unpacker for multi game scripter

mgs-unpack.c

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

uint8_t read_uint8(FILE *fp)
{
    int ch = fgetc(fp);
    uint8_t ret = 0;

    if (ch == EOF) return 0; /* XXX */

    return ch ^ 'R';
}
uint16_t read_uint16(FILE *fp)
{
    uint16_t ret = 0;
    ret |= read_uint8(fp) <<  0;
    ret |= read_uint8(fp) <<  8;
}
uint32_t read_uint32(FILE *fp)
{
    uint32_t ret = 0;
    ret |= read_uint8(fp) <<  0;
    ret |= read_uint8(fp) <<  8;
    ret |= read_uint8(fp) << 16;
    ret |= read_uint8(fp) << 24;
    return ret;
}

size_t read_block(FILE *fp, char *buf, size_t len)
{
    int i;
    for (i = 0; i < len; i++) {
        buf[i] = read_uint8(fp);
        if (feof(fp)) break;
    }
    return len;
}

char *progname = "mgs-unpack";

void usage()
{
    fprintf(stderr, "Usage: %s <l|x> <filename>\n", progname);
    exit(0);
}

struct _pack_dirent {
    uint32_t len;
    char filename[16];
} *entries;

int main(int argc, char *argv[])
{
    FILE *fp = stdin;
    unsigned short num = 0;
    int i;
    int flag_extract = 0;

    progname = argv[0];

    if (argc < 3) {
        usage();
    }

    if (!strcmp(argv[1], "l")) {
    } else if (!strcmp(argv[1], "x")) {
        flag_extract = 1;
    } else {
        usage();
    }

    if (!!strcmp(argv[2], "-")) fp = fopen(argv[2], "rb");
    if (fp == NULL) {
        fprintf(stderr, "Can't open the file; %s\n", argv[2]);
        return -1;
    }

    num = read_uint16(fp);
    if (num == (0x5a4d ^ 0x5252)) {
        fseek(fp, 217792, SEEK_SET);
        num = read_uint16(fp);
    }
    printf("Entries; %d\n", num);
    if (num > 0x100) {
        fprintf(stderr, "Too many file? num = %d\n", num);
        exit(0);
    }
    entries = malloc(sizeof(struct _pack_dirent) * num);
    if (entries == NULL) {
        perror("malloc");
        exit(0);
    }

    for (i = 0; i < num; i++) {
        struct _pack_dirent *ent = &entries[i];

        ent->len = read_uint32(fp);
        read_block(fp, ent->filename, 16);

        printf("%-16s  %d bytes\n", ent->filename, ent->len);
    }

    if (!flag_extract) return 0;

    for (i = 0; i < num; i++) {
        struct _pack_dirent *ent = &entries[i];
        uint32_t remain = ent->len;
        char buf[1024];
        FILE *fpw;

        fpw = fopen(ent->filename, "w+b");
        if (fpw == NULL) {
            fprintf(stderr, "Can't open the file for writing\n");
            return -1;
        }

        while (remain > 0) {
            int reqlen = remain < sizeof(buf) ? remain : sizeof(buf);
            int len = read_block(fp, buf, reqlen);
            if (len < reqlen) {
                fprintf(stderr, "Premature EOF is detected\n");
                return -1;
            }

            fwrite(buf, 1, len, fpw);

            remain -= reqlen;
        }

        fclose(fpw);
    }

    if (fp != stdin) fclose(fp);
}