Buffer non-pipe perf.data in a temporary file when streamed

This is mainly for testing. I don't want to special case things for this
all the time.

Change-Id: Ifc0621065fe0d5dd86fbebc70f89cfdc8a0ee43c
Reviewed-by: Milian Wolff <milian.wolff@kdab.com>

5 files changed, 110 insertions, 29 deletions

diff --git a/app/main.cpp b/app/main.cpp
index 361a029..c5d6039 100644
--- a/app/main.cpp
+++ b/app/main.cpp
@@ -27,6 +27,7 @@
 #include "perfunwind.h"
 
 #include <QAbstractSocket>
+#include <QTemporaryFile>
 #include <QCommandLineParser>
 #include <QCoreApplication>
 #include <QDebug>
@@ -53,7 +54,8 @@ enum ErrorCodes {
     HeaderError,
     DataError,
     MissingData,
-    InvalidOption
+    InvalidOption,
+    BufferingError
 };
 
 class PerfTcpSocket : public QTcpSocket {
@@ -242,35 +244,34 @@ int main(int argc, char *argv[])
     PerfHeader header(infile.data());
     PerfAttributes attributes;
     PerfFeatures features;
-    PerfData data(infile.data(), &unwind, &header, &attributes);
+    PerfData data(&unwind, &header, &attributes);
 
     features.setArchitecture(parser.value(arch).toLatin1());
 
-    QObject::connect(&header, &PerfHeader::finished, [&]() {
-        unwind.setByteOrder(static_cast<QSysInfo::Endian>(header.byteOrder()));
-        if (!header.isPipe()) {
-            const qint64 filePos = infile->pos();
-            if (!attributes.read(infile.data(), &header)) {
-                qWarning() << "Failed to read attributes";
-                qApp->exit(DataError);
-                return;
-            }
-            if (!features.read(infile.data(), &header)) {
-                qWarning() << "Failed to read features";
-                qApp->exit(DataError);
-                return;
-            }
-            infile->seek(filePos);
+    auto readFileHeader = [&]() {
+        const qint64 filePos = infile->pos();
+        if (!attributes.read(infile.data(), &header)) {
+            qWarning() << "Failed to read attributes";
+            qApp->exit(DataError);
+            return;
+        }
+        if (!features.read(infile.data(), &header)) {
+            qWarning() << "Failed to read features";
+            qApp->exit(DataError);
+            return;
+        }
+        infile->seek(filePos);
 
-            // first send features, as it may contain better event descriptions
-            unwind.features(features);
+        // first send features, as it may contain better event descriptions
+        unwind.features(features);
 
-            const auto& attrs = attributes.attributes();
-            for (auto it = attrs.begin(), end = attrs.end(); it != end; ++it) {
-                unwind.attr(PerfRecordAttr(it.value(), {it.key()}));
-            }
+        const auto& attrs = attributes.attributes();
+        for (auto it = attrs.begin(), end = attrs.end(); it != end; ++it) {
+            unwind.attr(PerfRecordAttr(it.value(), {it.key()}));
         }
+    };
 
+    auto readData = [&]() {
         const QByteArray &featureArch = features.architecture();
         unwind.setArchitecture(PerfRegisterInfo::archByName(featureArch));
 
@@ -280,11 +281,85 @@ int main(int argc, char *argv[])
             return;
         }
 
