LZX from XNB decompressor

lzxexe.c

// Decompresses LZX found in XNB (just a test tool for vgmstream, may be of use for XMemCompress testing).
// Needs lzx.c/h, see below

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>

/* lib from https://github.com/sumatrapdfreader/chmlib 
 * which is a cleaned-up version of https://github.com/jedwing/CHMLib */
#include "lzx.h"


/* Decompresses LZX used in XNB. Has 16b window and headered blocks (with input size and
 * optionally output size) and standard LZX inside, probably what's known as XMemCompress.
 * Info: https://github.com/MonoGame/MonoGame/blob/develop/MonoGame.Framework/Utilities/LzxStream/LzxDecoderStream.cs */

uint32_t read_u32le(uint8_t* buf) {
    return (buf[0] << 0) | (buf[1] << 8u) | (buf[2] << 16u) | (buf[3] << 24u);
}

int main(int argc, char *argv[]) {
    if (argc < 2) {
        printf("LZ4 decoder by bnnm\nUsage: %s infile\n", argv[0]);
        return 1;
    }

    FILE* f_out = NULL;
    FILE* f_in = NULL;

    f_in = fopen(argv[1], "rb");
    if (f_in == NULL) {
        printf("cannot open infile %s", argv[1]);
        goto end;
    }

    char s_out[32768];
    strcpy(s_out, argv[1]);
    strcat(s_out, ".dec");
    f_out = fopen(s_out, "wb");
    if (f_out == NULL) {
        printf("cannot open outfile %s", s_out);
        goto end;
    }

    fseek(f_in, 0, SEEK_END);
    int src_size = ftell(f_in);
    fseek(f_in, 0, SEEK_SET);

    uint8_t header[0x0e];
    fread(header, 1, sizeof(header), f_in);
    int dec_size = read_u32le(header + 0x0a);

    uint8_t dst[0x8000];
    uint8_t src[0x8000];

    struct lzx_state* strm = lzx_init(16);
    if (!strm) {
        printf("bad lzx init\n");
        goto end;
    }

    int bytes = 0;
    while (bytes < dec_size) {
        int src_size, dst_size, hi, lo;
       
        hi = fgetc(f_in);
        if (hi == 0xFF) {
            hi = fgetc(f_in);
            lo = fgetc(f_in);
            dst_size = (hi << 8) | lo;

            hi = fgetc(f_in);
            lo = fgetc(f_in);
            src_size = (hi << 8) | lo;
        }
        else {
            dst_size = 0x8000;

            lo = fgetc(f_in);
            src_size = (hi << 8) | lo;
        }

        if (src_size == 0 || dst_size == 0) {
            printf("EOF\n");
            break;
        }

        fread(src, sizeof(uint8_t), src_size, f_in);

        int ret = lzx_decompress(strm, src, dst, src_size, dst_size);
        if (ret != DECR_OK) {
            printf("ret=%i\n", ret);
            break;
        }
        
        fwrite(dst, sizeof(uint8_t), dst_size, f_out);
        
        bytes += dst_size;
    }

    lzx_teardown(strm);

end:
    fclose(f_in);
    fclose(f_out);
    return 0;
}