AK: Add InputStream abstraction and InputMemoryStream implementation.

AK/Stream.h

@@ -0,0 +1,169 @@
+/*
+ * Copyright (c) 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/Concepts.h>
+#include <AK/Forward.h>
+#include <AK/Span.h>
+#include <AK/StdLibExtras.h>
+
+namespace AK::Detail {
+
+class Stream {
+public:
+    virtual ~Stream()
+    {
+        ASSERT(!error() && !fatal());
+    }
+
+    bool error() const { return m_error; }
+    bool fatal() const { return m_fatal; }
+
+    bool handle_error() { return exchange(m_error, false); }
+
+    operator bool() const { return !m_error && !m_fatal; }
+
+protected:
+    mutable bool m_error { false };
+    mutable bool m_fatal { false };
+};
+
+}
+
+namespace AK {
+
+class InputStream : public AK::Detail::Stream {
+public:
+    virtual size_t read(Bytes) = 0;
+    virtual bool read_or_error(Bytes) = 0;
+    virtual bool eof() const = 0;
+    virtual bool discard_or_error(size_t count) = 0;
+};
+
+// clang-format off
+
+template<Concepts::Integral Integral>
+InputStream& operator>>(InputStream& stream, Integral& value)
+{
+    stream.read_or_error({ &value, sizeof(value) });
+    return stream;
+}
+
+#ifndef KERNEL
+template<Concepts::FloatingPoint FloatingPoint>
+InputStream& operator>>(InputStream& stream, FloatingPoint& value)
+{
+    stream.read_or_error({ &value, sizeof(value) });
+    return stream;
+}
+#endif
+
+// clang-format on
+
+inline InputStream& operator>>(InputStream& stream, bool& value)
+{
+    stream.read_or_error({ &value, sizeof(value) });
+    return stream;
+}
+
+inline InputStream& operator>>(InputStream& stream, Bytes bytes)
+{
+    stream.read_or_error(bytes);
+    return stream;
+}
+
+class InputMemoryStream final : public InputStream {
+    friend InputMemoryStream& operator>>(InputMemoryStream& stream, String& string);
+
+public:
+    InputMemoryStream(ReadonlyBytes bytes)
+        : m_bytes(bytes)
+    {
+    }
+
+    bool eof() const override { return m_offset >= m_bytes.size(); }
+
+    size_t read(Bytes bytes) override
+    {
+        const auto count = min(bytes.size(), remaining());
+        __builtin_memcpy(bytes.data(), m_bytes.data() + m_offset, count);
+        m_offset += count;
+        return count;
+    }
+
+    bool read_or_error(Bytes bytes) override
+    {
+        if (remaining() < bytes.size()) {
+            m_error = true;
+            return false;
+        }
+
+        __builtin_memcpy(bytes.data(), m_bytes.data() + m_offset, bytes.size());
+        m_offset += bytes.size();
+        return true;
+    }
+
+    bool discard_or_error(size_t count) override
+    {
+        if (remaining() < count) {
+            m_error = true;
+            return false;
+        }
+
+        m_offset += count;
+        return true;
+    }
+
+    void seek(size_t offset)
+    {
+        ASSERT(offset < m_bytes.size());
+        m_offset = offset;
+    }
+
+    u8 peek_or_error() const
+    {
+        if (remaining() == 0) {
+            m_error = true;
+            return 0;
+        }
+
+        return m_bytes[m_offset];
+    }
+
+    ReadonlyBytes bytes() const { return m_bytes; }
+    size_t offset() const { return m_offset; }
+    size_t remaining() const { return m_bytes.size() - m_offset; }
+
+private:
+    ReadonlyBytes m_bytes;
+    size_t m_offset { 0 };
+};
+
+}
+
+using AK::InputMemoryStream;
+using AK::InputStream;