Coverage Report

Created: 2024-05-04 12:45

/proc/self/cwd/external/zlib/inftrees.c
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/* inftrees.c -- generate Huffman trees for efficient decoding
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 * Copyright (C) 1995-2022 Mark Adler
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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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689k
#define MAXBITS 15
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const char inflate_copyright[] =
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   " inflate 1.2.13 Copyright 1995-2022 Mark Adler ";
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/*
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  If you use the zlib library in a product, an acknowledgment is welcome
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  in the documentation of your product. If for some reason you cannot
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  include such an acknowledgment, I would appreciate that you keep this
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  copyright string in the executable of your product.
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 */
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/*
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   Build a set of tables to decode the provided canonical Huffman code.
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   The code lengths are lens[0..codes-1].  The result starts at *table,
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   whose indices are 0..2^bits-1.  work is a writable array of at least
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   lens shorts, which is used as a work area.  type is the type of code
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   to be generated, CODES, LENS, or DISTS.  On return, zero is success,
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   -1 is an invalid code, and +1 means that ENOUGH isn't enough.  table
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   on return points to the next available entry's address.  bits is the
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   requested root table index bits, and on return it is the actual root
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   table index bits.  It will differ if the request is greater than the
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   longest code or if it is less than the shortest code.
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 */
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int ZLIB_INTERNAL inflate_table(type, lens, codes, table, bits, work)
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codetype type;
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unsigned short FAR *lens;
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unsigned codes;
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code FAR * FAR *table;
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unsigned FAR *bits;
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unsigned short FAR *work;
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14.7k
{
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14.7k
    unsigned len;               /* a code's length in bits */
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14.7k
    unsigned sym;               /* index of code symbols */
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14.7k
    unsigned min, max;          /* minimum and maximum code lengths */
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14.7k
    unsigned root;              /* number of index bits for root table */
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14.7k
    unsigned curr;              /* number of index bits for current table */
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14.7k
    unsigned drop;              /* code bits to drop for sub-table */
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14.7k
    int left;                   /* number of prefix codes available */
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14.7k
    unsigned used;              /* code entries in table used */
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14.7k
    unsigned huff;              /* Huffman code */
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14.7k
    unsigned incr;              /* for incrementing code, index */
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14.7k
    unsigned fill;              /* index for replicating entries */
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14.7k
    unsigned low;               /* low bits for current root entry */
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14.7k
    unsigned mask;              /* mask for low root bits */
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14.7k
    code here;                  /* table entry for duplication */
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14.7k
    code FAR *next;             /* next available space in table */
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14.7k
    const unsigned short FAR *base;     /* base value table to use */
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14.7k
    const unsigned short FAR *extra;    /* extra bits table to use */
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14.7k
    unsigned match;             /* use base and extra for symbol >= match */
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14.7k
    unsigned short count[MAXBITS+1];    /* number of codes of each length */
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14.7k
    unsigned short offs[MAXBITS+1];     /* offsets in table for each length */
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14.7k
    static const unsigned short lbase[31] = { /* Length codes 257..285 base */
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14.7k
        3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31,
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        35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258, 0, 0};
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14.7k
    static const unsigned short lext[31] = { /* Length codes 257..285 extra */
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        16, 16, 16, 16, 16, 16, 16, 16, 17, 17, 17, 17, 18, 18, 18, 18,
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        19, 19, 19, 19, 20, 20, 20, 20, 21, 21, 21, 21, 16, 194, 65};
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    static const unsigned short dbase[32] = { /* Distance codes 0..29 base */
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        1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193,
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        257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145,
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        8193, 12289, 16385, 24577, 0, 0};
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    static const unsigned short dext[32] = { /* Distance codes 0..29 extra */
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        16, 16, 16, 16, 17, 17, 18, 18, 19, 19, 20, 20, 21, 21, 22, 22,
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        23, 23, 24, 24, 25, 25, 26, 26, 27, 27,
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        28, 28, 29, 29, 64, 64};
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    /*
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       Process a set of code lengths to create a canonical Huffman code.  The
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       code lengths are lens[0..codes-1].  Each length corresponds to the
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       symbols 0..codes-1.  The Huffman code is generated by first sorting the
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       symbols by length from short to long, and retaining the symbol order
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       for codes with equal lengths.  Then the code starts with all zero bits
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       for the first code of the shortest length, and the codes are integer
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       increments for the same length, and zeros are appended as the length
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       increases.  For the deflate format, these bits are stored backwards
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       from their more natural integer increment ordering, and so when the
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       decoding tables are built in the large loop below, the integer codes
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       are incremented backwards.
