mirror of
https://github.com/wpilibsuite/allwpilib
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241 lines
9.2 KiB
C++
241 lines
9.2 KiB
C++
// Copyright (c) FIRST and other WPILib contributors.
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// Open Source Software; you can modify and/or share it under the terms of
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// the WPILib BSD license file in the root directory of this project.
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//===--- MemoryBuffer.h - Memory Buffer Interface ---------------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines the MemoryBuffer interface.
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//
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//===----------------------------------------------------------------------===//
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#pragma once
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#include <stdint.h>
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#include <cstddef>
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#include <memory>
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#include <string_view>
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#include <system_error>
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#include "wpi/span.h"
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// Duplicated from fs.h to avoid a dependency
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namespace fs {
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#if defined(_WIN32)
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// A Win32 HANDLE is a typedef of void*
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using file_t = void*;
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#else
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using file_t = int;
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#endif
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} // namespace fs
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namespace wpi {
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class MemoryBufferRef;
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/// This interface provides simple read-only access to a block of memory, and
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/// provides simple methods for reading files and standard input into a memory
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/// buffer.
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class MemoryBuffer {
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const uint8_t* m_bufferStart; // Start of the buffer.
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const uint8_t* m_bufferEnd; // End of the buffer.
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protected:
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MemoryBuffer() = default;
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void Init(const uint8_t* bufStart, const uint8_t* bufEnd);
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public:
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MemoryBuffer(const MemoryBuffer&) = delete;
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MemoryBuffer& operator=(const MemoryBuffer&) = delete;
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virtual ~MemoryBuffer();
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const uint8_t* begin() const { return m_bufferStart; }
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const uint8_t* end() const { return m_bufferEnd; }
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size_t size() const { return m_bufferEnd - m_bufferStart; }
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span<const uint8_t> GetBuffer() const { return {begin(), end()}; }
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/// Return an identifier for this buffer, typically the filename it was read
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/// from.
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virtual std::string_view GetBufferIdentifier() const {
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return "Unknown buffer";
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}
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/// Open the specified file as a MemoryBuffer, returning a new MemoryBuffer
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/// if successful, otherwise returning null. If FileSize is specified, this
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/// means that the client knows that the file exists and that it has the
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/// specified size.
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static std::unique_ptr<MemoryBuffer> GetFile(std::string_view filename,
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std::error_code& ec,
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int64_t fileSize = -1);
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/// Read all of the specified file into a MemoryBuffer as a stream
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/// (i.e. until EOF reached). This is useful for special files that
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/// look like a regular file but have 0 size (e.g. /proc/cpuinfo on Linux).
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static std::unique_ptr<MemoryBuffer> GetFileAsStream(
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std::string_view filename, std::error_code& ec);
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/// Given an already-open file descriptor, map some slice of it into a
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/// MemoryBuffer. The slice is specified by an \p Offset and \p MapSize.
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static std::unique_ptr<MemoryBuffer> GetOpenFileSlice(
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fs::file_t f, std::string_view filename, std::error_code& ec,
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uint64_t mapSize, int64_t offset);
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/// Given an already-open file descriptor, read the file and return a
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/// MemoryBuffer.
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static std::unique_ptr<MemoryBuffer> GetOpenFile(fs::file_t f,
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std::string_view filename,
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std::error_code& ec,
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uint64_t fileSize);
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/// Open the specified memory range as a MemoryBuffer.
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static std::unique_ptr<MemoryBuffer> GetMemBuffer(
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span<const uint8_t> inputData, std::string_view bufferName = "");
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static std::unique_ptr<MemoryBuffer> GetMemBuffer(MemoryBufferRef ref);
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/// Open the specified memory range as a MemoryBuffer, copying the contents
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/// and taking ownership of it.
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static std::unique_ptr<MemoryBuffer> GetMemBufferCopy(
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span<const uint8_t> inputData, std::string_view bufferName = "");
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/// Map a subrange of the specified file as a MemoryBuffer.
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static std::unique_ptr<MemoryBuffer> GetFileSlice(std::string_view filename,
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std::error_code& ec,
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uint64_t mapSize,
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uint64_t offset);
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//===--------------------------------------------------------------------===//
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// Provided for performance analysis.
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//===--------------------------------------------------------------------===//
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/// The kind of memory backing used to support the MemoryBuffer.
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enum BufferKind { MemoryBuffer_Malloc, MemoryBuffer_MMap };
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/// Return information on the memory mechanism used to support the
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/// MemoryBuffer.
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virtual BufferKind GetBufferKind() const = 0;
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MemoryBufferRef GetMemBufferRef() const;
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};
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/// This class is an extension of MemoryBuffer, which allows copy-on-write
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/// access to the underlying contents. It only supports creation methods that
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/// are guaranteed to produce a writable buffer. For example, mapping a file
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/// read-only is not supported.
