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//===--- raw_ostream.h - Raw output stream ----------------------*- C++ -*-===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// This file defines the raw_ostream class.
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringRef.h"
#include <cassert>
#include <cstddef>
#include <cstdint>
#include <cstring>
#include <string>
#include <system_error>
namespace llvm {
class formatv_object_base;
class format_object_base;
class FormattedString;
class FormattedNumber;
class FormattedBytes;
namespace sys {
namespace fs {
enum FileAccess : unsigned;
enum OpenFlags : unsigned;
enum CreationDisposition : unsigned;
} // end namespace fs
} // end namespace sys
/// 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 {
/// 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,
} BufferMode;
// color order matches ANSI escape sequence, don't change
enum class Colors {
BLACK = 0,
static const Colors BLACK = Colors::BLACK;
static const Colors RED = Colors::RED;
static const Colors GREEN = Colors::GREEN;
static const Colors YELLOW = Colors::YELLOW;
static const Colors BLUE = Colors::BLUE;
static const Colors MAGENTA = Colors::MAGENTA;
static const Colors CYAN = Colors::CYAN;
static const Colors WHITE = Colors::WHITE;
static const Colors SAVEDCOLOR = Colors::SAVEDCOLOR;
static const Colors RESET = Colors::RESET;
explicit raw_ostream(bool unbuffered = false)
: BufferMode(unbuffered ? Unbuffered : InternalBuffer) {
// Start out ready to flush.
OutBufStart = OutBufEnd = OutBufCur = nullptr;
raw_ostream(const raw_ostream &) = delete;
void operator=(const raw_ostream &) = delete;
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) {
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() {
SetBufferAndMode(nullptr, 0, Unbuffered);
size_t GetNumBytesInBuffer() const {
return OutBufCur - OutBufStart;
// Data Output Interface
void flush() {
if (OutBufCur != OutBufStart)
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(, Size);
if (Size) {
memcpy(OutBufCur,, 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.length());
raw_ostream &operator<<(const SmallVectorImpl<char> &Str) {
return write(, 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);
// Change the foreground color of text.
raw_ostream &operator<<(Colors C);
/// Output a formatted UUID with dash separators.
using uuid_t = uint8_t[16];
raw_ostream &write_uuid(const uuid_t UUID);
/// Output \p Str, turning '\\', '\t', '\n', '"', and anything that doesn't
/// satisfy llvm::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 &);
// Formatted output, see the formatv() function in Support/FormatVariadic.h.
raw_ostream &operator<<(const formatv_object_base &);
// Formatted output, see the format_bytes() function in Support/Format.h.
raw_ostream &operator<<(const FormattedBytes &);
/// indent - Insert 'NumSpaces' spaces.
raw_ostream &indent(unsigned NumSpaces);
/// write_zeros - Insert 'NumZeros' nulls.
raw_ostream &write_zeros(unsigned NumZeros);
/// 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) {
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(); }
// Enable or disable colors. Once disable_colors() is called,
// changeColor() has no effect until enable_colors() is called.
virtual void enable_colors(bool /*enable*/) {}
// Subclass Interface
/// 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;
/// Return the current position within the stream, not counting the bytes
/// currently in the buffer.
virtual uint64_t current_pos() const = 0;
/// 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
/// 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);
virtual void anchor();
/// 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;
void anchor() override;
explicit raw_pwrite_stream(bool Unbuffered = false)
: raw_ostream(Unbuffered) {}
void pwrite(const char *Ptr, size_t Size, uint64_t Offset) {
#ifndef NDEBUG
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");
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;
bool SupportsSeeking;
bool ColorEnabled = true;
#ifdef _WIN32
/// True if this fd refers to a Windows console device. Mintty and other
/// terminal emulators are TTYs, but they are not consoles.
bool IsWindowsConsole = false;
std::error_code EC;
uint64_t pos;
/// 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(std::error_code EC) { this->EC = EC; }
void anchor() override;
/// 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. This will not close the stdout
/// descriptor.
raw_fd_ostream(StringRef Filename, std::error_code &EC);
raw_fd_ostream(StringRef Filename, std::error_code &EC,
sys::fs::CreationDisposition Disp);
raw_fd_ostream(StringRef Filename, std::error_code &EC,
sys::fs::FileAccess Access);
raw_fd_ostream(StringRef Filename, std::error_code &EC,
sys::fs::OpenFlags Flags);
raw_fd_ostream(StringRef Filename, std::error_code &EC,
sys::fs::CreationDisposition Disp, sys::fs::FileAccess Access,
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. If FD is for stdout or
/// stderr, it will not be closed.
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;
void enable_colors(bool enable) override { ColorEnabled = enable; }
std::error_code error() const { return EC; }
/// 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 bool(EC); }
/// 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() { EC = std::error_code(); }
/// 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(); }
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() {
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;
/// 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) {
~raw_svector_ostream() override = default;
void flush() = delete;
/// Return a StringRef for the vector contents.
StringRef str() { return StringRef(, 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;
explicit raw_null_ostream() = default;
~raw_null_ostream() override;
class buffer_ostream : public raw_svector_ostream {
raw_ostream &OS;
SmallVector<char, 0> Buffer;
virtual void anchor() override;
buffer_ostream(raw_ostream &OS) : raw_svector_ostream(Buffer), OS(OS) {}
~buffer_ostream() override { OS << str(); }
} // end namespace llvm