[821] | 1 | #include "libbb.h"
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| 2 |
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| 3 | /* uncompress for busybox -- (c) 2002 Robert Griebl
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| 4 | *
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| 5 | * based on the original compress42.c source
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| 6 | * (see disclaimer below)
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| 7 | */
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| 8 |
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| 9 |
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| 10 | /* (N)compress42.c - File compression ala IEEE Computer, Mar 1992.
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| 11 | *
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| 12 | * Authors:
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| 13 | * Spencer W. Thomas (decvax!harpo!utah-cs!utah-gr!thomas)
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| 14 | * Jim McKie (decvax!mcvax!jim)
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| 15 | * Steve Davies (decvax!vax135!petsd!peora!srd)
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| 16 | * Ken Turkowski (decvax!decwrl!turtlevax!ken)
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| 17 | * James A. Woods (decvax!ihnp4!ames!jaw)
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| 18 | * Joe Orost (decvax!vax135!petsd!joe)
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| 19 | * Dave Mack (csu@alembic.acs.com)
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| 20 | * Peter Jannesen, Network Communication Systems
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| 21 | * (peter@ncs.nl)
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| 22 | *
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| 23 | * marc@suse.de : a small security fix for a buffer overflow
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| 24 | *
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| 25 | * [... History snipped ...]
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| 26 | *
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| 27 | */
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| 28 | #include <stdio.h>
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| 29 | #include <string.h>
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| 30 | #include <unistd.h>
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| 31 |
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| 32 | /* Default input buffer size */
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| 33 | #define IBUFSIZ 2048
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| 34 |
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| 35 | /* Default output buffer size */
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| 36 | #define OBUFSIZ 2048
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| 37 |
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| 38 | /* Defines for third byte of header */
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| 39 | #define MAGIC_1 (char_type)'\037' /* First byte of compressed file */
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| 40 | #define MAGIC_2 (char_type)'\235' /* Second byte of compressed file */
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| 41 | #define BIT_MASK 0x1f /* Mask for 'number of compresssion bits' */
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| 42 | /* Masks 0x20 and 0x40 are free. */
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| 43 | /* I think 0x20 should mean that there is */
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| 44 | /* a fourth header byte (for expansion). */
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| 45 | #define BLOCK_MODE 0x80 /* Block compresssion if table is full and */
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| 46 | /* compression rate is dropping flush tables */
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| 47 | /* the next two codes should not be changed lightly, as they must not */
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| 48 | /* lie within the contiguous general code space. */
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| 49 | #define FIRST 257 /* first free entry */
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| 50 | #define CLEAR 256 /* table clear output code */
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| 51 |
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| 52 | #define INIT_BITS 9 /* initial number of bits/code */
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| 53 |
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| 54 |
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| 55 | /* machine variants which require cc -Dmachine: pdp11, z8000, DOS */
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| 56 | #define FAST
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| 57 |
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| 58 | #define HBITS 17 /* 50% occupancy */
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| 59 | #define HSIZE (1<<HBITS)
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| 60 | #define HMASK (HSIZE-1)
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| 61 | #define HPRIME 9941
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| 62 | #define BITS 16
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| 63 | #undef MAXSEG_64K
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| 64 | #define MAXCODE(n) (1L << (n))
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| 65 |
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| 66 | /* Block compress mode -C compatible with 2.0 */
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| 67 | static int block_mode = BLOCK_MODE;
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| 68 |
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| 69 | /* user settable max # bits/code */
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| 70 | static int maxbits = BITS;
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| 71 |
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| 72 | /* Input buffer */
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| 73 | static unsigned char inbuf[IBUFSIZ + 64];
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| 74 |
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| 75 | /* Output buffer */
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| 76 | static unsigned char outbuf[OBUFSIZ + 2048];
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| 77 |
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| 78 |
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| 79 | static unsigned char htab[HSIZE];
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| 80 | static unsigned short codetab[HSIZE];
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| 81 |
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| 82 | #define htabof(i) htab[i]
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| 83 | #define codetabof(i) codetab[i]
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| 84 | #define tab_prefixof(i) codetabof(i)
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| 85 | #define tab_suffixof(i) ((unsigned char *)(htab))[i]
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| 86 | #define de_stack ((unsigned char *)&(htab[HSIZE-1]))
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| 87 | #define clear_htab() memset(htab, -1, sizeof(htab))
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| 88 | #define clear_tab_prefixof() memset(codetab, 0, 256);
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| 89 |
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| 90 |
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| 91 | /*
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| 92 | * Decompress stdin to stdout. This routine adapts to the codes in the
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| 93 | * file building the "string" table on-the-fly; requiring no table to
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| 94 | * be stored in the compressed file. The tables used herein are shared
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| 95 | * with those of the compress() routine. See the definitions above.
