AK: Move memory streams from LibCore

AK/MemoryStream.cpp

@@ -0,0 +1,275 @@
+/*
+ * Copyright (c) 2021, kleines Filmröllchen <filmroellchen@serenityos.org>.
+ * Copyright (c) 2022, Tim Schumacher <timschumi@gmx.de>.
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/ByteBuffer.h>
+#include <AK/FixedArray.h>
+#include <AK/MemMem.h>
+#include <AK/MemoryStream.h>
+
+namespace AK {
+
+FixedMemoryStream::FixedMemoryStream(Bytes bytes)
+    : m_bytes(bytes)
+{
+}
+
+FixedMemoryStream::FixedMemoryStream(ReadonlyBytes bytes)
+    : m_bytes({ const_cast<u8*>(bytes.data()), bytes.size() })
+    , m_writing_enabled(false)
+{
+}
+
+ErrorOr<NonnullOwnPtr<FixedMemoryStream>> FixedMemoryStream::construct(Bytes bytes)
+{
+    return adopt_nonnull_own_or_enomem<FixedMemoryStream>(new (nothrow) FixedMemoryStream(bytes));
+}
+
+ErrorOr<NonnullOwnPtr<FixedMemoryStream>> FixedMemoryStream::construct(ReadonlyBytes bytes)
+{
+    return adopt_nonnull_own_or_enomem<FixedMemoryStream>(new (nothrow) FixedMemoryStream(bytes));
+}
+
+bool FixedMemoryStream::is_eof() const
+{
+    return m_offset >= m_bytes.size();
+}
+
+bool FixedMemoryStream::is_open() const
+{
+    return true;
+}
+
+void FixedMemoryStream::close()
+{
+    // FIXME: It doesn't make sense to close a memory stream. Therefore, we don't do anything here. Is that fine?
+}
+
+ErrorOr<void> FixedMemoryStream::truncate(off_t)
+{
+    return Error::from_errno(EBADF);
+}
+
+ErrorOr<Bytes> FixedMemoryStream::read(Bytes bytes)
+{
+    auto to_read = min(remaining(), bytes.size());
+    if (to_read == 0)
+        return Bytes {};
+
+    m_bytes.slice(m_offset, to_read).copy_to(bytes);
+    m_offset += to_read;
+    return bytes.trim(to_read);
+}
+
+ErrorOr<size_t> FixedMemoryStream::seek(i64 offset, SeekMode seek_mode)
+{
+    switch (seek_mode) {
+    case SeekMode::SetPosition:
+        if (offset > static_cast<i64>(m_bytes.size()))
+            return Error::from_string_literal("Offset past the end of the stream memory");
+
+        m_offset = offset;
+        break;
+    case SeekMode::FromCurrentPosition:
+        if (offset + static_cast<i64>(m_offset) > static_cast<i64>(m_bytes.size()))
+            return Error::from_string_literal("Offset past the end of the stream memory");
+
+        m_offset += offset;
+        break;
+    case SeekMode::FromEndPosition:
+        if (offset > static_cast<i64>(m_bytes.size()))
+            return Error::from_string_literal("Offset past the start of the stream memory");
+
+        m_offset = m_bytes.size() - offset;
+        break;
+    }
+    return m_offset;
+}
+
+ErrorOr<size_t> FixedMemoryStream::write(ReadonlyBytes bytes)
+{
+    VERIFY(m_writing_enabled);
+
+    // FIXME: Can this not error?
