423 lines
11 KiB
C
423 lines
11 KiB
C
/*
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* encdata.c
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*
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* Encode a block into the output stream
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*/
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#include "encoder.h"
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#define OUT_CHAR \
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c = context->enc_LitData[l]; \
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OUTPUT_BITS(context->enc_main_tree_len[c], context->enc_main_tree_code[c]);
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/*
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* Macro to output bits into the encoding stream
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*/
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#define OUTPUT_BITS(N,X) \
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{ \
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context->enc_bitbuf |= (((ulong) (X)) << (context->enc_bitcount-(N))); \
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context->enc_bitcount -= (N); \
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while (context->enc_bitcount <= 16) \
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{ \
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if (context->enc_output_buffer_curpos >= context->enc_output_buffer_end) \
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{ \
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context->enc_output_overflow = true; \
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context->enc_output_buffer_curpos = context->enc_output_buffer_start; \
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} \
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*context->enc_output_buffer_curpos++ = (byte) ((context->enc_bitbuf >> 16) & 255); \
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*context->enc_output_buffer_curpos++ = (byte) (context->enc_bitbuf >> 24); \
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context->enc_bitbuf <<= 16; \
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context->enc_bitcount += 16; \
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} \
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}
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/*
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* Given the initial state of the repeated offset buffers at
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* the beginning of this block, calculate the final state of the
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* repeated offset buffers after outputting this block as if it
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* were compressed data.
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*
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* First try to do it the quick way, by starting at the last
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* match and working backwards, to find three consecutive matches
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* which don't use repeated offsets. If this fails, we'll have
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* to take the initial state of the three offsets at the beginning
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* of the block, and evolve them to the end of the block.
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*/
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void get_final_repeated_offset_states(t_encoder_context *context, ulong distances)
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{
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ulong MatchPos;
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signed long d; /* must be signed */
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byte consecutive;
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consecutive = 0;
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for (d = distances-1; d >= 0; d--)
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{
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if (context->enc_DistData[d] > 2)
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{
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/* NOT a repeated offset */
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consecutive++;
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/* do we have three consecutive non-repeated-offsets? */
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if (consecutive >= 3)
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break;
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}
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else
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{
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consecutive = 0;
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}
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}
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/*
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* If we didn't find three consecutive matches which
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* don't use repeated offsets, then we have to start
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* from the beginning and evolve the repeated offsets.
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*
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* Otherwise, we start at the first of the consecutive
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* matches.
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*/
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if (consecutive < 3)
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{
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d = 0;
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}
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for (; d < (signed long) distances; d++)
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{
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MatchPos = context->enc_DistData[d];
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if (MatchPos == 0)
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{
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}
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else if (MatchPos <= 2)
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{
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ulong temp;
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temp = context->enc_repeated_offset_at_literal_zero[MatchPos];
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context->enc_repeated_offset_at_literal_zero[MatchPos] = context->enc_repeated_offset_at_literal_zero[0];
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context->enc_repeated_offset_at_literal_zero[0] = temp;
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}
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else
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{
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context->enc_repeated_offset_at_literal_zero[2] = context->enc_repeated_offset_at_literal_zero[1];
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context->enc_repeated_offset_at_literal_zero[1] = context->enc_repeated_offset_at_literal_zero[0];
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context->enc_repeated_offset_at_literal_zero[0] = MatchPos-2;
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}
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}
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}
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/*
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* Encode a block with no compression
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*
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* bufpos is the position in the file from which the first
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* literal in this block starts. To reference memory, we will
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* use enc_MemWindow[bufpos] (remember that enc_MemWindow is
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* moved backwards every time we copymem).
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*
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* Since this data was originally matched into the compressor,
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* our recent match offsets will have been changed; however,
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* since this is an uncompressed block, the decoder won't be
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* updating them. Therefore, we need to tell the decoder
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* the state of the match offsets after it has finished
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* decoding the uncompressed data - we store these in this
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* block.
