LibIPC+IPCCompiler: Add IPC::Decoder, let classes decode themselves

This shaves ~5 seconds off of a full build, not too bad. Also it just
seems nicer to push this logic out to classes. It could be better but
it's a start. :^)

Libraries/LibIPC/Decoder.cpp

@@ -0,0 +1,115 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * 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 <AK/BufferStream.h>
+#include <LibIPC/Decoder.h>
+
+namespace IPC {
+
+bool Decoder::decode(bool& value)
+{
+    m_stream >> value;
+    return !m_stream.handle_read_failure();
+}
+
+bool Decoder::decode(u8& value)
+{
+    m_stream >> value;
+    return !m_stream.handle_read_failure();
+}
+
+bool Decoder::decode(u16& value)
+{
+    m_stream >> value;
+    return !m_stream.handle_read_failure();
+}
+
+bool Decoder::decode(u32& value)
+{
+    m_stream >> value;
+    return !m_stream.handle_read_failure();
+}
+
+bool Decoder::decode(u64& value)
+{
+    m_stream >> value;
+    return !m_stream.handle_read_failure();
+}
+
+bool Decoder::decode(i8& value)
+{
+    m_stream >> value;
+    return !m_stream.handle_read_failure();
+}
+
+bool Decoder::decode(i16& value)
+{
+    m_stream >> value;
+    return !m_stream.handle_read_failure();
+}
+
+bool Decoder::decode(i32& value)
+{
+    m_stream >> value;
+    return !m_stream.handle_read_failure();
+}
+
+bool Decoder::decode(i64& value)
+{
+    m_stream >> value;
+    return !m_stream.handle_read_failure();
+}
+
+bool Decoder::decode(float& value)
+{
+    m_stream >> value;
+    return !m_stream.handle_read_failure();
+}
+
+bool Decoder::decode(String& value)
+{
+    i32 length = 0;
+    m_stream >> length;
+    if (m_stream.handle_read_failure())
+        return false;
+    if (length < 0) {
+        value = {};
+        return true;
+    }
+    if (length == 0) {
+        value = String::empty();
+        return true;
+    }
+    char* text_buffer = nullptr;
+    auto text_impl = StringImpl::create_uninitialized(static_cast<size_t>(length), text_buffer);
+    for (size_t i = 0; i < static_cast<size_t>(length); ++i) {
+        m_stream >> text_buffer[i];
+    }
+    value = *text_impl;
+    return !m_stream.handle_read_failure();
+}
+
+}