+    auto const nwritten = bytes.copy_trimmed_to(m_bytes.slice(m_offset));
+    m_offset += nwritten;
+    return nwritten;
+}
+
+ErrorOr<void> FixedMemoryStream::write_entire_buffer(ReadonlyBytes bytes)
+{
+    if (remaining() < bytes.size())
+        return Error::from_string_literal("Write of entire buffer ends past the memory area");
+
+    TRY(write(bytes));
+    return {};
+}
+
+Bytes FixedMemoryStream::bytes()
+{
+    VERIFY(m_writing_enabled);
+    return m_bytes;
+}
+ReadonlyBytes FixedMemoryStream::bytes() const
+{
+    return m_bytes;
+}
+
+size_t FixedMemoryStream::offset() const
+{
+    return m_offset;
+}
+
+size_t FixedMemoryStream::remaining() const
+{
+    return m_bytes.size() - m_offset;
+}
+
+ErrorOr<Bytes> AllocatingMemoryStream::read(Bytes bytes)
+{
+    size_t read_bytes = 0;
+
+    while (read_bytes < bytes.size()) {
+        VERIFY(m_write_offset >= m_read_offset);
+
+        auto range = TRY(next_read_range());
+        if (range.size() == 0)
+            break;
+
+        auto copied_bytes = range.copy_trimmed_to(bytes.slice(read_bytes));
+
+        read_bytes += copied_bytes;
+        m_read_offset += copied_bytes;
+    }
+
+    cleanup_unused_chunks();
+
+    return bytes.trim(read_bytes);
+}
+
+ErrorOr<size_t> AllocatingMemoryStream::write(ReadonlyBytes bytes)
+{
+    size_t written_bytes = 0;
+
+    while (written_bytes < bytes.size()) {
+        VERIFY(m_write_offset >= m_read_offset);
+
+        auto range = TRY(next_write_range());
+
+        auto copied_bytes = bytes.slice(written_bytes).copy_trimmed_to(range);
+
+        written_bytes += copied_bytes;
+        m_write_offset += copied_bytes;
+    }
+
+    return written_bytes;
+}
+
+ErrorOr<void> AllocatingMemoryStream::discard(size_t count)
+{
+    VERIFY(m_write_offset >= m_read_offset);
+
+    if (count > used_buffer_size())
+        return Error::from_string_literal("Number of discarded bytes is higher than the number of allocated bytes");
+
+    m_read_offset += count;
+
+    cleanup_unused_chunks();
+
+    return {};
+}
+
+bool AllocatingMemoryStream::is_eof() const
+{
+    return used_buffer_size() == 0;
+}
+
+bool AllocatingMemoryStream::is_open() const
+{
+    return true;
+}
+
+void AllocatingMemoryStream::close()
+{
+}
+
+size_t AllocatingMemoryStream::used_buffer_size() const
+{
+    return m_write_offset - m_read_offset;
+}
+
+ErrorOr<Optional<size_t>> AllocatingMemoryStream::offset_of(ReadonlyBytes needle) const
+{
+    VERIFY(m_write_offset >= m_read_offset);
+
+    if (m_chunks.size() == 0)
+        return Optional<size_t> {};
+
+    // Ensure that we don't have to trim away more than one block.
+    VERIFY(m_read_offset < chunk_size);
+    VERIFY(m_chunks.size() * chunk_size - m_write_offset < chunk_size);
+
+    auto chunk_count = m_chunks.size();
+    auto search_spans = TRY(FixedArray<ReadonlyBytes>::create(chunk_count));
+
+    for (size_t i = 0; i < chunk_count; i++) {
+        search_spans[i] = m_chunks[i].span();
+    }
+
+    // Trimming is done first to ensure that we don't unintentionally shift around if the first and last chunks are the same.
+    search_spans[chunk_count - 1] = search_spans[chunk_count - 1].trim(m_write_offset % chunk_size);
+    search_spans[0] = search_spans[0].slice(m_read_offset);
+
+    return AK::memmem(search_spans.begin(), search_spans.end(), needle);
+}
+
+ErrorOr<ReadonlyBytes> AllocatingMemoryStream::next_read_range()
+{
+    VERIFY(m_write_offset >= m_read_offset);
+
+    size_t const chunk_index = m_read_offset / chunk_size;
+    size_t const chunk_offset = m_read_offset % chunk_size;
+    size_t const read_size = min(chunk_size - m_read_offset % chunk_size, m_write_offset - m_read_offset);
+
+    if (read_size == 0)
+        return ReadonlyBytes { static_cast<u8*>(nullptr), 0 };
+
+    VERIFY(chunk_index < m_chunks.size());
+
+    return ReadonlyBytes { m_chunks[chunk_index].data() + chunk_offset, read_size };
+}
+
+ErrorOr<Bytes> AllocatingMemoryStream::next_write_range()
+{
+    VERIFY(m_write_offset >= m_read_offset);
+
+    size_t const chunk_index = m_write_offset / chunk_size;
+    size_t const chunk_offset = m_write_offset % chunk_size;
+    size_t const write_size = chunk_size - m_write_offset % chunk_size;
+
+    if (chunk_index >= m_chunks.size())
+        TRY(m_chunks.try_append(TRY(Chunk::create_uninitialized(chunk_size))));
+
+    VERIFY(chunk_index < m_chunks.size());
+
+    return Bytes { m_chunks[chunk_index].data() + chunk_offset, write_size };
+}
+
+void AllocatingMemoryStream::cleanup_unused_chunks()
+{
+    // FIXME: Move these all at once.
+    while (m_read_offset >= chunk_size) {
+        VERIFY(m_write_offset >= m_read_offset);
+
+        auto buffer = m_chunks.take_first();
+        m_read_offset -= chunk_size;
+        m_write_offset -= chunk_size;
+
+        m_chunks.append(move(buffer));
+    }
+}
+
+}