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1 //===--- raw_ostream.cpp - Implement the raw_ostream classes --------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This implements support for bulk buffered stream output.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "llvm/Support/raw_ostream.h"
15 #include "llvm/ADT/STLExtras.h"
16 #include "llvm/ADT/SmallVector.h"
17 #include "llvm/ADT/StringExtras.h"
18 #include "llvm/Config/config.h"
19 #include "llvm/Support/Compiler.h"
20 #include "llvm/Support/ErrorHandling.h"
21 #include "llvm/Support/FileSystem.h"
22 #include "llvm/Support/Format.h"
23 #include "llvm/Support/Process.h"
24 #include "llvm/Support/Program.h"
25 #include <cctype>
26 #include <cerrno>
27 #include <sys/stat.h>
28 #include <system_error>
29 
30 // <fcntl.h> may provide O_BINARY.
31 #if defined(HAVE_FCNTL_H)
32 # include <fcntl.h>
33 #endif
34 
35 #if defined(HAVE_UNISTD_H)
36 # include <unistd.h>
37 #endif
38 #if defined(HAVE_SYS_UIO_H) && defined(HAVE_WRITEV)
39 #  include <sys/uio.h>
40 #endif
41 
42 #if defined(__CYGWIN__)
43 #include <io.h>
44 #endif
45 
46 #if defined(_MSC_VER)
47 #include <io.h>
48 #ifndef STDIN_FILENO
49 # define STDIN_FILENO 0
50 #endif
51 #ifndef STDOUT_FILENO
52 # define STDOUT_FILENO 1
53 #endif
54 #ifndef STDERR_FILENO
55 # define STDERR_FILENO 2
56 #endif
57 #endif
58 
59 using namespace llvm;
60 
~raw_ostream()61 raw_ostream::~raw_ostream() {
62   // raw_ostream's subclasses should take care to flush the buffer
63   // in their destructors.
64   assert(OutBufCur == OutBufStart &&
65          "raw_ostream destructor called with non-empty buffer!");
66 
67   if (BufferMode == InternalBuffer)
68     delete [] OutBufStart;
69 }
70 
71 // An out of line virtual method to provide a home for the class vtable.
handle()72 void raw_ostream::handle() {}
73 
preferred_buffer_size() const74 size_t raw_ostream::preferred_buffer_size() const {
75   // BUFSIZ is intended to be a reasonable default.
76   return BUFSIZ;
77 }
78 
SetBuffered()79 void raw_ostream::SetBuffered() {
80   // Ask the subclass to determine an appropriate buffer size.
81   if (size_t Size = preferred_buffer_size())
82     SetBufferSize(Size);
83   else
84     // It may return 0, meaning this stream should be unbuffered.
85     SetUnbuffered();
86 }
87 
SetBufferAndMode(char * BufferStart,size_t Size,BufferKind Mode)88 void raw_ostream::SetBufferAndMode(char *BufferStart, size_t Size,
89                                    BufferKind Mode) {
90   assert(((Mode == Unbuffered && !BufferStart && Size == 0) ||
91           (Mode != Unbuffered && BufferStart && Size != 0)) &&
92          "stream must be unbuffered or have at least one byte");
93   // Make sure the current buffer is free of content (we can't flush here; the
94   // child buffer management logic will be in write_impl).
95   assert(GetNumBytesInBuffer() == 0 && "Current buffer is non-empty!");
96 
97   if (BufferMode == InternalBuffer)
98     delete [] OutBufStart;
99   OutBufStart = BufferStart;
100   OutBufEnd = OutBufStart+Size;
101   OutBufCur = OutBufStart;
102   BufferMode = Mode;
103 
104   assert(OutBufStart <= OutBufEnd && "Invalid size!");
105 }
106 
operator <<(unsigned long N)107 raw_ostream &raw_ostream::operator<<(unsigned long N) {
108   // Zero is a special case.
