f140b49f5
Denys Vlasenko
2020-11-28
Subject
base32/64: code shrink
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libbb/uuencode.c+37 -29
| @@ -92,8 +92,8 @@ const char* FAST_FUNC decode_base64(char **pp_dst, const char *src) | |
| { | |
| char *dst = *pp_dst; | |
| unsigned ch = 0; | |
| + | unsigned t; |
| int i = 0; | |
| - | int t; |
| while ((t = (unsigned char)*src) != '\0') { | |
| src++; | |
| @@ -117,11 +117,11 @@ const char* FAST_FUNC decode_base64(char **pp_dst, const char *src) | |
| continue; | |
| ch = (ch << 6) | t; | |
| - | if (++i == 4) { |
| + | i = (i + 1) & 3; |
| + | if (i == 0) { |
| *dst++ = (char) (ch >> 16); | |
| *dst++ = (char) (ch >> 8); | |
| *dst++ = (char) ch; | |
| - | i = 0; |
| if (ch & 0x1000000) { /* was last input char '='? */ | |
| dst--; | |
| if (ch & (0x1000000 << 6)) /* was it "=="? */ | |
| @@ -140,9 +140,9 @@ 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; | |
| - | uint64_t ch = 0; |
| + | int64_t ch = 0; |
| + | unsigned t; |
| int i = 0; | |
| - | int t; |
| while ((t = (unsigned char)*src) != '\0') { | |
| src++; | |
| @@ -150,44 +150,52 @@ const char* FAST_FUNC decode_base32(char **pp_dst, const char *src) | |
| /* "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 |
| + | else { |
| + | t = (t | 0x20) - 'a'; |
| + | if (t > 25) |
| //TODO: add BASE64_FLAG_foo to die on bad char? | |
| - | continue; |
| + | continue; |
| + | } |
| - | ch = (ch << 5) | (unsigned)t; /* cast prevents pointless sign-extension of t */ |
| - | if (++i == 8) { |
| - | /* testcase: |
| - | * echo ' 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18' | base32 | base32 -d |
| - | * IOW, decoding of |
| - | * EAYSAMRAGMQDIIBVEA3CANZAHAQDSIBRGAQDCMJAGEZCAMJTEAYTIIBRGUQDCNRAGE3SAMJYBI== |
| - | * ==== |
| - | * should correctly stitch together the tail. |
| - | */ |
| - | if (t == 0) { |
| - | const char *s = src; |
| - | while (*--s == '=') |
| - | t--; |
| - | } |
| + | ch = (ch << 5) | t; |
| + | i = (i + 1) & 7; |
| + | if (i == 0) { |
| *dst++ = (char) (ch >> 32); | |
| + | if (src[-1] == '=') /* was last input char '='? */ |
| + | goto tail; |
| *dst++ = (char) (ch >> 24); | |
| *dst++ = (char) (ch >> 16); | |
| *dst++ = (char) (ch >> 8); | |
| *dst++ = (char) ch; | |
| - | i = 0; |
| - | if (t < 0) /* was last input char '='? */ |
| - | break; |
| } | |
| } | |
| - | if (t < 0) /* was last input char '='? */ |
| - | /* -t is the count of =, must be 1, 3, 4 or 6 */ |
| - | dst -= (-t + 1) * 2 / 3; /* discard last 1, 2, 3 or 4 bytes */ |
| *pp_dst = dst; | |
| /* i is zero here if full 8-char block was decoded */ | |
| return src - i; | |
| + | tail: |
| + | { |
| + | const char *s = src; |
| + | while (*--s == '=') |
| + | i++; |
| + | /* Why duplicate the below code? Testcase: |
| + | * echo ' 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18' | base32 | base32 -d |
| + | * IOW, decoding of |
| + | * EAYSAMRAGMQDIIBVEA3CANZAHAQDSIBRGAQDCMJAGEZCAMJTEAYTIIBRGUQDCNRAGE3SAMJYBI== |
| + | * ==== |
| + | * must correctly stitch together the tail, must not overwrite |
| + | * the tail before it is analyzed! (we can be decoding in-place) |
| + | * Else testcase fails, prints trailing extra NUL bytes. |
| + | */ |
| + | *dst++ = (char) (ch >> 24); |
| + | *dst++ = (char) (ch >> 16); |
| + | *dst++ = (char) (ch >> 8); |
| + | *dst++ = (char) ch; |
| + | dst -= (i+1) * 2 / 3; /* discard last 1, 2, 3 or 4 bytes */ |
| + | } |
| + | *pp_dst = dst; |
| + | return src; |
| } | |
| #endif | |