blob: 85e32d3b08863fbaba0e60af534ed4dbdd2e4afe [file] [log] [blame]
// Copyright 2015 The Vanadium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package localblobstore_testlib
import "math/rand"
// A RandReader contains a pointer to a rand.Read, and a size limit. Its
// pointers implement the Read() method from io.Reader, which yields bytes
// obtained from the random number generator.
type RandReader struct {
rand *rand.Rand // Source of random bytes.
pos int // Number of bytes read.
limit int // Max number of bytes that may be read.
insertInterval int // If non-zero, number of bytes between insertions of zero bytes.
eofErr error // error to be returned at the end of the stream
// NewRandReader() returns a new RandReader with the specified seed and size limit.
// It yields eofErr when the end of the stream is reached.
// If insertInterval is non-zero, a zero byte is inserted into the stream every
// insertInterval bytes, before resuming getting bytes from the random number
// generator.
func NewRandReader(seed int64, limit int, insertInterval int, eofErr error) *RandReader {
r := new(RandReader)
r.rand = rand.New(rand.NewSource(seed))
r.limit = limit
r.insertInterval = insertInterval
r.eofErr = eofErr
return r
// Read() implements the io.Reader Read() method for *RandReader.
func (r *RandReader) Read(buf []byte) (n int, err error) {
// Generate bytes up to the end of the stream, or the end of the buffer.
max := r.limit - r.pos
if len(buf) < max {
max = len(buf)
for ; n != max; n++ {
if r.insertInterval == 0 || (r.pos%r.insertInterval) != 0 {
buf[n] = byte(r.rand.Int31n(256))
} else {
buf[n] = 0
if r.pos == r.limit {
err = r.eofErr
return n, err