4f4a855d82
Reviewed-on: https://go-review.googlesource.com/c/158019 gotools/: * Makefile.am (go_cmd_vet_files): Update for Go1.12beta2 release. (GOTOOLS_TEST_TIMEOUT): Increase to 600. (check-runtime): Export LD_LIBRARY_PATH before computing GOARCH and GOOS. (check-vet): Copy golang.org/x/tools into check-vet-dir. * Makefile.in: Regenerate. gcc/testsuite/: * go.go-torture/execute/names-1.go: Stop using debug/xcoff, which is no longer externally visible. From-SVN: r268084
43 lines
1.3 KiB
Go
43 lines
1.3 KiB
Go
// Copyright 2014 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// +build linux freebsd
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package rand
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import (
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"internal/syscall/unix"
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)
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// maxGetRandomRead is platform dependent.
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func init() {
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altGetRandom = batched(getRandomBatch, maxGetRandomRead)
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}
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// batched returns a function that calls f to populate a []byte by chunking it
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// into subslices of, at most, readMax bytes.
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func batched(f func([]byte) bool, readMax int) func([]byte) bool {
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return func(buf []byte) bool {
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for len(buf) > readMax {
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if !f(buf[:readMax]) {
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return false
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}
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buf = buf[readMax:]
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}
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return len(buf) == 0 || f(buf)
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}
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}
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// If the kernel is too old to support the getrandom syscall(),
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// unix.GetRandom will immediately return ENOSYS and we will then fall back to
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// reading from /dev/urandom in rand_unix.go. unix.GetRandom caches the ENOSYS
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// result so we only suffer the syscall overhead once in this case.
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// If the kernel supports the getrandom() syscall, unix.GetRandom will block
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// until the kernel has sufficient randomness (as we don't use GRND_NONBLOCK).
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// In this case, unix.GetRandom will not return an error.
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func getRandomBatch(p []byte) (ok bool) {
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n, err := unix.GetRandom(p, 0)
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return n == len(p) && err == nil
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}
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