mirror of
https://gitlab.com/xCrystal/pokecrystal-board.git
synced 2024-09-09 09:51:34 -07:00
405 lines
16 KiB
C
405 lines
16 KiB
C
#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <stdarg.h>
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#define COMPRESSION_METHODS 72
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struct command {
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unsigned command: 3;
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unsigned count: 12;
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signed value: 17;
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};
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int main(int, char **);
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void error_exit(int, const char *, ...);
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void bit_flip(const unsigned char *, unsigned short, unsigned char *);
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unsigned char * read_file_into_buffer(const char *, unsigned short *);
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void write_commands_to_file(const char *, const struct command *, unsigned, const unsigned char *);
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void write_command_to_file(FILE *, struct command, const unsigned char *);
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struct command * compress(const unsigned char *, unsigned short *);
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struct command * try_compress(const unsigned char *, const unsigned char *, unsigned short *, unsigned);
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struct command find_best_copy(const unsigned char *, unsigned short, unsigned short, const unsigned char *, unsigned);
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unsigned short scan_forwards(const unsigned char *, unsigned short, const unsigned char *, unsigned short, short *);
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unsigned short scan_backwards(const unsigned char *, unsigned short, unsigned short, short *);
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struct command find_best_repetition(const unsigned char *, unsigned short, unsigned short);
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struct command pick_best_command(unsigned, struct command, ...);
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int is_better(struct command, struct command);
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short command_size(struct command);
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void optimize(struct command *, unsigned short);
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void repack(struct command **, unsigned short *);
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struct command * select_command_sequence(struct command **, const unsigned short *, unsigned, unsigned short *);
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struct command * merge_command_sequences(const struct command *, unsigned short, const struct command *, unsigned short, unsigned short *);
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unsigned short compressed_length(const struct command *, unsigned short);
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int main (int argc, char ** argv) {
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if (argc < 3) {
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fprintf(stderr, "usage: %s <source file> <compressed output>\n", *argv);
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return 3;
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}
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unsigned short size;
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unsigned char * file_buffer = read_file_into_buffer(argv[1], &size);
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struct command * compressed = compress(file_buffer, &size);
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write_commands_to_file(argv[2], compressed, size, file_buffer);
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free(file_buffer);
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free(compressed);
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return 0;
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}
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void error_exit (int error_code, const char * error, ...) {
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va_list ap;
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va_start(ap, error);
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fputs("error: ", stderr);
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vfprintf(stderr, error, ap);
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fputc('\n', stderr);
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exit(error_code);
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}
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void bit_flip (const unsigned char * data, unsigned short length, unsigned char * result) {
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unsigned char new_value, pos;
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while (length --) {
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new_value = 0;
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for (pos = 0; pos < 8; pos ++) new_value |= ((*data >> pos) & 1) << (7 - pos);
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*(result ++) = new_value;
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data ++;
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}
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}
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unsigned char * read_file_into_buffer (const char * file, unsigned short * size) {
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FILE * fp = fopen(file, "rb");
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if (!fp) error_exit(1, "could not open file %s for reading", file);
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unsigned char * buf = malloc(32769);
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int rv = fread(buf, 1, 32769, fp);
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fclose(fp);
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if (rv < 0) error_exit(1, "could not read from file %s", file);
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if (rv > 32768) error_exit(1, "file %s is too big", file);
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*size = rv;
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return buf;
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}
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void write_commands_to_file (const char * file, const struct command * commands, unsigned count, const unsigned char * input_stream) {
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FILE * fp = fopen(file, "wb");
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if (!fp) error_exit(1, "could not open file %s for writing", file);
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while (count --) write_command_to_file(fp, *(commands ++), input_stream);
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unsigned char terminator = -1;
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if (fwrite(&terminator, 1, 1, fp) != 1) error_exit(1, "could not write terminator to compressed output");
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fclose(fp);
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}
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void write_command_to_file (FILE * fp, struct command command, const unsigned char * input_stream) {
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if ((!command.count) || (command.count > 1024)) error_exit(2, "invalid command in output stream");
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unsigned char buf[4];
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unsigned char * pos = buf;
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int n;
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command.count --;
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if (command.count < 32)
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*(pos ++) = (command.command << 5) + command.count;
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else {
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*(pos ++) = 224 + (command.command << 2) + (command.count >> 8);
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*(pos ++) = command.count;
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}
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switch (command.command) {
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case 1: case 2:
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if ((command.value < 0) || (command.value >= (1 << (command.command << 3)))) error_exit(2, "invalid command in output stream");
