//===--- 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/CBindingWrapping.h"

#include "llvm/Support/ErrorOr.h"

#include <cstddef>

#include <cstdint>

#include <memory>

namespace llvm {

class MemoryBufferRef;

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"; }

  /// Open the specified file as a MemoryBuffer, returning a new MemoryBuffer

  /// if successful, otherwise returning null. If FileSize is specified, this

  /// means that the client knows that the file exists and that it has the

  /// specified size.

  ///

  /// \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.

  static ErrorOr<std::unique_ptr<MemoryBuffer>>

  getFile(const Twine &Filename, int64_t FileSize = -1,

          bool RequiresNullTerminator = true, bool IsVolatile = false);

  /// 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);

  /// 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.

  static ErrorOr<std::unique_ptr<MemoryBuffer>>

  getOpenFile(sys::fs::file_t FD, const Twine &Filename, uint64_t FileSize,

              bool RequiresNullTerminator = true, bool IsVolatile = false);

  /// 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, int64_t FileSize = -1,

                 bool RequiresNullTerminator = true);

  /// 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);

  //===--------------------------------------------------------------------===//

  // 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, int64_t FileSize = -1,

          bool IsVolatile = false);

  /// 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);

  /// 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.

  static std::unique_ptr<WritableMemoryBuffer>

  getNewUninitMemBuffer(size_t Size, const Twine &BufferName = "");

  /// 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;

};

class MemoryBufferRef {

  StringRef Buffer;

  StringRef Identifier;

public:

  MemoryBufferRef() = default;

  MemoryBufferRef(const MemoryBuffer& Buffer)

      : Buffer(Buffer.getBuffer()), Identifier(Buffer.getBufferIdentifier()) {}

  MemoryBufferRef(StringRef Buffer, StringRef Identifier)

      : Buffer(Buffer), Identifier(Identifier) {}

  StringRef getBuffer() const { return Buffer; }

  StringRef getBufferIdentifier() const { return Identifier; }

  const char *getBufferStart() const { return Buffer.begin(); }

  const char *getBufferEnd() const { return Buffer.end(); }

  size_t getBufferSize() const { return Buffer.size(); }

};

// Create wrappers for C Binding types (see CBindingWrapping.h).

DEFINE_SIMPLE_CONVERSION_FUNCTIONS(MemoryBuffer, LLVMMemoryBufferRef)

} // end namespace llvm

#endif // LLVM_SUPPORT_MEMORYBUFFER_H