Gleam File Streams

This Gleam library provides access to Erlang’s file streams for reading and writing files. If you don’t require streaming behaviour then consider using simplifile instead.

Usage

Add this library to your project:

gleam add file_streams

API documentation can be found at https://hexdocs.pm/file_streams/.

Binary File Streams & UTF-8

The following code writes data to a file using a file stream, then reads it back in using a second file stream, first as raw bytes and then as lines of UTF-8 text.

import file_streams/file_stream
import file_streams/file_stream_error

pub fn main() {
  let filename = "test.txt"

  // Write file
  let assert Ok(stream) = file_stream.open_write(filename)
  let assert Ok(Nil) =
    file_stream.write_bytes(stream, <<"Hello, world!\n":utf8>>)
  let assert Ok(Nil) = file_stream.write_chars(stream, "12")
  let assert Ok(Nil) = file_stream.close(stream)

  // Read file
  let assert Ok(stream) = file_stream.open_read(filename)
  let assert Ok(<<"Hello, world!\n":utf8>>) = file_stream.read_bytes(stream, 14)
  let assert Ok([49, 50]) =
    file_stream.read_list(stream, file_stream.read_uint8, 2)
  let assert Error(file_stream_error.Eof) = file_stream.read_bytes(stream, 1)

  // Reset file position to the start and read line by line
  let assert Ok(0) =
    file_stream.position(stream, file_stream.BeginningOfFile(0))
  let assert Ok("Hello, world!\n") = file_stream.read_line(stream)
  let assert Ok("12") = file_stream.read_line(stream)
  let assert Error(file_stream_error.Eof) = file_stream.read_line(stream)
  let assert Ok(Nil) = file_stream.close(stream)
}

Text File Streams

The following code reads a UTF-16 text file. The supported encodings are Latin1 (ISO 8859-1), UTF-8, UTF-16, and UTF-32.

import file_streams/file_stream
import file_streams/file_stream_error
import file_streams/text_encoding

pub fn main() {
  let filename = "test.txt"
  let encoding = text_encoding.Utf16(text_encoding.Little)

  // Write UTF-16 text file
  let assert Ok(stream) = file_stream.open_write_text(filename, encoding)
  let assert Ok(Nil) = file_stream.write_chars(stream, "Hello, world!\n")
  let assert Ok(Nil) = file_stream.write_chars(stream, "Gleam is cool!\n")
  let assert Ok(Nil) = file_stream.close(stream)

  // Read UTF-16 text file
  let assert Ok(stream) = file_stream.open_read_text(filename, encoding)
  let assert Ok("Hello, world!\n") = file_stream.read_line(stream)
  let assert Ok("Gleam") = file_stream.read_chars(stream, 5)
  let assert Ok(" is cool!\n") = file_stream.read_line(stream)
  let assert Error(file_stream_error.Eof) = file_stream.read_line(stream)
  let assert Ok(Nil) = file_stream.close(stream)
}

License

This library is published under the MIT license, a copy of which is included.