cen64/os/posix/save_file.c

//
// os/unix/save_file.c
//
// Functions for mapping save files into the address space.
//
// This file is subject to the terms and conditions defined in
// 'LICENSE', which is part of this source code package.
//

#include "save_file.h"
#include <fcntl.h>
#include <stddef.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

// Unmaps a save file from the host address space.
int close_save_file(const struct save_file *file) {
  munmap(file->ptr, file->size);
  close(file->fd);
  return 0;
}

// Maps a save into the host address space, returns a pointer.
int open_save_file(const char *path, size_t size, struct save_file *file, int *created) {
  struct stat sb;
  void *ptr;
  int fd;
  int my_created;

  // Open the file O_EXCL to see if it exists
  if ((fd = open(path, O_RDWR | O_CREAT | O_EXCL, 0666)) >= 0)
    my_created = 1;

  // Otherwise just open to the file
  else {
    if ((fd = open(path, O_RDWR)) == -1)
      return -1;
    my_created = 0;
  }

  if (created != NULL)
    *created = my_created;

  // Get the file's size, map it into the address space.
  if (fstat(fd, &sb) == -1) {
    close(fd);
    return -1;
  }

  if ((size_t)sb.st_size != size)
    if (ftruncate(fd, size) == -1) {
      close(fd);
      return -1;
    }

  if ((ptr = mmap(NULL, size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0)) == MAP_FAILED) {
    close(fd);
    return -1;
  }

  file->ptr = ptr;
  file->size = size;
  file->fd = fd;

  return 0;
}

// Opening a game boy save: don't set a specific size and don't create
// the file if it doesn't exist
int open_gb_save(const char *path, struct save_file *file) {
  struct stat sb;
  void *ptr;
  int fd;

  // try to open the file
  if ((fd = open(path, O_RDWR)) == -1)
    return -1;

  // Get the file's size, map it into the address space.
  if (fstat(fd, &sb) == -1) {
    close(fd);
    return -1;
  }

  if ((ptr = mmap(NULL, sb.st_size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0)) == MAP_FAILED) {
    close(fd);
    return -1;
  }

  file->ptr = ptr;
  file->size = sb.st_size;
  file->fd = fd;

  return 0;
}