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169 lines
4.6 KiB
169 lines
4.6 KiB
/*
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* io.c
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*/
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#include "encoder.h"
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/*
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* Similar to the optimisation we have for the decoder.
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*
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* Allow the encoder to "overrun" output buffer by up to X bytes
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* so that we don't have to check for the end of the buffer every
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* single time we call outbits() in encdata.c
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*/
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#define OUTPUT_EXTRA_BYTES 64
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static void encoder_translate_e8(t_encoder_context *context, byte *mem, long bytes);
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/*
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* Initialises output buffering
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*/
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bool init_compressed_output_buffer(t_encoder_context *context)
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{
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if (!(context->enc_output_buffer_start = (byte *) context->enc_malloc(
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context->enc_mallochandle,
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OUTPUT_BUFFER_SIZE)
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))
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{
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return false;
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}
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context->enc_output_buffer_curpos = context->enc_output_buffer_start;
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context->enc_output_buffer_end =
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context->enc_output_buffer_start+(OUTPUT_BUFFER_SIZE-OUTPUT_EXTRA_BYTES);
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return true;
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}
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void reset_translation(t_encoder_context *context)
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{
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context->enc_instr_pos = 0;
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}
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static long read_input_data(t_encoder_context *context, byte *mem, long amount)
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{
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if (amount <= context->enc_input_left)
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{
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memcpy(mem, context->enc_input_ptr, amount);
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context->enc_input_left -= amount;
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context->enc_input_ptr += amount;
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return amount;
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}
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else
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{
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long bytes_read;
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if (context->enc_input_left <= 0)
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return 0;
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bytes_read = context->enc_input_left;
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memcpy(mem, context->enc_input_ptr, context->enc_input_left);
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context->enc_input_ptr += context->enc_input_left;
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context->enc_input_left = 0;
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return bytes_read;
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}
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}
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long comp_read_input(t_encoder_context *context, ulong BufPos, long Size)
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{
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long bytes_read;
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if (Size <= 0)
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return 0;
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bytes_read = read_input_data(
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context,
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&context->enc_RealMemWindow[BufPos],
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Size
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);
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if (bytes_read < 0)
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return 0;
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/*
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* If no translation being performed for this file
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*/
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if (context->enc_file_size_for_translation == 0 ||
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context->enc_num_cfdata_frames >= E8_CFDATA_FRAME_THRESHOLD)
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{
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context->enc_num_cfdata_frames++;
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return bytes_read;
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}
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encoder_translate_e8(
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context,
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&context->enc_RealMemWindow[BufPos],
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bytes_read
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);
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context->enc_num_cfdata_frames++;
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return bytes_read;
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}
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static void encoder_translate_e8(t_encoder_context *context, byte *mem, long bytes)
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{
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long offset;
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long absolute;
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ulong end_instr_pos;
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byte temp[6];
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byte *mem_backup;
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if (bytes <= 6)
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{
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context->enc_instr_pos += bytes;
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return;
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}
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mem_backup = mem;
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/* backup these bytes */
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memcpy(temp, &mem[bytes-6], 6);
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/* overwrite them with 0xE8 */
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memset(&mem[bytes-6], 0xE8, 6);
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end_instr_pos = context->enc_instr_pos + bytes - 6;
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while (1)
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{
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while (*mem++ != 0xE8)
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context->enc_instr_pos++;
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if (context->enc_instr_pos >= end_instr_pos)
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break;
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offset = *(UNALIGNED long *) mem;
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absolute = context->enc_instr_pos + offset;
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if (absolute >= 0)
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{
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if ((ulong) absolute < context->enc_file_size_for_translation+context->enc_instr_pos)
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{
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if ((ulong) absolute >= context->enc_file_size_for_translation)
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absolute = offset - context->enc_file_size_for_translation;
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*(UNALIGNED ulong *) mem = (ulong) absolute;
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}
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}
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mem += 4;
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context->enc_instr_pos += 5;
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}
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/* restore the bytes */
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memcpy(&mem_backup[bytes-6], temp, 6);
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context->enc_instr_pos = end_instr_pos + 6;
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}
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