1  ///////////////////////////////////////////////////////////////////////////////
       2  //
       3  /// \file       vli_encoder.c
       4  /// \brief      Encodes variable-length integers
       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 "common.h"
      14  
      15  
      16  extern LZMA_API(lzma_ret)
      17  lzma_vli_encode(lzma_vli vli, size_t *vli_pos,
      18  		uint8_t *restrict out, size_t *restrict out_pos,
      19  		size_t out_size)
      20  {
      21  	// If we haven't been given vli_pos, work in single-call mode.
      22  	size_t vli_pos_internal = 0;
      23  	if (vli_pos == NULL) {
      24  		vli_pos = &vli_pos_internal;
      25  
      26  		// In single-call mode, we expect that the caller has
      27  		// reserved enough output space.
      28  		if (*out_pos >= out_size)
      29  			return LZMA_PROG_ERROR;
      30  	} else {
      31  		// This never happens when we are called by liblzma, but
      32  		// may happen if called directly from an application.
      33  		if (*out_pos >= out_size)
      34  			return LZMA_BUF_ERROR;
      35  	}
      36  
      37  	// Validate the arguments.
      38  	if (*vli_pos >= LZMA_VLI_BYTES_MAX || vli > LZMA_VLI_MAX)
      39  		return LZMA_PROG_ERROR;
      40  
      41  	// Shift vli so that the next bits to encode are the lowest. In
      42  	// single-call mode this never changes vli since *vli_pos is zero.
      43  	vli >>= *vli_pos * 7;
      44  
      45  	// Write the non-last bytes in a loop.
      46  	while (vli >= 0x80) {
      47  		// We don't need *vli_pos during this function call anymore,
      48  		// but update it here so that it is ready if we need to
      49  		// return before the whole integer has been decoded.
      50  		++*vli_pos;
      51  		assert(*vli_pos < LZMA_VLI_BYTES_MAX);
      52  
      53  		// Write the next byte.
      54  		out[*out_pos] = (uint8_t)(vli) | 0x80;
      55  		vli >>= 7;
      56  
      57  		if (++*out_pos == out_size)
      58  			return vli_pos == &vli_pos_internal
      59  					? LZMA_PROG_ERROR : LZMA_OK;
      60  	}
      61  
      62  	// Write the last byte.
      63  	out[*out_pos] = (uint8_t)(vli);
      64  	++*out_pos;
      65  	++*vli_pos;
      66  
      67  	return vli_pos == &vli_pos_internal ? LZMA_OK : LZMA_STREAM_END;
      68  
      69  }