From 98ffbd4811e1dbf1a8023421cc83515185e04be5 Mon Sep 17 00:00:00 2001
From: Tomaz Strazisnik <tomaz.strazisnik@inova.si>
Date: Mon, 2 Oct 2023 13:19:34 +0200
Subject: [PATCH] fix: using StringDecoder to decode fit strings

---
 src/fit2json.js       | 10 +++++++++-
 test/fit2json.spec.js |  7 +++++++
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/src/fit2json.js b/src/fit2json.js
index 81be2ed..b27b37c 100644
--- a/src/fit2json.js
+++ b/src/fit2json.js
@@ -1,4 +1,12 @@
 const constants = require('./constants');
+const { StringDecoder } = require('node:string_decoder');
+
+/**
+ * Parses the buffer as a UTF-8 string.
+ */
+function decodeString(buffer) {
+  return new StringDecoder('utf8').end(Buffer.from(buffer));
+}
 
 /**
  * Parses one record of a FIT file
@@ -169,7 +177,7 @@ function readDataField (baseType, fit, pointer, size, littleEndian) {
           result.push(fit.getUint8(pointer + i));
         }
       }
-      return String.fromCharCode(...result);
+      return decodeString(result);
   }
 }
 
diff --git a/test/fit2json.spec.js b/test/fit2json.spec.js
index 48128db..b786254 100644
--- a/test/fit2json.spec.js
+++ b/test/fit2json.spec.js
@@ -116,6 +116,13 @@ describe('/src/fit2json', () => {
       const result = fit2json.readDataField(0x07, fit, 0, 6, false);
       expect(result).to.equal('string');
     });
+
+    it('should decode the string base type (0x07) as UTF-8', () => {
+      const fit = new DataView(new Uint8Array([0xf0, 0x9f, 0x92, 0xaa]).buffer);
+      const result = fit2json.readDataField(0x07, fit, 0, 4, false);
+      expect(result).to.equal('\uD83D\uDCAA');
+    });
+
     it('should read a byte base type (0x0D) in big endian notation', () => {
       const fit = new DataView(new Uint8Array([115,116,114,105,110,103]).buffer);
       const result = fit2json.readDataField(0x0D, fit, 0, 6, false);