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#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <stddef.h>
#include <stdbool.h>
#include <string.h>
#include <assert.h>
#include <err.h>
static uint8_t
rotate_right(uint8_t b, const uint8_t count)
{
for (size_t i = 0; i < count; ++i) {
const bool drop = ((b & 0x01) == 0x01);
b = (b >> 1) | (drop ? 0x80 : 0);
}
return b;
}
static void
decode(uint8_t *data, const size_t size, const uint8_t count)
{
assert(data);
for (size_t i = 0; i < size; ++i)
data[i] = rotate_right(data[i], count);
}
static size_t
count_bits(const uint8_t byte)
{
static const uint8_t lut[16] = {
0, 1, 1, 2, 1, 2, 2, 3,
1, 2, 2, 3, 2, 3, 3, 4
};
return lut[byte & 0x0F] + lut[byte >> 4];
}
static uint8_t
text_rotation(const uint8_t *data, const size_t size)
{
assert(data);
if (size < 2 || (data[0] == 0 && data[1] == 0))
return 0;
const int seed = count_bits(data[1]) - count_bits(data[0]);
switch (abs(seed) % 5) {
case 0: return 1;
case 1: return 7;
case 2: return 2;
case 3: return 6;
case 4: return 3;
default:break;
}
assert(0 && "failed to detect rotation");
return 0;
}
static uint8_t
other_rotation(const uint8_t *data, const size_t size)
{
assert(data);
if (size < 13)
return 0;
const int seed = count_bits(data[2]) - count_bits(data[11]) + count_bits(data[12]);
switch (abs(seed) % 5) {
case 0: return 7;
case 1: return 1;
case 2: return 6;
case 3: return 2;
case 4: return 5;
default:break;
}
assert(0 && "failed to detect rotation");
return 0;
}
static uint8_t
item_rotation(const uint8_t *data, const size_t size)
{
assert(data);
(void)data, (void)size;
return 5;
}
int
main(int argc, char *argv[])
{
if (argc < 2)
errx(EXIT_FAILURE, "usage: %s (name | ability | spell | item | text) < data", argv[0]);
#define ARRAY_SIZE(x) (sizeof(x) / sizeof(x[0]))
const struct info {
const char *name;
size_t chunk;
uint8_t (*rotation)(const uint8_t *data, const size_t size);
} map[] = {
{ .name = "name", .chunk = 32 },
{ .name = "ability", .chunk = 1024, .rotation = other_rotation },
{ .name = "spell", .chunk = 1024, .rotation = other_rotation },
{ .name = "item", .chunk = 3072, .rotation = item_rotation },
{ .name = "text", .chunk = 255, .rotation = text_rotation },
};
const struct info *info = NULL;
for (size_t i = 0; i < ARRAY_SIZE(map); ++i) {
if (strcmp(map[i].name, argv[1]))
continue;
info = &map[i];
break;
}
if (!info)
errx(EXIT_FAILURE, "unknown file type '%s'", argv[1]);
uint8_t buf[4096];
assert(sizeof(buf) >= info->chunk);
size_t bytes;
while ((bytes = fread(buf, 1, info->chunk, stdin)) > 0) {
if (info->rotation)
decode(buf, bytes, info->rotation(buf, bytes));
fwrite(buf, 1, bytes, stdout);
}
return EXIT_SUCCESS;
}
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