//===--- MemoryBuffer.h - Memory Buffer Interface ---------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file defines the MemoryBuffer interface.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_SUPPORT_MEMORYBUFFER_H
#define LLVM_SUPPORT_MEMORYBUFFER_H
#include "llvm-c/Types.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/Twine.h"
#include "llvm/Support/Alignment.h"
#include "llvm/Support/CBindingWrapping.h"
#include "llvm/Support/ErrorOr.h"
#include "llvm/Support/MemoryBufferRef.h"
#include <cstddef>
#include <cstdint>
#include <memory>
namespace llvm {
namespace sys {
namespace fs {
// Duplicated from FileSystem.h to avoid a dependency.
#if defined(_WIN32)
// A Win32 HANDLE is a typedef of void*
using file_t = void *;
#else
using file_t = int;
#endif
} // namespace fs
} // namespace sys
/// This interface provides simple read-only access to a block of memory, and
/// provides simple methods for reading files and standard input into a memory
/// buffer. In addition to basic access to the characters in the file, this
/// interface guarantees you can read one character past the end of the file,
/// and that this character will read as '\0'.
///
/// The '\0' guarantee is needed to support an optimization -- it's intended to
/// be more efficient for clients which are reading all the data to stop
/// reading when they encounter a '\0' than to continually check the file
/// position to see if it has reached the end of the file.
class MemoryBuffer {
const char *BufferStart; // Start of the buffer.
const char *BufferEnd; // End of the buffer.
protected:
MemoryBuffer() = default;
void init(const char *BufStart, const char *BufEnd,
bool RequiresNullTerminator);
public:
MemoryBuffer(const MemoryBuffer &) = delete;
MemoryBuffer &operator=(const MemoryBuffer &) = delete;
virtual ~MemoryBuffer();
const char *getBufferStart() const { return BufferStart; }
const char *getBufferEnd() const { return BufferEnd; }
size_t getBufferSize() const { return BufferEnd-BufferStart; }
StringRef getBuffer() const {
return StringRef(BufferStart, getBufferSize());
}
/// Return an identifier for this buffer, typically the filename it was read
/// from.
virtual StringRef getBufferIdentifier() const { return "Unknown buffer"; }
/// For read-only MemoryBuffer_MMap, mark the buffer as unused in the near
/// future and the kernel can free resources associated with it. Further
/// access is supported but may be expensive. This calls
/// madvise(MADV_DONTNEED) on read-only file mappings on *NIX systems. This
/// function should not be called on a writable buffer.
virtual void dontNeedIfMmap() {}
/// Open the specified file as a MemoryBuffer, returning a new MemoryBuffer
/// if successful, otherwise returning null.
///
/// \param IsText Set to true to indicate that the file should be read in
/// text mode.
///
/// \param IsVolatile Set to true to indicate that the contents of the file
/// can change outside the user's control, e.g. when libclang tries to parse
/// while the user is editing/updating the file or if the file is on an NFS.
///
/// \param Alignment Set to indicate that the buffer should be aligned to at
/// least the specified alignment.
static ErrorOr<std::unique_ptr<MemoryBuffer>>
getFile(const Twine &Filename, bool IsText = false,
bool RequiresNullTerminator = true, bool IsVolatile = false,
std::optional<Align> Alignment = std::nullopt);
/// Read all of the specified file into a MemoryBuffer as a stream
/// (i.e. until EOF reached). This is useful for special files that
/// look like a regular file but have 0 size (e.g. /proc/cpuinfo on Linux).
static ErrorOr<std::unique_ptr<MemoryBuffer>>
getFileAsStream(const Twine &Filename);
/// Given an already-open file descriptor, map some slice of it into a
/// MemoryBuffer. The slice is specified by an \p Offset and \p MapSize.
/// Since this is in the middle of a file, the buffer is not null terminated.
static ErrorOr<std::unique_ptr<MemoryBuffer>>
getOpenFileSlice(sys::fs::file_t FD, const Twine &Filename, uint64_t MapSize,
int64_t Offset, bool IsVolatile = false,
std::optional<Align> Alignment = std::nullopt);
/// Given an already-open file descriptor, read the file and return a
/// MemoryBuffer.
///
/// \param IsVolatile Set to true to indicate that the contents of the file
/// can change outside the user's control, e.g. when libclang tries to parse
/// while the user is editing/updating the file or if the file is on an NFS.
///
/// \param Alignment Set to indicate that the buffer should be aligned to at
/// least the specified alignment.
static ErrorOr<std::unique_ptr<MemoryBuffer>>
getOpenFile(sys::fs::file_t FD, const Twine &Filename, uint64_t FileSize,
bool RequiresNullTerminator = true, bool IsVolatile = false,
std::optional<Align> Alignment = std::nullopt);
/// Open the specified memory range as a MemoryBuffer. Note that InputData
/// must be null terminated if RequiresNullTerminator is true.
static std::unique_ptr<MemoryBuffer>
getMemBuffer(StringRef InputData, StringRef BufferName = "",
bool RequiresNullTerminator = true);
static std::unique_ptr<MemoryBuffer>
getMemBuffer(MemoryBufferRef Ref, bool RequiresNullTerminator = true);
/// Open the specified memory range as a MemoryBuffer, copying the contents
/// and taking ownership of it. InputData does not have to be null terminated.
static std::unique_ptr<MemoryBuffer>
getMemBufferCopy(StringRef InputData, const Twine &BufferName = "");
/// Read all of stdin into a file buffer, and return it.
static ErrorOr<std::unique_ptr<MemoryBuffer>> getSTDIN();
/// Open the specified file as a MemoryBuffer, or open stdin if the Filename
/// is "-".
static ErrorOr<std::unique_ptr<MemoryBuffer>>
getFileOrSTDIN(const Twine &Filename, bool IsText = false,
bool RequiresNullTerminator = true,
std::optional<Align> Alignment = std::nullopt);
/// Map a subrange of the specified file as a MemoryBuffer.
static ErrorOr<std::unique_ptr<MemoryBuffer>>
getFileSlice(const Twine &Filename, uint64_t MapSize, uint64_t Offset,
bool IsVolatile = false,
std::optional<Align> Alignment = std::nullopt);
//===--------------------------------------------------------------------===//
// Provided for performance analysis.
