windows-server-2003/base/mspatch/lzx/decoder/decinit.c

/*
 * decinit.c
 *
 * Initialisation routines for LZX decoder
 */

#include "decoder.h"

#include <memory.h>
#pragma intrinsic(memset)

/*
 * Allocate memory for decompression
 */
bool NEAR allocate_decompression_memory(t_decoder_context *context)
{
    ulong   pos_start;

    context->dec_num_position_slots = 4;
    pos_start                                               = 4;

    while (1)
        {
        pos_start += 1L << dec_extra_bits[context->dec_num_position_slots];

        context->dec_num_position_slots++;

        if (pos_start >= context->dec_window_size)
            break;
        }

    if (!(context->dec_mem_window = (byte *) context->dec_malloc( context->dec_mallochandle, context->dec_window_size+(MAX_MATCH+4))))
        return false;

    return true;
}



/*
 * Set/reset decoder trees to initial state
 */
void NEAR reset_decoder_trees(t_decoder_context *context)
{
    memset(context->dec_main_tree_len, 0, MAIN_TREE_ELEMENTS);
    memset(context->dec_main_tree_prev_len, 0, MAIN_TREE_ELEMENTS);

    memset(context->dec_secondary_length_tree_len, 0, NUM_SECONDARY_LENGTHS);
    memset(context->dec_secondary_length_tree_prev_len, 0, NUM_SECONDARY_LENGTHS);
}


/*
 * Miscellaneous state initialisations
 */
void NEAR decoder_misc_init(t_decoder_context *context)
{
    context->dec_last_matchpos_offset[0]             = 1;
    context->dec_last_matchpos_offset[1]             = 1;
    context->dec_last_matchpos_offset[2]             = 1;

    context->dec_bufpos = 0;
    context->dec_position_at_start = 0;

    context->dec_decoder_state      = DEC_STATE_START_NEW_BLOCK;
    context->dec_block_size         = 0;

    /* so that initialise_decoder_bitbuf() will succeed */
    context->dec_block_type     = BLOCKTYPE_INVALID;

    context->dec_first_time_this_group      = true;
    context->dec_current_file_size          = 0;

    context->dec_error_condition = false;
}