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Diffstat (limited to 'libpng/inftrees.c')
| -rw-r--r-- | libpng/inftrees.c | 329 |
1 files changed, 0 insertions, 329 deletions
diff --git a/libpng/inftrees.c b/libpng/inftrees.c deleted file mode 100644 index 8a9c13f..0000000 --- a/libpng/inftrees.c +++ /dev/null @@ -1,329 +0,0 @@ -/* inftrees.c -- generate Huffman trees for efficient decoding - * Copyright (C) 1995-2005 Mark Adler - * For conditions of distribution and use, see copyright notice in zlib.h - */ - -#include "zutil.h" -#include "inftrees.h" - -#define MAXBITS 15 - -const char inflate_copyright[] = - " inflate 1.2.3 Copyright 1995-2005 Mark Adler "; -/* - If you use the zlib library in a product, an acknowledgment is welcome - in the documentation of your product. If for some reason you cannot - include such an acknowledgment, I would appreciate that you keep this - copyright string in the executable of your product. - */ - -/* - Build a set of tables to decode the provided canonical Huffman code. - The code lengths are lens[0..codes-1]. The result starts at *table, - whose indices are 0..2^bits-1. work is a writable array of at least - lens shorts, which is used as a work area. type is the type of code - to be generated, CODES, LENS, or DISTS. On return, zero is success, - -1 is an invalid code, and +1 means that ENOUGH isn't enough. table - on return points to the next available entry's address. bits is the - requested root table index bits, and on return it is the actual root - table index bits. It will differ if the request is greater than the - longest code or if it is less than the shortest code. - */ -int inflate_table(type, lens, codes, table, bits, work) -codetype type; -unsigned short FAR *lens; -unsigned codes; -code FAR * FAR *table; -unsigned FAR *bits; -unsigned short FAR *work; -{ - unsigned len; /* a code's length in bits */ - unsigned sym; /* index of code symbols */ - unsigned min, max; /* minimum and maximum code lengths */ - unsigned root; /* number of index bits for root table */ - unsigned curr; /* number of index bits for current table */ - unsigned drop; /* code bits to drop for sub-table */ - int left; /* number of prefix codes available */ - unsigned used; /* code entries in table used */ - unsigned huff; /* Huffman code */ - unsigned incr; /* for incrementing code, index */ - unsigned fill; /* index for replicating entries */ - unsigned low; /* low bits for current root entry */ - unsigned mask; /* mask for low root bits */ - code this; /* table entry for duplication */ - code FAR *next; /* next available space in table */ - const unsigned short FAR *base; /* base value table to use */ - const unsigned short FAR *extra; /* extra bits table to use */ - int end; /* use base and extra for symbol > end */ - unsigned short count[MAXBITS+1]; /* number of codes of each length */ - unsigned short offs[MAXBITS+1]; /* offsets in table for each length */ - static const unsigned short lbase[31] = { /* Length codes 257..285 base */ - 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31, - 35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258, 0, 0}; - static const unsigned short lext[31] = { /* Length codes 257..285 extra */ - 16, 16, 16, 16, 16, 16, 16, 16, 17, 17, 17, 17, 18, 18, 18, 18, - 19, 19, 19, 19, 20, 20, 20, 20, 21, 21, 21, 21, 16, 201, 196}; - static const unsigned short dbase[32] = { /* Distance codes 0..29 base */ - 1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193, - 257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145, - 8193, 12289, 16385, 24577, 0, 0}; - static const unsigned short dext[32] = { /* Distance codes 0..29 extra */ - 16, 16, 16, 16, 17, 17, 18, 18, 19, 19, 20, 20, 21, 21, 22, 22, - 23, 23, 24, 24, 25, 25, 26, 26, 27, 27, - 28, 28, 29, 29, 64, 64}; - - /* - Process a set of code lengths to create a canonical Huffman code. The - code lengths are lens[0..codes-1]. Each length corresponds to the - symbols 0..codes-1. The Huffman code is generated by first sorting the - symbols by length from short to long, and retaining the