ref: 9ac2cea1f7b76e81def9d98761315cdf7790275a
dir: /tools/lzcomp.c/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>
#define COMPRESSION_METHODS 72
struct command {
unsigned command: 3;
unsigned count: 12;
signed value: 17;
};
int main(int, char **);
void error_exit(int, const char *, ...);
void bit_flip(const unsigned char *, unsigned short, unsigned char *);
unsigned char * read_file_into_buffer(const char *, unsigned short *);
void write_commands_to_file(const char *, const struct command *, unsigned, const unsigned char *);
void write_command_to_file(FILE *, struct command, const unsigned char *);
struct command * compress(const unsigned char *, unsigned short *);
struct command * try_compress(const unsigned char *, const unsigned char *, unsigned short *, unsigned);
struct command find_best_copy(const unsigned char *, unsigned short, unsigned short, const unsigned char *, unsigned);
unsigned short scan_forwards(const unsigned char *, unsigned short, const unsigned char *, unsigned short, short *);
unsigned short scan_backwards(const unsigned char *, unsigned short, unsigned short, short *);
struct command find_best_repetition(const unsigned char *, unsigned short, unsigned short);
struct command pick_best_command(unsigned, struct command, ...);
int is_better(struct command, struct command);
short command_size(struct command);
void optimize(struct command *, unsigned short);
void repack(struct command **, unsigned short *);
struct command * select_command_sequence(struct command **, const unsigned short *, unsigned, unsigned short *);
struct command * merge_command_sequences(const struct command *, unsigned short, const struct command *, unsigned short, unsigned short *);
unsigned short compressed_length(const struct command *, unsigned short);
int main (int argc, char ** argv) {
if (argc < 3) {
fprintf(stderr, "usage: %s <source file> <compressed output>\n", *argv);
return 3;
}
unsigned short size;
unsigned char * file_buffer = read_file_into_buffer(argv[1], &size);
struct command * compressed = compress(file_buffer, &size);
write_commands_to_file(argv[2], compressed, size, file_buffer);
free(file_buffer);
free(compressed);
return 0;
}
void error_exit (int error_code, const char * error, ...) {
va_list ap;
va_start(ap, error);
fputs("error: ", stderr);
vfprintf(stderr, error, ap);
fputc('\n', stderr);
exit(error_code);
}
void bit_flip (const unsigned char * data, unsigned short length, unsigned char * result) {
unsigned char new_value, pos;
while (length --) {
new_value = 0;
for (pos = 0; pos < 8; pos ++) new_value |= ((*data >> pos) & 1) << (7 - pos);
*(result ++) = new_value;
data ++;
}
}
unsigned char * read_file_into_buffer (const char * file, unsigned short * size) {
FILE * fp = fopen(file, "rb");
if (!fp) error_exit(1, "could not open file %s for reading", file);
unsigned char * buf = malloc(32769);
int rv = fread(buf, 1, 32769, fp);
fclose(fp);
if (rv < 0) error_exit(1, "could not read from file %s", file);
if (rv > 32768) error_exit(1, "file %s is too big", file);
*size = rv;
return buf;
}
void write_commands_to_file (const char * file, const struct command * commands, unsigned count, const unsigned char * input_stream) {
FILE * fp = fopen(file, "wb");
if (!fp) error_exit(1, "could not open file %s for writing", file);
while (count --) write_command_to_file(fp, *(commands ++), input_stream);
unsigned char terminator = -1;
if (fwrite(&terminator, 1, 1, fp) != 1) error_exit(1, "could not write terminator to compressed output");
fclose(fp);
}
void write_command_to_file (FILE * fp, struct command command, const unsigned char * input_stream) {
if ((!command.count) || (command.count > 1024)) error_exit(2, "invalid command in output stream");
unsigned char buf[4];
unsigned char * pos = buf;
int n;
command.count --;
if (command.count < 32)
*(pos ++) = (command.command << 5) + command.count;
else {
*(pos ++) = 224 + (command.command << 2) + (command.count >> 8);
*(pos ++) = command.count;
}
switch (command.command) {
case 1: case 2:
if ((command.value < 0) || (command.value >= (1 << (command.command << 3)))) error_exit(2, "invalid command in output stream");
for (n = 0; n < command.command; n ++) *(pos ++) = command.value >> (n << 3);
case 0: case 3:
break;
default:
if ((command.value < -128) || (command.value > 32767)) error_exit(2, "invalid command in output stream");
if (command.value < 0)
*(pos ++) = command.value ^ 127;
else {
*(pos ++) = command.value >> 8;
*(pos ++) = command.value;
}
}
if ((int)fwrite(buf, 1, pos - buf, fp) != (pos - buf)) error_exit(1, "could not write command to compressed output");
if (command.command) return;
