Added GzipDevice

CMakeLists.txt

@@ -3,6 +3,7 @@ project(DbCoreLib)
 find_package(Qt5Core CONFIG REQUIRED)
 find_package(Qt5Test CONFIG REQUIRED)
 find_package(Qt5LinguistTools CONFIG REQUIRED)
+find_package(ZLIB REQUIRED)
 
 enable_testing()
 
@@ -11,6 +12,7 @@ set(HEADERS
     dbcorelib_global.h
     fifostream.h
     fixedsizematrix.h
+    gzipdevice.h
     randomdevice.h
     waverecorder.h
     utils/datastreamutils.h
@@ -21,6 +23,7 @@ set(HEADERS
 
 set(SOURCES
     fifostream.cpp
+    gzipdevice.cpp
     randomdevice.cpp
     waverecorder.cpp
     utils/fileutils.cpp
@@ -41,7 +44,7 @@ add_library(dbcorelib SHARED ${HEADERS} ${SOURCES} ${TRANSLATIONS_C})
 
 target_compile_definitions(dbcorelib PRIVATE DBCORELIB_LIBRARY)
 
-target_link_libraries(dbcorelib Qt5::Core)
+target_link_libraries(dbcorelib Qt5::Core z)
 
 target_include_directories(dbcorelib PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
 
@@ -50,4 +53,4 @@ add_dependencies(libs dbcorelib)
 
 add_executable(tst_fixedsizematrix tst_fixedsizematrix.cpp)
 add_test(tst_fixedsizematrix tst_fixedsizematrix)
-target_link_libraries(tst_fixedsizematrix Qt5::Core Qt5::Test dbcorelib)
+target_link_libraries(tst_fixedsizematrix stdc++ Qt5::Core Qt5::Test dbcorelib)

gzipdevice.cpp

@@ -0,0 +1,80 @@
+#include "gzipdevice.h"
+
+#include <QFile>
+
+#include <stdexcept>
+
+#include <zlib.h>
+
+GzipDevice::GzipDevice(QFile &file, QObject *parent) :
+    QIODevice(parent),
+    m_file(file),
+    m_strm(std::make_unique<z_stream>())
+{
+    if (!m_file.isOpen())
+        throw std::runtime_error("file is not open");
+
+    setOpenMode(QIODevice::ReadOnly);
+
+    // Prepare inflater status
+    m_strm->zalloc = Z_NULL;
+    m_strm->zfree = Z_NULL;
+    m_strm->opaque = Z_NULL;
+    m_strm->avail_in = 0;
+    m_strm->next_in = Z_NULL;
+
+    // Initialize inflater
+    m_result = inflateInit2(m_strm.get(), 15 + 16);
+    if (m_result != Z_OK)
+        throw std::runtime_error("could not init z_stream");
+}
+
+GzipDevice::~GzipDevice()
+{
+    inflateEnd(m_strm.get());
+}
+
+bool GzipDevice::isSequential() const
+{
+    return true;
+}
+
+bool GzipDevice::atEnd() const
+{
+    return m_result == Z_STREAM_END;
+}
+
+qint64 GzipDevice::readData(char *data, qint64 maxlen)
+{
+    if (m_strm->avail_in == 0)
+    {
+        m_strm->next_in = reinterpret_cast<unsigned char *>(m_readBuffer);
+        m_strm->avail_in = m_file.read(m_readBuffer, m_readBufferSize);
+    }
+
+    m_strm->next_out = reinterpret_cast<unsigned char*>(data);
+    m_strm->avail_out = maxlen;
+
+    m_result = inflate(m_strm.get(), Z_NO_FLUSH);
+
+    switch (m_result) {
+    case Z_NEED_DICT:
+        throw std::runtime_error("decompression failed: Z_NEED_DICT");
+    case Z_DATA_ERROR:
+        throw std::runtime_error("decompression failed: Z_DATA_ERROR");
+    case Z_MEM_ERROR:
+        throw std::runtime_error("decompression failed: Z_MEM_ERROR");
+    case Z_STREAM_ERROR:
+        throw std::runtime_error("decompression failed: Z_STREAM_ERROR");
+    }
+
+    return maxlen-m_strm->avail_out;
+}
+
+qint64 GzipDevice::writeData(const char *data, qint64 len)
+{
+    Q_UNUSED(data)
+    Q_UNUSED(len)
+    throw std::runtime_error("writing not allowed!");
+    return -1;
+}

gzipdevice.h

@@ -0,0 +1,30 @@
+#pragma once
+
+#include <QIODevice>
+
+#include <memory>
+
+class QFile;
+
+typedef struct z_stream_s z_stream;
+
+class GzipDevice : public QIODevice
+{
+public:
+    GzipDevice(QFile &file, QObject *parent = nullptr);
+    ~GzipDevice() override;
+
+    bool isSequential() const override;
+    bool atEnd() const override;
+
+protected:
+    qint64 readData(char *data, qint64 maxlen) override;
+    qint64 writeData(const char *data, qint64 len) override;
+
+private:
+    QFile &m_file;
+    static constexpr std::size_t m_readBufferSize { 32 * 1024 };
+    char m_readBuffer[m_readBufferSize];
+    const std::unique_ptr<z_stream> m_strm;
+    int m_result;
+};