blob: d0dcc7cc71fc0c9b35c12fd25a2a551e7253044b [file] [log] [blame]
// Copyright 2010 The Go 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 rand implements a cryptographically secure
// random number generator.
package rand
import "io"
// Reader is a global, shared instance of a cryptographically
// secure random number generator.
// On Linux, FreeBSD, Dragonfly, NetBSD and Solaris, Reader uses getrandom(2) if
// available, /dev/urandom otherwise.
// On OpenBSD and macOS, Reader uses getentropy(2).
// On other Unix-like systems, Reader reads from /dev/urandom.
// On Windows systems, Reader uses the ProcessPrng API.
// On JS/Wasm, Reader uses the Web Crypto API.
// On WASIP1/Wasm, Reader uses random_get from wasi_snapshot_preview1.
var Reader io.Reader
// Read is a helper function that calls Reader.Read using io.ReadFull.
// On return, n == len(b) if and only if err == nil.
func Read(b []byte) (n int, err error) {
return io.ReadFull(Reader, b)
// batched returns a function that calls f to populate a []byte by chunking it
// into subslices of, at most, readMax bytes.
func batched(f func([]byte) error, readMax int) func([]byte) error {
return func(out []byte) error {
for len(out) > 0 {
read := len(out)
if read > readMax {
read = readMax
if err := f(out[:read]); err != nil {
return err
out = out[read:]
return nil