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decode_signature: guess signature data length for efficiency

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We may end up allocating 1 or 2 extra bytes this way, but it is worth it
to simplify the method and not have to call base64_decode() a second
time. Use the hueristic that base64 encoding produces 3 bytes of decoded
data for every 4 bytes of encoded data.

Signed-off-by: Dan McGee <dan@archlinux.org>
This commit is contained in:
Dan McGee 2011-08-14 20:47:08 -05:00
parent f3f39cef84
commit fa4aad5b50
1 changed files with 5 additions and 15 deletions
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20
lib/libalpm/signing.c
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@ -169,22 +169,12 @@ error:
*/
static int decode_signature(const char *base64_data,
unsigned char **data, size_t *data_len) {
unsigned char *usline;
size_t len;
len = strlen(base64_data);
usline = (unsigned char *)base64_data;
int ret;
size_t destlen = 0;
/* get the necessary size for the buffer by passing 0 */
ret = base64_decode(NULL, &destlen, usline, len);
if(ret != 0 && ret != POLARSSL_ERR_BASE64_BUFFER_TOO_SMALL) {
goto error;
}
/* alloc our memory and repeat the call to decode */
size_t len = strlen(base64_data);
unsigned char *usline = (unsigned char *)base64_data;
/* reasonable allocation of expected length is 3/4 of encoded length */
size_t destlen = len * 3 / 4;
MALLOC(*data, destlen, goto error);
ret = base64_decode(*data, &destlen, usline, len);
if(ret != 0) {
if(base64_decode(*data, &destlen, usline, len)) {
goto error;
}
*data_len = destlen;