+ ...
+ }
+
+ so when inflate() is called again, the same case is attempted again, and
+ if the appropriate resources are provided, the machine proceeds to the
+ next state. The NEEDBITS() macro is usually the way the state evaluates
+ whether it can proceed or should return. NEEDBITS() does the return if
+ the requested bits are not available. The typical use of the BITS macros
+ is:
+
+ NEEDBITS(n);
+ ... do something with BITS(n) ...
+ DROPBITS(n);
+
+ where NEEDBITS(n) either returns from inflate() if there isn't enough
+ input left to load n bits into the accumulator, or it continues. BITS(n)
+ gives the low n bits in the accumulator. When done, DROPBITS(n) drops
+ the low n bits off the accumulator. INITBITS() clears the accumulator
+ and sets the number of available bits to zero. BYTEBITS() discards just
+ enough bits to put the accumulator on a byte boundary. After BYTEBITS()
+ and a NEEDBITS(8), then BITS(8) would return the next byte in the stream.
+
+ NEEDBITS(n) uses PULLBYTE() to get an available byte of input, or to return
+ if there is no input available. The decoding of variable length codes uses
+ PULLBYTE() directly in order to pull just enough bytes to decode the next
+ code, and no more.
+
+ Some states loop until they get enough input, making sure that enough
+ state information is maintained to continue the loop where it left off
+ if NEEDBITS() returns in the loop. For example, want, need, and keep
+ would all have to actually be part of the saved state in case NEEDBITS()
+ returns:
+
+ case STATEw:
+ while (want < need) {
+ NEEDBITS(n);
+ keep[want++] = BITS(n);
+ DROPBITS(n);
+ }
+ state = STATEx;
+ case STATEx:
+
+ As shown above, if the next state is also the next case, then the break
+ is omitted.
+
+ A state may also return if there is not enough output space available to
+ complete that state. Those states are copying stored data, writing a
+ literal byte, and copying a matching string.
+
+ When returning, a "goto inf_leave" is used to update the total counters,
+ update the check value, and determine whether any progress has been made
+ during that inflate() call in order to return the proper return code.
+ Progress is defined as a change in either strm->avail_in or strm->avail_out.
+ When there is a window, goto inf_leave will update the window with the last
+ output written. If a goto inf_leave occurs in the middle of decompression
+ and there is no window currently, goto inf_leave will create one and copy
+ output to the window for the next call of inflate().
+
+ In this implementation, the flush parameter of inflate() only affects the
+ return code (per zlib.h). inflate() always writes as much as possible to
+ strm->next_out, given the space available and the provided input--the effect
+ documented in zlib.h of Z_SYNC_FLUSH. Furthermore, inflate() always defers
+ the allocation of and copying into a sliding window until necessary, which
+ provides the effect documented in zlib.h for Z_FINISH when the entire input
+ stream available. So the only thing the flush parameter actually does is:
+ when flush is set to Z_FINISH, inflate() cannot return Z_OK. Instead it
+ will return Z_BUF_ERROR if it has not reached the end of the stream.
