AK: Move memory streams into their own header.

AK/MemoryStream.h

@@ -0,0 +1,299 @@
+/*
+ * 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/ByteBuffer.h>
+#include <AK/MemMem.h>
+#include <AK/Stream.h>
+#include <AK/Vector.h>
+
+namespace AK {
+
+class InputMemoryStream final : public InputStream {
+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()) {
+            set_recoverable_error();
+            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) {
+            set_recoverable_error();
+            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) {
+            set_recoverable_error();
+            return 0;
+        }
+
+        return m_bytes[m_offset];
+    }
+
+    // LEB128 is a variable-length encoding for integers
+    bool read_LEB128_unsigned(size_t& result)
+    {
+        const auto backup = m_offset;
+
+        result = 0;
+        size_t num_bytes = 0;
+        while (true) {
+            // Note. The implementation in AK::BufferStream::read_LEB128_unsigned read one
+            //       past the end, this is fixed here.
+            if (eof()) {
+                m_offset = backup;
+                set_recoverable_error();
+                return false;
+            }
+
+            const u8 byte = m_bytes[m_offset];
+            result = (result) | (static_cast<size_t>(byte & ~(1 << 7)) << (num_bytes * 7));
+            ++m_offset;
+            if (!(byte & (1 << 7)))
+                break;
+            ++num_bytes;
+        }
+
+        return true;
+    }
+
+    // LEB128 is a variable-length encoding for integers
+    bool read_LEB128_signed(ssize_t& result)
+    {
+        const auto backup = m_offset;
+
+        result = 0;
+        size_t num_bytes = 0;
+        u8 byte = 0;
+
+        do {
+            // Note. The implementation in AK::BufferStream::read_LEB128_unsigned read one
+            //       past the end, this is fixed here.
+            if (eof()) {
+                m_offset = backup;
+                set_recoverable_error();
+                return false;
+            }
+
+            byte = m_bytes[m_offset];
+            result = (result) | (static_cast<size_t>(byte & ~(1 << 7)) << (num_bytes * 7));
+            ++m_offset;
+            ++num_bytes;
+        } while (byte & (1 << 7));
+
+        if (num_bytes * 7 < sizeof(size_t) * 4 && (byte & 0x40)) {
+            // sign extend
+            result |= ((size_t)(-1) << (num_bytes * 7));
+        }
+
+        return true;
+    }
+
+    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 };
+};
+
+// All data written to this stream can be read from it. Reading and writing is done
+// using different offsets, meaning that it is not necessary to seek to the start
+// before reading; this behaviour differs from BufferStream.
+class DuplexMemoryStream final : public DuplexStream {
+public:
+    static constexpr size_t chunk_size = 4 * 1024;
+
+    bool eof() const override { return m_write_offset == m_read_offset; }
+
+    bool discard_or_error(size_t count) override
+    {
+        if (m_write_offset - m_read_offset < count) {
+            set_recoverable_error();
+            return false;
+        }
+
+        m_read_offset += count;
+        try_discard_chunks();
+        return true;
+    }
+
+    Optional<size_t> offset_of(ReadonlyBytes value) const
+    {
+        if (value.size() > remaining())
+            return {};
+
+        // First, find which chunk we're in.
+        auto chunk_index = (m_read_offset - m_base_offset) / chunk_size;
+        auto last_written_chunk_index = (m_write_offset - m_base_offset) / chunk_size;
+        auto first_chunk_index = chunk_index;
+        auto last_written_chunk_offset = m_write_offset % chunk_size;
+        auto first_chunk_offset = m_read_offset % chunk_size;
+        size_t last_chunk_offset = 0;
+        auto found_value = false;
+
+        for (; chunk_index <= last_written_chunk_index; ++chunk_index) {
+            auto chunk_bytes = m_chunks[chunk_index].bytes();
+            size_t chunk_offset = 0;
+            if (chunk_index == last_written_chunk_index) {
+                chunk_bytes = chunk_bytes.slice(0, last_written_chunk_offset);
+            }
+            if (chunk_index == first_chunk_index) {
+                chunk_bytes = chunk_bytes.slice(first_chunk_offset);
+                chunk_offset = first_chunk_offset;
+            }
+
+            // See if 'value' is in this chunk,
+            auto position = AK::memmem(chunk_bytes.data(), chunk_bytes.size(), value.data(), value.size());
+            if (!position)
+                continue; // Not in this chunk either :(
+
+            // We found it!
+            found_value = true;
+            last_chunk_offset = (const u8*)position - chunk_bytes.data() + chunk_offset;
+            break;
+        }
+
+        if (found_value) {
+            if (first_chunk_index == chunk_index)
+                return last_chunk_offset - first_chunk_offset;
+
+            return (chunk_index - first_chunk_index) * chunk_size + last_chunk_offset - first_chunk_offset;
+        }
+
+        // No dice.
+        return {};
+    }
+
+    size_t read(Bytes bytes) override
+    {
+        size_t nread = 0;
+        while (bytes.size() - nread > 0 && m_write_offset - m_read_offset - nread > 0) {
+            const auto chunk_index = (m_read_offset - m_base_offset) / chunk_size;
+            const auto chunk_bytes = m_chunks[chunk_index].bytes().slice(m_read_offset % chunk_size).trim(m_write_offset - m_read_offset - nread);
+            nread += chunk_bytes.copy_trimmed_to(bytes.slice(nread));
+        }
+
+        m_read_offset += nread;
+
+        try_discard_chunks();
+
+        return nread;
+    }
+
+    bool read_or_error(Bytes bytes) override
+    {
+        if (m_write_offset - m_read_offset < bytes.size()) {
+            set_recoverable_error();
+            return false;
+        }
+
+        read(bytes);
+        return true;
+    }
+
+    size_t write(ReadonlyBytes bytes) override
+    {
+        size_t nwritten = 0;
+        while (bytes.size() - nwritten > 0) {
+            if ((m_write_offset + nwritten) % chunk_size == 0)
+                m_chunks.append(ByteBuffer::create_uninitialized(chunk_size));
+
+            nwritten += bytes.copy_trimmed_to(m_chunks.last().bytes().slice(m_write_offset % chunk_size));
+        }
+
+        m_write_offset += nwritten;
+        return nwritten;
+    }
+
+    bool write_or_error(ReadonlyBytes bytes) override
+    {
+        write(bytes);
+        return true;
+    }
+
+    size_t roffset() const { return m_read_offset; }
+    size_t woffset() const { return m_write_offset; }
+
+    size_t remaining() const { return m_write_offset - m_read_offset; }
+
+private:
+    void try_discard_chunks()
+    {
+        while (m_read_offset - m_base_offset >= chunk_size) {
+            m_chunks.take_first();
+            m_base_offset += chunk_size;
+        }
+    }
+
+    Vector<ByteBuffer> m_chunks;
+    size_t m_write_offset { 0 };
+    size_t m_read_offset { 0 };
+    size_t m_base_offset { 0 };
+};
+
+}
+
+using AK::DuplexMemoryStream;
+using AK::InputMemoryStream;
+using AK::InputStream;