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*/
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void encode_uncompressed_block(t_encoder_context *context, ulong bufpos, ulong block_size)
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{
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int i;
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int j;
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bool block_size_odd;
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ulong val;
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/*
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* Align on a byte boundary
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*/
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output_bits(context, context->enc_bitcount-16, 0);
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/*
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* Now output the contents of the repeated offset
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* buffers, since we need to preserve the state of
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* the encoder
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*/
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for (i = 0; i < NUM_REPEATED_OFFSETS; i++)
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{
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val = context->enc_repeated_offset_at_literal_zero[i];
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for (j = 0; j < sizeof(long); j++)
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{
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*context->enc_output_buffer_curpos++ = (byte) val;
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val >>= 8;
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}
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}
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block_size_odd = block_size & 1;
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/*
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* Write out uncompressed data
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*/
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while (block_size > 0)
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{
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*context->enc_output_buffer_curpos++ = context->enc_MemWindow[bufpos];
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bufpos++;
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block_size--;
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context->enc_input_running_total++;
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if (context->enc_input_running_total == CHUNK_SIZE)
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{
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perform_flush_output_callback(context);
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context->enc_num_block_splits = 0;
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}
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}
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/*
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* Add pad byte to keep the output word-aligned
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*/
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if (block_size_odd)
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{
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*context->enc_output_buffer_curpos++ = 0;
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}
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context->enc_bitcount = 32;
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context->enc_bitbuf = 0;
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}
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/*
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* Estimate the size of the data in the buffer, in bytes
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*/
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ulong estimate_compressed_block_size(t_encoder_context *context)
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{
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ulong block_size = 0; /* output size in bits */
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ulong i;
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byte mpslot;
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/* Estimation of tree size */
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block_size = 150*8;
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/* Tally bits to output characters */
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for (i = 0; i < NUM_CHARS; i++)
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block_size += (context->enc_main_tree_len[i]*context->enc_main_tree_freq[i]);
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/* Tally bits to output matches */
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for (mpslot = 0; mpslot < context->enc_num_position_slots; mpslot++)
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{
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long element;
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int primary;
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element = NUM_CHARS + (mpslot << NL_SHIFT);
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/* For primary == NUM_PRIMARY_LENGTHS we have secondary lengths */
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for (primary = 0; primary <= NUM_PRIMARY_LENGTHS; primary++)
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{
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block_size += ((context->enc_main_tree_len[element] + enc_extra_bits[mpslot]) *
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context->enc_main_tree_freq[element]);
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element++;
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}
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}
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for (i = 0; i < NUM_SECONDARY_LENGTHS; i++)
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block_size += (context->enc_secondary_tree_freq[i] * context->enc_secondary_tree_len[i]);
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/* round up */
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return (block_size+7) >> 3;
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}
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/*
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* Encode block with NO special encoding of the lower 3
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* position bits
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*/
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void encode_verbatim_block(t_encoder_context *context, ulong literal_to_end_at)
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{
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ulong MatchPos;
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ulong d = 0;
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ulong l = 0;
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byte MatchLength;
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byte c;
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byte mpSlot;
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while (l < literal_to_end_at)
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{
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if (!IsMatch(l))
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{
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OUT_CHAR;
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l++;
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context->enc_input_running_total++;
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}
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else
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{
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/* Note, 0 means MatchLen=3, 1 means MatchLen=4, ... */
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MatchLength = context->enc_LitData[l++];
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/* Delta match pos */
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MatchPos = context->enc_DistData[d++];
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mpSlot = (byte) MP_SLOT(MatchPos);
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if (MatchLength < NUM_PRIMARY_LENGTHS)
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{
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OUTPUT_BITS(
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context->enc_main_tree_len[ NUM_CHARS+(mpSlot<<NL_SHIFT)+MatchLength],
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context->enc_main_tree_code[NUM_CHARS+(mpSlot<<NL_SHIFT)+MatchLength]
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);
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}
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else
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{
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OUTPUT_BITS(
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context->enc_main_tree_len [(NUM_CHARS+NUM_PRIMARY_LENGTHS)+(mpSlot<<NL_SHIFT)],
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context->enc_main_tree_code[(NUM_CHARS+NUM_PRIMARY_LENGTHS)+(mpSlot<<NL_SHIFT)]
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);
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OUTPUT_BITS(
