From 061df50cea0ecbae30832a5a0b6f09d4b335d5f9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Luis=20D=C3=ADaz=20M=C3=A1s?= <piponazo@gmail.com>
Date: Thu, 6 Jan 2022 16:55:14 +0100
Subject: [PATCH] keyTXTChunk improvement

---
 src/pngchunk_int.cpp        | 20 +++++++++-----------
 unitTests/test_pngimage.cpp |  2 +-
 2 files changed, 10 insertions(+), 12 deletions(-)

diff --git a/src/pngchunk_int.cpp b/src/pngchunk_int.cpp
index 56dbd42f..c3c2a1b4 100644
--- a/src/pngchunk_int.cpp
+++ b/src/pngchunk_int.cpp
@@ -107,20 +107,18 @@ namespace Exiv2 {
         const int offset = stripHeader ? 8 : 0;
         if (data.size() <= offset)
           throw Error(kerFailedToReadImageData);
-        const byte *key = data.c_data(offset);
 
-        // Find null chatecter at end of keyword.
-        int keysize=0;
-        while (key[keysize] != 0)
-        {
-            keysize++;
-            // look if keysize is valid.
-            if (keysize+offset >= data.size())
-                throw Error(kerFailedToReadImageData);
-            /// \todo move conditional out of the loop
+        // Search for null char until the end of the DataBuf
+        const byte* dataPtr = data.c_data();
+        int keysize=offset;
+        while (dataPtr[keysize] != 0 && keysize < data.size()) {
+          keysize++;
         }
 
-        return DataBuf(key, keysize);
+        if (keysize == data.size())
+            throw Error(kerFailedToReadImageData);
+
+        return DataBuf(dataPtr+offset, keysize-offset);
     }
 
     DataBuf PngChunk::parseTXTChunk(const DataBuf& data,
diff --git a/unitTests/test_pngimage.cpp b/unitTests/test_pngimage.cpp
index 0474bc31..82fec574 100644
--- a/unitTests/test_pngimage.cpp
+++ b/unitTests/test_pngimage.cpp
@@ -39,7 +39,7 @@ TEST(PngChunk, keyTxtChunkExtractsKeywordCorrectlyInPresenceOfNullChar)
   DataBuf key = Internal::PngChunk::keyTXTChunk(chunkBuf, true);
   ASSERT_EQ(21, key.size());
 
-  ASSERT_TRUE(std::equal(key.data(), key.data()+key.size(), data.data()+8, data.data()+8+key.size()));
+  ASSERT_TRUE(std::equal(key.data(), key.data()+key.size(), data.data()+8));
 }