1 // Copyright 2010 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 // Package rand implements a cryptographically secure 6 // random number generator. 7 package rand 8 9 import "io" 10 11 // Reader is a global, shared instance of a cryptographically 12 // secure random number generator. 13 // 14 // On Linux and FreeBSD, Reader uses getrandom(2) if available, /dev/urandom otherwise. 15 // On OpenBSD, Reader uses getentropy(2). 16 // On other Unix-like systems, Reader reads from /dev/urandom. 17 // On Windows systems, Reader uses the RtlGenRandom API. 18 // On Wasm, Reader uses the Web Crypto API. 19 var Reader io.Reader 20 21 // Read is a helper function that calls Reader.Read using io.ReadFull. 22 // On return, n == len(b) if and only if err == nil. 23 func Read(b []byte) (n int, err error) { 24 return io.ReadFull(Reader, b) 25 } 26 27 // batched returns a function that calls f to populate a []byte by chunking it 28 // into subslices of, at most, readMax bytes. 29 func batched(f func([]byte) error, readMax int) func([]byte) error { 30 return func(out []byte) error { 31 for len(out) > 0 { 32 read := len(out) 33 if read > readMax { 34 read = readMax 35 } 36 if err := f(out[:read]); err != nil { 37 return err 38 } 39 out = out[read:] 40 } 41 return nil 42 } 43 } 44