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| 96 | */
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| 97 |
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| 98 | int uncompress(int fd_in, int fd_out)
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| 99 | {
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| 100 | unsigned char *stackp;
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| 101 | long int code;
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| 102 | int finchar;
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| 103 | long int oldcode;
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| 104 | long int incode;
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| 105 | int inbits;
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| 106 | int posbits;
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| 107 | int outpos;
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| 108 | int insize;
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| 109 | int bitmask;
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| 110 | long int free_ent;
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| 111 | long int maxcode;
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| 112 | long int maxmaxcode;
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| 113 | int n_bits;
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| 114 | int rsize = 0;
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| 115 |
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| 116 | insize = 0;
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| 117 |
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| 118 | inbuf[0] = bb_xread_char(fd_in);
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| 119 |
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| 120 | maxbits = inbuf[0] & BIT_MASK;
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| 121 | block_mode = inbuf[0] & BLOCK_MODE;
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| 122 | maxmaxcode = MAXCODE(maxbits);
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| 123 |
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| 124 | if (maxbits > BITS) {
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| 125 | bb_error_msg("compressed with %d bits, can only handle %d bits", maxbits,
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| 126 | BITS);
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| 127 | return -1;
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| 128 | }
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| 129 |
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| 130 | maxcode = MAXCODE(n_bits = INIT_BITS) - 1;
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| 131 | bitmask = (1 << n_bits) - 1;
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| 132 | oldcode = -1;
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| 133 | finchar = 0;
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| 134 | outpos = 0;
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| 135 | posbits = 0 << 3;
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| 136 |
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| 137 | free_ent = ((block_mode) ? FIRST : 256);
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| 138 |
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| 139 | /* As above, initialize the first 256 entries in the table. */
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| 140 | clear_tab_prefixof();
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| 141 |
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| 142 | for (code = 255; code >= 0; --code) {
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| 143 | tab_suffixof(code) = (unsigned char) code;
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| 144 | }
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| 145 |
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| 146 | do {
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| 147 | resetbuf:;
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| 148 | {
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| 149 | int i;
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| 150 | int e;
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| 151 | int o;
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| 152 |
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| 153 | e = insize - (o = (posbits >> 3));
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| 154 |
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| 155 | for (i = 0; i < e; ++i)
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| 156 | inbuf[i] = inbuf[i + o];
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| 157 |
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| 158 | insize = e;
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| 159 | posbits = 0;
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| 160 | }
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| 161 |
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| 162 | if (insize < (int) sizeof(inbuf) - IBUFSIZ) {
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| 163 | rsize = safe_read(fd_in, inbuf + insize, IBUFSIZ);
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| 164 | insize += rsize;
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| 165 | }
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| 166 |
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| 167 | inbits = ((rsize > 0) ? (insize - insize % n_bits) << 3 :
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| 168 | (insize << 3) - (n_bits - 1));
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| 169 |
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| 170 | while (inbits > posbits) {
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| 171 | if (free_ent > maxcode) {
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| 172 | posbits =
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| 173 | ((posbits - 1) +
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| 174 | ((n_bits << 3) -
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| 175 | (posbits - 1 + (n_bits << 3)) % (n_bits << 3)));
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| 176 | ++n_bits;
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| 177 | if (n_bits == maxbits) {
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| 178 | maxcode = maxmaxcode;
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| 179 | } else {
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| 180 | maxcode = MAXCODE(n_bits) - 1;
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| 181 | }
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| 182 | bitmask = (1 << n_bits) - 1;
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| 183 | goto resetbuf;
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| 184 | }
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| 185 | {
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| 186 | unsigned char *p = &inbuf[posbits >> 3];
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| 187 |
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| 188 | code =
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| 189 | ((((long) (p[0])) | ((long) (p[1]) << 8) |
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| 190 | ((long) (p[2]) << 16)) >> (posbits & 0x7)) & bitmask;
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| 191 | }
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| 192 | posbits += n_bits;
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| 193 |