109   if (N == 0)
110     return *this << '0';
111 
112   char NumberBuffer[20];
113   char *EndPtr = NumberBuffer+sizeof(NumberBuffer);
114   char *CurPtr = EndPtr;
115 
116   while (N) {
117     *--CurPtr = '0' + char(N % 10);
118     N /= 10;
119   }
120   return write(CurPtr, EndPtr-CurPtr);
121 }
122 
operator <<(long N)123 raw_ostream &raw_ostream::operator<<(long N) {
124   if (N <  0) {
125     *this << '-';
126     // Avoid undefined behavior on LONG_MIN with a cast.
127     N = -(unsigned long)N;
128   }
129 
130   return this->operator<<(static_cast<unsigned long>(N));
131 }
132 
operator <<(unsigned long long N)133 raw_ostream &raw_ostream::operator<<(unsigned long long N) {
134   // Output using 32-bit div/mod when possible.
135   if (N == static_cast<unsigned long>(N))
136     return this->operator<<(static_cast<unsigned long>(N));
137 
138   char NumberBuffer[20];
139   char *EndPtr = NumberBuffer+sizeof(NumberBuffer);
140   char *CurPtr = EndPtr;
141 
142   while (N) {
143     *--CurPtr = '0' + char(N % 10);
144     N /= 10;
145   }
146   return write(CurPtr, EndPtr-CurPtr);
147 }
148 
operator <<(long long N)149 raw_ostream &raw_ostream::operator<<(long long N) {
150   if (N < 0) {
151     *this << '-';
152     // Avoid undefined behavior on INT64_MIN with a cast.
153     N = -(unsigned long long)N;
154   }
155 
156   return this->operator<<(static_cast<unsigned long long>(N));
157 }
158 
write_hex(unsigned long long N)159 raw_ostream &raw_ostream::write_hex(unsigned long long N) {
160   // Zero is a special case.
161   if (N == 0)
162     return *this << '0';
163 
164   char NumberBuffer[20];
165   char *EndPtr = NumberBuffer+sizeof(NumberBuffer);
166   char *CurPtr = EndPtr;
167 
168   while (N) {
169     uintptr_t x = N % 16;
170     *--CurPtr = (x < 10 ? '0' + x : 'a' + x - 10);
171     N /= 16;
172   }
173 
174   return write(CurPtr, EndPtr-CurPtr);
175 }
176 
write_escaped(StringRef Str,bool UseHexEscapes)177 raw_ostream &raw_ostream::write_escaped(StringRef Str,
178                                         bool UseHexEscapes) {
179   for (unsigned i = 0, e = Str.size(); i != e; ++i) {
180     unsigned char c = Str[i];
181 
182     switch (c) {
183     case '\\':
184       *this << '\\' << '\\';
185       break;
186     case '\t':
187       *this << '\\' << 't';
188       break;
189     case '\n':
190       *this << '\\' << 'n';
191       break;
192     case '"':
193       *this << '\\' << '"';
194       break;
195     default:
196       if (std::isprint(c)) {
197         *this << c;
198         break;
199       }
200 
201       // Write out the escaped representation.
202       if (UseHexEscapes) {
203         *this << '\\' << 'x';
204         *this << hexdigit((c >> 4 & 0xF));
205         *this << hexdigit((c >> 0) & 0xF);
206       } else {
207         // Always use a full 3-character octal escape.
208         *this << '\\';
209         *this << char('0' + ((c >> 6) & 7));
210         *this << char('0' + ((c >> 3) & 7));
211         *this << char('0' + ((c >> 0) & 7));
212       }
213     }
214   }
215 
216   return *this;
217 }
218 
operator <<(const void * P)219 raw_ostream &raw_ostream::operator<<(const void *P) {
220   *this << '0' << 'x';
221 
222   return write_hex((uintptr_t) P);
223 }
224 
operator <<(double N)225 raw_ostream &raw_ostream::operator<<(double N) {
226 #ifdef _WIN32
227   // On MSVCRT and compatible, output of %e is incompatible to Posix
228   // by default. Number of exponent digits should be at least 2. "%+03d"
229   // FIXME: Implement our formatter to here or Support/Format.h!
