From 872de8deef877b8b7e0c97ddb6cafd8e0dc3fbc3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?L=C3=A9a=20Saviot?= <lea.saviot@numworks.com>
Date: Fri, 14 Jun 2019 13:50:30 +0200
Subject: [PATCH] [ion/utf8_helper] Fix StringGlyphLength

---
 ion/src/shared/unicode/utf8_helper.cpp | 9 ++++++---
 ion/test/utf8_helper.cpp               | 3 ++-
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/ion/src/shared/unicode/utf8_helper.cpp b/ion/src/shared/unicode/utf8_helper.cpp
index a972fc079..2b4391f7d 100644
--- a/ion/src/shared/unicode/utf8_helper.cpp
+++ b/ion/src/shared/unicode/utf8_helper.cpp
@@ -340,13 +340,16 @@ size_t StringGlyphLength(const char * s, int maxSize) {
     return 0;
   }
   UTF8Decoder decoder(s);
-  CodePoint codePoint = decoder.nextCodePoint();
+  CodePoint codePoint = 0;
   size_t glyphIndex = 0;
-  while (codePoint != UCodePointNull && (maxSize < 0 || ((decoder.stringPosition() - s) <= maxSize))) {
+  while (maxSize < 0 || ((decoder.stringPosition() - s) < maxSize)) {
+    codePoint = decoder.nextCodePoint();
+    if (codePoint == UCodePointNull) {
+      break;
+    }
     if (!codePoint.isCombining()) {
       glyphIndex++;
     }
-    codePoint = decoder.nextCodePoint();
   }
   return glyphIndex;
 }
diff --git a/ion/test/utf8_helper.cpp b/ion/test/utf8_helper.cpp
index 975b5cff1..23912121f 100644
--- a/ion/test/utf8_helper.cpp
+++ b/ion/test/utf8_helper.cpp
@@ -10,5 +10,6 @@ QUIZ_CASE(ion_utf8_helper_glyph_length) {
   assert_string_glyph_length_is("1ᴇ3", -1, 3);
   assert_string_glyph_length_is("∑∫𝐢", -1, 3);
   assert_string_glyph_length_is("123", 2, 2);
-  assert_string_glyph_length_is("1ᴇ3", 2, 1);
+  uint8_t testString[] = {'a', 'b', 'c', 0b11111111, 0b11111111, 0}; // Malformed utf-8 string
+  assert_string_glyph_length_is((const char *)testString, 3, 3);
 }