command.count ++;
if (fwrite(input_stream + command.value, 1, command.count, fp) != command.count) error_exit(1, "could not write data to compressed output");
}
struct command * compress (const unsigned char * data, unsigned short * size) {
unsigned char * bitflipped = malloc(*size);
bit_flip(data, *size, bitflipped);
struct command * compressed_sequences[COMPRESSION_METHODS];
unsigned short lengths[COMPRESSION_METHODS];
unsigned current;
for (current = 0; current < COMPRESSION_METHODS; current ++) {
lengths[current] = *size;
compressed_sequences[current] = try_compress(data, bitflipped, lengths + current, current);
}
free(bitflipped);
struct command * result = select_command_sequence(compressed_sequences, lengths, COMPRESSION_METHODS, size);
for (current = 0; current < COMPRESSION_METHODS; current ++) free(compressed_sequences[current]);
return result;
}
struct command * try_compress (const unsigned char * data, const unsigned char * bitflipped, unsigned short * length, unsigned flags) {
struct command * commands = malloc(sizeof(struct command) * *length);
memset(commands, -1, sizeof(struct command) * *length);
struct command * current_command = commands;
unsigned short position = 0, previous_data = 0;
unsigned char lookahead = 0, lookahead_flag = (flags >> 3) % 3;
struct command copy, repetition;
while (position < *length) {
copy = find_best_copy(data, position, *length, bitflipped, flags);
repetition = find_best_repetition(data, position, *length);
if (flags & 1)
*current_command = pick_best_command(2, repetition, copy);
else
*current_command = pick_best_command(2, copy, repetition);
*current_command = pick_best_command(2, (struct command) {.command = 0, .count = 1, .value = position}, *current_command);
if (flags & 2) {
if (previous_data && (previous_data != 32) && (previous_data != 1024) && (command_size(*current_command) == current_command -> count))
*current_command = (struct command) {.command = 0, .count = 1, .value = position};
}
if (lookahead_flag) {
if (lookahead >= lookahead_flag)
lookahead = 0;
else if (current_command -> command) {
lookahead ++;
*current_command = (struct command) {.command = 0, .count = 1, .value = position};
}
}
if (current_command -> command)
previous_data = 0;
else
previous_data += current_command -> count;
position += (current_command ++) -> count;
}
optimize(commands, current_command - commands);
repack(&commands, length);
return commands;
}
struct command find_best_copy (const unsigned char * data, unsigned short position, unsigned short length, const unsigned char * bitflipped, unsigned flags) {
struct command simple = {.command = 7};
struct command flipped = simple, backwards = simple;
short count, offset;
if ((count = scan_forwards(data + position, length - position, data, position, &offset)))
simple = (struct command) {.command = 4, .count = count, .value = offset};
if ((count = scan_forwards(data + position, length - position, bitflipped, position, &offset)))
flipped = (struct command) {.command = 5, .count = count, .value = offset};
if ((count = scan_backwards(data, length - position, position, &offset)))
backwards = (struct command) {.command = 6, .count = count, .value = offset};
struct command command;
switch (flags / 24) {
case 0: command = pick_best_command(3, simple, backwards, flipped); break;
case 1: command = pick_best_command(3, backwards, flipped, simple); break;
case 2: command = pick_best_command(3, flipped, backwards, simple);
}
if ((flags & 4) && (command.count > 32)) command.count = 32;
return command;
}
unsigned short scan_forwards (const unsigned char * target, unsigned short limit, const unsigned char * source, unsigned short real_position, short * offset) {
unsigned short best_match, best_length = 0;
unsigned short current_length;
unsigned short position;
for (position = 0; position < real_position; position ++) {
if (source[position] != *target) continue;
for (current_length = 0; (current_length < limit) && (source[position + current_length] == target[current_length]); current_length ++);
if (current_length > 1024) current_length = 1024;
if (current_length < best_length) continue;
best_match = position;
best_length = current_length;
}
if (!best_length) return 0;
if ((best_match + 128) >= real_position)
*offset = best_match - real_position;
else
*offset = best_match;
return best_length;
}
unsigned short scan_backwards (const unsigned char * data, unsigned short limit, unsigned short real_position, short * offset) {
if (real_position < limit) limit = real_position;
unsigned short best_match, best_length = 0;
unsigned short current_length;
unsigned short position;
