LibIPC: Let's start building custom message codecs for LibIPC

Instead of using ByteBuffer (which always malloc() their storage) for
IPC message encoding, we now use a Vector<u8, 1024>, which means that
messages smaller than 1 KB avoid heap allocation entirely.

DevTools/IPCCompiler/main.cpp

@@ -201,6 +201,7 @@ int main(int argc, char** argv)
     dbg() << "#include <AK/OwnPtr.h>";
     dbg() << "#include <LibDraw/Color.h>";
     dbg() << "#include <LibDraw/Rect.h>";
+    dbg() << "#include <LibIPC/IEncoder.h>";
     dbg() << "#include <LibIPC/IEndpoint.h>";
     dbg() << "#include <LibIPC/IMessage.h>";
     dbg();
@@ -358,11 +359,11 @@ int main(int argc, char** argv)
             dbg() << "        size_in_bytes = stream.offset();";
             dbg() << "        return make<" << name << ">(" << builder.to_string() << ");";
             dbg() << "    }";
-            dbg() << "    virtual ByteBuffer encode() const override";
+            dbg() << "    virtual IMessageBuffer encode() const override";
             dbg() << "    {";
             // FIXME: Support longer messages:
-            dbg() << "        auto buffer = ByteBuffer::create_uninitialized(4096);";
-            dbg() << "        BufferStream stream(buffer);";
+            dbg() << "        IMessageBuffer buffer;";
+            dbg() << "        IEncoder stream(buffer);";
             dbg() << "        stream << endpoint_magic();";
             dbg() << "        stream << (int)MessageID::" << name << ";";
             for (auto& parameter : parameters) {
@@ -398,7 +399,6 @@ int main(int argc, char** argv)
                     dbg() << "        stream << m_" << parameter.name << ";";
                 }
             }
-            dbg() << "        stream.snip();";
             dbg() << "        return buffer;";
             dbg() << "    }";
             for (auto& parameter : parameters) {

Libraries/LibIPC/IEncoder.h

@@ -0,0 +1,95 @@
+#pragma once
+
+#include <LibIPC/IMessage.h>
+
+class IEncoder {
+public:
+    explicit IEncoder(IMessageBuffer& buffer)
+        : m_buffer(buffer)
+    {
+    }
+
+    IEncoder& operator<<(bool value)
+    {
+        return *this << (u8)value;
+    }
+
+    IEncoder& operator<<(u8 value)
+    {
+        m_buffer.append(value);
+        return *this;
+    }
+
+    IEncoder& operator<<(u16 value)
+    {
+        m_buffer.ensure_capacity(m_buffer.size() + 2);
+        m_buffer.unchecked_append((u8)value);
+        m_buffer.unchecked_append((u8)(value >> 8));
+        return *this;
+    }
+
+    IEncoder& operator<<(u32 value)
+    {
+        m_buffer.ensure_capacity(m_buffer.size() + 4);
+        m_buffer.unchecked_append((u8)value);
+        m_buffer.unchecked_append((u8)(value >> 8));
+        m_buffer.unchecked_append((u8)(value >> 16));
+        m_buffer.unchecked_append((u8)(value >> 24));
+        return *this;
+    }
+
+    IEncoder& operator<<(i8 value)
+    {
+        m_buffer.append((u8)value);
+        return *this;
+    }
+
+    IEncoder& operator<<(i16 value)
+    {
+        m_buffer.ensure_capacity(m_buffer.size() + 2);
+        m_buffer.unchecked_append((u8)value);
+        m_buffer.unchecked_append((u8)(value >> 8));
+        return *this;
+    }
+
+    IEncoder& operator<<(i32 value)
+    {
+        m_buffer.ensure_capacity(m_buffer.size() + 4);
+        m_buffer.unchecked_append((u8)value);
+        m_buffer.unchecked_append((u8)(value >> 8));
+        m_buffer.unchecked_append((u8)(value >> 16));
+        m_buffer.unchecked_append((u8)(value >> 24));
+        return *this;
+    }
+
+#ifdef __serenity__
+    IEncoder& operator<<(size_t value)
+    {
+        return *this << (u32)value;
+    }
+#endif
+
+    IEncoder& operator<<(float value)
+    {
+        union bits {
+            float as_float;
+            u32 as_u32;
+        } u;
+        u.as_float = value;
+        return *this << u.as_u32;
+    }
+
+    IEncoder& operator<<(const char* value)
+    {
+        return *this << StringView(value);
+    }
+
+    IEncoder& operator<<(const StringView& value)
+    {
+        m_buffer.append((const u8*)value.characters_without_null_termination(), value.length());
+        return *this;
+    }
+
+private:
+    IMessageBuffer& m_buffer;
+};

Libraries/LibIPC/IMessage.h

@@ -1,7 +1,8 @@
 #pragma once
 
 #include <AK/String.h>
-#include <AK/ByteBuffer.h>
+
+typedef Vector<u8, 1024> IMessageBuffer;
 
 class IMessage {
 public:
@@ -10,7 +11,7 @@ public:
     virtual int endpoint_magic() const = 0;
     virtual int message_id() const = 0;
     virtual String message_name() const = 0;
-    virtual ByteBuffer encode() const = 0;
+    virtual IMessageBuffer encode() const = 0;
 
 protected:
     IMessage();