230 #if __cplusplus >= 201103L && defined(__MINGW32__)
231   // FIXME: It should be generic to C++11.
232   if (N == 0.0 && std::signbit(N))
233     return *this << "-0.000000e+00";
234 #else
235   int fpcl = _fpclass(N);
236 
237   // negative zero
238   if (fpcl == _FPCLASS_NZ)
239     return *this << "-0.000000e+00";
240 #endif
241 
242   char buf[16];
243   unsigned len;
244   len = snprintf(buf, sizeof(buf), "%e", N);
245   if (len <= sizeof(buf) - 2) {
246     if (len >= 5 && buf[len - 5] == 'e' && buf[len - 3] == '0') {
247       int cs = buf[len - 4];
248       if (cs == '+' || cs == '-') {
249         int c1 = buf[len - 2];
250         int c0 = buf[len - 1];
251         if (isdigit(static_cast<unsigned char>(c1)) &&
252             isdigit(static_cast<unsigned char>(c0))) {
253           // Trim leading '0': "...e+012" -> "...e+12\0"
254           buf[len - 3] = c1;
255           buf[len - 2] = c0;
256           buf[--len] = 0;
257         }
258       }
259     }
260     return this->operator<<(buf);
261   }
262 #endif
263   return this->operator<<(format("%e", N));
264 }
265 
266 
267 
flush_nonempty()268 void raw_ostream::flush_nonempty() {
269   assert(OutBufCur > OutBufStart && "Invalid call to flush_nonempty.");
270   size_t Length = OutBufCur - OutBufStart;
271   OutBufCur = OutBufStart;
272   write_impl(OutBufStart, Length);
273 }
274 
write(unsigned char C)275 raw_ostream &raw_ostream::write(unsigned char C) {
276   // Group exceptional cases into a single branch.
277   if (LLVM_UNLIKELY(OutBufCur >= OutBufEnd)) {
278     if (LLVM_UNLIKELY(!OutBufStart)) {
279       if (BufferMode == Unbuffered) {
280         write_impl(reinterpret_cast<char*>(&C), 1);
281         return *this;
282       }
283       // Set up a buffer and start over.
284       SetBuffered();
285       return write(C);
286     }
287 
288     flush_nonempty();
289   }
290 
291   *OutBufCur++ = C;
292   return *this;
293 }
294 
write(const char * Ptr,size_t Size)295 raw_ostream &raw_ostream::write(const char *Ptr, size_t Size) {
296   // Group exceptional cases into a single branch.
297   if (LLVM_UNLIKELY(size_t(OutBufEnd - OutBufCur) < Size)) {
298     if (LLVM_UNLIKELY(!OutBufStart)) {
299       if (BufferMode == Unbuffered) {
300         write_impl(Ptr, Size);
301         return *this;
302       }
303       // Set up a buffer and start over.
304       SetBuffered();
305       return write(Ptr, Size);
306     }
307 
308     size_t NumBytes = OutBufEnd - OutBufCur;
309 
310     // If the buffer is empty at this point we have a string that is larger
311     // than the buffer. Directly write the chunk that is a multiple of the
312     // preferred buffer size and put the remainder in the buffer.
313     if (LLVM_UNLIKELY(OutBufCur == OutBufStart)) {
314       size_t BytesToWrite = Size - (Size % NumBytes);
315       write_impl(Ptr, BytesToWrite);
316       size_t BytesRemaining = Size - BytesToWrite;
317       if (BytesRemaining > size_t(OutBufEnd - OutBufCur)) {
318         // Too much left over to copy into our buffer.
319         return write(Ptr + BytesToWrite, BytesRemaining);
320       }
321       copy_to_buffer(Ptr + BytesToWrite, BytesRemaining);
322       return *this;
323     }
324 
325     // We don't have enough space in the buffer to fit the string in. Insert as
326     // much as possible, flush and start over with the remainder.
