From 2110af0c65101495932482c5e77310dfc209da62 Mon Sep 17 00:00:00 2001
From: Blaine Bublitz <blaine.bublitz@gmail.com>
Date: Wed, 1 Sep 2021 02:03:47 -0700
Subject: [PATCH] Add support for get/set of a partial hash (#16)

* Add support for get/set of a partial hash

* make actually mergable
---
 README.md |  8 ++++++++
 index.js  |  8 ++++++++
 test.js   | 16 ++++++++++++++++
 3 files changed, 32 insertions(+)

diff --git a/README.md b/README.md
index 2eb4f1b..7b42b13 100644
--- a/README.md
+++ b/README.md
@@ -44,6 +44,14 @@ Update the hash with a new piece of data. `data` should be a buffer or uint8arra
 
 Digest the hash.
 
+#### `hash.getPartialHash()`
+
+Returns the current partial hash.
+
+#### `hash.setPartialHash(data)`
+
+Set the hash to a previously set hash. `data` should be the result of `getPartialHash()` (which returns uint8array)
+
 #### `var promise = blake2b.ready([cb])`
 
 Wait for the WASM code to load. Returns the WebAssembly instance promise as well for convenience.
diff --git a/index.js b/index.js
index 8409eb5..4c61835 100644
--- a/index.js
+++ b/index.js
@@ -123,6 +123,14 @@ Blake2b.ready = function (cb) {
 
 Blake2b.prototype.ready = Blake2b.ready
 
+Blake2b.prototype.getPartialHash = function () {
+  return wasm.memory.slice(this.pointer, this.pointer + 216);
+}
+
+Blake2b.prototype.setPartialHash = function (ph) {
+  wasm.memory.set(ph, this.pointer);
+}
+
 function noop () {}
 
 function hexSlice (buf, start, len) {
diff --git a/test.js b/test.js
index cc90b8f..ed95aa8 100644
--- a/test.js
+++ b/test.js
@@ -55,6 +55,22 @@ blake2b.ready(function () {
     t.end()
   })
 
+  tape('allows getting & setting a partial hash', function (t) {
+    var a = blake2b(64)
+    var b = blake2b(64)
+
+    var partialHash = a
+      .update(Buffer.from('hello'))
+      .update(Buffer.from(' '))
+      .update(Buffer.from('world'))
+      .getPartialHash()
+
+    b.setPartialHash(partialHash)
+
+    t.same(a.digest(), b.digest())
+    t.end()
+  })
+
   vectors.forEach(function (vector, i) {
     tape('test-vectors.json #' + i, function (t) {
       var key = vector.key && Buffer.from(vector.key, 'hex')