symbol order - for codes with equal lengths. Then the code starts with all zero bits - for the first code of the shortest length, and the codes are integer - increments for the same length, and zeros are appended as the length - increases. For the deflate format, these bits are stored backwards - from their more natural integer increment ordering, and so when the - decoding tables are built in the large loop below, the integer codes - are incremented backwards. - - This routine assumes, but does not check, that all of the entries in - lens[] are in the range 0..MAXBITS. The caller must assure this. - 1..MAXBITS is interpreted as that code length. zero means that that - symbol does not occur in this code. - - The codes are sorted by computing a count of codes for each length, - creating from that a table of starting indices for each length in the - sorted table, and then entering the symbols in order in the sorted - table. The sorted table is work[], with that space being provided by - the caller. - - The length counts are used for other purposes as well, i.e. finding - the minimum and maximum length codes, determining if there are any - codes at all, checking for a valid set of lengths, and looking ahead - at length counts to determine sub-table sizes when building the - decoding tables. - */ - - /* accumulate lengths for codes (assumes lens[] all in 0..MAXBITS) */ - for (len = 0; len <= MAXBITS; len++) - count[len] = 0; - for (sym = 0; sym < codes; sym++) - count[lens[sym]]++; - - /* bound code lengths, force root to be within code lengths */ - root = *bits; - for (max = MAXBITS; max >= 1; max--) - if (count[max] != 0) break; - if (root > max) root = max; - if (max == 0) { /* no symbols to code at all */ - this.op = (unsigned char)64; /* invalid code marker */ - this.bits = (unsigned char)1; - this.val = (unsigned short)0; - *(*table)++ = this; /* make a table to force an error */ - *(*table)++ = this; - *bits = 1; - return 0; /* no symbols, but wait for decoding to report error */ - } - for (min = 1; min <= MAXBITS; min++) - if (count[min] != 0) break; - if (root < min) root = min; - - /* check for an over-subscribed or incomplete set of lengths */ - left = 1; - for (len = 1; len <= MAXBITS; len++) { - left <<= 1; - left -= count[len]; - if (left < 0) return -1; /* over-subscribed */ - } - if (left > 0 && (type == CODES || max != 1)) - return -1; /* incomplete set */ - - /* generate offsets into symbol table for each length for sorting */ - offs[1] = 0; - for (len = 1; len < MAXBITS; len++) - offs[len + 1] = offs[len] + count[len]; - - /* sort symbols by length, by symbol order within each length */ - for (sym = 0; sym < codes; sym++) - if (lens[sym] != 0) work[offs[lens[sym]]++] = (unsigned short)sym; - - /* - Create and fill in decoding tables. In this loop, the table being - filled is at next and has curr index bits. The code being used is huff - with length len. That code is converted to an index by dropping drop - bits off of the bottom. For codes where len is less than drop + curr, - those top drop + curr - len bits are incremented through all values to - fill the table with replicated entries. - - root is the number of index bits for the root table. When len exceeds - root, sub-tables are created pointed to by the root entry with an index - of the low root bits of huff. This is saved in low to check for when a - new sub-table should be started. drop is zero when the root table is - being filled, and drop is root when sub-tables are being filled. - - When a new sub-table is needed, it is necessary to look ahead in the - code lengths to determine what size sub-table is needed. The length - counts are used for this, and so count[] is decremented as codes are - entered in the tables. - - used keeps track of how many table entries have been allocated from the - provided *table space. It is checked when a LENS table is being made - against the space in *table, ENOUGH, minus the maximum space needed by - the worst case distance code, MAXD. This should never happen, but the - sufficiency of ENOUGH has not