327     copy_to_buffer(Ptr, NumBytes);
328     flush_nonempty();
329     return write(Ptr + NumBytes, Size - NumBytes);
330   }
331 
332   copy_to_buffer(Ptr, Size);
333 
334   return *this;
335 }
336 
copy_to_buffer(const char * Ptr,size_t Size)337 void raw_ostream::copy_to_buffer(const char *Ptr, size_t Size) {
338   assert(Size <= size_t(OutBufEnd - OutBufCur) && "Buffer overrun!");
339 
340   // Handle short strings specially, memcpy isn't very good at very short
341   // strings.
342   switch (Size) {
343   case 4: OutBufCur[3] = Ptr[3]; // FALL THROUGH
344   case 3: OutBufCur[2] = Ptr[2]; // FALL THROUGH
345   case 2: OutBufCur[1] = Ptr[1]; // FALL THROUGH
346   case 1: OutBufCur[0] = Ptr[0]; // FALL THROUGH
347   case 0: break;
348   default:
349     memcpy(OutBufCur, Ptr, Size);
350     break;
351   }
352 
353   OutBufCur += Size;
354 }
355 
356 // Formatted output.
operator <<(const format_object_base & Fmt)357 raw_ostream &raw_ostream::operator<<(const format_object_base &Fmt) {
358   // If we have more than a few bytes left in our output buffer, try
359   // formatting directly onto its end.
360   size_t NextBufferSize = 127;
361   size_t BufferBytesLeft = OutBufEnd - OutBufCur;
362   if (BufferBytesLeft > 3) {
363     size_t BytesUsed = Fmt.print(OutBufCur, BufferBytesLeft);
364 
365     // Common case is that we have plenty of space.
366     if (BytesUsed <= BufferBytesLeft) {
367       OutBufCur += BytesUsed;
368       return *this;
369     }
370 
371     // Otherwise, we overflowed and the return value tells us the size to try
372     // again with.
373     NextBufferSize = BytesUsed;
374   }
375 
376   // If we got here, we didn't have enough space in the output buffer for the
377   // string.  Try printing into a SmallVector that is resized to have enough
378   // space.  Iterate until we win.
379   SmallVector<char, 128> V;
380 
381   while (1) {
382     V.resize(NextBufferSize);
383 
384     // Try formatting into the SmallVector.
385     size_t BytesUsed = Fmt.print(V.data(), NextBufferSize);
386 
387     // If BytesUsed fit into the vector, we win.
388     if (BytesUsed <= NextBufferSize)
389       return write(V.data(), BytesUsed);
390 
391     // Otherwise, try again with a new size.
392     assert(BytesUsed > NextBufferSize && "Didn't grow buffer!?");
393     NextBufferSize = BytesUsed;
394   }
395 }
396 
397 /// indent - Insert 'NumSpaces' spaces.
indent(unsigned NumSpaces)398 raw_ostream &raw_ostream::indent(unsigned NumSpaces) {
399   static const char Spaces[] = "                                "
400                                "                                "
401                                "                ";
402 
403   // Usually the indentation is small, handle it with a fastpath.
404   if (NumSpaces < array_lengthof(Spaces))
405     return write(Spaces, NumSpaces);
406 
407   while (NumSpaces) {
408     unsigned NumToWrite = std::min(NumSpaces,
409                                    (unsigned)array_lengthof(Spaces)-1);
410     write(Spaces, NumToWrite);
411     NumSpaces -= NumToWrite;
412   }
413   return *this;
414 }
415 
416 
417 //===----------------------------------------------------------------------===//
418 //  Formatted Output
419 //===----------------------------------------------------------------------===//
420 
421 // Out of line virtual method.
home()422 void format_object_base::home() {
423 }
424 
425 //===----------------------------------------------------------------------===//
426 //  raw_fd_ostream
427 //===----------------------------------------------------------------------===//
428 
429 /// raw_fd_ostream - Open the specified file for writing. If an error
430 /// occurs, information about the error is put into ErrorInfo, and the
431 /// stream should be immediately destroyed; the string will be empty
432 /// if no error occurred.
