LibAudio: Add generic Audio::Loader class

The Audio::Loader class is able to load different types of audio files
by using a generic plugin interface for all file formats. Every new
loader will have to derive from Audio::LoaderPlugin to provide a common
API.

This makes it easy to add support for more audio file formats in the future.

Libraries/LibAudio/CMakeLists.txt

@@ -1,5 +1,6 @@
 set(SOURCES
     ClientConnection.cpp
+    Loader.cpp
     WavLoader.cpp
     WavWriter.cpp
 )

Libraries/LibAudio/Loader.cpp

@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2018-2020, the SerenityOS developers.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <LibAudio/WavLoader.h>
+
+namespace Audio {
+
+Loader::Loader(const StringView& path)
+{
+    m_plugin = make<WavLoaderPlugin>(path);
+    if (m_plugin->sniff())
+        return;
+    m_plugin = nullptr;
+}
+
+}

Libraries/LibAudio/Loader.h

@@ -0,0 +1,91 @@
+/*
+ * Copyright (c) 2018-2020, the SerenityOS developers.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/RefCounted.h>
+#include <AK/RefPtr.h>
+#include <AK/StringView.h>
+#include <LibCore/File.h>
+
+namespace Audio {
+
+class LoaderPlugin {
+public:
+    virtual ~LoaderPlugin() { }
+
+    virtual bool sniff() = 0;
+
+    virtual bool has_error() { return false; }
+    virtual const char* error_string() { return ""; }
+
+    virtual RefPtr<Buffer> get_more_samples(size_t max_bytes_to_read_from_input = 128 * KiB) = 0;
+
+    virtual void reset() = 0;
+    virtual void seek(const int position) = 0;
+
+    virtual int loaded_samples() = 0;
+    virtual int total_samples() = 0;
+    virtual u32 sample_rate() = 0;
+    virtual u16 num_channels() = 0;
+    virtual u16 bits_per_sample() = 0;
+    virtual RefPtr<Core::File> file() = 0;
+};
+
+class Loader : public RefCounted<Loader> {
+public:
+    static NonnullRefPtr<Loader> create(const StringView& path) { return adopt(*new Loader(path)); }
+
+    bool has_error() const { return m_plugin ? m_plugin->has_error() : true; }
+    const char* error_string() const { return m_plugin ? m_plugin->error_string() : "No loader plugin available"; }
+
+    RefPtr<Buffer> get_more_samples(size_t max_bytes_to_read_from_input = 128 * KiB) const { return m_plugin ? m_plugin->get_more_samples(max_bytes_to_read_from_input) : nullptr; }
+
+    void reset() const
+    {
+        if (m_plugin)
+            m_plugin->reset();
+    }
+    void seek(const int position) const
+    {
+        if (m_plugin)
+            m_plugin->seek(position);
+    }
+
+    int loaded_samples() const { return m_plugin ? m_plugin->loaded_samples() : 0; }
+    int total_samples() const { return m_plugin ? m_plugin->total_samples() : 0; }
+    u32 sample_rate() const { return m_plugin ? m_plugin->sample_rate() : 0; }
+    u16 num_channels() const { return m_plugin ? m_plugin->num_channels() : 0; }
+    u16 bits_per_sample() const { return m_plugin ? m_plugin->bits_per_sample() : 0; }
+    RefPtr<Core::File> file() const { return m_plugin ? m_plugin->file() : nullptr; }
+
+private:
+    Loader(const StringView& path);
+
+    mutable OwnPtr<LoaderPlugin> m_plugin;
+};
+
+}

Libraries/LibAudio/WavLoader.cpp

@@ -33,7 +33,7 @@
 
 namespace Audio {
 
-WavLoader::WavLoader(const StringView& path)
+WavLoaderPlugin::WavLoaderPlugin(const StringView& path)
     : m_file(Core::File::construct(path))
 {
     if (!m_file->open(Core::IODevice::ReadOnly)) {
@@ -41,13 +41,19 @@ WavLoader::WavLoader(const StringView& path)
         return;
     }
 
