mirror of https://github.com/madler/zlib.git
- added inflateBackWrap() for stand-alone validation of inflateBack(). Moreover, inflateBackWrap() exhibits identical functionality as in inflate(). - added comments for code revisions - added log in ChangeLogpull/793/head
icodywu
2 years ago
parent
befb971b78
commit
cfa12c8c77
8 changed files with 733 additions and 6 deletions
@ -0,0 +1,646 @@ |
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/* infbackwrap.c -- zlib decompression
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* Copyright (C) 2023-2039 Cody Wu |
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* For conditions of distribution and use, see copyright notice in zlib.h |
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*/ |
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#include "zutil.h" |
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#include "inftrees.h" |
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#include "inflate.h" |
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#include "inffast.h" |
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/* function prototypes */ |
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local int inflateStateCheck OF((z_streamp strm)); |
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local void fixedtables OF((struct inflate_state FAR* state)); |
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local int updatewindow OF((z_streamp strm, const unsigned char FAR* end, |
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unsigned copy)); |
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local unsigned syncsearch OF((unsigned FAR* have, const unsigned char FAR* buf, |
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unsigned len)); |
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local int inflateStateCheck(strm) |
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z_streamp strm; |
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{ |
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struct inflate_state FAR* state; |
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if (strm == Z_NULL || |
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strm->zalloc == (alloc_func)0 || strm->zfree == (free_func)0) |
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return 1; |
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state = (struct inflate_state FAR*)strm->state; |
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if (state == Z_NULL || state->strm != strm || |
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state->mode < HEAD || state->mode > SYNC) |
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return 1; |
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return 0; |
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} |
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/*
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Update the window with the last wsize (normally 32K) bytes written before |
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returning. If window does not exist yet, create it. This is only called |
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when a window is already in use, or when output has been written during this |
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inflate call, but the end of the deflate stream has not been reached yet. |
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It is also called to create a window for dictionary data when a dictionary |
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is loaded. |
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Providing output buffers larger than 32K to inflate() should provide a speed |
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advantage, since only the last 32K of output is copied to the sliding window |
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upon return from inflate(), and since all distances after the first 32K of |
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output will fall in the output data, making match copies simpler and faster. |
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The advantage may be dependent on the size of the processor's data caches. |
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*/ |
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local int updatewindow(strm, end, copy) |
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z_streamp strm; |
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const Bytef* end; |
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unsigned copy; |
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{ |
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struct inflate_state FAR* state; |
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unsigned dist; |
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state = (struct inflate_state FAR*)strm->state; |
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/* if it hasn't been done already, allocate space for the window */ |
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if (state->window == Z_NULL) { |
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state->window = (unsigned char FAR*) |
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ZALLOC(strm, 1U << state->wbits, |
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sizeof(unsigned char)); |
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if (state->window == Z_NULL) return 1; |
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} |
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/* if window not in use yet, initialize */ |
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if (state->wsize == 0) { |
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state->wsize = 1U << state->wbits; |
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state->wnext = 0; |
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state->whave = 0; |
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} |
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/* copy state->wsize or less output bytes into the circular window */ |
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if (copy >= state->wsize) { |
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zmemcpy(state->window, end - state->wsize, state->wsize); |
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state->wnext = 0; |
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state->whave = state->wsize; |
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} |
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else { |
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dist = state->wsize - state->wnext; |
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if (dist > copy) dist = copy; |
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zmemcpy(state->window + state->wnext, end - copy, dist); |
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copy -= dist; |
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if (copy) { |
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zmemcpy(state->window, end - copy, copy); |
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state->wnext = copy; |
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state->whave = state->wsize; |
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} |
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else { |
