crypto/rand module code refactoring

src/crypto/rand/rand_batched.go

@@ -0,0 +1,42 @@
+// Copyright 2014 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.
+
+// +build linux freebsd
+
+package rand
+
+import (
+	"internal/syscall/unix"
+)
+
+// maxGetRandomRead is platform dependent.
+func init() {
+	altGetRandom = batched(getRandomLinux, maxGetRandomRead)
+}
+
+// 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) bool, readMax int) func([]byte) bool {
+	return func(buf []byte) bool {
+		for len(buf) > readMax {
+			if !f(buf[:readMax]) {
+				return false
+			}
+			buf = buf[readMax:]
+		}
+		return len(buf) == 0 || f(buf)
+	}
+}
+
+// If the kernel is too old to support the getrandom syscall(),
+// unix.GetRandom will immediately return ENOSYS and we will then fall back to
+// reading from /dev/urandom in rand_unix.go. unix.GetRandom caches the ENOSYS
+// result so we only suffer the syscall overhead once in this case.
+// If the kernel supports the getrandom() syscall, unix.GetRandom will block
+// until the kernel has sufficient randomness (as we don't use GRND_NONBLOCK).
+// In this case, unix.GetRandom will not return an error.
+func getRandomLinux(p []byte) (ok bool) {
+	n, err := unix.GetRandom(p, 0)
+	return n == len(p) && err == nil
+}

src/crypto/rand/rand_freebsd.go

@@ -2,44 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build freebsd
-
 package rand
 
-import (
-	"internal/syscall/unix"
-)
-
-func init() {
-	altGetRandom = batched(getRandomFreeBSD, maxGetRandomRead)
-}
-
 // maxGetRandomRead is the maximum number of bytes to ask for in one call to the
 // getrandom() syscall. In FreeBSD at most 256 bytes will be returned per call.
 const maxGetRandomRead = (1 << 8)
-
-// 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) bool, readMax int) func([]byte) bool {
-	return func(buf []byte) bool {
-		for len(buf) > readMax {
-			if !f(buf[:readMax]) {
-				return false
-			}
-			buf = buf[readMax:]
-		}
-		return len(buf) == 0 || f(buf)
-	}
-}
-
-// If the kernel is too old (before 12) to support the getrandom syscall(),
-// unix.GetRandom will immediately return ENOSYS and we will then fall back to
-// reading from /dev/urandom in rand_unix.go. unix.GetRandom caches the ENOSYS
-// result so we only suffer the syscall overhead once in this case.
-// If the kernel supports the getrandom() syscall, unix.GetRandom will block
-// until the kernel has sufficient randomness (as we don't use GRND_NONBLOCK).
-// In this case, unix.GetRandom will not return an error.
-func getRandomFreeBSD(p []byte) (ok bool) {
-	n, err := unix.GetRandom(p, 0)
-	return n == len(p) && err == nil
-}

src/crypto/rand/rand_linux.go

@@ -1,19 +1,9 @@
-// Copyright 2014 The Go Authors. All rights reserved.
+// Copyright 2018 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.
 
-// +build linux
-
 package rand
 
-import (
-	"internal/syscall/unix"
-)
-
-func init() {
-	altGetRandom = batched(getRandomLinux, maxGetRandomRead)
-}
-
 // maxGetRandomRead is the maximum number of bytes to ask for in one call to the
 // getrandom() syscall. In linux at most 2^25-1 bytes will be returned per call.
 // From the manpage
@@ -22,29 +12,3 @@ func init() {
 //	   is returned by a single call to getrandom() on systems where int
 //	   has a size of 32 bits.
 const maxGetRandomRead = (1 << 25) - 1
-
-// 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) bool, readMax int) func([]byte) bool {
-	return func(buf []byte) bool {
-		for len(buf) > readMax {
-			if !f(buf[:readMax]) {
-				return false
-			}
-			buf = buf[readMax:]
-		}
-		return len(buf) == 0 || f(buf)
-	}
-}
-
-// If the kernel is too old (before 3.17) to support the getrandom syscall(),
-// unix.GetRandom will immediately return ENOSYS and we will then fall back to
-// reading from /dev/urandom in rand_unix.go. unix.GetRandom caches the ENOSYS
-// result so we only suffer the syscall overhead once in this case.
-// If the kernel supports the getrandom() syscall, unix.GetRandom will block
-// until the kernel has sufficient randomness (as we don't use GRND_NONBLOCK).
-// In this case, unix.GetRandom will not return an error.
-func getRandomLinux(p []byte) (ok bool) {
-	n, err := unix.GetRandom(p, 0)
-	return n == len(p) && err == nil
-}