//===--------------------------------------------------------------------===//
/// The kind of memory backing used to support the MemoryBuffer.
enum BufferKind {
MemoryBuffer_Malloc,
MemoryBuffer_MMap
};
/// Return information on the memory mechanism used to support the
/// MemoryBuffer.
virtual BufferKind getBufferKind() const = 0;
MemoryBufferRef getMemBufferRef() const;
};
/// This class is an extension of MemoryBuffer, which allows copy-on-write
/// access to the underlying contents. It only supports creation methods that
/// are guaranteed to produce a writable buffer. For example, mapping a file
/// read-only is not supported.
class WritableMemoryBuffer : public MemoryBuffer {
protected:
WritableMemoryBuffer() = default;
public:
using MemoryBuffer::getBuffer;
using MemoryBuffer::getBufferEnd;
using MemoryBuffer::getBufferStart;
// const_cast is well-defined here, because the underlying buffer is
// guaranteed to have been initialized with a mutable buffer.
char *getBufferStart() {
return const_cast<char *>(MemoryBuffer::getBufferStart());
}
char *getBufferEnd() {
return const_cast<char *>(MemoryBuffer::getBufferEnd());
}
MutableArrayRef<char> getBuffer() {
return {getBufferStart(), getBufferEnd()};
}
static ErrorOr<std::unique_ptr<WritableMemoryBuffer>>
getFile(const Twine &Filename, bool IsVolatile = false,
std::optional<Align> Alignment = std::nullopt);
/// Map a subrange of the specified file as a WritableMemoryBuffer.
static ErrorOr<std::unique_ptr<WritableMemoryBuffer>>
getFileSlice(const Twine &Filename, uint64_t MapSize, uint64_t Offset,
bool IsVolatile = false,
std::optional<Align> Alignment = std::nullopt);
/// Allocate a new MemoryBuffer of the specified size that is not initialized.
/// Note that the caller should initialize the memory allocated by this
/// method. The memory is owned by the MemoryBuffer object.
///
/// \param Alignment Set to indicate that the buffer should be aligned to at
/// least the specified alignment.
static std::unique_ptr<WritableMemoryBuffer>
getNewUninitMemBuffer(size_t Size, const Twine &BufferName = "",
std::optional<Align> Alignment = std::nullopt);
/// Allocate a new zero-initialized MemoryBuffer of the specified size. Note
/// that the caller need not initialize the memory allocated by this method.
/// The memory is owned by the MemoryBuffer object.
static std::unique_ptr<WritableMemoryBuffer>
getNewMemBuffer(size_t Size, const Twine &BufferName = "");
private:
// Hide these base class factory function so one can't write
// WritableMemoryBuffer::getXXX()
// and be surprised that he got a read-only Buffer.
using MemoryBuffer::getFileAsStream;
using MemoryBuffer::getFileOrSTDIN;
using MemoryBuffer::getMemBuffer;
using MemoryBuffer::getMemBufferCopy;
using MemoryBuffer::getOpenFile;
using MemoryBuffer::getOpenFileSlice;
using MemoryBuffer::getSTDIN;
};
/// This class is an extension of MemoryBuffer, which allows write access to
/// the underlying contents and committing those changes to the original source.
/// It only supports creation methods that are guaranteed to produce a writable
/// buffer. For example, mapping a file read-only is not supported.
class WriteThroughMemoryBuffer : public MemoryBuffer {
protected:
WriteThroughMemoryBuffer() = default;
public:
using MemoryBuffer::getBuffer;
using MemoryBuffer::getBufferEnd;
using MemoryBuffer::getBufferStart;
// const_cast is well-defined here, because the underlying buffer is
// guaranteed to have been initialized with a mutable buffer.
char *getBufferStart() {
return const_cast<char *>(MemoryBuffer::getBufferStart());
}
char *getBufferEnd() {
return const_cast<char *>(MemoryBuffer::getBufferEnd());
}
MutableArrayRef<char> getBuffer() {
return {getBufferStart(), getBufferEnd()};
}
static ErrorOr<std::unique_ptr<WriteThroughMemoryBuffer>>
getFile(const Twine &Filename, int64_t FileSize = -1);
/// Map a subrange of the specified file as a ReadWriteMemoryBuffer.
static ErrorOr<std::unique_ptr<WriteThroughMemoryBuffer>>
getFileSlice(const Twine &Filename, uint64_t MapSize, uint64_t Offset);
private:
// Hide these base class factory function so one can't write
// WritableMemoryBuffer::getXXX()
// and be surprised that he got a read-only Buffer.
using MemoryBuffer::getFileAsStream;
using MemoryBuffer::getFileOrSTDIN;
using MemoryBuffer::getMemBuffer;
using MemoryBuffer::getMemBufferCopy;
using MemoryBuffer::getOpenFile;
using MemoryBuffer::getOpenFileSlice;
using MemoryBuffer::getSTDIN;
};
// Create wrappers for C Binding types (see CBindingWrapping.h).
DEFINE_SIMPLE_CONVERSION_FUNCTIONS(MemoryBuffer, LLVMMemoryBufferRef)
} // end namespace llvm
#endif // LLVM_SUPPORT_MEMORYBUFFER_H