text: //===--- raw_ostream.h - Raw output stream ----------------------*- C++ -*-===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  //  This file defines the raw_ostream class.
  //
  //===----------------------------------------------------------------------===//
  
  #ifndef LLVM_SUPPORT_RAW_OSTREAM_H
  #define LLVM_SUPPORT_RAW_OSTREAM_H
  
  #include "llvm/ADT/SmallVector.h"
  #include "llvm/ADT/StringRef.h"
  #include "llvm/Support/DataTypes.h"
  #include <system_error>
  
  namespace llvm {
  class format_object_base;
  class FormattedString;
  class FormattedNumber;
  template <typename T> class SmallVectorImpl;
  
  namespace sys {
  namespace fs {
  enum OpenFlags : unsigned;
  }
  }
  
  /// This class implements an extremely fast bulk output stream that can *only*
  /// output to a stream.  It does not support seeking, reopening, rewinding, line
  /// buffered disciplines etc. It is a simple buffer that outputs
  /// a chunk at a time.
  class raw_ostream {
  private:
    void operator=(const raw_ostream &) = delete;
    raw_ostream(const raw_ostream &) = delete;
  
    /// The buffer is handled in such a way that the buffer is
    /// uninitialized, unbuffered, or out of space when OutBufCur >=
    /// OutBufEnd. Thus a single comparison suffices to determine if we
    /// need to take the slow path to write a single character.
    ///
    /// The buffer is in one of three states:
    ///  1. Unbuffered (BufferMode == Unbuffered)
    ///  1. Uninitialized (BufferMode != Unbuffered && OutBufStart == 0).
    ///  2. Buffered (BufferMode != Unbuffered && OutBufStart != 0 &&
    ///               OutBufEnd - OutBufStart >= 1).
    ///
    /// If buffered, then the raw_ostream owns the buffer if (BufferMode ==
    /// InternalBuffer); otherwise the buffer has been set via SetBuffer and is
    /// managed by the subclass.
    ///
    /// If a subclass installs an external buffer using SetBuffer then it can wait
    /// for a \see write_impl() call to handle the data which has been put into
    /// this buffer.
    char *OutBufStart, *OutBufEnd, *OutBufCur;
  
    enum BufferKind {
      Unbuffered = 0,
      InternalBuffer,
      ExternalBuffer
    } BufferMode;
  
  public:
    // color order matches ANSI escape sequence, don't change
    enum Colors {
      BLACK=0,
      RED,
      GREEN,
      YELLOW,
      BLUE,
      MAGENTA,
      CYAN,
      WHITE,
      SAVEDCOLOR
    };
  
    explicit raw_ostream(bool unbuffered = false)
        : BufferMode(unbuffered ? Unbuffered : InternalBuffer) {
      // Start out ready to flush.
      OutBufStart = OutBufEnd = OutBufCur = nullptr;
    }
  
    virtual ~raw_ostream();
  
    /// tell - Return the current offset with the file.
    uint64_t tell() const { return current_pos() + GetNumBytesInBuffer(); }
  
    //===--------------------------------------------------------------------===//
    // Configuration Interface
    //===--------------------------------------------------------------------===//
  
    /// Set the stream to be buffered, with an automatically determined buffer
    /// size.
    void SetBuffered();
  
    /// Set the stream to be buffered, using the specified buffer size.
    void SetBufferSize(size_t Size) {
      flush();
      SetBufferAndMode(new char[Size], Size, InternalBuffer);
    }
  
    size_t GetBufferSize() const {
      // If we're supposed to be buffered but haven't actually gotten around
      // to allocating the buffer yet, return the value that would be used.
      if (BufferMode != Unbuffered && OutBufStart == nullptr)
        return preferred_buffer_size();
  
      // Otherwise just return the size of the allocated buffer.
      return OutBufEnd - OutBufStart;
    }
  
    /// Set the stream to be unbuffered. When unbuffered, the stream will flush
    /// after every write. This routine will also flush the buffer immediately
    /// when the stream is being set to unbuffered.
    void SetUnbuffered() {
      flush();
      SetBufferAndMode(nullptr, 0, Unbuffered);
    }
  
    size_t GetNumBytesInBuffer() const {
      return OutBufCur - OutBufStart;
    }
  
    //===--------------------------------------------------------------------===//
    // Data Output Interface
    //===--------------------------------------------------------------------===//
  
    void flush() {
      if (OutBufCur != OutBufStart)
        flush_nonempty();
    }
  
    raw_ostream &operator<<(char C) {
      if (OutBufCur >= OutBufEnd)
        return write(C);
      *OutBufCur++ = C;
      return *this;
    }
  
    raw_ostream &operator<<(unsigned char C) {
      if (OutBufCur >= OutBufEnd)
        return write(C);
      *OutBufCur++ = C;
      return *this;
    }
  
    raw_ostream &operator<<(signed char C) {
      if (OutBufCur >= OutBufEnd)
        return write(C);
      *OutBufCur++ = C;
      return *this;
    }
  
    raw_ostream &operator<<(StringRef Str) {
      // Inline fast path, particularly for strings with a known length.
      size_t Size = Str.size();
  