+ */
+
+int ZEXPORT inflate(strm, flush)
+z_streamp strm;
+int flush;
+{
+ struct inflate_state FAR *state;
+ unsigned char FAR *next; /* next input */
+ unsigned char FAR *put; /* next output */
+ unsigned have, left; /* available input and output */
+ unsigned long hold; /* bit buffer */
+ unsigned bits; /* bits in bit buffer */
+ unsigned in, out; /* save starting available input and output */
+ unsigned copy; /* number of stored or match bytes to copy */
+ unsigned char FAR *from; /* where to copy match bytes from */
+ code this; /* current decoding table entry */
+ code last; /* parent table entry */
+ unsigned len; /* length to copy for repeats, bits to drop */
+ int ret; /* return code */
+#ifdef GUNZIP
+ unsigned char hbuf[4]; /* buffer for gzip header crc calculation */
+#endif
+ static const unsigned short order[19] = /* permutation of code lengths */
+ {16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15};
+
+ if (strm == Z_NULL || strm->state == Z_NULL || strm->next_out == Z_NULL ||
+ (strm->next_in == Z_NULL && strm->avail_in != 0))
+ return Z_STREAM_ERROR;
+
+ state = (struct inflate_state FAR *)strm->state;
+ if (state->mode == TYPE) state->mode = TYPEDO; /* skip check */
+ LOAD();
+ in = have;
+ out = left;
+ ret = Z_OK;
+ for (;;)
+ switch (state->mode) {
+ case HEAD:
+ if (state->wrap == 0) {
+ state->mode = TYPEDO;
+ break;
+ }
+ NEEDBITS(16);
+#ifdef GUNZIP
+ if ((state->wrap & 2) && hold == 0x8b1f) { /* gzip header */
+ state->check = crc32(0L, Z_NULL, 0);
+ CRC2(state->check, hold);
+ INITBITS();
+ state->mode = FLAGS;
+ break;
+ }
+ state->flags = 0; /* expect zlib header */
+ if (!(state->wrap & 1) || /* check if zlib header allowed */
+#else
+ if (
+#endif
+ ((BITS(8) << 8) + (hold >> 8)) % 31) {
+ strm->msg = (char *)"incorrect header check";
+ state->mode = BAD;
+ break;
+ }
+ if (BITS(4) != Z_DEFLATED) {
+ strm->msg = (char *)"unknown compression method";
+ state->mode = BAD;
+ break;
+ }
+ DROPBITS(4);
+ if (BITS(4) + 8 > state->wbits) {
+ strm->msg = (char *)"invalid window size";
+ state->mode = BAD;
+ break;
+ }
+ Tracev((stderr, "inflate: zlib header ok\n"));
+ strm->adler = state->check = adler32(0L, Z_NULL, 0);
+ state->mode = hold & 0x200 ? DICTID : TYPE;
+ INITBITS();
+ break;
+#ifdef GUNZIP
+ case FLAGS:
+ NEEDBITS(16);
+ state->flags = (int)(hold);
+ if ((state->flags & 0xff) != Z_DEFLATED) {
+ strm->msg = (char *)"unknown compression method";
+ state->mode = BAD;
+ break;
+ }
+ if (state->flags & 0xe000) {
+ strm->msg = (char *)"unknown header flags set";
+ state->mode = BAD;
+ break;
+ }
+ if (state->flags & 0x0200) CRC2(state->check, hold);
+ INITBITS();
+ state->mode = TIME;
+ case TIME:
+ NEEDBITS(32);
+ if (state->flags & 0x0200) CRC4(state->check, hold);
+ INITBITS();
+ state->mode = OS;
+ case OS:
+ NEEDBITS(16);
+ if (state->flags & 0x0200) CRC2(state->check, hold);
+ INITBITS();
+ state->mode = EXLEN;
+ case EXLEN:
+ if (state->flags & 0x0400) {
+ NEEDBITS(16);
+ state->length = (unsigned)(hold);
+ if (state->flags & 0x0200) CRC2(state->check, hold);
+ INITBITS();
+ }
+ state->mode = EXTRA;
+ case EXTRA:
+ if (state->flags & 0x0400) {
+ copy = state->length;
+ if (copy > have) copy = have;
+ if (copy) {
+ if (state->flags & 0x0200)