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       This routine assumes, but does not check, that all of the entries in
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       lens[] are in the range 0..MAXBITS.  The caller must assure this.
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       1..MAXBITS is interpreted as that code length.  zero means that that
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       symbol does not occur in this code.
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       The codes are sorted by computing a count of codes for each length,
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       creating from that a table of starting indices for each length in the
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       sorted table, and then entering the symbols in order in the sorted
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       table.  The sorted table is work[], with that space being provided by
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       the caller.
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       The length counts are used for other purposes as well, i.e. finding
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       the minimum and maximum length codes, determining if there are any
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       codes at all, checking for a valid set of lengths, and looking ahead
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       at length counts to determine sub-table sizes when building the
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       decoding tables.
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     */
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    /* accumulate lengths for codes (assumes lens[] all in 0..MAXBITS) */
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250k
    for (len = 0; len <= MAXBITS; len++)
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235k
        count[len] = 0;
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1.41M
    for (sym = 0; sym < codes; sym++)
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1.40M
        count[lens[sym]]++;
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    /* bound code lengths, force root to be within code lengths */
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14.7k
    root = *bits;
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128k
    for (max = MAXBITS; max >= 1; max--)
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128k
        if (count[max] != 0) break;
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14.7k
    if (root > max) root = max;
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    if (max == 0) {                     /* no symbols to code at all */
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        here.op = (unsigned char)64;    /* invalid code marker */
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        here.bits = (unsigned char)1;
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        here.val = (unsigned short)0;
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        *(*table)++ = here;             /* make a table to force an error */
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        *(*table)++ = here;
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        *bits = 1;
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        return 0;     /* no symbols, but wait for decoding to report error */
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    }
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31.1k
    for (min = 1; min < max; min++)
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        if (count[min] != 0) break;
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    if (root < min) root = min;
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    /* check for an over-subscribed or incomplete set of lengths */
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14.4k
    left = 1;
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224k
    for (len = 1; len <= MAXBITS; len++) {
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210k
        left <<= 1;
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210k
        left -= count[len];
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210k
        if (left < 0) return -1;        /* over-subscribed */
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210k
    }
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13.7k
    if (left > 0 && (type == CODES || max != 1))
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        return -1;                      /* incomplete set */
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    /* generate offsets into symbol table for each length for sorting */
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13.3k
    offs[1] = 0;
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200k
    for (len = 1; len < MAXBITS; len++)
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186k
        offs[len + 1] = offs[len] + count[len];
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    /* sort symbols by length, by symbol order within each length */
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1.35M
    for (sym = 0; sym < codes; sym++)
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1.34M
        if (lens[sym] != 0) work[offs[lens[sym]]++] = (unsigned short)sym;
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    /*
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       Create and fill in decoding tables.  In this loop, the table being
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       filled is at next and has curr index bits.  The code being used is huff
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       with length len.  That code is converted to an index by dropping drop
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       bits off of the bottom.  For codes where len is less than drop + curr,
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       those top drop + curr - len bits are incremented through all values to
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       fill the table with replicated entries.
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       root is the number of index bits for the root table.  When len exceeds
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       root, sub-tables are created pointed to by the root entry with an index
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       of the low root bits of huff.  This is saved in low to check for when a
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       new sub-table should be started.  drop is zero when the root table is
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       being filled, and drop is root when sub-tables are being filled.
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       When a new sub-table is needed, it is necessary to look ahead in the
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       code lengths to determine what size sub-table is needed.  The length
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       counts are used for this, and so count[] is decremented as codes are
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       entered in the tables.
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       used keeps track of how many table entries have been allocated from the
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       provided *table space.  It is checked for LENS and DIST tables against
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       the constants ENOUGH_LENS and ENOUGH_DISTS to guard against changes in
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       the initial root table size constants.  See the comments in inftrees.h
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       for more information.
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       sym increments through all symbols, and the loop terminates when
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       all codes of length max, i.e. all codes, have been processed.  This
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       routine permits incomplete codes, so another loop after this one fills
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       in the rest of the decoding tables with invalid code markers.