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for (n = 0; n < command.command; n ++) *(pos ++) = command.value >> (n << 3);
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case 0: case 3:
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break;
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default:
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if ((command.value < -128) || (command.value > 32767)) error_exit(2, "invalid command in output stream");
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if (command.value < 0)
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*(pos ++) = command.value ^ 127;
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else {
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*(pos ++) = command.value >> 8;
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*(pos ++) = command.value;
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}
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}
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if ((int)fwrite(buf, 1, pos - buf, fp) != (pos - buf)) error_exit(1, "could not write command to compressed output");
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if (command.command) return;
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command.count ++;
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if (fwrite(input_stream + command.value, 1, command.count, fp) != command.count) error_exit(1, "could not write data to compressed output");
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}
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struct command * compress (const unsigned char * data, unsigned short * size) {
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unsigned char * bitflipped = malloc(*size);
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bit_flip(data, *size, bitflipped);
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struct command * compressed_sequences[COMPRESSION_METHODS];
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unsigned short lengths[COMPRESSION_METHODS];
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unsigned current;
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for (current = 0; current < COMPRESSION_METHODS; current ++) {
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lengths[current] = *size;
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compressed_sequences[current] = try_compress(data, bitflipped, lengths + current, current);
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}
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free(bitflipped);
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struct command * result = select_command_sequence(compressed_sequences, lengths, COMPRESSION_METHODS, size);
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for (current = 0; current < COMPRESSION_METHODS; current ++) free(compressed_sequences[current]);
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return result;
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}
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struct command * try_compress (const unsigned char * data, const unsigned char * bitflipped, unsigned short * length, unsigned flags) {
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struct command * commands = malloc(sizeof(struct command) * *length);
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memset(commands, -1, sizeof(struct command) * *length);
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struct command * current_command = commands;
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unsigned short position = 0, previous_data = 0;
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unsigned char lookahead = 0, lookahead_flag = (flags >> 3) % 3;
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struct command copy, repetition;
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while (position < *length) {
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copy = find_best_copy(data, position, *length, bitflipped, flags);
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repetition = find_best_repetition(data, position, *length);
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if (flags & 1)
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*current_command = pick_best_command(2, repetition, copy);
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else
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*current_command = pick_best_command(2, copy, repetition);
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*current_command = pick_best_command(2, (struct command) {.command = 0, .count = 1, .value = position}, *current_command);
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if (flags & 2) {
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if (previous_data && (previous_data != 32) && (previous_data != 1024) && (command_size(*current_command) == current_command -> count))
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*current_command = (struct command) {.command = 0, .count = 1, .value = position};
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}
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if (lookahead_flag) {
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if (lookahead >= lookahead_flag)
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lookahead = 0;
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else if (current_command -> command) {
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lookahead ++;
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*current_command = (struct command) {.command = 0, .count = 1, .value = position};
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}
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}
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if (current_command -> command)
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previous_data = 0;
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else
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previous_data += current_command -> count;
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position += (current_command ++) -> count;
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}
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optimize(commands, current_command - commands);
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repack(&commands, length);
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return commands;
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}
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struct command find_best_copy (const unsigned char * data, unsigned short position, unsigned short length, const unsigned char * bitflipped, unsigned flags) {
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struct command simple = {.command = 7};
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struct command flipped = simple, backwards = simple;
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short count, offset;
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if ((count = scan_forwards(data + position, length - position, data, position, &offset)))
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simple = (struct command) {.command = 4, .count = count, .value = offset};
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if ((count = scan_forwards(data + position, length - position, bitflipped, position, &offset)))
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flipped = (struct command) {.command = 5, .count = count, .value = offset};
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if ((count = scan_backwards(data, length - position, position, &offset)))
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backwards = (struct command) {.command = 6, .count = count, .value = offset};
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struct command command;
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switch (flags / 24) {
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case 0: command = pick_best_command(3, simple, backwards, flipped); break;
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case 1: command = pick_best_command(3, backwards, flipped, simple); break;
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case 2: command = pick_best_command(3, flipped, backwards, simple);
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}
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if ((flags & 4) && (command.count > 32)) command.count = 32;
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return command;
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}
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unsigned short scan_forwards (const unsigned char * target, unsigned short limit, const unsigned char * source, unsigned short real_position, short * offset) {