      // Make sure we can use the fast path.
      if (Size > (size_t)(OutBufEnd - OutBufCur))
        return write(Str.data(), Size);
  
      if (Size) {
        memcpy(OutBufCur, Str.data(), Size);
        OutBufCur += Size;
      }
      return *this;
    }
  
    raw_ostream &operator<<(const char *Str) {
      // Inline fast path, particularly for constant strings where a sufficiently
      // smart compiler will simplify strlen.
  
      return this->operator<<(StringRef(Str));
    }
  
    raw_ostream &operator<<(const std::string &Str) {
      // Avoid the fast path, it would only increase code size for a marginal win.
      return write(Str.data(), Str.length());
    }
  
    raw_ostream &operator<<(const llvm::SmallVectorImpl<char> &Str) {
      return write(Str.data(), Str.size());
    }
  
    raw_ostream &operator<<(unsigned long N);
    raw_ostream &operator<<(long N);
    raw_ostream &operator<<(unsigned long long N);
    raw_ostream &operator<<(long long N);
    raw_ostream &operator<<(const void *P);
    raw_ostream &operator<<(unsigned int N) {
      return this->operator<<(static_cast<unsigned long>(N));
    }
  
    raw_ostream &operator<<(int N) {
      return this->operator<<(static_cast<long>(N));
    }
  
    raw_ostream &operator<<(double N);
  
    /// Output \p N in hexadecimal, without any prefix or padding.
    raw_ostream &write_hex(unsigned long long N);
  
    /// Output \p Str, turning '\\', '\t', '\n', '"', and anything that doesn't
    /// satisfy std::isprint into an escape sequence.
    raw_ostream &write_escaped(StringRef Str, bool UseHexEscapes = false);
  
    raw_ostream &write(unsigned char C);
    raw_ostream &write(const char *Ptr, size_t Size);
  
    // Formatted output, see the format() function in Support/Format.h.
    raw_ostream &operator<<(const format_object_base &Fmt);
  
    // Formatted output, see the leftJustify() function in Support/Format.h.
    raw_ostream &operator<<(const FormattedString &);
  
    // Formatted output, see the formatHex() function in Support/Format.h.
    raw_ostream &operator<<(const FormattedNumber &);
  
    /// indent - Insert 'NumSpaces' spaces.
    raw_ostream &indent(unsigned NumSpaces);
  
    /// Changes the foreground color of text that will be output from this point
    /// forward.
    /// @param Color ANSI color to use, the special SAVEDCOLOR can be used to
    /// change only the bold attribute, and keep colors untouched
    /// @param Bold bold/brighter text, default false
    /// @param BG if true change the background, default: change foreground
    /// @returns itself so it can be used within << invocations
    virtual raw_ostream &changeColor(enum Colors Color,
                                     bool Bold = false,
                                     bool BG = false) {
      (void)Color;
      (void)Bold;
      (void)BG;
      return *this;
    }
  
    /// Resets the colors to terminal defaults. Call this when you are done
    /// outputting colored text, or before program exit.
    virtual raw_ostream &resetColor() { return *this; }
  
    /// Reverses the foreground and background colors.
    virtual raw_ostream &reverseColor() { return *this; }
  
    /// This function determines if this stream is connected to a "tty" or
    /// "console" window. That is, the output would be displayed to the user
    /// rather than being put on a pipe or stored in a file.
    virtual bool is_displayed() const { return false; }
  
    /// This function determines if this stream is displayed and supports colors.
    virtual bool has_colors() const { return is_displayed(); }
  
    //===--------------------------------------------------------------------===//
    // Subclass Interface
    //===--------------------------------------------------------------------===//
  
  private:
    /// The is the piece of the class that is implemented by subclasses.  This
    /// writes the \p Size bytes starting at
    /// \p Ptr to the underlying stream.
    ///
    /// This function is guaranteed to only be called at a point at which it is
    /// safe for the subclass to install a new buffer via SetBuffer.
    ///
    /// \param Ptr The start of the data to be written. For buffered streams this
    /// is guaranteed to be the start of the buffer.
    ///
    /// \param Size The number of bytes to be written.
    ///
    /// \invariant { Size > 0 }
    virtual void write_impl(const char *Ptr, size_t Size) = 0;
  
