AK: Add a Stream wrapper that counts read bytes

AK/CMakeLists.txt

@@ -3,6 +3,7 @@ set(AK_SOURCES
     Base64.cpp
     CircularBuffer.cpp
     ConstrainedStream.cpp
+    CountingStream.cpp
     DOSPackedTime.cpp
     DeprecatedFlyString.cpp
     DeprecatedString.cpp

AK/CountingStream.cpp

@@ -0,0 +1,58 @@
+/*
+ * Copyright (c) 2023, Tim Schumacher <timschumi@gmx.de>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/CountingStream.h>
+
+namespace AK {
+
+CountingStream::CountingStream(MaybeOwned<Stream> stream)
+    : m_stream(move(stream))
+{
+}
+
+u64 CountingStream::read_bytes() const
+{
+    return m_read_bytes;
+}
+
+ErrorOr<Bytes> CountingStream::read_some(Bytes bytes)
+{
+    auto result = TRY(m_stream->read_some(bytes));
+
+    m_read_bytes += result.size();
+
+    return result;
+}
+
+ErrorOr<void> CountingStream::discard(size_t discarded_bytes)
+{
+    TRY(m_stream->discard(discarded_bytes));
+
+    m_read_bytes += discarded_bytes;
+
+    return {};
+}
+
+ErrorOr<size_t> CountingStream::write_some(ReadonlyBytes bytes)
+{
+    return m_stream->write_some(bytes);
+}
+
+bool CountingStream::is_eof() const
+{
+    return m_stream->is_eof();
+}
+
+bool CountingStream::is_open() const
+{
+    return m_stream->is_open();
+}
+
+void CountingStream::close()
+{
+}
+
+}

AK/CountingStream.h

@@ -0,0 +1,32 @@
+/*
+ * Copyright (c) 2023, Tim Schumacher <timschumi@gmx.de>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/MaybeOwned.h>
+#include <AK/Stream.h>
+
+namespace AK {
+
+class CountingStream : public Stream {
+public:
+    CountingStream(MaybeOwned<Stream>);
+
+    u64 read_bytes() const;
+
+    virtual ErrorOr<Bytes> read_some(Bytes) override;
+    virtual ErrorOr<void> discard(size_t discarded_bytes) override;
+    virtual ErrorOr<size_t> write_some(ReadonlyBytes) override;
+    virtual bool is_eof() const override;
+    virtual bool is_open() const override;
+    virtual void close() override;
+
+private:
+    MaybeOwned<Stream> m_stream;
+    u64 m_read_bytes { 0 };
+};
+
+}

AK/Forward.h

@@ -23,6 +23,7 @@ class Bitmap;
 using ByteBuffer = Detail::ByteBuffer<32>;
 class CircularBuffer;
 class ConstrainedStream;
+class CountingStream;
 class DeprecatedFlyString;
 class DeprecatedString;
 class DeprecatedStringCodePointIterator;
@@ -157,6 +158,7 @@ using AK::Bytes;
 using AK::CircularBuffer;
 using AK::CircularQueue;
 using AK::ConstrainedStream;
+using AK::CountingStream;
 using AK::DeprecatedFlyString;
 using AK::DeprecatedString;
 using AK::DeprecatedStringCodePointIterator;