raw_fd_ostream(const char * Filename,std::string & ErrorInfo,sys::fs::OpenFlags Flags)433 raw_fd_ostream::raw_fd_ostream(const char *Filename, std::string &ErrorInfo,
434                                sys::fs::OpenFlags Flags)
435     : Error(false), UseAtomicWrites(false), pos(0) {
436   assert(Filename && "Filename is null");
437   ErrorInfo.clear();
438 
439   // Handle "-" as stdout. Note that when we do this, we consider ourself
440   // the owner of stdout. This means that we can do things like close the
441   // file descriptor when we're done and set the "binary" flag globally.
442   if (Filename[0] == '-' && Filename[1] == 0) {
443     FD = STDOUT_FILENO;
444     // If user requested binary then put stdout into binary mode if
445     // possible.
446     if (!(Flags & sys::fs::F_Text))
447       sys::ChangeStdoutToBinary();
448     // Close stdout when we're done, to detect any output errors.
449     ShouldClose = true;
450     return;
451   }
452 
453   std::error_code EC = sys::fs::openFileForWrite(Filename, FD, Flags);
454 
455   if (EC) {
456     ErrorInfo = "Error opening output file '" + std::string(Filename) + "': " +
457                 EC.message();
458     ShouldClose = false;
459     return;
460   }
461 
462   // Ok, we successfully opened the file, so it'll need to be closed.
463   ShouldClose = true;
464 }
465 
466 /// raw_fd_ostream ctor - FD is the file descriptor that this writes to.  If
467 /// ShouldClose is true, this closes the file when the stream is destroyed.
raw_fd_ostream(int fd,bool shouldClose,bool unbuffered)468 raw_fd_ostream::raw_fd_ostream(int fd, bool shouldClose, bool unbuffered)
469   : raw_ostream(unbuffered), FD(fd),
470     ShouldClose(shouldClose), Error(false), UseAtomicWrites(false) {
471 #ifdef O_BINARY
472   // Setting STDOUT to binary mode is necessary in Win32
473   // to avoid undesirable linefeed conversion.
474   // Don't touch STDERR, or w*printf() (in assert()) would barf wide chars.
475   if (fd == STDOUT_FILENO)
476     setmode(fd, O_BINARY);
477 #endif
478 
479   // Get the starting position.
480   off_t loc = ::lseek(FD, 0, SEEK_CUR);
481   if (loc == (off_t)-1)
482     pos = 0;
483   else
484     pos = static_cast<uint64_t>(loc);
485 }
486 
~raw_fd_ostream()487 raw_fd_ostream::~raw_fd_ostream() {
488   if (FD >= 0) {
489     flush();
490     if (ShouldClose)
491       while (::close(FD) != 0)
492         if (errno != EINTR) {
493           error_detected();
494           break;
495         }
496   }
497 
498 #ifdef __MINGW32__
499   // On mingw, global dtors should not call exit().
500   // report_fatal_error() invokes exit(). We know report_fatal_error()
501   // might not write messages to stderr when any errors were detected
502   // on FD == 2.
503   if (FD == 2) return;
504 #endif
505 
506   // If there are any pending errors, report them now. Clients wishing
507   // to avoid report_fatal_error calls should check for errors with
508   // has_error() and clear the error flag with clear_error() before
509   // destructing raw_ostream objects which may have errors.
510   if (has_error())
511     report_fatal_error("IO failure on output stream.", /*GenCrashDiag=*/false);
512 }
513 
514 
write_impl(const char * Ptr,size_t Size)515 void raw_fd_ostream::write_impl(const char *Ptr, size_t Size) {
516   assert(FD >= 0 && "File already closed.");
517   pos += Size;
518 
519   do {
520     ssize_t ret;
521 
522     // Check whether we should attempt to use atomic writes.
523     if (LLVM_LIKELY(!UseAtomicWrites)) {
524       ret = ::write(FD, Ptr, Size);
525     } else {
526       // Use ::writev() where available.