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state->wnext += dist; |
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if (state->wnext == state->wsize) state->wnext = 0; |
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if (state->whave < state->wsize) state->whave += dist; |
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} |
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} |
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return 0; |
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} |
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/* Macros for inflateBackWrap(), all copied from inflate.c */ |
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/* check function to use adler32() for zlib or crc32() for gzip */ |
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#ifdef GUNZIP |
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# define UPDATE_CHECK(check, buf, len) \ |
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(state->flags ? crc32(check, buf, len) : adler32(check, buf, len)) |
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#else |
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# define UPDATE_CHECK(check, buf, len) adler32(check, buf, len) |
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#endif |
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/* check macros for header crc */ |
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#ifdef GUNZIP |
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# define CRC2(check, word) \ |
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do { \
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hbuf[0] = (unsigned char)(word); \
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hbuf[1] = (unsigned char)((word) >> 8); \
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check = crc32(check, hbuf, 2); \
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} while (0) |
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# define CRC4(check, word) \ |
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do { \
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hbuf[0] = (unsigned char)(word); \
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hbuf[1] = (unsigned char)((word) >> 8); \
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hbuf[2] = (unsigned char)((word) >> 16); \
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hbuf[3] = (unsigned char)((word) >> 24); \
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check = crc32(check, hbuf, 4); \
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} while (0) |
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#endif |
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/* Load registers with state in inflate() for speed */ |
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#define LOAD() \ |
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do { \
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next = strm->next_in; \
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have = strm->avail_in; \
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hold = state->hold; \
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bits = state->bits; \
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} while (0) |
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/* Restore state from registers in inflate() */ |
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#define RESTORE() \ |
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do { \
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strm->next_out = out_buf.bufPtr; \
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strm->avail_out = out_buf.bufPtrEnd - out_buf.bufPtr; \
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strm->next_in = next; \
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strm->avail_in = have; \
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state->hold = hold; \
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state->bits = bits; \
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} while (0) |
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/* Clear the input bit accumulator */ |
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#define INITBITS() \ |
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do { \
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hold = 0; \
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bits = 0; \
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} while (0) |
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/* Get a byte of input into the bit accumulator, or return from inflate()
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if there is no input available. */ |
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#define PULLBYTE() \ |
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do { \
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if (have == 0) goto inf_leave; \
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have--; \
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hold += (unsigned long)(*next++) << bits; \
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bits += 8; \
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} while (0) |
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/* Assure that there are at least n bits in the bit accumulator. If there is
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not enough available input to do that, then return from inflate(). */ |
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#define NEEDBITS(n) \ |
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do { \
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while (bits < (unsigned)(n)) \
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PULLBYTE(); \
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} while (0) |
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/* Return the low n bits of the bit accumulator (n < 16) */ |
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#define BITS(n) \ |
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((unsigned)hold & ((1U << (n)) - 1)) |
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/* Remove n bits from the bit accumulator */ |
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#define DROPBITS(n) \ |
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do { \
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hold >>= (n); \
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bits -= (unsigned)(n); \
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} while (0) |
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/* Remove zero to seven bits as needed to go to a byte boundary */ |
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#define BYTEBITS() \ |
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do { \
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hold >>= bits & 7; \
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bits -= bits & 7; \
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} while (0) |
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/*
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inflate()/inflateBackWrap() uses a state machine to process as much input data and generate as |
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much output data as possible before returning. The state machine is |
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structured roughly as follows: |
