ref: 6c26e2617c8cabdb8e05ca0f7180123a169b13a2
dir: /tools/lz/merging.c/
#include "proto.h" 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; 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 ++) { if (backwards) seq = count - seq; new = merge_command_sequences(current, *final_length, sequences[(seq + min_sequence) % count], lengths[(seq + min_sequence) % count], final_length); 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; }