Function gen_codes

extlibs/minizip/src/trees.c:585–620

=========================================================================== * Generate the codes for a given tree and bit counts (which need not be * optimal). * IN assertion: the array bl_count contains the bit length statistics for * the given tree and the field len is set for all tree elements. * OUT assertion: the field code is set for all tree elements of non * zero code length. */

(tree, max_code, bl_count)

 *     zero code length.
 */
local void gen_codes(tree, max_code, bl_count)
ct_data* tree; /* the tree to decorate */
int max_code; /* largest code with non zero frequency */
ushf* bl_count; /* number of codes at each bit length */
{
    ush next_code[MAX_BITS + 1]; /* next code value for each bit length */
    unsigned code = 0; /* running code value */
    int bits; /* bit index */
    int n; /* code index */

    /* The distribution counts are first used to generate the code values
     * without bit reversal.
     */
    for (bits = 1; bits <= MAX_BITS; bits++)
    {
        code = (code + bl_count[bits - 1]) << 1;
        next_code[bits] = (ush)code;
    }
    /* Check that the bit counts in bl_count are consistent. The last code
     * must be all ones.
     */
    Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1,
        "inconsistent bit counts");
    Tracev((stderr,"\ngen_codes: max_code %d ", max_code));

    for (n = 0; n <= max_code; n++)
    {
        int len = tree[n].Len;
        if (len == 0) continue;
        /* Now reverse the bits */
        tree[n].Code = (ush)bi_reverse(next_code[len]++, len);

        Tracecv(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ",
            n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1));
    }
}

/* ===========================================================================
 * Construct one Huffman tree and assigns the code bit strings and lengths.