1 files changed, 101 insertions, 0 deletions
diff --git a/common/csrand/csrand.go b/common/csrand/csrand.go
new file mode 100644
index 0000000..45849d3
--- /dev/null
+++ b/common/csrand/csrand.go
@@ -0,0 +1,101 @@
+/*
+ * Copyright (c) 2014, Yawning Angel <yawning at torproject dot org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ *  * Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ *
+ *  * Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+// Package csrand implements the math/rand interface over crypto/rand, along
+// with some utility functions for common random number/byte related tasks.
+//
+// Not all of the convinience routines are replicated, only those that are
+// immediately useful.  The Rand variable provides access to the full math/rand
+// API.
+package csrand
+
+import (
+	cryptRand "crypto/rand"
+	"encoding/binary"
+	"fmt"
+	"io"
+	"math/rand"
+)
+
+var (
+	csRandSourceInstance csRandSource
+
+	// Rand is a math/rand instance backed by crypto/rand CSPRNG.
+	Rand = rand.New(csRandSourceInstance)
+)
+
+type csRandSource struct {
+	// This does not keep any state as it is backed by crypto/rand.
+}
+
+func (r csRandSource) Int63() int64 {
+	var src [8]byte
+	if err := Bytes(src[:]); err != nil {
+		panic(err)
+	}
+	val := binary.BigEndian.Uint64(src[:])
+	val &= (1<<63 - 1)
+
+	return int64(val)
+}
+
+func (r csRandSource) Seed(seed int64) {
+	// No-op.
+}
+
+// Intn returns, as a int, a pseudo random number in [0, n).
+func Intn(n int) int {
+	return Rand.Intn(n)
+}
+
+// Float64 returns, as a float64, a pesudo random number in [0.0,1.0).
+func Float64() float64 {
+	return Rand.Float64()
+}
+
+// IntRange returns a uniformly distributed int [min, max].
+func IntRange(min, max int) int {
+	if max < min {
+		panic(fmt.Sprintf("IntRange: min > max (%d, %d)", min, max))
+	}
+
+	r := (max + 1) - min
+	ret := Rand.Intn(r)
+	return ret + min
+}
+
+// Bytes fills the slice with random data.
+func Bytes(buf []byte) error {
+	if _, err := io.ReadFull(cryptRand.Reader, buf); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// Reader is a alias of rand.Reader.
+var Reader = cryptRand.Reader