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| -rw-r--r-- | toys/pending/compress.c | 158 |
1 files changed, 158 insertions, 0 deletions
diff --git a/toys/pending/compress.c b/toys/pending/compress.c new file mode 100644 index 00000000..24729dc5 --- /dev/null +++ b/toys/pending/compress.c @@ -0,0 +1,158 @@ +/* compress.c - deflate/inflate code for zip, gzip, zlib, and raw + * + * Copyright 2014 Rob Landley <rob@landley.net> + * + * The inflate/deflate code lives here, so the various things that use it + * either live here or call these commands to pipe data through them. + * + * Divergence from posix: replace obsolete "compress" with mutiplexer. + * + * See RFCs 1950 (zlib), 1951 (deflate), and 1952 (gzip) + * LSB 4.1 has gzip, gunzip, and zcat + * TODO: zip -d DIR -x LIST -list -quiet -no overwrite -overwrite -p to stdout + +// Accept many different kinds of command line argument: + +USE_COMPRESS(NEWTOY(compress, "zglrcd9[-cd][!zglr]", TOYFLAG_USR|TOYFLAG_BIN)) + +//zip unzip gzip gunzip zcat + +config COMPRESS + bool "compress" + default n + help + usage: compress [-zglrcd9] [FILE] + + Compress or decompress file (or stdin) using "deflate" algorithm. + + -c compress + -d decompress + -g gzip + -l zlib + -r raw (default) + -z zip +*/ + +#define FOR_compress +#include "toys.h" + +GLOBALS( + // base offset and extra bits tables (length and distance) + char lenbits[29], distbits[30]; + unsigned short lenbase[29], distbase[30]; +) + +// little endian bit buffer +struct bitbuf { + int fd, pos, len, max; + char buf[]; +}; + +struct bitbuf *get_bitbuf(int fd, int size) +{ + struct bitbuf *bb = xmalloc(sizeof(struct bitbuf)+size); + + memset(bb, 0, sizeof(struct bitbuf)); + bb->max = size; + bb->fd = fd; + + return bb; +} + +int get_bits(struct bitbuf *bb, int bits) +{ + int result = 0, offset = 0; + + while (bits) { + int click = bb->pos >> 3, blow, blen; + + // Load more data if buffer empty + if (click == bb->len) { + bb->len = read(bb->fd, bb->buf, bb->max); + if (bb->len < 1) perror_exit("inflate EOF"); + bb->pos = click = 0; + } + + // grab bits from next byte + blow = bb->pos & 7; + blen = 8-blow; + if (blen > bits) blen = bits; + result |= ((bb->buf[click] >> blow) & ((1<<blen)-1)) << offset; + offset += blen; + bits -= blen; + bb->pos += blen; + } + + return result; +} + +static int deflate(struct bitbuf *buf) +{ + return 0; +} + +static void init_deflate(void) +{ + int i, n = 1; + + // Calculate lenbits, lenbase, distbits, distbase + *TT.lenbase = 3; + for (i = 0; i<sizeof(TT.lenbits)-1; i++) { + if (i>4) { + if (!(i&3)) { + TT.lenbits[i]++; + n <<= 1; + } + if (i == 27) n--; + else TT.lenbits[i+1] = TT.lenbits[i]; + } + TT.lenbase[i+1] = n + TT.lenbase[i]; + } + n = 0; + for (i = 0; i<sizeof(TT.distbits); i++) { + TT.distbase[i] = 1<<n; + if (i) TT.distbase[i] += TT.distbase[i-1]; + if (i>3 && !(i&1)) n++; + TT.distbits[i] = n; + } +} + +// Return true/false whether we consumed a gzip header. +static int is_gzip(struct bitbuf *bb) +{ + int flags; + + // Confirm signature + if (get_bits(bb, 24) != 0x088b1f || (flags = get_bits(bb, 8)) > 31) return 0; + get_bits(bb, 6*8); + + // Skip extra, name, comment, header CRC fields + if (flags & 4) get_bits(bb, 16); + if (flags & 8) while (get_bits(bb, 8)); + if (flags & 16) while (get_bits(bb, 8)); + if (flags & 2) get_bits(bb, 16); + + return 1; +} + +static void do_gzip(int fd, char *name) +{ + struct bitbuf *bb = get_bitbuf(fd, sizeof(toybuf)); + + printf("is_gzip=%d\n", is_gzip(bb)); + + // tail: crc32, len32 + + free(bb); +} + +// Parse many different kinds of command line argument: + +void compress_main(void) +{ + // 31, 139, 8 + // &2 = skip 2 bytes + init_deflate(); + + loopfiles(toys.optargs, do_gzip); +} |