FEX/Source/Common/FileFormatCheck.cpp

// SPDX-License-Identifier: MIT
#include <FEXCore/fextl/string.h>

#include <fcntl.h>
#include <stdint.h>
#include <sys/stat.h>
#include <unistd.h>

namespace FEX::FormatCheck {
bool IsSquashFS(const fextl::string& Filename) {
  // If it is a regular file then we need to check if it is a valid archive
  struct SquashFSHeader {
    uint32_t magic;
    uint32_t inode_count;
    uint32_t mtime;
    uint32_t block_size;
    uint32_t fragment_entry_count;
    uint16_t compression_id;
    uint16_t block_log;
    uint16_t flags;
    uint16_t id_count;
    uint16_t version_major;
    uint16_t version_minor;
    uint64_t More[8]; // More things that don't matter to us
  };

  SquashFSHeader Header {};
  int fd = open(Filename.c_str(), O_RDONLY | O_CLOEXEC);
  if (fd == -1) {
    return false;
  }

  if (pread(fd, reinterpret_cast<char*>(&Header), sizeof(SquashFSHeader), 0) != sizeof(SquashFSHeader)) {
    close(fd);
    return false;
  }

  close(fd);

  // Make sure the cookie matches
  if (Header.magic == 0x73717368) {
    // Sanity check the version
    uint32_t version = (uint32_t)Header.version_major << 16 | Header.version_minor;
    if (version >= 0x00040000) {
      // Everything is sane, we can add it
      return true;
    }
  }
  return false;
}

bool IsEroFS(const fextl::string& Filename) {
  // v1 of EroFS has a 128byte header
  // This lives within a fixed offset inside of the first superblock of the file
  // Each superblock is 4096bytes
  //
  // We only care about the uint32_t at the start of this offset which is the cookie
  struct EroFSHeader {
    uint32_t Magic;
    // Additional data after this if necessary in the future.
  };

  constexpr size_t HEADER_OFFSET = 1024;
  constexpr uint32_t COOKIE_MAGIC_V1 = 0xE0F5E1E2;

  EroFSHeader Header {};
  int fd = open(Filename.c_str(), O_RDONLY | O_CLOEXEC);
  if (fd == -1) {
    return false;
  }

  if (pread(fd, reinterpret_cast<char*>(&Header), sizeof(EroFSHeader), HEADER_OFFSET) != sizeof(EroFSHeader)) {
    close(fd);
    return false;
  }

  close(fd);

  return Header.Magic == COOKIE_MAGIC_V1;
}
} // namespace FEX::FormatCheck