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authorDenys Vlasenko <vda.linux@googlemail.com>2020-11-27 21:25:34 +0100
committerDenys Vlasenko <vda.linux@googlemail.com>2020-11-27 21:25:34 +0100
commit2cd37d65e221f7267e97360d21f55a2318b25355 (patch)
treef126ad654f2c58e3f46c65d369ffd236bce36513
parent170b8628fabff2d81606cac052a35f8cf91cc7b2 (diff)
downloadbusybox-2cd37d65e221f7267e97360d21f55a2318b25355.tar.gz
libbb: faster and smaller decode_base32()
function old new delta decode_base32 275 224 -51 Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
-rw-r--r--libbb/uuencode.c84
1 files changed, 34 insertions, 50 deletions
diff --git a/libbb/uuencode.c b/libbb/uuencode.c
index 2e9edb219..7c7f1cf1c 100644
--- a/libbb/uuencode.c
+++ b/libbb/uuencode.c
@@ -82,7 +82,7 @@ void FAST_FUNC bb_uuencode(char *p, const void *src, int length, const char *tbl
}
/*
- * Decode base64 encoded string. Stops on NUL after terminating "=" or "==".
+ * Decode base64 encoded string.
*
* Returns: pointer to the undecoded part of source.
* If points to '\0', then the source was fully decoded.
@@ -139,61 +139,45 @@ const char* FAST_FUNC decode_base64(char **pp_dst, const char *src)
const char* FAST_FUNC decode_base32(char **pp_dst, const char *src)
{
char *dst = *pp_dst;
- const char *src_tail;
-
- while (1) {
- unsigned char five_bit[8];
- int count = 0;
-
- /* Fetch up to eight 5-bit values */
- src_tail = src;
- while (count < 8) {
- char *table_ptr;
- int ch;
+ uint64_t ch = 0;
+ int i = 0;
- /* Get next _valid_ character.
- * bb_uuenc_tbl_base32[] contains this string:
- * 0 1 2 3
- * 01234567890123456789012345678901
- * "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567="
- */
- do {
- ch = *src;
- if (ch == '\0') {
- if (count == 0) {
- src_tail = src;
- }
- goto ret;
- }
- src++;
- table_ptr = strchr(bb_uuenc_tbl_base32, toupper(ch));
- } while (!table_ptr);
+ while (*src) {
+ int t = (unsigned char)*src++;
- /* Convert encoded character to decimal */
- ch = table_ptr - bb_uuenc_tbl_base32;
+ /* "if" forest is faster than strchr(bb_uuenc_tbl_base32, t) */
+ if (t >= '2' && t <= '7')
+ t = t - '2' + 26;
+ else if ((t|0x20) >= 'a' && (t|0x20) <= 'z')
+ t = (t|0x20) - 'a';
+ else if (t == '=' && i > 1)
+ t = 0;
+ else
+//TODO: add BASE64_FLAG_foo to die on bad char?
+ continue;
- /* ch is 32 if char was '=', otherwise 0..31 */
- if (ch == 32)
+ ch = (ch << 5) | t;
+ if (++i == 8) {
+ *dst++ = (char) (ch >> 32);
+ *dst++ = (char) (ch >> 24);
+ *dst++ = (char) (ch >> 16);
+ *dst++ = (char) (ch >> 8);
+ *dst++ = (char) ch;
+ if (t == 0 && src[-1] == '=') { /* was last input char '='? */
+ const char *s = src;
+ while (*--s == '=' && --i != 0)
+ continue;
+ i = 8 - i; /* count of =, must be 1, 3, 4 or 6 */
+ dst -= (i+1) * 2 / 3; /* discard last 1, 2, 3 or 4 bytes */
+ i = 0;
break;
- five_bit[count] = ch;
- count++;
+ }
+ i = 0;
}
-
- /* Transform 5-bit values to 8-bit ones */
- if (count > 1) // xxxxx xxx-- ----- ----- ----- ----- ----- -----
- *dst++ = five_bit[0] << 3 | five_bit[1] >> 2;
- if (count > 3) // ----- ---xx xxxxx x---- ----- ----- ----- -----
- *dst++ = five_bit[1] << 6 | five_bit[2] << 1 | five_bit[3] >> 4;
- if (count > 4) // ----- ----- ----- -xxxx xxxx- ----- ----- -----
- *dst++ = five_bit[3] << 4 | five_bit[4] >> 1;
- if (count > 6) // ----- ----- ----- ----- ----x xxxxx xx--- -----
- *dst++ = five_bit[4] << 7 | five_bit[5] << 2 | five_bit[6] >> 3;
- if (count > 7) // ----- ----- ----- ----- ----- ----- --xxx xxxxx
- *dst++ = five_bit[6] << 5 | five_bit[7];
- } /* while (1) */
- ret:
+ }
*pp_dst = dst;
- return src_tail;
+ /* i should be zero here if full 8-char block was decoded */
+ return src - i;
}
#endif