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     */
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    /* set up for code type */
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13.3k
    switch (type) {
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5.47k
    case CODES:
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5.47k
        base = extra = work;    /* dummy value--not used */
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5.47k
        match = 20;
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5.47k
        break;
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4.05k
    case LENS:
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4.05k
        base = lbase;
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        extra = lext;
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4.05k
        match = 257;
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4.05k
        break;
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3.81k
    default:    /* DISTS */
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3.81k
        base = dbase;
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        extra = dext;
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        match = 0;
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    }
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    /* initialize state for loop */
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13.3k
    huff = 0;                   /* starting code */
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13.3k
    sym = 0;                    /* starting code symbol */
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13.3k
    len = min;                  /* starting code length */
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13.3k
    next = *table;              /* current table to fill in */
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13.3k
    curr = root;                /* current table index bits */
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13.3k
    drop = 0;                   /* current bits to drop from code for index */
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13.3k
    low = (unsigned)(-1);       /* trigger new sub-table when len > root */
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13.3k
    used = 1U << root;          /* use root table entries */
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13.3k
    mask = used - 1;            /* mask for comparing low */
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    /* check available table space */
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13.3k
    if ((type == LENS && used > ENOUGH_LENS) ||
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13.3k
        (type == DISTS && used > ENOUGH_DISTS))
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0
        return 1;
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    /* process all codes and make table entries */
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908k
    for (;;) {
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        /* create table entry */
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908k
        here.bits = (unsigned char)(len - drop);
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908k
        if (work[sym] + 1U < match) {
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766k
            here.op = (unsigned char)0;
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766k
            here.val = work[sym];
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766k
        }
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141k
        else if (work[sym] >= match) {
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137k
            here.op = (unsigned char)(extra[work[sym] - match]);
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137k
            here.val = base[work[sym] - match];
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137k
        }
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4.05k
        else {
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4.05k
            here.op = (unsigned char)(32 + 64);         /* end of block */
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4.05k
            here.val = 0;
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4.05k
        }
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        /* replicate for those indices with low len bits equal to huff */
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908k
        incr = 1U << (len - drop);
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908k
        fill = 1U << curr;
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908k
        min = fill;                 /* save offset to next table */
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2.30M
        do {
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2.30M
            fill -= incr;
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2.30M
            next[(huff >> drop) + fill] = here;
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2.30M
        } while (fill != 0);
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        /* backwards increment the len-bit code huff */
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908k
        incr = 1U << (len - 1);
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1.80M
        while (huff & incr)
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895k
            incr >>= 1;
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908k
        if (incr != 0) {
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895k
            huff &= incr - 1;
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895k
            huff += incr;
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895k
        }
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13.1k
        else
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13.1k
            huff = 0;
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        /* go to next symbol, update count, len */
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908k
        sym++;
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908k
        if (--(count[len]) == 0) {
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74.7k
            if (len == max) break;
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61.4k
            len = lens[work[sym]];
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61.4k
        }
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        /* create new sub-table if needed */
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895k
        if (len > root && (huff & mask) != low) {
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            /* if first time, transition to sub-tables */
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84.0k
            if (drop == 0)
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5.49k
                drop = root;
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            /* increment past last table */
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84.0k
            next += min;            /* here min is 1 << curr */
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            /* determine length of next table */
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84.0k
            curr = len - drop;
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84.0k
            left = (int)(1 << curr);
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98.3k
            while (curr + drop < max) {
270
90.2k
                left -= count[curr + drop];
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90.2k
                if (left <= 0) break;
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14.3k
                curr++;
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14.3k
                left <<= 1;
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14.3k
            }
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            /* check for enough space */
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84.0k
            used += 1U << curr;
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84.0k
            if ((type == LENS && used > ENOUGH_LENS) ||
279
84.0k
                (type == DISTS && used > ENOUGH_DISTS))
280
0
                return 1;
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282
            /* point entry in root table to sub-table */
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84.0k
            low = huff & mask;
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84.0k
            (*table)[low].op = (unsigned char)curr;
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84.0k
            (*table)[low].bits = (unsigned char)root;
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84.0k
            (*table)[low].val = (unsigned short)(next - *table);
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84.0k
        }
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895k
    }
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290
    /* fill in remaining table entry if code is incomplete (guaranteed to have
291
       at most one remaining entry, since if the code is incomplete, the
292
       maximum code length that was allowed to get this far is one bit) */
293
13.3k
    if (huff != 0) {
294
221
        here.op = (unsigned char)64;            /* invalid code marker */
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221
        here.bits = (unsigned char)(len - drop);
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221
        here.val = (unsigned short)0;
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221
        next[huff] = here;
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221
    }
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300
    /* set return parameters */
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13.3k
    *table += used;
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13.3k
    *bits = root;
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13.3k
    return 0;
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13.3k
}