50 lines
1.4 KiB
C
50 lines
1.4 KiB
C
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#include <stdint.h>
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#include "internal.h"
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#include "hammer.h"
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#define LSB(range) (0:range)
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#define MSB(range) (1:range)
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#define LDB(range,i) (((i)>>LSB(range))&((1<<(MSB(range)-LSB(range)+1))-1))
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long long read_bits(parse_state_t* state, int count) {
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long long out = 0;
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int offset = 0;
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while (count) {
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int segment, segment_len;
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// Read a segment...
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if (state->endianness & BIT_BIG_ENDIAN) {
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if (count >= state->bit_offset) {
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segment_len = state->bit_offset;
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state->bit_offset = 8;
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segment = state->input[state->index] & ((1 << segment_len) - 1);
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state->index++;
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} else {
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segment_len = count;
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state->bit_offset -= count;
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segment = (state->input[state->index] >> state->bit_offset) & ((1 << segment_len) - 1);
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}
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} else { // BIT_LITTLE_ENDIAN
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if (count + state->bit_offset >= 8) {
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segment_len = 8 - state->bit_offset;
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segment = (state->input[state->index] >> state->bit_offset);
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state->index++;
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state->bit_offset = 0;
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} else {
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segment_len = count;
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segment = (state->input[state->index] >> state->bit_offset) & ((1 << segment_len) - 1);
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state->bit_offset += segment_len;
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}
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}
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// have a valid segment; time to assemble the byte
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if (state->endianness & BYTE_BIG_ENDIAN) {
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out = out << segment_len | segment;
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} else { // BYTE_LITTLE_ENDIAN
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out |= segment << offset;
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offset += segment_len;
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}
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count -= segment_len;
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}
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return out;
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}
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