idk.c

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

#define _3DSX_MAGIC 0x58534433  // '3DSX'
#define _SMDH_MAGIC 0x48444d53  // 'SMDH'
#define _IVFC_MAGIC 0x43465649  // 'IVFC'
typedef struct
{
    uint32_t magic;
    uint16_t headerSize, relocHdrSize;
    uint32_t formatVer;
    uint32_t flags;

    // Sizes of the code, rodata and data segments +
    // size of the BSS section (uninitialized latter half of the data segment)
    uint32_t codeSegSize, rodataSegSize, dataSegSize, bssSize;
    // offset and size of smdh
    uint32_t smdhOffset, smdhSize;
    // offset to filesystem
    uint32_t fsOffset;
} _3DSX_Header;

typedef struct {
    uint64_t logicalOfs;
    uint64_t hashDataSize;
    uint32_t blocksize;  // in log2
    uint32_t reserved;
} _LevelData;

typedef struct {
    uint32_t magic1;  // "IVFC"
    uint32_t magic2;  //0x10000
    uint32_t masterhashSize;

    _LevelData level1Data;
    _LevelData level2Data;
    _LevelData level3Data;
    uint32_t reserved;
    uint32_t optionalInfoSize;
} _IVFC_Header;

typedef struct {
    // Each one is UTF-16 encoded.
    uint8_t shortDesc[0x80];
    uint8_t longDesc[0x100];
    uint8_t Publisher[0x80];
} _APPT_Header;

typedef struct
{
    // Applicaiton settings
    uint8_t ageRating[0x10];
    uint32_t regLockout;
    uint8_t mmID[0xC];  //M(atch)M(aker)ID
    uint32_t flag;
    uint16_t vEula;
    uint16_t reserved;
    uint32_t OADF;   // Optimal Animation Default Frame ???
    uint32_t CECID;  // Street pass ID
} _APPS_Header;

typedef struct {
    uint8_t small[0x480];  // these encoding is word-order crap.
    uint8_t large[0x1200];
} _ICON_Header;

typedef struct {
    uint32_t magic;
    uint16_t version, reserved1;
    _APPT_Header titles[16];  // 0x200 bytes long
    _APPS_Header applicationSetting;
    uint64_t reserved2;
    _ICON_Header iconGraphic;
} _SMDH_Header;

void print_help(char *filename) {
    printf("Usage %s [file.3dsx]\n", filename);
}

int main(int argv, char *argc[]) {
    FILE *f = NULL;
    _3DSX_Header _3dsx_header;
    _SMDH_Header _smdh_header;
    uint8_t buf[4];
    if (argv == 2) {
        f = fopen(argc[1], "rb");
    } else {
        print_help(argc[0]);
        return 1;
    }

    if (f == NULL) {
        printf("ERROR: can't open file\n");
        print_help(argc[0]);
        return 2;
    }
    fread(&buf, 1, 4, f);  // read 4 byte off
    rewind(f);
    if (buf == _3DSX_MAGIC) {
        // 3DSX.

    } else if (buf == _SMDH_MAGIC) {
        // SMDH.
    } else if (buf == _IVFC_MAGIC) {
        // IVFC.
    } else {
        printf("This file isn't supported! bailing out.\n");
        return 3;
    }

    //FILE *f = fopen("test.3dsx", "rb");

    return 0;
}