windows-xp/Source/XPSP1/NT/enduser/stuff/itss/lzx/decoder/decinit.c

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

#include "decoder.h"


/* 
 * 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;
	}

#ifdef BIT16
    if (DComp_Init(context))
        return false;
#else
	if (!(context->dec_mem_window = (byte *) context->dec_malloc(context->dec_window_size+(MAX_MATCH+4))))
		return false;
#endif

	return true; 
}


/*
 * Free decompression memory
 */
void NEAR free_decompression_memory(t_decoder_context *context)
{
#ifdef BIT16
    DComp_Close(context);
#else
	if (context->dec_mem_window)
	{
		context->dec_free(context->dec_mem_window);
		context->dec_mem_window = NULL;
	}
#endif
}


/*
 * 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;
}