From ba4ea177e9b1aa34ad96f1512b2acc9022978633 Mon Sep 17 00:00:00 2001
From: Shandar Denys <msden.ua@gmail.com>
Date: Wed, 25 Oct 2023 23:38:27 +0300
Subject: [PATCH] add digest256

---
 digest256.mjs | 41 +++++++++++++++++++++++++++++++++++++++++
 package.json  |  2 +-
 test.mjs      | 39 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 81 insertions(+), 1 deletion(-)
 create mode 100644 digest256.mjs

diff --git a/digest256.mjs b/digest256.mjs
new file mode 100644
index 0000000..7e584fa
--- /dev/null
+++ b/digest256.mjs
@@ -0,0 +1,41 @@
+import sha224 from './sha224.mjs'
+const { compress } = sha224
+
+const maxLength = 248n
+
+const u32Mask = 0xffff_ffffn
+
+const hashMask = u32Mask << 224n;
+
+const byteMask = 0x08n << maxLength
+
+const dataMask = (1n << 248n) - 1n
+
+// a length of the sequence in bits.
+// The function returns 255 if the digest is a hash.
+/** @type {(bu256: bigint) => bigint} */
+const len = bu256 => (bu256 >> maxLength) & u32Mask
+
+/** @type {(nu8: number) => bigint} */
+const byteToDigest = nu8 => BigInt(nu8) | byteMask
+
+/** @type {(bu256: bigint) => bigint} */
+const getData = bu256 => bu256 & dataMask
+
+/** @type {(a: bigint) => (b: bigint) => bigint} */
+const merge = a => b => {
+    const lenA = len(a)
+    const lenB = len(b)
+    const lenAB = lenA + lenB
+    if (lenAB <= maxLength) {
+        const data = getData(a) | (getData(b) << lenA);
+        return data | (lenAB << maxLength)
+    }
+    return compress(a | (b << 256n))
+}
+
+export default {
+    merge,
+    byteToDigest,
+    len
+}
\ No newline at end of file
diff --git a/package.json b/package.json
index f5f4c7e..e2ac415 100644
--- a/package.json
+++ b/package.json
@@ -5,7 +5,7 @@
   "main": "index.mjs",
   "scripts": {
     "tsc": "tsc",
-    "test": "tsc & node test.mjs"
+    "test": "tsc & node --trace-uncaught test.mjs"
   },
   "repository": {
     "type": "git",
diff --git a/test.mjs b/test.mjs
index 2f9d767..cf08b8a 100644
--- a/test.mjs
+++ b/test.mjs
@@ -1,7 +1,9 @@
 import index from './index.mjs'
 import sha224 from './sha224.mjs'
+import digest256 from './digest256.mjs'
 const { getParityBit } = index
 const { compress } = sha224
+const { merge, byteToDigest, len } = digest256
 
 {
   const parity = getParityBit(0n)
@@ -17,4 +19,41 @@ const { compress } = sha224
   const hash = compress(0x8000_0000n)
   const result = hash.toString(16)
   if (result !== 'ffffffffc5b3e42f828ea62a15a2b01f288234c4476102bb2a3a2bc9d14a028c') { throw result }
+}
+
+{
+  const a = byteToDigest(0x12)
+  if (a !== 0x0800_0000_0000_0000_0000_0000_0000_0000_0000_0000_0000_0000_0000_0000_0000_0012n) { throw a.toString(16) }
+  const b = byteToDigest(0x34)
+  if (b !== 0x0800_0000_0000_0000_0000_0000_0000_0000_0000_0000_0000_0000_0000_0000_0000_0034n) { throw b.toString(16) }
+  const lenA = len(a)
+  if (lenA !== 8n) { throw lenA.toString(16) }
+
+  const c = merge(a)(b)
+  if (c !== 0x1000_0000_0000_0000_0000_0000_0000_0000_0000_0000_0000_0000_0000_0000_0000_3412n) { throw c.toString(16) }
+
+  const c2 = merge(c)(c)
+  if (c2 !== 0x2000_0000_0000_0000_0000_0000_0000_0000_0000_0000_0000_0000_0000_0000_3412_3412n) { throw c2.toString(16) }
+
+  const c4 = merge(c2)(c2)
+  if (c4 !== 0x4000_0000_0000_0000_0000_0000_0000_0000_0000_0000_0000_0000_3412_3412_3412_3412n) { throw c4.toString(16) }
+
+  const c8 = merge(c4)(c4)
+  if (c8 !== 0x8000_0000_0000_0000_0000_0000_0000_0000_3412_3412_3412_3412_3412_3412_3412_3412n) { throw c8.toString(16) }
+
+  const c12 = merge(c8)(c4)
+  if (c12 !== 0xc000_0000_0000_0000_3412_3412_3412_3412_3412_3412_3412_3412_3412_3412_3412_3412n) { throw c12.toString(16) }
+
+  const c16 = merge(c8)(c8)
+  if (len(c16) !== 0xffn) { throw c16.toString(16) }
+
+  {
+    const result = merge(a)(0n)
+    if (result !== a) { throw result }
+  }
+
+  {
+    const result = merge(0n)(a)
+    if (result !== a) { throw result }
+  }
 }
\ No newline at end of file