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for (;;) switch (state) { |
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... |
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case STATEn: |
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if (not enough input data or output space to make progress) |
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return; |
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... make progress ... |
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state = STATEm; |
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break; |
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... |
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} |
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so when inflate() is called again, the same case is attempted again, and |
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if the appropriate resources are provided, the machine proceeds to the |
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next state. The NEEDBITS() macro is usually the way the state evaluates |
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whether it can proceed or should return. NEEDBITS() does the return if |
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the requested bits are not available. The typical use of the BITS macros |
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is: |
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NEEDBITS(n); |
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... do something with BITS(n) ... |
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DROPBITS(n); |
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where NEEDBITS(n) either returns from inflate() if there isn't enough |
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input left to load n bits into the accumulator, or it continues. BITS(n) |
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gives the low n bits in the accumulator. When done, DROPBITS(n) drops |
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the low n bits off the accumulator. INITBITS() clears the accumulator |
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and sets the number of available bits to zero. BYTEBITS() discards just |
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enough bits to put the accumulator on a byte boundary. After BYTEBITS() |
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and a NEEDBITS(8), then BITS(8) would return the next byte in the stream. |
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NEEDBITS(n) uses PULLBYTE() to get an available byte of input, or to return |
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if there is no input available. The decoding of variable length codes uses |
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PULLBYTE() directly in order to pull just enough bytes to decode the next |
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code, and no more. |
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Some states loop until they get enough input, making sure that enough |
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state information is maintained to continue the loop where it left off |
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if NEEDBITS() returns in the loop. For example, want, need, and keep |
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would all have to actually be part of the saved state in case NEEDBITS() |
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returns: |
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case STATEw: |
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while (want < need) { |
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NEEDBITS(n); |
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keep[want++] = BITS(n); |
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DROPBITS(n); |
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} |
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state = STATEx; |
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case STATEx: |
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As shown above, if the next state is also the next case, then the break |
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is omitted. |
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A state may also return if there is not enough output space available to |
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complete that state. Those states are copying stored data, writing a |
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literal byte, and copying a matching string. |
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When returning, a "goto inf_leave" is used to update the total counters, |
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update the check value, and determine whether any progress has been made |
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during that inflate() call in order to return the proper return code. |
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Progress is defined as a change in either strm->avail_in or strm->avail_out. |
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When there is a window, goto inf_leave will update the window with the last |
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output written. If a goto inf_leave occurs in the middle of decompression |
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and there is no window currently, goto inf_leave will create one and copy |
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output to the window for the next call of inflate(). |
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In this implementation, the flush parameter of inflate() only affects the |
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return code (per zlib.h). inflate() always writes as much as possible to |
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strm->next_out, given the space available and the provided input--the effect |
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documented in zlib.h of Z_SYNC_FLUSH. Furthermore, inflate() always defers |
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the allocation of and copying into a sliding window until necessary, which |
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provides the effect documented in zlib.h for Z_FINISH when the entire input |
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stream available. So the only thing the flush parameter actually does is: |
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when flush is set to Z_FINISH, inflate() cannot return Z_OK. Instead it |
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will return Z_BUF_ERROR if it has not reached the end of the stream. |
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*/ |
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/* Wrapper function of inflateBack():
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* It is mostly copied from, and carries out the same functionality as, inflate(). |
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* It allows for stand-alone validation of infateBack(). |
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* it allows for the performance comparison of infateBackWrap() vs. |
