pokecrystal-board/tools/lz/merging.c

103 lines
5.1 KiB
C
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#include "proto.h"
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struct command * select_optimal_sequence (struct command ** sequences, const unsigned short * lengths, unsigned short * final_length) {
struct command * compressor_sequences[NUM_COMPRESSORS * 2];
unsigned short compressor_lengths[NUM_COMPRESSORS * 2];
struct command * inverted_sequences[COMPRESSION_METHODS];
unsigned short inverted_lengths[COMPRESSION_METHODS];
unsigned p, current, method = 0;
for (current = 0; current < NUM_COMPRESSORS; current ++) {
compressor_sequences[current] = select_command_sequence(sequences + method, lengths + method, compressors[current].methods, compressor_lengths + current);
compressor_sequences[current + NUM_COMPRESSORS] = select_command_sequence(sequences + method, lengths + method, -(int) compressors[current].methods,
compressor_lengths + (current + NUM_COMPRESSORS));
for (p = 0; p < compressors[current].methods; p ++) {
inverted_sequences[method + compressors[current].methods - 1 - p] = sequences[method + p];
inverted_lengths[method + compressors[current].methods - 1 - p] = lengths[method + p];
}
method += compressors[current].methods;
}
unsigned short final_lengths[8];
struct command * final_sequences[8] = {
select_command_sequence(compressor_sequences, compressor_lengths, NUM_COMPRESSORS, final_lengths),
select_command_sequence(compressor_sequences, compressor_lengths, -NUM_COMPRESSORS, final_lengths + 1),
select_command_sequence(compressor_sequences + NUM_COMPRESSORS, compressor_lengths + NUM_COMPRESSORS, NUM_COMPRESSORS, final_lengths + 2),
select_command_sequence(compressor_sequences + NUM_COMPRESSORS, compressor_lengths + NUM_COMPRESSORS, -NUM_COMPRESSORS, final_lengths + 3),
select_command_sequence(sequences, lengths, COMPRESSION_METHODS, final_lengths + 4),
select_command_sequence(sequences, lengths, -COMPRESSION_METHODS, final_lengths + 5),
select_command_sequence(inverted_sequences, inverted_lengths, COMPRESSION_METHODS, final_lengths + 6),
select_command_sequence(inverted_sequences, inverted_lengths, -COMPRESSION_METHODS, final_lengths + 7)
};
for (current = 0; current < (2 * NUM_COMPRESSORS); current ++) free(compressor_sequences[current]);
struct command * result = select_command_sequence(final_sequences, final_lengths, 8, final_length);
for (current = 0; current < 8; current ++) free(final_sequences[current]);
return result;
}
struct command * select_command_sequence (struct command ** sequences, const unsigned short * lengths, int count, unsigned short * final_length) {
// negative count indicates iterating backwards
unsigned short min_sequence = 0, min_length = compressed_length(*sequences, *lengths);
unsigned short seq, len;
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int backwards = 0;
if (count < 0) {
backwards = 1;
count = -count;
}
for (seq = 1; seq < count; seq ++) {
len = compressed_length(sequences[seq], lengths[seq]);
if (len < min_length) {
min_sequence = seq;
min_length = len;
}
}
*final_length = lengths[min_sequence];
struct command * current = malloc(*final_length * sizeof(struct command));
memcpy(current, sequences[min_sequence], *final_length * sizeof(struct command));
struct command * new;
for (seq = 1; seq < count; seq ++) {
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if (backwards) seq = count - seq;
new = merge_command_sequences(current, *final_length, sequences[(seq + min_sequence) % count], lengths[(seq + min_sequence) % count], final_length);
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if (backwards) seq = count - seq; // restore the value for the loop
free(current);
current = new;
}
return current;
}
struct command * merge_command_sequences (const struct command * current, unsigned short current_length, const struct command * new, unsigned short new_length,
unsigned short * result_length) {
struct command * result = malloc(sizeof(struct command) * (current_length + new_length));
struct command * current_command = result;
const struct command * saved_current;
const struct command * saved_new;
unsigned short current_pos, new_pos;
while (current_length) {
if (current -> count == new -> count) {
*(current_command ++) = pick_best_command(2, *(current ++), *(new ++));
current_length --;
continue;
}
saved_current = current;
saved_new = new;
current_pos = (current ++) -> count;
new_pos = (new ++) -> count;
current_length --;
while (current_pos != new_pos)
if (current_pos < new_pos) {
current_pos += (current ++) -> count;
current_length --;
} else
new_pos += (new ++) -> count;
current_pos = compressed_length(saved_current, current - saved_current);
new_pos = compressed_length(saved_new, new - saved_new);
if (new_pos < current_pos) {
memcpy(current_command, saved_new, sizeof(struct command) * (new - saved_new));
current_command += new - saved_new;
} else {
memcpy(current_command, saved_current, sizeof(struct command) * (current - saved_current));
current_command += current - saved_current;
}
}
*result_length = current_command - result;
return result;
}