
while (res < *out + *out_len) {
char a = from_b64(in[0]);
char b = from_b64(in[1]);
char c = in[2] == '=' ? 0 : from_b64(in[2]);
char d = in[3] == '=' ? 0 : from_b64(in[3]);
if ((a | b | c | d) & 0xC0) {
free(*out);
*out = NULL;
*out_len = 0;
return -1;
}
res[0] = (a << 2) | ((b & 0x30) >> 4);
res[1] = ((b & 0x0F) << 4) | ((c & 0x3C) >> 2);
res[2] = ((c & 0x03) << 6) | d;
if (in[2] == '=') {
if (in[3] != '=') {
free(*out);
*out = NULL;
*out_len = 0;
return -1;
}
*out_len = *out_len - 1;
}
if (in[3] == '=') {
if (res + 3 < *out + *out_len) {
free(*out);
*out = NULL;
*out_len = 0;
return -1;
}
*out_len = *out_len - 1;
}
in += 4;
res += 3;
}
return 0;
}
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