7467e905e
Denys Vlasenko
2020-11-28
Subject
base32/64: code shrink
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Commit Diff GitHub →
libbb/uuencode.c+43 -32
| @@ -93,9 +93,10 @@ const char* FAST_FUNC decode_base64(char **pp_dst, const char *src) | |
| char *dst = *pp_dst; | |
| unsigned ch = 0; | |
| int i = 0; | |
| + | int t; |
| - | while (*src) { |
| - | int t = (unsigned char)*src++; |
| + | while ((t = (unsigned char)*src) != '\0') { |
| + | src++; |
| /* "if" forest is faster than strchr(bb_uuenc_tbl_base64, t) */ | |
| if (t >= '0' && t <= '9') | |
| @@ -131,7 +132,7 @@ const char* FAST_FUNC decode_base64(char **pp_dst, const char *src) | |
| } | |
| } | |
| *pp_dst = dst; | |
| - | /* i should be zero here if full 4-char block was decoded */ |
| + | /* i is zero here if full 4-char block was decoded */ |
| return src - i; /* -i rejects truncations: e.g. "MQ" and "MQ=" (correct encoding is "MQ==" -> "1") */ | |
| } | |
| @@ -141,9 +142,10 @@ const char* FAST_FUNC decode_base32(char **pp_dst, const char *src) | |
| char *dst = *pp_dst; | |
| uint64_t ch = 0; | |
| int i = 0; | |
| + | int t; |
| - | while (*src) { |
| - | int t = (unsigned char)*src++; |
| + | while ((t = (unsigned char)*src) != '\0') { |
| + | src++; |
| /* "if" forest is faster than strchr(bb_uuenc_tbl_base32, t) */ | |
| if (t >= '2' && t <= '7') | |
| @@ -156,27 +158,35 @@ const char* FAST_FUNC decode_base32(char **pp_dst, const char *src) | |
| //TODO: add BASE64_FLAG_foo to die on bad char? | |
| continue; | |
| - | ch = (ch << 5) | t; |
| + | 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--; |
| + | } |
| *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; |
| - | } |
| 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 should be zero here if full 8-char block was decoded */ |
| + | /* i is zero here if full 8-char block was decoded */ |
| return src - i; | |
| } | |
| #endif | |
| @@ -193,19 +203,20 @@ void FAST_FUNC read_base64(FILE *src_stream, FILE *dst_stream, int flags) | |
| #define uu_style_end (flags & BASE64_FLAG_UU_STOP) | |
| #define base32 (flags & BASE64_32) | |
| - | /* uuencoded files have 61 byte lines. Use 64 byte buffer |
| - | * to process line at a time. |
| + | /* uuencoded files have 61 byte lines. |
| + | * base32/64 have 76 byte lines by default. |
| + | * Use 80 byte buffer to process one line at a time. |
| */ | |
| - | enum { BUFFER_SIZE = 64 }; |
| - | |
| - | char in_buf[BUFFER_SIZE + 2]; |
| - | char out_buf[BUFFER_SIZE / 4 * 3 + 2]; |
| - | char *out_tail; |
| - | const char *in_tail; |
| + | enum { BUFFER_SIZE = 80 }; |
| + | /* decoded data is shorter than input, can use single buffer for both */ |
| + | char buf[BUFFER_SIZE + 2]; |
| int term_seen = 0; | |
| int in_count = 0; | |
| while (1) { | |
| + | char *out_tail; |
| + | const char *in_tail; |
| + | |
| while (in_count < BUFFER_SIZE) { | |
| int ch = fgetc(src_stream); | |
| if (ch == exit_char) { | |
| @@ -224,23 +235,23 @@ void FAST_FUNC read_base64(FILE *src_stream, FILE *dst_stream, int flags) | |
| */ | |
| if (ch <= ' ') | |
| break; | |
| - | in_buf[in_count++] = ch; |
| + | buf[in_count++] = ch; |
| } | |
| - | in_buf[in_count] = '\0'; |
| + | buf[in_count] = '\0'; |
| /* Did we encounter "====" line? */ | |
| - | if (uu_style_end && strcmp(in_buf, "====") == 0) |
| + | if (uu_style_end && strcmp(buf, "====") == 0) |
| return; | |
| - | out_tail = out_buf; |
| + | out_tail = buf; |
| #if ENABLE_BASE32 | |
| if (base32) | |
| - | in_tail = decode_base32(&out_tail, in_buf); |
| + | in_tail = decode_base32(&out_tail, buf); |
| else | |
| #endif | |
| - | in_tail = decode_base64(&out_tail, in_buf); |
| + | in_tail = decode_base64(&out_tail, buf); |
| - | fwrite(out_buf, (out_tail - out_buf), 1, dst_stream); |
| + | fwrite(buf, (out_tail - buf), 1, dst_stream); |
| if (term_seen) { | |
| /* Did we consume ALL characters? */ | |
| @@ -252,6 +263,6 @@ void FAST_FUNC read_base64(FILE *src_stream, FILE *dst_stream, int flags) | |
| /* It was partial decode */ | |
| in_count = strlen(in_tail); | |
| - | memmove(in_buf, in_tail, in_count); |
| + | memmove(buf, in_tail, in_count); |
| } | |
| } | |