+        data.setSource(infile.data());
         QObject::connect(infile.data(), &QIODevice::aboutToClose, &data, &PerfData::finishReading);
         QObject::connect(&data, &PerfData::finished, infile.data(), [&](){ infile->disconnect(); });
         QObject::connect(infile.data(), &QIODevice::readyRead, &data, &PerfData::read);
         if (infile->bytesAvailable() > 0)
             data.read();
+    };
+
+    auto writeBytes = [](QIODevice *target, const char *data, qint64 length) {
+        qint64 pos = 0;
+        while (pos < length) {
+            const qint64 written = target->write(data + pos, length - pos);
+            if (written < 0)
+                return false;
+            pos += written;
+        }
+        return true;
+    };
+
+    QScopedPointer<QIODevice> tempfile;
+    auto bufferSequentialData = [&](){
+        QByteArray buffer(1 << 25, Qt::Uninitialized);
+        const qint64 read = infile->read(buffer.data(), buffer.length());
+        if (read < 0) {
+            qWarning() << "Failed to read from input.";
+            qApp->exit(BufferingError);
+            return;
+        }
+
+        if (!writeBytes(tempfile.data(), buffer.data(), read)) {
+            qWarning() << "Failed to write buffer file.";
+            qApp->exit(BufferingError);
+            return;
+        }
+    };
+
+    QObject::connect(&header, &PerfHeader::finished, [&]() {
+        unwind.setByteOrder(static_cast<QSysInfo::Endian>(header.byteOrder()));
+        if (!header.isPipe()) {
+            if (infile->isSequential()) {
+                qWarning() << "Reading a non-pipe perf.data from a stream requires buffering.";
+                tempfile.reset(new QTemporaryFile);
+                if (!tempfile->open(QIODevice::ReadWrite)) {
+                    qWarning() << "Failed to open buffer file.";
+                    qApp->exit(BufferingError);
+                    return;
+                }
+
+                // We've checked this when parsing the header.
+                Q_ASSERT(header.size() <= std::numeric_limits<int>::max());
+                const QByteArray fakeHeader(static_cast<int>(header.size()), 0);
+                if (!writeBytes(tempfile.data(), fakeHeader.data(), fakeHeader.length())) {
+                    qWarning() << "Failed to write fake header to buffer file.";
+                    qApp->exit(BufferingError);
+                    return;
+                }
+
+                QObject::connect(infile.data(), &QIODevice::readyRead, bufferSequentialData);
+                QObject::connect(infile.data(), &QIODevice::aboutToClose, [&]() {
+                    infile->disconnect();
+                    infile.swap(tempfile);
+                    if (!infile->reset()) {
+                        qWarning() << "Cannot reset buffer file.";
+                        qApp->exit(BufferingError);
+                        return;
+                    }
+                    readFileHeader();
+                    readData();
+                });
+
+                if (infile->bytesAvailable() > 0)
+                    bufferSequentialData();
+            } else {
+                readFileHeader();
+                readData();
+            }
+        } else {
+            readData();
+        }
     });
 
     QObject::connect(&header, &PerfHeader::error, []() {
diff --git a/app/perfdata.cpp b/app/perfdata.cpp
index ba1d05e..ce67043 100644
--- a/app/perfdata.cpp
+++ b/app/perfdata.cpp
@@ -28,12 +28,16 @@
 
 static const int intMax = std::numeric_limits<int>::max();
 
-PerfData::PerfData(QIODevice *source, PerfUnwind *destination, const PerfHeader *header,
-                   PerfAttributes *attributes) :
-    m_source(source), m_destination(destination), m_header(header), m_attributes(attributes)
+PerfData::PerfData(PerfUnwind *destination, const PerfHeader *header, PerfAttributes *attributes) :
+    m_source(nullptr), m_destination(destination), m_header(header), m_attributes(attributes)
 {
 }
 
+void PerfData::setSource(QIODevice *source)
+{
+    m_source = source;
+}
+
 PerfData::ReadStatus PerfData::processEvents(QDataStream &stream)
 {
     const quint16 headerSize = PerfEventHeader::fixedLength();
diff --git a/app/perfdata.h b/app/perfdata.h
index f6b9db3..13d31a0 100644
--- a/app/perfdata.h
+++ b/app/perfdata.h
@@ -463,8 +463,8 @@ class PerfData : public QObject
 {
     Q_OBJECT
 public:
-    PerfData(QIODevice *source, PerfUnwind *destination, const PerfHeader *header,
-             PerfAttributes *attributes);
+    PerfData(PerfUnwind *destination, const PerfHeader *header, PerfAttributes *attributes);
+    void setSource(QIODevice *source);
 
 public slots:
     void read();
diff --git a/app/perfheader.cpp b/app/perfheader.cpp
index b34e31b..d08d6c3 100644
--- a/app/perfheader.cpp
+++ b/app/perfheader.cpp
@@ -101,6 +101,7 @@ void PerfHeader::read()
     }
 
     disconnect(m_source, &QIODevice::readyRead, this, &PerfHeader::read);
+    m_source = nullptr;
     emit finished();
 }
 
diff --git a/tests/auto/perfdata/tst_perfdata.cpp b/tests/auto/perfdata/tst_perfdata.cpp
index 7ab1971..45bb5ea 100644
--- a/tests/auto/perfdata/tst_perfdata.cpp
+++ b/tests/auto/perfdata/tst_perfdata.cpp
@@ -66,7 +66,8 @@ static void process(PerfUnwind *unwind, QIODevice *input)
 {
     PerfHeader header(input);
     PerfAttributes attributes;
-    PerfData data(input, unwind, &header, &attributes);
+    PerfData data(unwind, &header, &attributes);
+    data.setSource(input);
 
     QSignalSpy spy(&data, SIGNAL(finished()));
     QObject::connect(&header, &PerfHeader::finished, &data, [&](){