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class WritableMemoryBuffer : public MemoryBuffer {
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protected:
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WritableMemoryBuffer() = default;
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public:
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using MemoryBuffer::begin;
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using MemoryBuffer::end;
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using MemoryBuffer::GetBuffer;
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using MemoryBuffer::size;
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// const_cast is well-defined here, because the underlying buffer is
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// guaranteed to have been initialized with a mutable buffer.
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uint8_t* begin() { return const_cast<uint8_t*>(MemoryBuffer::begin()); }
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uint8_t* end() { return const_cast<uint8_t*>(MemoryBuffer::end()); }
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span<uint8_t> GetBuffer() { return {begin(), end()}; }
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static std::unique_ptr<WritableMemoryBuffer> GetFile(
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std::string_view filename, std::error_code& ec, int64_t fileSize = -1);
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/// Map a subrange of the specified file as a WritableMemoryBuffer.
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static std::unique_ptr<WritableMemoryBuffer> GetFileSlice(
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std::string_view filename, std::error_code& ec, uint64_t mapSize,
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uint64_t offset);
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/// Allocate a new MemoryBuffer of the specified size that is not initialized.
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/// Note that the caller should initialize the memory allocated by this
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/// method. The memory is owned by the MemoryBuffer object.
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static std::unique_ptr<WritableMemoryBuffer> GetNewUninitMemBuffer(
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size_t size, std::string_view bufferName = "");
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/// Allocate a new zero-initialized MemoryBuffer of the specified size. Note
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/// that the caller need not initialize the memory allocated by this method.
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/// The memory is owned by the MemoryBuffer object.
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static std::unique_ptr<WritableMemoryBuffer> GetNewMemBuffer(
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size_t size, std::string_view bufferName = "");
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private:
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// Hide these base class factory function so one can't write
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// WritableMemoryBuffer::getXXX()
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// and be surprised that they got a read-only Buffer.
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using MemoryBuffer::GetFileAsStream;
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using MemoryBuffer::GetMemBuffer;
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using MemoryBuffer::GetMemBufferCopy;
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using MemoryBuffer::GetOpenFile;
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using MemoryBuffer::GetOpenFileSlice;
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};
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/// This class is an extension of MemoryBuffer, which allows write access to
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/// the underlying contents and committing those changes to the original source.
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/// It only supports creation methods that are guaranteed to produce a writable
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/// buffer. For example, mapping a file read-only is not supported.
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class WriteThroughMemoryBuffer : public MemoryBuffer {
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protected:
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WriteThroughMemoryBuffer() = default;
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public:
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using MemoryBuffer::begin;
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using MemoryBuffer::end;
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using MemoryBuffer::GetBuffer;
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using MemoryBuffer::size;
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// const_cast is well-defined here, because the underlying buffer is
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// guaranteed to have been initialized with a mutable buffer.
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uint8_t* begin() { return const_cast<uint8_t*>(MemoryBuffer::begin()); }
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uint8_t* end() { return const_cast<uint8_t*>(MemoryBuffer::end()); }
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span<uint8_t> GetBuffer() { return {begin(), end()}; }
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static std::unique_ptr<WriteThroughMemoryBuffer> GetFile(
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std::string_view filename, std::error_code& ec, int64_t fileSize = -1);
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/// Map a subrange of the specified file as a ReadWriteMemoryBuffer.
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static std::unique_ptr<WriteThroughMemoryBuffer> GetFileSlice(
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std::string_view filename, std::error_code& ec, uint64_t mapSize,
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uint64_t offset);
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private:
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// Hide these base class factory function so one can't write
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// WritableMemoryBuffer::getXXX()
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// and be surprised that they got a read-only Buffer.
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using MemoryBuffer::GetFileAsStream;
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using MemoryBuffer::GetMemBuffer;
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using MemoryBuffer::GetMemBufferCopy;
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using MemoryBuffer::GetOpenFile;
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using MemoryBuffer::GetOpenFileSlice;
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};
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class MemoryBufferRef {
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span<const uint8_t> m_buffer;
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std::string_view m_id;
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public:
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MemoryBufferRef() = default;
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MemoryBufferRef(MemoryBuffer& buffer) // NOLINT
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: m_buffer(buffer.GetBuffer()), m_id(buffer.GetBufferIdentifier()) {}
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MemoryBufferRef(span<const uint8_t> buffer, std::string_view id)
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: m_buffer(buffer), m_id(id) {}
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span<const uint8_t> GetBuffer() const { return m_buffer; }
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std::string_view GetBufferIdentifier() const { return m_id; }
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const uint8_t* begin() const { return m_buffer.begin(); }
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const uint8_t* end() const { return m_buffer.end(); }
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size_t size() const { return m_buffer.size(); }
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};
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} // namespace wpi
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