thepigeongenerator/mcaselector-lite
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start writing code for decompressing chunk data.

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I still haven't much of an idea where I'll take this, but it's a start.

I know it is needed for block filtering and such, I still need to find a
way how I'll actually implement it.
This commit is contained in:
Quinn
2025-09-05 21:24:21 +02:00
parent 2cfae0fce4
commit 5de0c77992
1 changed files with 35 additions and 0 deletions
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35
src/dat/mcx.c
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@@ -2,6 +2,7 @@
* Licensed under the MIT Licence. See LICENSE for details */ * Licensed under the MIT Licence. See LICENSE for details */
#include "mcx.h" #include "mcx.h"
#include <archive.h>
#include <assert.h> #include <assert.h>
#include <endian.h> #include <endian.h>
#include <stdint.h> #include <stdint.h>
@@ -9,12 +10,46 @@
#include <string.h> #include <string.h>
#include <time.h> #include <time.h>
#include "../error.h"
#include "../util/intdef.h" #include "../util/intdef.h"
#define SECTOR 0x1000 // sector size #define SECTOR 0x1000 // sector size
#define TABLE 0x800 // table (total) element count #define TABLE 0x800 // table (total) element count
#define CHUNKS 0x400 // amount of chunks in a file #define CHUNKS 0x400 // amount of chunks in a file
enum mcx_compression {
MCX_COMPRESSION_GZIP = 0x01,
MCX_COMPRESSION_ZLIB = 0x02,
MCX_COMPRESSION_NONE = 0x03,
MCX_COMPRESSION_LZ4 = 0x04,
MCX_COMPRESSION_CUSTOM = 0x7F,
};
/* first 4 bytes is an i32 indicating remaining bytes, the following byte defines the compression scheme */
static void mcx_loadchunk(const u8 *restrict buf, const i32 *restrict table, int idx) {
const u8 *chunk = buf + (be32toh(table[idx]) >> 8) * SECTOR;
i32 len;
memcpy(&len, chunk, 4);
len = be32toh(len);
chunk += 4;
if (*chunk != MCX_COMPRESSION_CUSTOM) {
struct archive *archive = archive_read_new();
archive_read_support_format_raw(archive);
switch (*chunk) {
case MCX_COMPRESSION_GZIP: archive_read_support_filter_gzip(archive); break;
case MCX_COMPRESSION_ZLIB: archive_read_support_filter_zlib(archive); break; // BUG: this does not exist, but will have to do for now
case MCX_COMPRESSION_LZ4: archive_read_support_filter_lz4(archive); break;
case MCX_COMPRESSION_CUSTOM: // TODO: implement using filtering any format
default: fatal("compression type of '%ihh' is unsupported!", *chunk);
}
// TODO: implement decompression, somehow.
// https://github.com/libarchive/libarchive/wiki/Examples#user-content-A_Universal_Decompressor
}
}
/* Moves chunks `src_s` to `src_e` (inclusive) from `src`, back onto `dst`. */ /* Moves chunks `src_s` to `src_e` (inclusive) from `src`, back onto `dst`. */
static void mvchunks(u8 *dst, u8 *src, u32 *restrict table, int src_s, int src_e) { static void mvchunks(u8 *dst, u8 *src, u32 *restrict table, int src_s, int src_e) {
assert(src > dst); assert(src > dst);