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* inflate() under different system environments. |
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*/ |
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typedef struct { |
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unsigned char* bufPtr; |
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unsigned char* bufPtrEnd; |
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} OutBuffer; |
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/* Call - back input function for inflateBack() */ |
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local unsigned inb(void* desc, unsigned char** buf) |
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{ |
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z_stream* strm = (z_stream*)desc; |
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*buf = strm->next_in; |
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unsigned len = strm->avail_in > UINT_MAX ? UINT_MAX : (unsigned)strm->avail_in; |
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strm->next_in += len; |
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strm->avail_in -= len; |
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return len; |
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} |
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/* Call - back output function for inflateBack() */ |
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local int outb(void* desc, unsigned char* buf, unsigned len) |
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{ |
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OutBuffer* outBuf = (OutBuffer*)desc; |
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if (outBuf->bufPtr + len > outBuf->bufPtrEnd) |
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return 1; |
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zmemcpy(outBuf->bufPtr, buf, len); |
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outBuf->bufPtr += len; |
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return 0; |
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} |
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int ZEXPORT inflateBackWrap(strm, flush) |
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z_streamp strm; |
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int flush; |
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{ |
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struct inflate_state FAR* state; |
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z_const unsigned char FAR* next; /* next input */ |
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unsigned have; /* available input size */ |
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unsigned long hold; /* bit buffer */ |
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unsigned bits; /* bits in bit buffer */ |
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unsigned in, out; /* save starting available input and output */ |
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unsigned copy; /* number of stored or match bytes to copy */ |
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unsigned len; /* length to copy for repeats, bits to drop */ |
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int ret; /* return code */ |
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#ifdef GUNZIP |
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unsigned char hbuf[4]; /* buffer for gzip header crc calculation */ |
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#endif |
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if (inflateStateCheck(strm) || strm->next_out == Z_NULL || |
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(strm->next_in == Z_NULL && strm->avail_in != 0)) |
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return Z_STREAM_ERROR; |
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unsigned char dummyDict[] = ""; /*dummy Dictionary to initialize window*/ |
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updatewindow(strm, dummyDict, 0); |
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OutBuffer out_buf; |
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out_buf.bufPtr = strm->next_out; |
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out_buf.bufPtrEnd = strm->next_out + strm->avail_out; |
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state = (struct inflate_state FAR*)strm->state; |
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if (state->mode == TYPE) state->mode = TYPEDO; /* skip check */ |
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LOAD(); |
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in = have; |
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out = strm->avail_out; |
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ret = Z_OK; |
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for (;;) |
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switch (state->mode) { |
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case HEAD: |
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if (state->wrap == 0) { |
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state->mode = TYPEDO; |
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break; |
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} |
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NEEDBITS(16); |
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#ifdef GUNZIP |
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if ((state->wrap & 2) && hold == 0x8b1f) { /* gzip header */ |
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if (state->wbits == 0) |
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state->wbits = 15; |
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state->check = crc32(0L, Z_NULL, 0); |
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CRC2(state->check, hold); |
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INITBITS(); |
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state->mode = FLAGS; |
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break; |
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} |
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if (state->head != Z_NULL) |
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state->head->done = -1; |
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if (!(state->wrap & 1) || /* check if zlib header allowed */ |
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#else |
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if ( |
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#endif |
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((BITS(8) << 8) + (hold >> 8)) % 31) { |
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strm->msg = (char*)"incorrect header check"; |
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state->mode = BAD; |
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break; |
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} |
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if (BITS(4) != Z_DEFLATED) { |
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strm->msg = (char*)"unknown compression method"; |
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state->mode = BAD; |
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break; |
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} |
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DROPBITS(4); |
