### Function

# GLib MappedFile new

since: 2.8

#### Declaration

    GMappedFile*
    g_mapped_file_new (
      const gchar* filename,
      gboolean writable,
      GError** error
    )

#### Description

Maps a file into memory. On UNIX, this is using the `mmap()` function.

If `writable` is `TRUE`, the mapped buffer may be modified, otherwise it is an error to modify the mapped buffer. Modifications to the buffer are not visible to other processes mapping the same file, and are not written back to the file.

Note that modifications of the underlying file might affect the contents of the `GMappedFile`. Therefore, mapping should only be used if the file will not be modified, or if all modifications of the file are done atomically (e.g. using g_file_set_contents()).

If `filename` is the name of an empty, regular file, the function will successfully return an empty `GMappedFile`. In other cases of size 0 (e.g. device files such as /dev/null), `error` will be set to the `GFileError` value `G_FILE_ERROR_INVAL`.

Available since: 2.8

#### Parameters

`filename`

  Type: `const gchar*`

  The path of the file to load, in the GLib filename encoding.

  The data is owned by the caller of the function.
  The value is a file system path, using the OS encoding.

`writable`

  Type: `gboolean`

  Whether the mapping should be writable.

`error`

  Type: `GError **`

  The return location for a recoverable error.

  The argument can be `NULL`.
  If the return location is not `NULL`, then you must initialize it to a `NULL` `GError*`.
  The argument will be left initialized to `NULL` by the function if there are no errors.
  In case of error, the argument will be set to a newly allocated `GError`; the caller will take ownership of the data, and be responsible for freeing it.

#### Return value

Type: `GMappedFile`

A newly allocated `GMappedFile` which must be unref’d with g_mapped_file_unref(), or `NULL` if the mapping failed.

The caller of the function takes ownership of the data, and is responsible for freeing it.