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//===-- llvm/Support/FormattedStream.cpp - Formatted streams ----*- 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 contains the implementation of formatted_raw_ostream.
#include "llvm/Support/FormattedStream.h"
#include "llvm/Support/ConvertUTF.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/Unicode.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
using namespace llvm;
/// UpdatePosition - Examine the given char sequence and figure out which
/// column we end up in after output, and how many line breaks are contained.
/// This assumes that the input string is well-formed UTF-8, and takes into
/// account Unicode characters which render as multiple columns wide.
void formatted_raw_ostream::UpdatePosition(const char *Ptr, size_t Size) {
unsigned &Column = Position.first;
unsigned &Line = Position.second;
auto ProcessUTF8CodePoint = [&Line, &Column](StringRef CP) {
int Width = sys::unicode::columnWidthUTF8(CP);
if (Width != sys::unicode::ErrorNonPrintableCharacter)
Column += Width;
// The only special whitespace characters we care about are single-byte.
if (CP.size() > 1)
switch (CP[0]) {
case '\n':
Line += 1;
case '\r':
Column = 0;
case '\t':
// Assumes tab stop = 8 characters.
Column += (8 - (Column & 0x7)) & 0x7;
// If we have a partial UTF-8 sequence from the previous buffer, check that
// first.
if (PartialUTF8Char.size()) {
size_t BytesFromBuffer =
getNumBytesForUTF8(PartialUTF8Char[0]) - PartialUTF8Char.size();
if (Size < BytesFromBuffer) {
// If we still don't have enough bytes for a complete code point, just
// append what we have.
PartialUTF8Char.append(StringRef(Ptr, Size));
} else {
// The first few bytes from the buffer will complete the code point.
// Concatenate them and process their effect on the line and column
// numbers.
PartialUTF8Char.append(StringRef(Ptr, BytesFromBuffer));
Ptr += BytesFromBuffer;
Size -= BytesFromBuffer;
// Now scan the rest of the buffer.
unsigned NumBytes;
for (const char *End = Ptr + Size; Ptr < End; Ptr += NumBytes) {
NumBytes = getNumBytesForUTF8(*Ptr);
// The buffer might end part way through a UTF-8 code unit sequence for a
// Unicode scalar value if it got flushed. If this happens, we can't know
// the display width until we see the rest of the code point. Stash the
// bytes we do have, so that we can reconstruct the whole code point later,
// even if the buffer is being flushed.
if ((unsigned)(End - Ptr) < NumBytes) {
PartialUTF8Char = StringRef(Ptr, End - Ptr);
ProcessUTF8CodePoint(StringRef(Ptr, NumBytes));
/// ComputePosition - Examine the current output and update line and column
/// counts.
void formatted_raw_ostream::ComputePosition(const char *Ptr, size_t Size) {
// If our previous scan pointer is inside the buffer, assume we already
// scanned those bytes. This depends on raw_ostream to not change our buffer
// in unexpected ways.
if (Ptr <= Scanned && Scanned <= Ptr + Size)
// Scan all characters added since our last scan to determine the new
// column.
UpdatePosition(Scanned, Size - (Scanned - Ptr));
UpdatePosition(Ptr, Size);
// Update the scanning pointer.
Scanned = Ptr + Size;
/// PadToColumn - Align the output to some column number.
/// \param NewCol - The column to move to.
formatted_raw_ostream &formatted_raw_ostream::PadToColumn(unsigned NewCol) {
// Figure out what's in the buffer and add it to the column count.
ComputePosition(getBufferStart(), GetNumBytesInBuffer());
// Output spaces until we reach the desired column.
indent(std::max(int(NewCol - getColumn()), 1));
return *this;
void formatted_raw_ostream::write_impl(const char *Ptr, size_t Size) {
// Figure out what's in the buffer and add it to the column count.
ComputePosition(Ptr, Size);
// Write the data to the underlying stream (which is unbuffered, so
// the data will be immediately written out).
TheStream->write(Ptr, Size);
// Reset the scanning pointer.
Scanned = nullptr;
/// fouts() - This returns a reference to a formatted_raw_ostream for
/// standard output. Use it like: fouts() << "foo" << "bar";
formatted_raw_ostream &llvm::fouts() {
static formatted_raw_ostream S(outs());
return S;
/// ferrs() - This returns a reference to a formatted_raw_ostream for
/// standard error. Use it like: ferrs() << "foo" << "bar";
formatted_raw_ostream &llvm::ferrs() {
static formatted_raw_ostream S(errs());
return S;
/// fdbgs() - This returns a reference to a formatted_raw_ostream for
/// the debug stream. Use it like: fdbgs() << "foo" << "bar";
formatted_raw_ostream &llvm::fdbgs() {
static formatted_raw_ostream S(dbgs());
return S;