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len = BITS(4) + 8; |
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if (state->wbits == 0) |
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state->wbits = len; |
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if (len > 15 || len > state->wbits) { |
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strm->msg = (char*)"invalid window size"; |
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state->mode = BAD; |
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break; |
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} |
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state->dmax = 1U << len; |
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state->flags = 0; /* indicate zlib header */ |
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Tracev((stderr, "inflate: zlib header ok\n")); |
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strm->adler = state->check = adler32(0L, Z_NULL, 0); |
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state->mode = hold & 0x200 ? DICTID : TYPE; |
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INITBITS(); |
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break; |
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#ifdef GUNZIP |
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case FLAGS: |
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NEEDBITS(16); |
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state->flags = (int)(hold); |
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if ((state->flags & 0xff) != Z_DEFLATED) { |
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strm->msg = (char*)"unknown compression method"; |
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state->mode = BAD; |
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break; |
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} |
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if (state->flags & 0xe000) { |
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strm->msg = (char*)"unknown header flags set"; |
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state->mode = BAD; |
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break; |
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} |
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if (state->head != Z_NULL) |
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state->head->text = (int)((hold >> 8) & 1); |
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if ((state->flags & 0x0200) && (state->wrap & 4)) |
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CRC2(state->check, hold); |
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INITBITS(); |
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state->mode = TIME; |
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/* fallthrough */ |
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case TIME: |
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NEEDBITS(32); |
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if (state->head != Z_NULL) |
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state->head->time = hold; |
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if ((state->flags & 0x0200) && (state->wrap & 4)) |
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CRC4(state->check, hold); |
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INITBITS(); |
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state->mode = OS; |
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/* fallthrough */ |
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case OS: |
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NEEDBITS(16); |
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if (state->head != Z_NULL) { |
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state->head->xflags = (int)(hold & 0xff); |
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state->head->os = (int)(hold >> 8); |
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} |
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if ((state->flags & 0x0200) && (state->wrap & 4)) |
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CRC2(state->check, hold); |
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INITBITS(); |
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state->mode = EXLEN; |
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/* fallthrough */ |
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case EXLEN: |
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if (state->flags & 0x0400) { |
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NEEDBITS(16); |
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state->length = (unsigned)(hold); |
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if (state->head != Z_NULL) |
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state->head->extra_len = (unsigned)hold; |
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if ((state->flags & 0x0200) && (state->wrap & 4)) |
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CRC2(state->check, hold); |
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INITBITS(); |
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} |
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else if (state->head != Z_NULL) |
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state->head->extra = Z_NULL; |
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state->mode = EXTRA; |
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/* fallthrough */ |
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case EXTRA: |
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if (state->flags & 0x0400) { |
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copy = state->length; |
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if (copy > have) copy = have; |
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if (copy) { |
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if (state->head != Z_NULL && |
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state->head->extra != Z_NULL && |
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(len = state->head->extra_len - state->length) < |
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state->head->extra_max) { |
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zmemcpy(state->head->extra + len, next, |
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len + copy > state->head->extra_max ? |
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state->head->extra_max - len : copy); |
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} |
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if ((state->flags & 0x0200) && (state->wrap & 4)) |
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state->check = crc32(state->check, next, copy); |
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have -= copy; |
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next += copy; |
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state->length -= copy; |
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} |
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if (state->length) goto inf_leave; |
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} |
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state->length = 0; |
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state->mode = NAME; |