been proven exhaustively, hence the check. - This assumes that when type == LENS, bits == 9. - - sym increments through all symbols, and the loop terminates when - all codes of length max, i.e. all codes, have been processed. This - routine permits incomplete codes, so another loop after this one fills - in the rest of the decoding tables with invalid code markers. - */ - - /* set up for code type */ - switch (type) { - case CODES: - base = extra = work; /* dummy value--not used */ - end = 19; - break; - case LENS: - base = lbase; - base -= 257; - extra = lext; - extra -= 257; - end = 256; - break; - default: /* DISTS */ - base = dbase; - extra = dext; - end = -1; - } - - /* initialize state for loop */ - huff = 0; /* starting code */ - sym = 0; /* starting code symbol */ - len = min; /* starting code length */ - next = *table; /* current table to fill in */ - curr = root; /* current table index bits */ - drop = 0; /* current bits to drop from code for index */ - low = (unsigned)(-1); /* trigger new sub-table when len > root */ - used = 1U << root; /* use root table entries */ - mask = used - 1; /* mask for comparing low */ - - /* check available table space */ - if (type == LENS && used >= ENOUGH - MAXD) - return 1; - - /* process all codes and make table entries */ - for (;;) { - /* create table entry */ - this.bits = (unsigned char)(len - drop); - if ((int)(work[sym]) < end) { - this.op = (unsigned char)0; - this.val = work[sym]; - } - else if ((int)(work[sym]) > end) { - this.op = (unsigned char)(extra[work[sym]]); - this.val = base[work[sym]]; - } - else { - this.op = (unsigned char)(32 + 64); /* end of block */ - this.val = 0; - } - - /* replicate for those indices with low len bits equal to huff */ - incr = 1U << (len - drop); - fill = 1U << curr; - min = fill; /* save offset to next table */ - do { - fill -= incr; - next[(huff >> drop) + fill] = this; - } while (fill != 0); - - /* backwards increment the len-bit code huff */ - incr = 1U << (len - 1); - while (huff & incr) - incr >>= 1; - if (incr != 0) { - huff &= incr - 1; - huff += incr; - } - else - huff = 0; - - /* go to next symbol, update count, len */ - sym++; - if (--(count[len]) == 0) { - if (len == max) break; - len = lens[work[sym]]; - } - - /* create new sub-table if needed */ - if (len > root && (huff & mask) != low) { - /* if first time, transition to sub-tables */ - if (drop == 0) - drop = root; - - /* increment past last table */ - next += min; /* here min is 1 << curr */ - - /* determine length of next table */ - curr = len - drop; - left = (int)(1 << curr); - while (curr + drop < max) { - left -= count[curr + drop]; - if (left <= 0) break; - curr++; - left <<= 1; - } - - /* check for enough space */ - used += 1U << curr; - if (type == LENS && used >= ENOUGH - MAXD) - return 1; - - /* point entry in root table to sub-table */ - low = huff & mask; - (*table)[low].op = (unsigned char)curr; - (*table)[low].bits = (unsigned char)root; - (*table)[low].val = (unsigned short)(next - *table); - } - } - - /* - Fill in rest of table for incomplete codes. This loop is similar to the - loop above in incrementing huff for table indices. It is assumed that - len is equal to curr + drop, so there is no loop needed to increment - through high index bits. When the current sub-table is filled, the loop - drops back to the root table to fill in any remaining entries there. - */ - this.op = (unsigned char)64; /* invalid code marker */ - this.bits = (unsigned char)(len - drop); - this.val = (unsigned short)0; - while (huff != 0) { - /* when done with sub-table, drop back to root table */ - if (drop != 0 && (huff & mask) != low) { - drop = 0; - len = root; - next = *table; - this.bits = (unsigned char)len; - } - - /* put invalid code marker in table */ - next[huff >> drop] = this; - - /* backwards increment the len-bit code huff */ - incr = 1U << (len - 1); - while (huff & incr) - incr >>= 1; - if (incr != 0) { - huff &= incr - 1; - huff += incr; - } - else - huff = 0; - } - - /* set return parameters */ - *table += used; - *bits = root; - return 0; -} |