+ state->check = crc32(state->check, next, copy);
+ have -= copy;
+ next += copy;
+ state->length -= copy;
+ }
+ if (state->length) goto inf_leave;
+ }
+ state->mode = NAME;
+ case NAME:
+ if (state->flags & 0x0800) {
+ if (have == 0) goto inf_leave;
+ copy = 0;
+ do {
+ len = (unsigned)(next[copy++]);
+ } while (len && copy < have);
+ if (state->flags & 0x02000)
+ state->check = crc32(state->check, next, copy);
+ have -= copy;
+ next += copy;
+ if (len) goto inf_leave;
+ }
+ state->mode = COMMENT;
+ case COMMENT:
+ if (state->flags & 0x1000) {
+ if (have == 0) goto inf_leave;
+ copy = 0;
+ do {
+ len = (unsigned)(next[copy++]);
+ } while (len && copy < have);
+ if (state->flags & 0x02000)
+ state->check = crc32(state->check, next, copy);
+ have -= copy;
+ next += copy;
+ if (len) goto inf_leave;
+ }
+ state->mode = HCRC;
+ case HCRC:
+ if (state->flags & 0x0200) {
+ NEEDBITS(16);
+ if (hold != (state->check & 0xffff)) {
+ strm->msg = (char *)"header crc mismatch";
+ state->mode = BAD;
+ break;
+ }
+ INITBITS();
+ }
+ strm->adler = state->check = crc32(0L, Z_NULL, 0);
+ state->mode = TYPE;
+ break;
+#endif
+ case DICTID:
+ NEEDBITS(32);
+ strm->adler = state->check = REVERSE(hold);
+ INITBITS();
+ state->mode = DICT;
+ case DICT:
+ if (state->havedict == 0) {
+ RESTORE();
+ return Z_NEED_DICT;
+ }
+ strm->adler = state->check = adler32(0L, Z_NULL, 0);
+ state->mode = TYPE;
+ case TYPE:
+ if (flush == Z_BLOCK) goto inf_leave;
+ case TYPEDO:
+ if (state->last) {
+ BYTEBITS();
+ state->mode = CHECK;
+ break;
+ }
+ NEEDBITS(3);
+ state->last = BITS(1);
+ DROPBITS(1);
+ switch (BITS(2)) {
+ case 0: /* stored block */
+ Tracev((stderr, "inflate: stored block%s\n",
+ state->last ? " (last)" : ""));
+ state->mode = STORED;
+ break;
+ case 1: /* fixed block */
+ fixedtables(state);
+ Tracev((stderr, "inflate: fixed codes block%s\n",
+ state->last ? " (last)" : ""));
+ state->mode = LEN; /* decode codes */
+ break;
+ case 2: /* dynamic block */
+ Tracev((stderr, "inflate: dynamic codes block%s\n",
+ state->last ? " (last)" : ""));
+ state->mode = TABLE;
+ break;
+ case 3:
+ strm->msg = (char *)"invalid block type";
+ state->mode = BAD;
+ }
+ DROPBITS(2);
+ break;
+ case STORED:
+ BYTEBITS(); /* go to byte boundary */
+ NEEDBITS(32);
+ if ((hold & 0xffff) != ((hold >> 16) ^ 0xffff)) {
+ strm->msg = (char *)"invalid stored block lengths";
+ state->mode = BAD;
+ break;
+ }
+ state->length = (unsigned)hold & 0xffff;
+ Tracev((stderr, "inflate: stored length %u\n",
+ state->length));
+ INITBITS();
+ state->mode = COPY;
+ case COPY:
+ copy = state->length;
+ if (copy) {
+ if (copy > have) copy = have;
+ if (copy > left) copy = left;
+ if (copy == 0) goto inf_leave;
+ zmemcpy(put, next, copy);
+ have -= copy;
+ next += copy;
+ left -= copy;
+ put += copy;
+ state->length -= copy;
+ break;
+ }
+ Tracev((stderr, "inflate: stored end\n"));
+ state->mode = TYPE;
+ break;
+ case TABLE:
+ NEEDBITS(14);
+ state->nlen = BITS(5) + 257;
+ DROPBITS(5);
+ state->ndist = BITS(5) + 1;
+ DROPBITS(5);
+ state->ncode = BITS(4) + 4;
+ DROPBITS(4);
+#ifndef PKZIP_BUG_WORKAROUND
+ if (state->nlen > 286 || state->ndist > 30) {
+ strm->msg = (char *)"too many length or distance symbols";
+ state->mode = BAD;
+ break;
+ }
projects / wxWidgets.git / blobdiff