    // An out of line virtual method to provide a home for the class vtable.
    virtual void handle();
  
    /// Return the current position within the stream, not counting the bytes
    /// currently in the buffer.
    virtual uint64_t current_pos() const = 0;
  
  protected:
    /// Use the provided buffer as the raw_ostream buffer. This is intended for
    /// use only by subclasses which can arrange for the output to go directly
    /// into the desired output buffer, instead of being copied on each flush.
    void SetBuffer(char *BufferStart, size_t Size) {
      SetBufferAndMode(BufferStart, Size, ExternalBuffer);
    }
  
    /// Return an efficient buffer size for the underlying output mechanism.
    virtual size_t preferred_buffer_size() const;
  
    /// Return the beginning of the current stream buffer, or 0 if the stream is
    /// unbuffered.
    const char *getBufferStart() const { return OutBufStart; }
  
    //===--------------------------------------------------------------------===//
    // Private Interface
    //===--------------------------------------------------------------------===//
  private:
    /// Install the given buffer and mode.
    void SetBufferAndMode(char *BufferStart, size_t Size, BufferKind Mode);
  
    /// Flush the current buffer, which is known to be non-empty. This outputs the
    /// currently buffered data and resets the buffer to empty.
    void flush_nonempty();
  
    /// Copy data into the buffer. Size must not be greater than the number of
    /// unused bytes in the buffer.
    void copy_to_buffer(const char *Ptr, size_t Size);
  };
  
  /// An abstract base class for streams implementations that also support a
  /// pwrite operation. This is useful for code that can mostly stream out data,
  /// but needs to patch in a header that needs to know the output size.
  class raw_pwrite_stream : public raw_ostream {
    virtual void pwrite_impl(const char *Ptr, size_t Size, uint64_t Offset) = 0;
  
  public:
    explicit raw_pwrite_stream(bool Unbuffered = false)
        : raw_ostream(Unbuffered) {}
    void pwrite(const char *Ptr, size_t Size, uint64_t Offset) {
  #ifndef NDBEBUG
      uint64_t Pos = tell();
      // /dev/null always reports a pos of 0, so we cannot perform this check
      // in that case.
      if (Pos)
        assert(Size + Offset <= Pos && "We don't support extending the stream");
  #endif
      pwrite_impl(Ptr, Size, Offset);
    }
  };
  
  //===----------------------------------------------------------------------===//
  // File Output Streams
  //===----------------------------------------------------------------------===//
  
  /// A raw_ostream that writes to a file descriptor.
  ///
  class raw_fd_ostream : public raw_pwrite_stream {
    int FD;
    bool ShouldClose;
  
    /// Error This flag is true if an error of any kind has been detected.
    ///
    bool Error;
  
    uint64_t pos;
  
    bool SupportsSeeking;
  
    /// See raw_ostream::write_impl.
    void write_impl(const char *Ptr, size_t Size) override;
  
    void pwrite_impl(const char *Ptr, size_t Size, uint64_t Offset) override;
  
    /// Return the current position within the stream, not counting the bytes
    /// currently in the buffer.
    uint64_t current_pos() const override { return pos; }
  
    /// Determine an efficient buffer size.
    size_t preferred_buffer_size() const override;
  
    /// Set the flag indicating that an output error has been encountered.
    void error_detected() { Error = true; }
  
  public:
    /// Open the specified file for writing. If an error occurs, information
    /// about the error is put into EC, and the stream should be immediately
    /// destroyed;
    /// \p Flags allows optional flags to control how the file will be opened.
    ///
    /// As a special case, if Filename is "-", then the stream will use
    /// STDOUT_FILENO instead of opening a file. Note that it will still consider
    /// itself to own the file descriptor. In particular, it will close the
    /// file descriptor when it is done (this is necessary to detect
    /// output errors).
    raw_fd_ostream(StringRef Filename, std::error_code &EC,
                   sys::fs::OpenFlags Flags);
  
    /// FD is the file descriptor that this writes to.  If ShouldClose is true,
    /// this closes the file when the stream is destroyed.
    raw_fd_ostream(int fd, bool shouldClose, bool unbuffered=false);
  
    ~raw_fd_ostream() override;
  