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unsigned short best_match, best_length = 0;
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unsigned short current_length;
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unsigned short position;
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for (position = 0; position < real_position; position ++) {
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if (source[position] != *target) continue;
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for (current_length = 0; (current_length < limit) && (source[position + current_length] == target[current_length]); current_length ++);
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if (current_length > 1024) current_length = 1024;
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if (current_length < best_length) continue;
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best_match = position;
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best_length = current_length;
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}
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if (!best_length) return 0;
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if ((best_match + 128) >= real_position)
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*offset = best_match - real_position;
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else
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*offset = best_match;
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return best_length;
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}
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unsigned short scan_backwards (const unsigned char * data, unsigned short limit, unsigned short real_position, short * offset) {
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if (real_position < limit) limit = real_position;
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unsigned short best_match, best_length = 0;
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unsigned short current_length;
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unsigned short position;
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for (position = 0; position < real_position; position ++) {
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if (data[position] != data[real_position]) continue;
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for (current_length = 0; (current_length < limit) && (data[position - current_length] == data[real_position + current_length]); current_length ++);
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if (current_length > 1024) current_length = 1024;
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if (current_length < best_length) continue;
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best_match = position;
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best_length = current_length;
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}
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if (!best_length) return 0;
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if ((best_match + 128) >= real_position)
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*offset = best_match - real_position;
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else
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*offset = best_match;
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return best_length;
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}
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struct command find_best_repetition (const unsigned char * data, unsigned short position, unsigned short length) {
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if ((position + 1) >= length) return data[position] ? ((struct command) {.command = 7}) : ((struct command) {.command = 3, .count = 1});
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unsigned char value[2] = {data[position], data[position + 1]};
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unsigned repcount, limit = length - position;
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if (limit > 1024) limit = 1024;
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for (repcount = 2; (repcount < limit) && (data[position + repcount] == value[repcount & 1]); repcount ++);
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struct command result;
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result.count = repcount;
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if (*value != value[1]) {
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if (!*value && (repcount < 3)) return (struct command) {.command = 3, .count = 1};
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result.command = 2;
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result.value = ((unsigned) (*value)) | (((unsigned) (value[1])) << 8);
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} else if (*value) {
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result.command = 1;
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result.value = *value;
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} else
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result.command = 3;
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return result;
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}
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struct command pick_best_command (unsigned count, struct command command, ...) {
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struct command result = command;
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va_list ap;
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va_start(ap, command);
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while (-- count) {
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command = va_arg(ap, struct command);
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if (is_better(command, result)) result = command;
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}
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va_end(ap);
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return result;
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}
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int is_better (struct command new, struct command old) {
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if (new.command == 7) return 0;
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if (old.command == 7) return 1;
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short new_savings = new.count - command_size(new), old_savings = old.count - command_size(old);
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return new_savings > old_savings;
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}
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short command_size (struct command command) {
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short header_size = 1 + (command.count > 32);
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if (command.command & 4) return header_size + 1 + (command.value >= 0);
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return header_size + command.command[(short []) {command.count, 1, 2, 0}];
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}
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void optimize (struct command * commands, unsigned short count) {
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while (count && (commands -> command == 7)) commands ++, count --;
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if (count < 2) return;
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struct command * end = commands + count;
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struct command * next = commands + 1;
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while (next < end) {
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if (next -> command == 7) goto skip;
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if (
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!(commands -> command) &&
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(command_size(*next) == next -> count) &&
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((commands -> count + next -> count) <= 1024) &&
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((commands -> count > 32) || ((commands -> count + next -> count) <= 32))
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) {
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commands -> count += next -> count;
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next -> command = 7;
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goto skip;
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}
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if (next -> command != commands -> command) goto accept;
