117 строки
2.4 KiB
C
117 строки
2.4 KiB
C
#include <stdlib.h>
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#include <stdint.h>
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#include <stdio.h>
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#include <string.h>
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#include <dmg/dmg.h>
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#include <dmg/adc.h>
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size_t adc_decompress(size_t in_size, unsigned char *input, size_t avail_size, unsigned char *output, size_t *bytes_written)
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{
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if (in_size == 0)
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return 0;
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bool output_full = false;
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unsigned char *inp = input;
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unsigned char *outp = output;
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int chunk_type;
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int chunk_size;
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int offset;
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int i;
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while (inp - input < in_size) {
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chunk_type = adc_chunk_type(*inp);
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switch (chunk_type) {
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case ADC_PLAIN:
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chunk_size = adc_chunk_size(*inp);
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if (outp + chunk_size - output > avail_size) {
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output_full = true;
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break;
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}
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memcpy(outp, inp + 1, chunk_size);
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inp += chunk_size + 1;
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outp += chunk_size;
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break;
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case ADC_2BYTE:
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chunk_size = adc_chunk_size(*inp);
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offset = adc_chunk_offset(inp);
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if (outp + chunk_size - output > avail_size) {
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output_full = true;
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break;
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}
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if (offset == 0) {
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memset(outp, *(outp - offset - 1), chunk_size);
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outp += chunk_size;
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inp += 2;
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} else {
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for (i = 0; i < chunk_size; i++) {
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memcpy(outp, outp - offset - 1, 1);
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outp++;
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}
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inp += 2;
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}
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break;
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case ADC_3BYTE:
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chunk_size = adc_chunk_size(*inp);
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offset = adc_chunk_offset(inp);
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if (outp + chunk_size - output > avail_size) {
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output_full = true;
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break;
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}
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if (offset == 0) {
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memset(outp, *(outp - offset - 1), chunk_size);
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outp += chunk_size;
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inp += 3;
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} else {
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for (i = 0; i < chunk_size; i++) {
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memcpy(outp, outp - offset - 1, 1);
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outp++;
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}
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inp += 3;
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}
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break;
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}
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if (output_full)
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break;
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}
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*bytes_written = outp - output;
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return inp - input;
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}
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int adc_chunk_type(char _byte)
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{
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if (_byte & 0x80)
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return ADC_PLAIN;
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if (_byte & 0x40)
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return ADC_3BYTE;
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return ADC_2BYTE;
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}
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int adc_chunk_size(char _byte)
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{
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switch (adc_chunk_type(_byte)) {
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case ADC_PLAIN:
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return (_byte & 0x7F) + 1;
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case ADC_2BYTE:
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return ((_byte & 0x3F) >> 2) + 3;
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case ADC_3BYTE:
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return (_byte & 0x3F) + 4;
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}
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return -1;
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}
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int adc_chunk_offset(unsigned char *chunk_start)
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{
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unsigned char *c = chunk_start;
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switch (adc_chunk_type(*c)) {
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case ADC_PLAIN:
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return 0;
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case ADC_2BYTE:
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return ((((unsigned char)*c & 0x03)) << 8) + (unsigned char)*(c + 1);
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case ADC_3BYTE:
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return (((unsigned char)*(c + 1)) << 8) + (unsigned char)*(c + 2);
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}
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return -1;
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}
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