    /// Manually flush the stream and close the file. Note that this does not call
    /// fsync.
    void close();
  
    bool supportsSeeking() { return SupportsSeeking; }
  
    /// Flushes the stream and repositions the underlying file descriptor position
    /// to the offset specified from the beginning of the file.
    uint64_t seek(uint64_t off);
  
    raw_ostream &changeColor(enum Colors colors, bool bold=false,
                             bool bg=false) override;
    raw_ostream &resetColor() override;
  
    raw_ostream &reverseColor() override;
  
    bool is_displayed() const override;
  
    bool has_colors() const override;
  
    /// Return the value of the flag in this raw_fd_ostream indicating whether an
    /// output error has been encountered.
    /// This doesn't implicitly flush any pending output.  Also, it doesn't
    /// guarantee to detect all errors unless the stream has been closed.
    bool has_error() const {
      return Error;
    }
  
    /// Set the flag read by has_error() to false. If the error flag is set at the
    /// time when this raw_ostream's destructor is called, report_fatal_error is
    /// called to report the error. Use clear_error() after handling the error to
    /// avoid this behavior.
    ///
    ///   "Errors should never pass silently.
    ///    Unless explicitly silenced."
    ///      - from The Zen of Python, by Tim Peters
    ///
    void clear_error() {
      Error = false;
    }
  };
  
  /// This returns a reference to a raw_ostream for standard output. Use it like:
  /// outs() << "foo" << "bar";
  raw_ostream &outs();
  
  /// This returns a reference to a raw_ostream for standard error. Use it like:
  /// errs() << "foo" << "bar";
  raw_ostream &errs();
  
  /// This returns a reference to a raw_ostream which simply discards output.
  raw_ostream &nulls();
  
  //===----------------------------------------------------------------------===//
  // Output Stream Adaptors
  //===----------------------------------------------------------------------===//
  
  /// A raw_ostream that writes to an std::string.  This is a simple adaptor
  /// class. This class does not encounter output errors.
  class raw_string_ostream : public raw_ostream {
    std::string &OS;
  
    /// See raw_ostream::write_impl.
    void write_impl(const char *Ptr, size_t Size) override;
  
    /// Return the current position within the stream, not counting the bytes
    /// currently in the buffer.
    uint64_t current_pos() const override { return OS.size(); }
  
  public:
    explicit raw_string_ostream(std::string &O) : OS(O) {}
    ~raw_string_ostream() override;
  
    /// Flushes the stream contents to the target string and returns  the string's
    /// reference.
    std::string& str() {
      flush();
      return OS;
    }
  };
  
  /// A raw_ostream that writes to an SmallVector or SmallString.  This is a
  /// simple adaptor class. This class does not encounter output errors.
  /// raw_svector_ostream operates without a buffer, delegating all memory
  /// management to the SmallString. Thus the SmallString is always up-to-date,
  /// may be used directly and there is no need to call flush().
  class raw_svector_ostream : public raw_pwrite_stream {
    SmallVectorImpl<char> &OS;
  
    /// See raw_ostream::write_impl.
    void write_impl(const char *Ptr, size_t Size) override;
  
    void pwrite_impl(const char *Ptr, size_t Size, uint64_t Offset) override;
  
    /// Return the current position within the stream.
    uint64_t current_pos() const override;
  
  public:
    /// Construct a new raw_svector_ostream.
    ///
    /// \param O The vector to write to; this should generally have at least 128
    /// bytes free to avoid any extraneous memory overhead.
    explicit raw_svector_ostream(SmallVectorImpl<char> &O) : OS(O) {
      SetUnbuffered();
    }
    ~raw_svector_ostream() override {}
  
    void flush() = delete;
  
    /// Return a StringRef for the vector contents.
    StringRef str() { return StringRef(OS.data(), OS.size()); }
  };
  
  /// A raw_ostream that discards all output.
  class raw_null_ostream : public raw_pwrite_stream {
    /// See raw_ostream::write_impl.
    void write_impl(const char *Ptr, size_t size) override;
    void pwrite_impl(const char *Ptr, size_t Size, uint64_t Offset) override;
  
    /// Return the current position within the stream, not counting the bytes
    /// currently in the buffer.
    uint64_t current_pos() const override;
  
  public:
    explicit raw_null_ostream() {}
    ~raw_null_ostream() override;
  };
  
  class buffer_ostream : public raw_svector_ostream {
    raw_ostream &OS;
    SmallVector<char, 0> Buffer;
  
  public:
    buffer_ostream(raw_ostream &OS) : raw_svector_ostream(Buffer), OS(OS) {}
    ~buffer_ostream() override { OS << str(); }
  };
  
  } // end llvm namespace
  
  #endif // LLVM_SUPPORT_RAW_OSTREAM_H
  