From c140d9ab8ee5d56f6a024d156e6fe45cda13a026 Mon Sep 17 00:00:00 2001
From: Ahmad Samir <a.samirh78@gmail.com>
Date: Sun, 4 May 2025 20:13:50 +0300
Subject: [PATCH] qdataurl: modify the percent-decoded byte array directly

Parse the content-type first, then slice the byte array. This is useful
especially for large base64 payloads.

Drive-by, use QUrl::toEncoded(), it's the same result but more succinct
syntax; pointed out in code review. Also remove an old comment, it's not
relevant anymore since QUrl::encodedPath() isn't available any more in
Qt 6.0:
https://code.qt.io/cgit/qt/qt.git/commit/?id=c0d237b7aa6e0257e3c3eee7336deaed1cf68252

Change-Id: Id69345f315dab934d0f2867008bf4fe29d63cac9
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
---
 src/corelib/io/qdataurl.cpp | 45 ++++++++++++++++++-------------------
 1 file changed, 22 insertions(+), 23 deletions(-)

diff --git a/src/corelib/io/qdataurl.cpp b/src/corelib/io/qdataurl.cpp
index 86a5175b708..23bc114d9d4 100644
--- a/src/corelib/io/qdataurl.cpp
+++ b/src/corelib/io/qdataurl.cpp
@@ -30,34 +30,14 @@ Q_CORE_EXPORT bool qDecodeDataUrl(const QUrl &uri, QString &mimeType, QByteArray
     if (uri.scheme() != "data"_L1 || !uri.host().isEmpty())
         return false;
 
-    // the following would have been the correct thing, but
-    // reality often differs from the specification. People have
-    // data: URIs with ? and #
-    //QByteArray data = QByteArray::fromPercentEncoding(uri.path(QUrl::FullyEncoded).toLatin1());
-    const QByteArray dataArray =
-            QByteArray::fromPercentEncoding(uri.url(QUrl::FullyEncoded | QUrl::RemoveScheme).toLatin1());
-    auto data = QLatin1StringView{dataArray};
-
+    payload = QByteArray::fromPercentEncoding(uri.toEncoded(QUrl::RemoveScheme));
     // parse it:
-    const qsizetype pos = data.indexOf(u',');
+    const qsizetype pos = payload.indexOf(',');
     if (pos != -1) {
-        payload = QByteArray{data.sliced(pos + 1)};
+        auto data = QLatin1StringView{payload};
         data.truncate(pos);
         data = data.trimmed();
 
-        // find out if the payload is encoded in Base64
-        constexpr auto base64 = ";base64"_L1; // per the RFC, at the end of `data`
-        if (data.endsWith(base64, Qt::CaseInsensitive)) {
-            auto r = QByteArray::fromBase64Encoding(std::move(payload));
-            if (!r) {
-                // just in case someone uses `payload` without checking the returned bool
-                payload = {};
-                return false; // decoding failed
-            }
-            payload = std::move(r.decoded);
-            data.chop(base64.size());
-        }
-
         QLatin1StringView mime;
         QLatin1StringView charsetParam;
         constexpr auto charset = "charset"_L1;
@@ -88,7 +68,26 @@ Q_CORE_EXPORT bool qDecodeDataUrl(const QUrl &uri, QString &mimeType, QByteArray
         else
             mimeType = mime;
 
+        // find out if the payload is encoded in Base64
+        constexpr auto base64 = ";base64"_L1; // per the RFC, at the end of `data`
+        const bool isBas64 = data.endsWith(base64, Qt::CaseInsensitive);
+
+        payload.slice(pos + 1);
+        data = {};
+
+        if (isBas64) {
+            auto r = QByteArray::fromBase64Encoding(std::move(payload));
+            if (!r) {
+                // just in case someone uses `payload` without checking the returned bool
+                payload = {};
+                return false; // decoding failed
+            }
+            payload = std::move(r.decoded);
+        }
+
         return true;
+    } else {
+        payload = {};
     }
 
     return false;