1 files changed, 45 insertions, 0 deletions
diff --git a/src/crypto/rand/rand.go b/src/crypto/rand/rand.go
new file mode 100644
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--- /dev/null
+++ b/src/crypto/rand/rand.go
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+// 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
+	}
+}