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switch (commands -> command) {
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case 0:
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if ((commands -> value + commands -> count) != next -> value) break;
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commands -> count += next -> count;
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next -> command = 7;
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if (commands -> count <= 1024) goto skip;
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next -> command = 0;
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next -> value = commands -> value + 1024;
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next -> count = commands -> count - 1024;
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commands -> count = 1024;
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break;
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case 1:
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if (commands -> value != next -> value) break;
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case 3:
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if ((commands -> count + next -> count) <= 1024) {
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commands -> count += next -> count;
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next -> command = 7;
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goto skip;
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}
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next -> count = (commands -> count + next -> count) - 1024;
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commands -> count = 1024;
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break;
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}
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accept:
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commands = next;
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skip:
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next ++;
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}
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}
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void repack (struct command ** commands, unsigned short * length) {
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struct command * new_commands = malloc(sizeof(struct command) * *length);
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struct command * current = new_commands;
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unsigned short p;
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for (p = 0; p < *length; p ++) if (p[*commands].command != 7) *(current ++) = p[*commands];
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free(*commands);
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*commands = new_commands;
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*length = current - new_commands;
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}
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struct command * select_command_sequence (struct command ** sequences, const unsigned short * lengths, unsigned count, unsigned short * final_length) {
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unsigned short min_sequence = 0, min_length = compressed_length(*sequences, *lengths);
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unsigned short seq, len;
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for (seq = 1; seq < count; seq ++) {
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len = compressed_length(sequences[seq], lengths[seq]);
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if (len < min_length) {
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min_sequence = seq;
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min_length = len;
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}
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}
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*final_length = lengths[min_sequence];
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struct command * current = malloc(*final_length * sizeof(struct command));
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memcpy(current, sequences[min_sequence], *final_length * sizeof(struct command));
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struct command * new;
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for (seq = 1; seq < count; seq ++) {
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new = merge_command_sequences(current, *final_length, sequences[(seq + min_sequence) % count], lengths[(seq + min_sequence) % count], final_length);
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free(current);
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current = new;
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}
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return current;
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}
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struct command * merge_command_sequences (const struct command * current, unsigned short current_length, const struct command * new, unsigned short new_length,
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unsigned short * result_length) {
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struct command * result = malloc(sizeof(struct command) * (current_length + new_length));
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struct command * current_command = result;
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const struct command * saved_current;
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const struct command * saved_new;
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unsigned short current_pos, new_pos;
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while (current_length) {
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if (current -> count == new -> count) {
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*(current_command ++) = pick_best_command(2, *(current ++), *(new ++));
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current_length --;
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continue;
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}
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saved_current = current;
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saved_new = new;
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current_pos = (current ++) -> count;
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new_pos = (new ++) -> count;
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current_length --;
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while (current_pos != new_pos)
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if (current_pos < new_pos) {
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current_pos += (current ++) -> count;
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current_length --;
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} else
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new_pos += (new ++) -> count;
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current_pos = compressed_length(saved_current, current - saved_current);
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new_pos = compressed_length(saved_new, new - saved_new);
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if (new_pos < current_pos) {
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memcpy(current_command, saved_new, sizeof(struct command) * (new - saved_new));
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current_command += new - saved_new;
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} else {
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memcpy(current_command, saved_current, sizeof(struct command) * (current - saved_current));
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current_command += current - saved_current;
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}
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}
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*result_length = current_command - result;
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return result;
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}
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unsigned short compressed_length (const struct command * commands, unsigned short count) {
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unsigned short current, total = 0;
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for (current = 0; current < count; current ++) if (commands[current].command != 7) total += command_size(commands[current]);
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return total;
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}
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