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authorDenys Vlasenko <vda.linux@googlemail.com>2011-10-28 14:15:00 (GMT)
committer Denys Vlasenko <vda.linux@googlemail.com>2011-10-28 14:15:00 (GMT)
commite6094d95b5d5a1a4c76aff99d89c8a4f44c5d59a (patch)
tree6fa00e6b32449af762e0b0e8b5d9d6e34c529de3
parent73d249e704cfdf8632c120599c1ddfeceb81dd32 (diff)
downloadbusybox-e6094d95b5d5a1a4c76aff99d89c8a4f44c5d59a.tar.gz
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libbb: shrink base64 decoding a bit
function old new delta bb_uuenc_tbl_base64 67 66 -1 decode_base64 182 161 -21 Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
-rw-r--r--libbb/uuencode.c42
1 files changed, 23 insertions, 19 deletions
diff --git a/libbb/uuencode.c b/libbb/uuencode.c
index 46ca796..f7b2484 100644
--- a/libbb/uuencode.c
+++ b/libbb/uuencode.c
@@ -10,7 +10,7 @@
#include "libbb.h"
/* Conversion table. for base 64 */
-const char bb_uuenc_tbl_base64[65 + 2] ALIGN1 = {
+const char bb_uuenc_tbl_base64[65 + 1] ALIGN1 = {
'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',
'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
@@ -20,7 +20,7 @@ const char bb_uuenc_tbl_base64[65 + 2] ALIGN1 = {
'w', 'x', 'y', 'z', '0', '1', '2', '3',
'4', '5', '6', '7', '8', '9', '+', '/',
'=' /* termination character */,
- '\n', '\0' /* needed for uudecode.c */
+ '\0' /* needed for uudecode.c only */
};
const char bb_uuenc_tbl_std[65] ALIGN1 = {
@@ -77,7 +77,7 @@ void FAST_FUNC bb_uuencode(char *p, const void *src, int length, const char *tbl
*
* Returns: pointer to the undecoded part of source.
* If points to '\0', then the source was fully decoded.
- * (*dst): advanced past the last written byte.
+ * (*pp_dst): advanced past the last written byte.
*/
const char* FAST_FUNC decode_base64(char **pp_dst, const char *src)
{
@@ -85,10 +85,10 @@ const char* FAST_FUNC decode_base64(char **pp_dst, const char *src)
const char *src_tail;
while (1) {
- unsigned char translated[4];
+ unsigned char six_bit[4];
int count = 0;
- /* Process one group of 4 chars */
+ /* Fetch up to four 6-bit values */
src_tail = src;
while (count < 4) {
char *table_ptr;
@@ -97,8 +97,8 @@ const char* FAST_FUNC decode_base64(char **pp_dst, const char *src)
/* Get next _valid_ character.
* bb_uuenc_tbl_base64[] contains this string:
* 0 1 2 3 4 5 6
- * 012345678901234567890123456789012345678901234567890123456789012345
- * "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=\n"
+ * 01234567890123456789012345678901234567890123456789012345678901234
+ * "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="
*/
do {
ch = *src;
@@ -117,33 +117,37 @@ const char* FAST_FUNC decode_base64(char **pp_dst, const char *src)
src++;
table_ptr = strchr(bb_uuenc_tbl_base64, ch);
//TODO: add BASE64_FLAG_foo to die on bad char?
-//Note that then we may need to still allow '\r' (for mail processing)
} while (!table_ptr);
/* Convert encoded character to decimal */
ch = table_ptr - bb_uuenc_tbl_base64;
- if (ch == 65) { /* '\n' */
- continue;
- }
/* ch is 64 if char was '=', otherwise 0..63 */
- translated[count] = ch & 63; /* 64 -> 0 */
- if (ch == 64) { /* '=' */
+ if (ch == 64)
break;
- }
+ six_bit[count] = ch;
count++;
}
- /* Merge 6 bit chars to 8 bit.
+ /* Transform 6-bit values to 8-bit ones.
* count can be < 4 when we decode the tail:
- * "eQ==" -> "y", not "y NUL NUL"
+ * "eQ==" -> "y", not "y NUL NUL".
+ * Note that (count > 1) is always true,
+ * "x===" encoding is not valid:
+ * even a single zero byte encodes as "AA==".
+ * However, with current logic we come here with count == 1
+ * when we decode "==" tail.
*/
if (count > 1)
- *dst++ = translated[0] << 2 | translated[1] >> 4;
+ *dst++ = six_bit[0] << 2 | six_bit[1] >> 4;
if (count > 2)
- *dst++ = translated[1] << 4 | translated[2] >> 2;
+ *dst++ = six_bit[1] << 4 | six_bit[2] >> 2;
if (count > 3)
- *dst++ = translated[2] << 6 | translated[3];
+ *dst++ = six_bit[2] << 6 | six_bit[3];
+ /* Note that if we decode "AA==" and ate first '=',
+ * we just decoded one char (count == 2) and now we'll
+ * do the loop once more to decode second '='.
+ */
} /* while (1) */
ret:
*pp_dst = dst;