IDBFS is provides a POSIX-like file system interface for browser-based JavaScript.

• idbfs.js
• idbfs.min.js

Getting Started

IDBFS is partly based on the fs module from node.js. The API is asynchronous and most methods require the caller to provide a callback function. Errors are passed to callbacks through the first parameter.

To create a new file system or open an existing one, create a new FileSystem instance and pass the name of the file system. A new IndexedDB database is created for each file system.

Example

<script>
  var fs = new IDBFS.FileSystem('local');
  fs.open('/myfile', 'w+', function(err, fd) {
    if (err) throw err;
    fs.close(fd, function(err) {
      if (err) throw err;
      fs.stat('/myfile', function(err, stats) {
        if (err) throw err;
        console.log('stats: ' + JSON.stringify(stats));
      });
    });
  });
</script>

As with node.js, there is no guarantee that file system operations will be executed in the order they are invoked. Ensure proper ordering by chaining operations in callbacks.

API Reference

Callbacks for methods that accept them are non-optional. The first callback parameter is reserved for passing errors. It will be undefined if no errors occurred and should always be checked.

IDBFS.FileSystem(name, flags)

File system constructor, invoked to open an existing file system or create a new one. Accepts a name and optional flags. Use 'FORMAT' to force IDBFS for format the file system.

fs.stat(path, callback)

Asynchronous stat(2). Callback gets (error, stats), where stats is an object like

    {
      node: <string> // internal node id (unique)
      dev: <string> // file system name
      size: <number> // file size in bytes
      nlinks: <number> // number of links
      atime: <number> // last access time
      mtime: <number> // last modified time
      ctime: <number> // creation time
      type: <string> // file type (FILE, DIRECTORY, ...)
    }

fs.fstat(fd, callback)

Asynchronous stat(2). Callback gets (error, stats). See fs.stat.

fs.link(oldpath, newpath, callback)

Asynchronous link(2). Callback gets no additional agruments.

fs.unlink(path, callback)

Asynchronous unlink(2). Callback gets no additional agruments.

fs.rmdir(path, callback)

Asynchronous rmdir(2). Callback gets no additional agruments.

fs.mkdir(path, callback)

Asynchronous mkdir(2). Callback gets no additional agruments.

fs.close(fd, callback)

Asynchronous close(2). Callback gets no additional agruments.

fs.open(path, flags, callback)

Asynchronous open(2). Flags can be

• 'r': Open file for reading. An exception occurs if the file does not exist.
• 'r+': Open file for reading and writing. An exception occurs if the file does not exist.
• 'w': Open file for writing. The file is created (if it does not exist) or truncated (if it exists).
• 'w+': Open file for reading and writing. The file is created (if it does not exist) or truncated (if it exists).
• 'a': Open file for appending. The file is created if it does not exist.
• 'a+': Open file for reading and appending. The file is created if it does not exist.

Callback gets (error, fd), where fd is the file descriptor.

Unlike node.js, IDBFS does not accept the optional mode parameter since it doesn't yet implement file permissions.

fs.write(fd, buffer, offset, length, position, callback)

Write bytes from buffer to the file specified by fd, where offset and length describe the part of the buffer to be written. The position refers to the offset from the beginning of the file where this data should be written. If position is null, the data will be written at the current position. See pwrite(2).

The callback gets (error, nbytes), where nbytes is the number of bytes written.

fs.writeFile(filename, data, [options], callback)

Asynchronously writes data to a file. data can be a string or a buffer, in which case any encoding option is ignored. The options argument is optional, and can take the form "utf8" (i.e., an encoding) or be an object literal: { encoding: "utf8", flag: "w" }. If no encoding is specified, and data is a string, the encoding defaults to 'utf8'. The callback gets (error).

// Write UTF8 text file
fs.writeFile('/myfile.txt', "...data...", function (err) {
  if (err) throw err;
});

// Write binary file
fs.writeFile('/myfile', buffer, function (err) {
  if (err) throw err;
});

fs.read(fd, buffer, offset, length, position, callback)

Read bytes from the file specified by fd into buffer, where offset and length describe the part of the buffer to be used. The position refers to the offset from the beginning of the file where this data should be read. If position is null, the data will be written at the current position. See pread(2).

The callback gets (error, nbytes), where nbytes is the number of bytes read.

fs.readFile(filename, [options], callback)

Asynchronously reads the entire contents of a file. The options argument is optional, and can take the form "utf8" (i.e., an encoding) or be an object literal: { encoding: "utf8", flag: "r" }. If no encoding is specified, the raw binary buffer is returned on the callback. The callback gets (error, data), where data is the contents of the file.

// Read UTF8 text file
fs.readFile('/myfile.txt', 'utf8', function (err, data) {
  if (err) throw err;
  console.log(data);
});

// Read binary file
fs.readFile('/myfile.txt', function (err, data) {
  if (err) throw err;
  console.log(data);
});

fs.lseek(fd, offset, whence, callback)

Asynchronous lseek(2), where whence can be SET, CUR, or END. Callback gets (error, pos), where pos is the resulting offset, in bytes, from the beginning of the file.

fs.readdir(path, callback)

Asynchronous readdir(3). Reads the contents of a directory. Callback gets (error, files), where files is an array containing the names of each file in the directory, excluding . and ...