From 7efd2a6d59d1de38d0b0ae83415589a08b30f8d9 Mon Sep 17 00:00:00 2001
From: asynts <asynts@gmail.com>
Date: Tue, 1 Sep 2020 16:16:32 +0200
Subject: [PATCH] AK: Add OutputMemoryStream class.

---
 AK/Forward.h                  |  2 ++
 AK/MemoryStream.h             | 16 ++++++++++++++++
 AK/Tests/TestMemoryStream.cpp | 11 +++++++++++
 3 files changed, 29 insertions(+)

diff --git a/AK/Forward.h b/AK/Forward.h
index 1f2c47cd66..6550f7d39f 100644
--- a/AK/Forward.h
+++ b/AK/Forward.h
@@ -53,6 +53,7 @@ class InputMemoryStream;
 class DuplexMemoryStream;
 class OutputStream;
 class InputBitStream;
+class OutputMemoryStream;
 
 template<size_t Capacity>
 class CircularDuplexStream;
@@ -150,6 +151,7 @@ using AK::LogStream;
 using AK::NonnullOwnPtr;
 using AK::NonnullRefPtr;
 using AK::Optional;
+using AK::OutputMemoryStream;
 using AK::OutputStream;
 using AK::OwnPtr;
 using AK::ReadonlyBytes;
diff --git a/AK/MemoryStream.h b/AK/MemoryStream.h
index dc8818698e..b8bc5577ce 100644
--- a/AK/MemoryStream.h
+++ b/AK/MemoryStream.h
@@ -308,8 +308,24 @@ private:
     size_t m_base_offset { 0 };
 };
 
+class OutputMemoryStream final : public OutputStream {
+public:
+    size_t write(ReadonlyBytes bytes) override { return m_stream.write(bytes); }
+    bool write_or_error(ReadonlyBytes bytes) override { return m_stream.write_or_error(bytes); }
+
+    ByteBuffer copy_into_contiguous_buffer() const { return m_stream.copy_into_contiguous_buffer(); }
+
+    Optional<size_t> offset_of(ReadonlyBytes value) const { return m_stream.offset_of(value); }
+
+    size_t size() const { return m_stream.woffset(); }
+
+private:
+    DuplexMemoryStream m_stream;
+};
+
 }
 
 using AK::DuplexMemoryStream;
 using AK::InputMemoryStream;
 using AK::InputStream;
+using AK::OutputMemoryStream;
diff --git a/AK/Tests/TestMemoryStream.cpp b/AK/Tests/TestMemoryStream.cpp
index 611b24ef60..61e8266af4 100644
--- a/AK/Tests/TestMemoryStream.cpp
+++ b/AK/Tests/TestMemoryStream.cpp
@@ -160,4 +160,15 @@ TEST_CASE(read_endian_values)
     EXPECT_EQ(value2, 0x04050607u);
 }
 
+TEST_CASE(write_endian_values)
+{
+    const u8 expected[] { 4, 3, 2, 1, 1, 2, 3, 4 };
+
+    OutputMemoryStream stream;
+    stream << LittleEndian<u32> { 0x01020304 } << BigEndian<u32> { 0x01020304 };
+
+    EXPECT_EQ(stream.size(), 8u);
+    EXPECT(compare({ expected, sizeof(expected) }, stream.copy_into_contiguous_buffer()));
+}
+
 TEST_MAIN(MemoryStream)