-    if (!parse_header())
+    valid = parse_header();
+    if (!valid)
         return;
 
     m_resampler = make<ResampleHelper>(m_sample_rate, 44100);
 }
 
-RefPtr<Buffer> WavLoader::get_more_samples(size_t max_bytes_to_read_from_input)
+bool WavLoaderPlugin::sniff()
+{
+    return valid;
+}
+
+RefPtr<Buffer> WavLoaderPlugin::get_more_samples(size_t max_bytes_to_read_from_input)
 {
 #ifdef AWAVLOADER_DEBUG
     dbgln("Read WAV of format PCM with num_channels {} sample rate {}, bits per sample {}", m_num_channels, m_sample_rate, m_bits_per_sample);
@@ -64,7 +70,7 @@ RefPtr<Buffer> WavLoader::get_more_samples(size_t max_bytes_to_read_from_input)
     return buffer;
 }
 
-void WavLoader::seek(const int position)
+void WavLoaderPlugin::seek(const int position)
 {
     if (position < 0 || position > m_total_samples)
         return;
@@ -73,12 +79,12 @@ void WavLoader::seek(const int position)
     m_file->seek(position * m_num_channels * (m_bits_per_sample / 8));
 }
 
-void WavLoader::reset()
+void WavLoaderPlugin::reset()
 {
     seek(0);
 }
 
-bool WavLoader::parse_header()
+bool WavLoaderPlugin::parse_header()
 {
     Core::IODeviceStreamReader stream(*m_file);
 

Libraries/LibAudio/WavLoader.h

@@ -31,33 +31,38 @@
 #include <AK/String.h>
 #include <AK/StringView.h>
 #include <LibAudio/Buffer.h>
+#include <LibAudio/Loader.h>
 #include <LibCore/File.h>
 
 namespace Audio {
 class Buffer;
 
 // Parses a WAV file and produces an Audio::Buffer.
-class WavLoader {
+class WavLoaderPlugin : public LoaderPlugin {
 public:
-    explicit WavLoader(const StringView& path);
+    explicit WavLoaderPlugin(const StringView& path);
 
-    bool has_error() const { return !m_error_string.is_null(); }
-    const char* error_string() { return m_error_string.characters(); }
+    virtual bool sniff() override;
 
-    RefPtr<Buffer> get_more_samples(size_t max_bytes_to_read_from_input = 128 * KiB);
+    virtual bool has_error() override { return !m_error_string.is_null(); }
+    virtual const char* error_string() override { return m_error_string.characters(); }
 
-    void reset();
-    void seek(const int position);
+    virtual RefPtr<Buffer> get_more_samples(size_t max_bytes_to_read_from_input = 128 * KiB) override;
 
-    int loaded_samples() const { return m_loaded_samples; }
-    int total_samples() const { return m_total_samples; }
-    u32 sample_rate() const { return m_sample_rate; }
-    u16 num_channels() const { return m_num_channels; }
-    u16 bits_per_sample() const { return m_bits_per_sample; }
-    RefPtr<Core::File> file() const { return m_file; }
+    virtual void reset() override;
+    virtual void seek(const int position) override;
+
+    virtual int loaded_samples() override { return m_loaded_samples; }
+    virtual int total_samples() override { return m_total_samples; }
+    virtual u32 sample_rate() override { return m_sample_rate; }
+    virtual u16 num_channels() override { return m_num_channels; }
+    virtual u16 bits_per_sample() override { return m_bits_per_sample; }
+    virtual RefPtr<Core::File> file() override { return m_file; }
 
 private:
     bool parse_header();
+
+    bool valid { false };
     RefPtr<Core::File> m_file;
     String m_error_string;
     OwnPtr<ResampleHelper> m_resampler;