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/* fallthrough */ |
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case NAME: |
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if (state->flags & 0x0800) { |
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if (have == 0) goto inf_leave; |
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copy = 0; |
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do { |
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len = (unsigned)(next[copy++]); |
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if (state->head != Z_NULL && |
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state->head->name != Z_NULL && |
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state->length < state->head->name_max) |
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state->head->name[state->length++] = (Bytef)len; |
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} while (len && copy < have); |
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if ((state->flags & 0x0200) && (state->wrap & 4)) |
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state->check = crc32(state->check, next, copy); |
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have -= copy; |
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next += copy; |
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if (len) goto inf_leave; |
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} |
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else if (state->head != Z_NULL) |
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state->head->name = Z_NULL; |
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state->length = 0; |
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state->mode = COMMENT; |
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/* fallthrough */ |
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case COMMENT: |
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if (state->flags & 0x1000) { |
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if (have == 0) goto inf_leave; |
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copy = 0; |
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do { |
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len = (unsigned)(next[copy++]); |
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if (state->head != Z_NULL && |
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state->head->comment != Z_NULL && |
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state->length < state->head->comm_max) |
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state->head->comment[state->length++] = (Bytef)len; |
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} while (len && copy < have); |
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if ((state->flags & 0x0200) && (state->wrap & 4)) |
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state->check = crc32(state->check, next, copy); |
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have -= copy; |
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next += copy; |
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if (len) goto inf_leave; |
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} |
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else if (state->head != Z_NULL) |
||||
state->head->comment = Z_NULL; |
||||
state->mode = HCRC; |
||||
/* fallthrough */ |
||||
case HCRC: |
||||
if (state->flags & 0x0200) { |
||||
NEEDBITS(16); |
||||
if ((state->wrap & 4) && hold != (state->check & 0xffff)) { |
||||
strm->msg = (char*)"header crc mismatch"; |
||||
state->mode = BAD; |
||||
break; |
||||
} |
||||
INITBITS(); |
||||
} |
||||
if (state->head != Z_NULL) { |
||||
state->head->hcrc = (int)((state->flags >> 9) & 1); |
||||
state->head->done = 1; |
||||
} |
||||
strm->adler = state->check = crc32(0L, Z_NULL, 0); |
||||
state->mode = TYPE; |
||||
break; |
||||
#endif |
||||
case DICTID: |
||||
NEEDBITS(32); |
||||
strm->adler = state->check = ZSWAP32(hold); |
||||
INITBITS(); |
||||
state->mode = DICT; |
||||
/* fallthrough */ |
||||
case DICT: |
||||
if (state->havedict == 0) { |
||||
RESTORE(); |
||||
return Z_NEED_DICT; |
||||
} |
||||
strm->adler = state->check = adler32(0L, Z_NULL, 0); |
||||
state->mode = TYPE; |
||||
/* fallthrough */ |
||||
case TYPE: |
||||
if (flush == Z_BLOCK || flush == Z_TREES) goto inf_leave; |
||||
|
||||
|
||||
/* Call inflateBack() */ |
||||
RESTORE(); |
||||
ret = inflateBack(strm, inb, strm, outb, &out_buf); |
||||
if (ret == Z_DATA_ERROR) { |
||||
state->mode = BAD; |
||||
break; |
||||
} |
||||
LOAD(); |
||||
state->mode = CHECK; |
||||
/* fall through */ |
||||
|
||||
case CHECK: |
||||
if (state->wrap) { |
||||
NEEDBITS(32); |
||||
strm->next_out = out_buf.bufPtr; |
||||
strm->avail_out = out_buf.bufPtrEnd - out_buf.bufPtr; |
||||
out -= strm->avail_out; |
||||
strm->total_out += out; |
||||
state->total += out; |
||||
if ((state->wrap & 4) && out) |
||||
strm->adler = state->check = |
||||
UPDATE_CHECK(state->check, strm->next_out - out, out); |
||||
out = strm->avail_out; |
||||
if ((state->wrap & 4) && ( |
||||
#ifdef GUNZIP |
||||
state->flags ? hold : |
||||
#endif |
||||
ZSWAP32(hold)) != state->check) { |
||||
strm->msg = (char*)"incorrect data check"; |
||||
state->mode = BAD; |
||||
break; |
||||
} |
||||
INITBITS(); |
||||
Tracev((stderr, "inflate: check matches trailer\n")); |
||||
} |
||||
#ifdef GUNZIP |
||||
state->mode = LENGTH; |
||||
/* fallthrough */ |
||||
case LENGTH: |
||||
if (state->wrap && state->flags) { |
||||
NEEDBITS(32); |
||||
if ((state->wrap & 4) && hold != (state->total & 0xffffffff)) { |
||||
strm->msg = (char*)"incorrect length check"; |
||||
state->mode = BAD; |
||||
break; |
||||
} |
||||
INITBITS(); |
||||
Tracev((stderr, "inflate: length matches trailer\n")); |
||||
} |
||||
#endif |
||||
state->mode = DONE; |
||||
/* fallthrough */ |
||||
case DONE: |
||||
ret = Z_STREAM_END; |
||||
goto inf_leave; |
||||
case BAD: |
||||
ret = Z_DATA_ERROR; |
||||
goto inf_leave; |
||||
case MEM: |
||||
return Z_MEM_ERROR; |
||||
case SYNC: |
||||
/* fallthrough */ |
||||
default: |
||||
return Z_STREAM_ERROR; |
||||
} |
||||
|
||||
/*Return from inflate()/inflateBackWrap(), updating the total counts and the check value.
|
||||
If there was no progress during the inflate() call, return a buffer |
||||
error. Call updatewindow() to create and/or update the window state. |
||||
Note: a memory error from inflate() is non-recoverable. |
||||
*/ |
||||
inf_leave: |
||||
RESTORE(); |
||||
if (state->wsize || (out != strm->avail_out && state->mode < BAD && |
||||
(state->mode < CHECK || flush != Z_FINISH))) |
||||
if (updatewindow(strm, strm->next_out, out - strm->avail_out)) { |
||||
state->mode = MEM; |
||||
return Z_MEM_ERROR; |
||||
} |
||||
in -= strm->avail_in; |
||||
out -= strm->avail_out; |
||||
strm->total_in += in; |
||||
strm->total_out += out; |
||||
state->total += out; |
||||
if ((state->wrap & 4) && out) |
||||
strm->adler = state->check = |
||||
UPDATE_CHECK(state->check, strm->next_out - out, out); |
||||
strm->data_type = (int)state->bits + (state->last ? 64 : 0) + |
||||
(state->mode == TYPE ? 128 : 0) + |
||||
(state->mode == LEN_ || state->mode == COPY_ ? 256 : 0); |
||||
if (((in == 0 && out == 0) || flush == Z_FINISH) && ret == Z_OK) |
||||
ret = Z_BUF_ERROR; |
||||
return ret; |
||||
} |
||||
Loading…
Reference in new issue