QNetworkReply: Fix missing final emission of readyRead

If we receive compressed data we will decompress it as it comes in,
in some cases the final byte we receive doesn't actually contribute
to the final output. If this byte is handled by itself then, when
combined with QNetworkReply's signal compression, we ended up not
emitting the readyRead signal for any of the data we received while
compressing the signals.

So, instead of relying on checking difference in bytes downloaded
for each batch of data received we keep track of how much data
we had received the last time we emitted readyRead.

Pick-to: 6.3 6.4 6.4.0
Fixes: QTBUG-106354
Change-Id: I4777be29b46bf0de968667e9de9d975c735ac6e6
Reviewed-by: Konrad Kujawa <konrad.kujawa@qt.io>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>

2 files changed, 6 insertions, 4 deletions

diff --git a/src/network/access/qnetworkreplyhttpimpl.cpp b/src/network/access/qnetworkreplyhttpimpl.cpp
index 08ef1866bd..e609653aa4 100644
--- a/src/network/access/qnetworkreplyhttpimpl.cpp
+++ b/src/network/access/qnetworkreplyhttpimpl.cpp
@@ -1035,9 +1035,6 @@ void QNetworkReplyHttpImplPrivate::replyDownloadData(QByteArray d)
 
     // cache this, we need it later and it's invalidated when dealing with compressed data
     auto dataSize = d.size();
-    // Grab this to compare later (only relevant for compressed data) in case none of the data
-    // will be propagated to the user
-    const qint64 previousBytesDownloaded = bytesDownloaded;
 
     if (cacheEnabled && isCachingAllowed() && !cacheSaveDevice)
         initCacheSaveDevice();
@@ -1121,11 +1118,12 @@ void QNetworkReplyHttpImplPrivate::replyDownloadData(QByteArray d)
 
     // This can occur when downloading compressed data as some of the data may be the content
     // encoding's header. Don't emit anything for this.
-    if (previousBytesDownloaded == bytesDownloaded) {
+    if (lastReadyReadEmittedSize == bytesDownloaded) {
         if (readBufferMaxSize)
             emit q->readBufferFreed(dataSize);
         return;
     }
+    lastReadyReadEmittedSize = bytesDownloaded;
 
     QVariant totalSize = cookedHeaders.value(QNetworkRequest::ContentLengthHeader);
 
diff --git a/src/network/access/qnetworkreplyhttpimpl_p.h b/src/network/access/qnetworkreplyhttpimpl_p.h
index 55953ae878..11897d1420 100644
--- a/src/network/access/qnetworkreplyhttpimpl_p.h
+++ b/src/network/access/qnetworkreplyhttpimpl_p.h
@@ -200,6 +200,10 @@ public:
 
     qint64 bytesDownloaded;
     qint64 bytesBuffered;
+    // We use this to keep track of whether or not we need to emit readyRead
+    // when we deal with signal compression (delaying emission) + decompressing
+    // data (potentially receiving bytes that don't end up in the final output):
+    qint64 lastReadyReadEmittedSize = 0;
 
     QTimer *transferTimeout;