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context->enc_secondary_tree_len[ MatchLength - NUM_PRIMARY_LENGTHS],
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context->enc_secondary_tree_code[MatchLength - NUM_PRIMARY_LENGTHS]
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);
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}
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if (enc_extra_bits[ mpSlot ])
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{
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OUTPUT_BITS(
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enc_extra_bits[mpSlot],
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MatchPos & enc_slot_mask[mpSlot]
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);
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}
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context->enc_input_running_total += (MatchLength+MIN_MATCH);
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}
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if (context->enc_input_running_total == CHUNK_SIZE)
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{
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perform_flush_output_callback(context);
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context->enc_num_block_splits = 0;
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}
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_ASSERTE (context->enc_input_running_total < CHUNK_SIZE);
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}
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}
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/*
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* aligned block encoding
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*/
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void encode_aligned_block(t_encoder_context *context, ulong literal_to_end_at)
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{
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ulong MatchPos;
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byte MatchLength;
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byte c;
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byte mpSlot;
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byte Lower;
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ulong l = 0;
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ulong d = 0;
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while (l < literal_to_end_at)
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{
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if (!IsMatch(l))
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{
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OUT_CHAR;
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l++;
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context->enc_input_running_total++;
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}
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else
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{
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/* Note, 0 means MatchLen=3, 1 means MatchLen=4, ... */
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MatchLength = context->enc_LitData[l++];
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/* Delta match pos */
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MatchPos = context->enc_DistData[d++];
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mpSlot = (byte) MP_SLOT(MatchPos);
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if (MatchLength < NUM_PRIMARY_LENGTHS)
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{
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OUTPUT_BITS(
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context->enc_main_tree_len[ NUM_CHARS+(mpSlot<<NL_SHIFT)+MatchLength],
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context->enc_main_tree_code[NUM_CHARS+(mpSlot<<NL_SHIFT)+MatchLength]
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);
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}
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else
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{
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OUTPUT_BITS(
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context->enc_main_tree_len[ (NUM_CHARS+NUM_PRIMARY_LENGTHS)+(mpSlot<<NL_SHIFT)],
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context->enc_main_tree_code[(NUM_CHARS+NUM_PRIMARY_LENGTHS)+(mpSlot<<NL_SHIFT)]
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);
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OUTPUT_BITS(
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context->enc_secondary_tree_len[ MatchLength - NUM_PRIMARY_LENGTHS],
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context->enc_secondary_tree_code[MatchLength - NUM_PRIMARY_LENGTHS]
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);
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}
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if (enc_extra_bits[ mpSlot ] >= 3)
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{
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if (enc_extra_bits[ mpSlot ] > 3)
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{
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OUTPUT_BITS(
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enc_extra_bits[mpSlot] - 3,
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(MatchPos >> 3) & ( (1 << (enc_extra_bits[mpSlot]-3)) -1)
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);
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}
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Lower = (byte) (MatchPos & 7);
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OUTPUT_BITS(
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context->enc_aligned_tree_len[Lower],
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context->enc_aligned_tree_code[Lower]
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);
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}
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else if (enc_extra_bits[ mpSlot ])
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{
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OUTPUT_BITS(
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enc_extra_bits[mpSlot],
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MatchPos & enc_slot_mask[ mpSlot ]
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);
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}
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context->enc_input_running_total += (MatchLength+MIN_MATCH);
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}
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if (context->enc_input_running_total == CHUNK_SIZE)
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{
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perform_flush_output_callback(context);
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context->enc_num_block_splits = 0;
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}
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_ASSERTE (context->enc_input_running_total < CHUNK_SIZE);
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}
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}
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void perform_flush_output_callback(t_encoder_context *context)
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{
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long output_size;
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/*
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* Do this only if there is any input to account for, so we don't
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* end up outputting blocks where comp_size > 0 and uncmp_size = 0.
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*/
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if (context->enc_input_running_total > 0)
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{
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flush_output_bit_buffer(context);
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output_size = (long)(context->enc_output_buffer_curpos - context->enc_output_buffer_start);
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if (output_size > 0)
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{
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(*context->enc_output_callback_function)(
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context->enc_fci_data,
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context->enc_output_buffer_start,
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(long) (context->enc_output_buffer_curpos - context->enc_output_buffer_start),
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context->enc_input_running_total
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);
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}
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}
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context->enc_input_running_total = 0;
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context->enc_output_buffer_curpos = context->enc_output_buffer_start;
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/* initialise bit buffer */
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context->enc_bitcount = 32;
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context->enc_bitbuf = 0;
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}
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