From 249007c594f48d66573e662134fbb7a652b11c70 Mon Sep 17 00:00:00 2001
From: Alexandre Trovato <alexandre.trovato@gmail.com>
Date: Wed, 3 Mar 2021 22:02:58 +0100
Subject: [PATCH] Diff left

---
 lib/hci-socket/gatt.js | 42 ++++++++++++++++++++++++++++++++----------
 1 file changed, 32 insertions(+), 10 deletions(-)

diff --git a/lib/hci-socket/gatt.js b/lib/hci-socket/gatt.js
index 535487a4f..e81049c28 100644
--- a/lib/hci-socket/gatt.js
+++ b/lib/hci-socket/gatt.js
@@ -676,6 +676,17 @@ Gatt.prototype.notify = function (serviceUuid, characteristicUuid, notify) {
   });
 };
 
+function reverse (src) {
+  const buffer = Buffer.alloc(src.length);
+
+  for (let i = 0, j = src.length - 1; i <= j; ++i, --j) {
+    buffer[i] = src[j];
+    buffer[j] = src[i];
+  }
+
+  return buffer;
+}
+
 Gatt.prototype.discoverDescriptors = function (serviceUuid, characteristicUuid) {
   const characteristic = this._characteristics[serviceUuid][characteristicUuid];
   const descriptors = [];
@@ -684,24 +695,35 @@ Gatt.prototype.discoverDescriptors = function (serviceUuid, characteristicUuid)
 
   const callback = data => {
     const opcode = data[0];
-    let i = 0;
 
     if (opcode === ATT_OP_FIND_INFO_RESP) {
       const format = data[1];
-      const elen = 2 + (format === 0x01 ? 2 : 16);
-      const num = (data.length - 2) / (elen);
-      for (i = 0; i < num; i++) {
-        const offset = 2 + (i * elen);
-        descriptors.push({
-          handle: data.readUInt16LE(offset + 0),
-          uuid: (format === 0x01) ? data.readUInt16LE(offset + 2).toString(16) : data.slice(offset + 2).slice(0, 16).toString('hex').match(/.{1,2}/g).reverse().join('')
-        });
+      let pos = 2; // skip first 2 bytes (opcode, format)
+
+      while (data.length > pos) {
+        switch (format) {
+          case 1:
+            descriptors.push({
+              handle: data.readUInt16LE(pos),
+              uuid: data.readUInt16LE(pos + 2).toString(16)
+            });
+            pos = pos + 4;
+            break;
+
+          case 2:
+            descriptors.push({
+              handle: data.readUInt16LE(pos),
+              uuid: reverse(data.slice(pos + 2, pos + 2 + 16)).toString('hex')
+            });
+            pos = pos + 18;
+            break;
+        }
       }
     }
 
     if (opcode !== ATT_OP_FIND_INFO_RESP || descriptors[descriptors.length - 1].handle === characteristic.endHandle) {
       const descriptorUuids = [];
-      for (i = 0; i < descriptors.length; i++) {
+      for (let i = 0; i < descriptors.length; i++) {
         descriptorUuids.push(descriptors[i].uuid);
 
         this._descriptors[serviceUuid][characteristicUuid][descriptors[i].uuid] = descriptors[i];