ruby--ruby/spec/ruby/core/io/pread_spec.rb

# -*- encoding: utf-8 -*-
require_relative '../../spec_helper'

platform_is_not :windows do
  describe "IO#pread" do
    before :each do
      @fname = tmp("io_pread.txt")
      @contents = "1234567890"
      touch(@fname) { |f| f.write @contents }
      @file = File.open(@fname, "r+")
    end

    after :each do
      @file.close
      rm_r @fname
    end

    it "accepts a length, and an offset" do
      @file.pread(4, 0).should == "1234"
      @file.pread(3, 4).should == "567"
    end

    it "accepts a length, an offset, and an output buffer" do
      buffer = "foo"
      @file.pread(3, 4, buffer)
      buffer.should == "567"
    end

    it "does not advance the file pointer" do
      @file.pread(4, 0).should == "1234"
      @file.read.should == "1234567890"
    end

    it "raises EOFError if end-of-file is reached" do
      -> { @file.pread(1, 10) }.should raise_error(EOFError)
    end

    it "raises IOError when file is not open in read mode" do
      File.open(@fname, "w") do |file|
        -> { file.pread(1, 1) }.should raise_error(IOError)
      end
    end

    it "raises IOError when file is closed" do
      file = File.open(@fname, "r+")
      file.close
      -> { file.pread(1, 1) }.should raise_error(IOError)
    end
  end
end