1  ///////////////////////////////////////////////////////////////////////////////
       2  //
       3  /// \file       delta_common.c
       4  /// \brief      Common stuff for Delta encoder and decoder
       5  //
       6  //  Author:     Lasse Collin
       7  //
       8  //  This file has been put into the public domain.
       9  //  You can do whatever you want with this file.
      10  //
      11  ///////////////////////////////////////////////////////////////////////////////
      12  
      13  #include "delta_common.h"
      14  #include "delta_private.h"
      15  
      16  
      17  static void
      18  delta_coder_end(void *coder_ptr, const lzma_allocator *allocator)
      19  {
      20  	lzma_delta_coder *coder = coder_ptr;
      21  	lzma_next_end(&coder->next, allocator);
      22  	lzma_free(coder, allocator);
      23  	return;
      24  }
      25  
      26  
      27  extern lzma_ret
      28  lzma_delta_coder_init(lzma_next_coder *next, const lzma_allocator *allocator,
      29  		const lzma_filter_info *filters)
      30  {
      31  	// Allocate memory for the decoder if needed.
      32  	lzma_delta_coder *coder = next->coder;
      33  	if (coder == NULL) {
      34  		coder = lzma_alloc(sizeof(lzma_delta_coder), allocator);
      35  		if (coder == NULL)
      36  			return LZMA_MEM_ERROR;
      37  
      38  		next->coder = coder;
      39  
      40  		// End function is the same for encoder and decoder.
      41  		next->end = &delta_coder_end;
      42  		coder->next = LZMA_NEXT_CODER_INIT;
      43  	}
      44  
      45  	// Validate the options.
      46  	if (lzma_delta_coder_memusage(filters[0].options) == UINT64_MAX)
      47  		return LZMA_OPTIONS_ERROR;
      48  
      49  	// Set the delta distance.
      50  	const lzma_options_delta *opt = filters[0].options;
      51  	coder->distance = opt->dist;
      52  
      53  	// Initialize the rest of the variables.
      54  	coder->pos = 0;
      55  	memzero(coder->history, LZMA_DELTA_DIST_MAX);
      56  
      57  	// Initialize the next decoder in the chain, if any.
      58  	return lzma_next_filter_init(&coder->next, allocator, filters + 1);
      59  }
      60  
      61  
      62  extern uint64_t
      63  lzma_delta_coder_memusage(const void *options)
      64  {
      65  	const lzma_options_delta *opt = options;
      66  
      67  	if (opt == NULL || opt->type != LZMA_DELTA_TYPE_BYTE
      68  			|| opt->dist < LZMA_DELTA_DIST_MIN
      69  			|| opt->dist > LZMA_DELTA_DIST_MAX)
      70  		return UINT64_MAX;
      71  
      72  	return sizeof(lzma_delta_coder);
      73  }