serenity/AK/ByteBuffer.h

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/*
* Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2021, Gunnar Beutner <gbeutner@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <AK/Assertions.h>
#include <AK/Error.h>
#include <AK/Span.h>
#include <AK/Types.h>
#include <AK/kmalloc.h>
namespace AK {
namespace Detail {
template<size_t inline_capacity>
class ByteBuffer {
public:
ByteBuffer() = default;
~ByteBuffer()
{
clear();
}
ByteBuffer(ByteBuffer const& other)
{
MUST(try_resize(other.size()));
VERIFY(m_size == other.size());
__builtin_memcpy(data(), other.data(), other.size());
}
ByteBuffer(ByteBuffer&& other)
{
move_from(move(other));
}
ByteBuffer& operator=(ByteBuffer&& other)
{
if (this != &other) {
if (!m_inline)
kfree_sized(m_outline_buffer, m_outline_capacity);
move_from(move(other));
}
return *this;
}
ByteBuffer& operator=(ByteBuffer const& other)
{
if (this != &other) {
if (m_size > other.size()) {
trim(other.size(), true);
} else {
MUST(try_resize(other.size()));
}
__builtin_memcpy(data(), other.data(), other.size());
}
return *this;
}
[[nodiscard]] static ErrorOr<ByteBuffer> create_uninitialized(size_t size)
{
auto buffer = ByteBuffer();
TRY(buffer.try_resize(size));
return { move(buffer) };
}
[[nodiscard]] static ErrorOr<ByteBuffer> create_zeroed(size_t size)
{
auto buffer = TRY(create_uninitialized(size));
buffer.zero_fill();
VERIFY(size == 0 || (buffer[0] == 0 && buffer[size - 1] == 0));
return { move(buffer) };
}
[[nodiscard]] static ErrorOr<ByteBuffer> copy(void const* data, size_t size)
{
auto buffer = TRY(create_uninitialized(size));
if (buffer.m_inline && size > inline_capacity)
VERIFY_NOT_REACHED();
if (size != 0)
__builtin_memcpy(buffer.data(), data, size);
return { move(buffer) };
}
[[nodiscard]] static ErrorOr<ByteBuffer> copy(ReadonlyBytes bytes)
{
return copy(bytes.data(), bytes.size());
}
template<size_t other_inline_capacity>
bool operator==(ByteBuffer<other_inline_capacity> const& other) const
{
if (size() != other.size())
return false;
// So they both have data, and the same length.
return !__builtin_memcmp(data(), other.data(), size());
}
[[nodiscard]] u8& operator[](size_t i)
{
VERIFY(i < m_size);
return data()[i];
}
[[nodiscard]] u8 const& operator[](size_t i) const
{
VERIFY(i < m_size);
return data()[i];
}
[[nodiscard]] bool is_empty() const { return m_size == 0; }
[[nodiscard]] size_t size() const { return m_size; }
#ifdef AK_COMPILER_GCC
# pragma GCC diagnostic push
// Workaround for https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109727
# pragma GCC diagnostic ignored "-Warray-bounds"
#endif
[[nodiscard]] u8* data()
{
return m_inline ? m_inline_buffer : m_outline_buffer;
}
[[nodiscard]] u8 const* data() const { return m_inline ? m_inline_buffer : m_outline_buffer; }
#ifdef AK_COMPILER_GCC
# pragma GCC diagnostic pop
#endif
[[nodiscard]] Bytes bytes()
{
return { data(), size() };
}
[[nodiscard]] ReadonlyBytes bytes() const { return { data(), size() }; }
[[nodiscard]] AK::Bytes span() { return { data(), size() }; }
[[nodiscard]] AK::ReadonlyBytes span() const { return { data(), size() }; }
[[nodiscard]] u8* offset_pointer(size_t offset) { return data() + offset; }
[[nodiscard]] u8 const* offset_pointer(size_t offset) const { return data() + offset; }
[[nodiscard]] void* end_pointer() { return data() + m_size; }
[[nodiscard]] void const* end_pointer() const { return data() + m_size; }
[[nodiscard]] ErrorOr<ByteBuffer> slice(size_t offset, size_t size) const
{
// I cannot hand you a slice I don't have
VERIFY(offset + size <= this->size());
return copy(offset_pointer(offset), size);
}
void clear()
{
if (!m_inline) {
kfree_sized(m_outline_buffer, m_outline_capacity);
m_inline = true;
}
m_size = 0;
}
ALWAYS_INLINE void resize(size_t new_size)
{
MUST(try_resize(new_size));
}
ALWAYS_INLINE void ensure_capacity(size_t new_capacity)
{
MUST(try_ensure_capacity(new_capacity));
}
ErrorOr<void> try_resize(size_t new_size)
{
if (new_size <= m_size) {
trim(new_size, false);
return {};
}
TRY(try_ensure_capacity(new_size));
m_size = new_size;
return {};
}
ErrorOr<void> try_ensure_capacity(size_t new_capacity)
{
if (new_capacity <= capacity())
return {};
return try_ensure_capacity_slowpath(new_capacity);
}
/// Return a span of bytes past the end of this ByteBuffer for writing.
