util.go

package awstesting

import (
	"io"
)

// ZeroReader is a io.Reader which will always write zeros to the byte slice provided.
type ZeroReader struct{}

// Read fills the provided byte slice with zeros returning the number of bytes written.
func (r *ZeroReader) Read(b []byte) (int, error) {
	for i := 0; i < len(b); i++ {
		b[i] = 0
	}
	return len(b), nil
}

// ReadCloser is a io.ReadCloser for unit testing.
// Designed to test for leaks and whether a handle has
// been closed
type ReadCloser struct {
	Size     int
	Closed   bool
	set      bool
	FillData func(bool, []byte, int, int)
}

// Read will call FillData and fill it with whatever data needed.
// Decrements the size until zero, then return io.EOF.
func (r *ReadCloser) Read(b []byte) (int, error) {
	if r.Closed {
		return 0, io.EOF
	}

	delta := len(b)
	if delta > r.Size {
		delta = r.Size
	}
	r.Size -= delta

	for i := 0; i < delta; i++ {
		b[i] = 'a'
	}

	if r.FillData != nil {
		r.FillData(r.set, b, r.Size, delta)
	}
	r.set = true

	if r.Size > 0 {
		return delta, nil
	}
	return delta, io.EOF
}

// Close sets Closed to true and returns no error
func (r *ReadCloser) Close() error {
	r.Closed = true
	return nil
}