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| 194 |
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| 195 | if (oldcode == -1) {
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| 196 | outbuf[outpos++] = (unsigned char) (finchar =
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| 197 | (int) (oldcode = code));
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| 198 | continue;
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| 199 | }
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| 200 |
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| 201 | if (code == CLEAR && block_mode) {
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| 202 | clear_tab_prefixof();
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| 203 | free_ent = FIRST - 1;
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| 204 | posbits =
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| 205 | ((posbits - 1) +
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| 206 | ((n_bits << 3) -
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| 207 | (posbits - 1 + (n_bits << 3)) % (n_bits << 3)));
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| 208 | maxcode = MAXCODE(n_bits = INIT_BITS) - 1;
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| 209 | bitmask = (1 << n_bits) - 1;
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| 210 | goto resetbuf;
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| 211 | }
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| 212 |
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| 213 | incode = code;
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| 214 | stackp = de_stack;
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| 215 |
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| 216 | /* Special case for KwKwK string. */
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| 217 | if (code >= free_ent) {
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| 218 | if (code > free_ent) {
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| 219 | unsigned char *p;
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| 220 |
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| 221 | posbits -= n_bits;
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| 222 | p = &inbuf[posbits >> 3];
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| 223 |
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| 224 | bb_error_msg
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| 225 | ("insize:%d posbits:%d inbuf:%02X %02X %02X %02X %02X (%d)",
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| 226 | insize, posbits, p[-1], p[0], p[1], p[2], p[3],
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| 227 | (posbits & 07));
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| 228 | bb_error_msg("uncompress: corrupt input");
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| 229 | return -1;
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| 230 | }
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| 231 |
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| 232 | *--stackp = (unsigned char) finchar;
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| 233 | code = oldcode;
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| 234 | }
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| 235 |
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| 236 | /* Generate output characters in reverse order */
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| 237 | while ((long int) code >= (long int) 256) {
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| 238 | *--stackp = tab_suffixof(code);
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| 239 | code = tab_prefixof(code);
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| 240 | }
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| 241 |
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| 242 | *--stackp = (unsigned char) (finchar = tab_suffixof(code));
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| 243 |
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| 244 | /* And put them out in forward order */
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| 245 | {
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| 246 | int i;
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| 247 |
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| 248 | if (outpos + (i = (de_stack - stackp)) >= OBUFSIZ) {
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| 249 | do {
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| 250 | if (i > OBUFSIZ - outpos) {
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| 251 | i = OBUFSIZ - outpos;
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| 252 | }
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| 253 |
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| 254 | if (i > 0) {
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| 255 | memcpy(outbuf + outpos, stackp, i);
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| 256 | outpos += i;
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| 257 | }
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| 258 |
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| 259 | if (outpos >= OBUFSIZ) {
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| 260 | write(fd_out, outbuf, outpos);
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| 261 | outpos = 0;
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| 262 | }
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| 263 | stackp += i;
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| 264 | } while ((i = (de_stack - stackp)) > 0);
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| 265 | } else {
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| 266 | memcpy(outbuf + outpos, stackp, i);
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| 267 | outpos += i;
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| 268 | }
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| 269 | }
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| 270 |
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| 271 | /* Generate the new entry. */
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| 272 | if ((code = free_ent) < maxmaxcode) {
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| 273 | tab_prefixof(code) = (unsigned short) oldcode;
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| 274 | tab_suffixof(code) = (unsigned char) finchar;
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| 275 | free_ent = code + 1;
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| 276 | }
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| 277 |
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| 278 | /* Remember previous code. */
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| 279 | oldcode = incode;
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| 280 | }
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| 281 |
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| 282 | } while (rsize > 0);
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| 283 |
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| 284 | if (outpos > 0) {
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| 285 | write(fd_out, outbuf, outpos);
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| 286 | }
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| 287 |
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| 288 | return 0;
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| 289 | }
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