/// Ensures that the required space is available.
ErrorOr<Bytes> get_bytes_for_writing(size_t length)
{
auto const old_size = size();
TRY(try_resize(old_size + length));
return Bytes { data() + old_size, length };
}
/// Like get_bytes_for_writing, but crashes if allocation fails.
Bytes must_get_bytes_for_writing(size_t length)
{
return MUST(get_bytes_for_writing(length));
}
void append(u8 byte)
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{
MUST(try_append(byte));
}
void append(ReadonlyBytes bytes)
{
MUST(try_append(bytes));
}
void append(void const* data, size_t data_size) { append({ data, data_size }); }
ErrorOr<void> try_append(u8 byte)
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{
auto old_size = size();
auto new_size = old_size + 1;
VERIFY(new_size > old_size);
TRY(try_resize(new_size));
data()[old_size] = byte;
return {};
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}
ErrorOr<void> try_append(ReadonlyBytes bytes)
{
return try_append(bytes.data(), bytes.size());
}
ErrorOr<void> try_append(void const* data, size_t data_size)
{
if (data_size == 0)
return {};
VERIFY(data != nullptr);
auto old_size = size();
TRY(try_resize(size() + data_size));
__builtin_memcpy(this->data() + old_size, data, data_size);
return {};
}
void operator+=(ByteBuffer const& other)
{
MUST(try_append(other.data(), other.size()));
}
void overwrite(size_t offset, void const* data, size_t data_size)
{
// make sure we're not told to write past the end
VERIFY(offset + data_size <= size());
__builtin_memmove(this->data() + offset, data, data_size);
}
void zero_fill()
{
__builtin_memset(data(), 0, m_size);
}
operator Bytes() { return bytes(); }
operator ReadonlyBytes() const { return bytes(); }
ALWAYS_INLINE size_t capacity() const { return m_inline ? inline_capacity : m_outline_capacity; }
private:
void move_from(ByteBuffer&& other)
{
m_size = other.m_size;
m_inline = other.m_inline;
if (!other.m_inline) {
m_outline_buffer = other.m_outline_buffer;
m_outline_capacity = other.m_outline_capacity;
} else {
VERIFY(other.m_size <= inline_capacity);
__builtin_memcpy(m_inline_buffer, other.m_inline_buffer, other.m_size);
}
other.m_size = 0;
other.m_inline = true;
}
void trim(size_t size, bool may_discard_existing_data)
{
VERIFY(size <= m_size);
if (!m_inline && size <= inline_capacity)
shrink_into_inline_buffer(size, may_discard_existing_data);
m_size = size;
}
NEVER_INLINE void shrink_into_inline_buffer(size_t size, bool may_discard_existing_data)
{
// m_inline_buffer and m_outline_buffer are part of a union, so save the pointer
auto* outline_buffer = m_outline_buffer;
auto outline_capacity = m_outline_capacity;
if (!may_discard_existing_data)
__builtin_memcpy(m_inline_buffer, outline_buffer, size);
kfree_sized(outline_buffer, outline_capacity);
m_inline = true;
}
NEVER_INLINE ErrorOr<void> try_ensure_capacity_slowpath(size_t new_capacity)
{
// When we are asked to raise the capacity by very small amounts,
// the caller is perhaps appending very little data in many calls.
// To avoid copying the entire ByteBuffer every single time,
// we raise the capacity exponentially, by a factor of roughly 1.5.
// This is most noticeable in Lagom, where kmalloc_good_size is just a no-op.
new_capacity = max(new_capacity, (capacity() * 3) / 2);
new_capacity = kmalloc_good_size(new_capacity);
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auto* new_buffer = static_cast<u8*>(kmalloc(new_capacity));
if (!new_buffer)
return Error::from_errno(ENOMEM);
if (m_inline) {
__builtin_memcpy(new_buffer, data(), m_size);
} else if (m_outline_buffer) {
__builtin_memcpy(new_buffer, m_outline_buffer, min(new_capacity, m_outline_capacity));
kfree_sized(m_outline_buffer, m_outline_capacity);
}
m_outline_buffer = new_buffer;
m_outline_capacity = new_capacity;
m_inline = false;
return {};
}
union {
u8 m_inline_buffer[inline_capacity];
struct {
u8* m_outline_buffer;
size_t m_outline_capacity;
};
};
size_t m_size { 0 };
bool m_inline { true };
};
}
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template<>
struct Traits<ByteBuffer> : public GenericTraits<ByteBuffer> {
static unsigned hash(ByteBuffer const& byte_buffer)
{
return Traits<ReadonlyBytes>::hash(byte_buffer.span());
}
static bool equals(ByteBuffer const& byte_buffer, Bytes const& other)
{
return byte_buffer.bytes() == other;
}
static bool equals(ByteBuffer const& byte_buffer, ReadonlyBytes const& other)
{
return byte_buffer.bytes() == other;
}
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};
}