for (position = 0; position < real_position; position ++) {
if (data[position] != data[real_position]) continue;
for (current_length = 0; (current_length < limit) && (data[position - current_length] == data[real_position + current_length]); current_length ++);
if (current_length > 1024) current_length = 1024;
if (current_length < best_length) continue;
best_match = position;
best_length = current_length;
}
if (!best_length) return 0;
if ((best_match + 128) >= real_position)
*offset = best_match - real_position;
else
*offset = best_match;
return best_length;
}
struct command find_best_repetition (const unsigned char * data, unsigned short position, unsigned short length) {
if ((position + 1) >= length) return data[position] ? ((struct command) {.command = 7}) : ((struct command) {.command = 3, .count = 1});
unsigned char value[2] = {data[position], data[position + 1]};
unsigned repcount, limit = length - position;
if (limit > 1024) limit = 1024;
for (repcount = 2; (repcount < limit) && (data[position + repcount] == value[repcount & 1]); repcount ++);
struct command result;
result.count = repcount;
if (*value != value[1]) {
if (!*value && (repcount < 3)) return (struct command) {.command = 3, .count = 1};
result.command = 2;
result.value = ((unsigned) (*value)) | (((unsigned) (value[1])) << 8);
} else if (*value) {
result.command = 1;
result.value = *value;
} else
result.command = 3;
return result;
}
struct command pick_best_command (unsigned count, struct command command, ...) {
struct command result = command;
va_list ap;
va_start(ap, command);
while (-- count) {
command = va_arg(ap, struct command);
if (is_better(command, result)) result = command;
}
va_end(ap);
return result;
}
int is_better (struct command new, struct command old) {
if (new.command == 7) return 0;
if (old.command == 7) return 1;
short new_savings = new.count - command_size(new), old_savings = old.count - command_size(old);
return new_savings > old_savings;
}
short command_size (struct command command) {
short header_size = 1 + (command.count > 32);
if (command.command & 4) return header_size + 1 + (command.value >= 0);
return header_size + command.command[(short []) {command.count, 1, 2, 0}];
}
void optimize (struct command * commands, unsigned short count) {
while (count && (commands -> command == 7)) commands ++, count --;
if (count < 2) return;
struct command * end = commands + count;
struct command * next = commands + 1;
while (next < end) {
if (next -> command == 7) goto skip;
if (
!(commands -> command) &&
(command_size(*next) == next -> count) &&
((commands -> count + next -> count) <= 1024) &&
((commands -> count > 32) || ((commands -> count + next -> count) <= 32))
) {
commands -> count += next -> count;
next -> command = 7;
goto skip;
}
if (next -> command != commands -> command) goto accept;
switch (commands -> command) {
case 0:
if ((commands -> value + commands -> count) != next -> value) break;
commands -> count += next -> count;
next -> command = 7;
if (commands -> count <= 1024) goto skip;
next -> command = 0;
next -> value = commands -> value + 1024;
next -> count = commands -> count - 1024;
commands -> count = 1024;
break;
case 1:
if (commands -> value != next -> value) break;
case 3:
if ((commands -> count + next -> count) <= 1024) {
commands -> count += next -> count;
next -> command = 7;
goto skip;
}
next -> count = (commands -> count + next -> count) - 1024;
commands -> count = 1024;
break;
}
accept:
commands = next;
skip:
next ++;
}
}
void repack (struct command ** commands, unsigned short * length) {
struct command * new_commands = malloc(sizeof(struct command) * *length);
struct command * current = new_commands;
unsigned short p;
for (p = 0; p < *length; p ++) if (p[*commands].command != 7) *(current ++) = p[*commands];
free(*commands);
*commands = new_commands;
*length = current - new_commands;
}
struct command * select_command_sequence (struct command ** sequences, const unsigned short * lengths, unsigned count, unsigned short * final_length) {
unsigned short min_sequence = 0, min_length = compressed_length(*sequences, *lengths);
unsigned short seq, len;
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 ++) {
new = merge_command_sequences(current, *final_length, sequences[(seq + min_sequence) % count], lengths[(seq + min_sequence) % count], final_length);
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;
}
unsigned short compressed_length (const struct command * commands, unsigned short count) {
unsigned short current, total = 0;
for (current = 0; current < count; current ++) if (commands[current].command != 7) total += command_size(commands[current]);
return total;
}