1 files changed, 59 insertions, 0 deletions
diff --git a/std/node/_crypto/randomBytes.ts b/std/node/_crypto/randomBytes.ts
new file mode 100644
index 000000000..7b8276151
--- /dev/null
+++ b/std/node/_crypto/randomBytes.ts
@@ -0,0 +1,59 @@
+import Buffer from "../buffer.ts";
+
+export const MAX_RANDOM_VALUES = 65536;
+export const MAX_SIZE = 4294967295;
+
+function generateRandomBytes(size: number) {
+  if (size > MAX_SIZE) {
+    throw new RangeError(
+      `The value of "size" is out of range. It must be >= 0 && <= ${MAX_SIZE}. Received ${size}`,
+    );
+  }
+
+  const bytes = Buffer.allocUnsafe(size);
+
+  //Work around for getRandomValues max generation
+  if (size > MAX_RANDOM_VALUES) {
+    for (let generated = 0; generated < size; generated += MAX_RANDOM_VALUES) {
+      crypto.getRandomValues(
+        bytes.slice(generated, generated + MAX_RANDOM_VALUES),
+      );
+    }
+  } else {
+    crypto.getRandomValues(bytes);
+  }
+
+  return bytes;
+}
+
+/**
+ * @param size Buffer length, must be equal or greater than zero
+ */
+export default function randomBytes(size: number): Buffer;
+export default function randomBytes(
+  size: number,
+  cb?: (err: Error | null, buf?: Buffer) => void,
+): void;
+export default function randomBytes(
+  size: number,
+  cb?: (err: Error | null, buf?: Buffer) => void,
+): Buffer | void {
+  if (typeof cb === "function") {
+    try {
+      cb(null, generateRandomBytes(size));
+    } catch (e) {
+      //NodeJS nonsense
+      //If the size is out of range it will throw sync, otherwise throw async
+      if (
+        e instanceof RangeError &&
+        e.message.includes('The value of "size" is out of range')
+      ) {
+        throw e;
+      } else {
+        cb(e);
+      }
+    }
+  } else {
+    return generateRandomBytes(size);
+  }
+}