527 #if defined(HAVE_WRITEV)
528       const void *Addr = static_cast<const void *>(Ptr);
529       struct iovec IOV = {const_cast<void *>(Addr), Size };
530       ret = ::writev(FD, &IOV, 1);
531 #else
532       ret = ::write(FD, Ptr, Size);
533 #endif
534     }
535 
536     if (ret < 0) {
537       // If it's a recoverable error, swallow it and retry the write.
538       //
539       // Ideally we wouldn't ever see EAGAIN or EWOULDBLOCK here, since
540       // raw_ostream isn't designed to do non-blocking I/O. However, some
541       // programs, such as old versions of bjam, have mistakenly used
542       // O_NONBLOCK. For compatibility, emulate blocking semantics by
543       // spinning until the write succeeds. If you don't want spinning,
544       // don't use O_NONBLOCK file descriptors with raw_ostream.
545       if (errno == EINTR || errno == EAGAIN
546 #ifdef EWOULDBLOCK
547           || errno == EWOULDBLOCK
548 #endif
549           )
550         continue;
551 
552       // Otherwise it's a non-recoverable error. Note it and quit.
553       error_detected();
554       break;
555     }
556 
557     // The write may have written some or all of the data. Update the
558     // size and buffer pointer to reflect the remainder that needs
559     // to be written. If there are no bytes left, we're done.
560     Ptr += ret;
561     Size -= ret;
562   } while (Size > 0);
563 }
564 
close()565 void raw_fd_ostream::close() {
566   assert(ShouldClose);
567   ShouldClose = false;
568   flush();
569   while (::close(FD) != 0)
570     if (errno != EINTR) {
571       error_detected();
572       break;
573     }
574   FD = -1;
575 }
576 
seek(uint64_t off)577 uint64_t raw_fd_ostream::seek(uint64_t off) {
578   flush();
579   pos = ::lseek(FD, off, SEEK_SET);
580   if (pos != off)
581     error_detected();
582   return pos;
583 }
584 
preferred_buffer_size() const585 size_t raw_fd_ostream::preferred_buffer_size() const {
586 #if !defined(_MSC_VER) && !defined(__MINGW32__) && !defined(__minix)
587   // Windows and Minix have no st_blksize.
588   assert(FD >= 0 && "File not yet open!");
589   struct stat statbuf;
590   if (fstat(FD, &statbuf) != 0)
591     return 0;
592 
593   // If this is a terminal, don't use buffering. Line buffering
594   // would be a more traditional thing to do, but it's not worth
595   // the complexity.
596   if (S_ISCHR(statbuf.st_mode) && isatty(FD))
597     return 0;
598   // Return the preferred block size.
599   return statbuf.st_blksize;
600 #else
601   return raw_ostream::preferred_buffer_size();
602 #endif
603 }
604 
changeColor(enum Colors colors,bool bold,bool bg)605 raw_ostream &raw_fd_ostream::changeColor(enum Colors colors, bool bold,
606                                          bool bg) {
607   if (sys::Process::ColorNeedsFlush())
608     flush();
609   const char *colorcode =
610     (colors == SAVEDCOLOR) ? sys::Process::OutputBold(bg)
611     : sys::Process::OutputColor(colors, bold, bg);
612   if (colorcode) {
613     size_t len = strlen(colorcode);
614     write(colorcode, len);
615     // don't account colors towards output characters
616     pos -= len;
617   }
618   return *this;
619 }
620 
resetColor()621 raw_ostream &raw_fd_ostream::resetColor() {
622   if (sys::Process::ColorNeedsFlush())
623     flush();
624   const char *colorcode = sys::Process::ResetColor();
625   if (colorcode) {
626     size_t len = strlen(colorcode);
627     write(colorcode, len);
628     // don't account colors towards output characters
629     pos -= len;
630   }
631   return *this;
632 }
633 
reverseColor()634 raw_ostream &raw_fd_ostream::reverseColor() {
635   if (sys::Process::ColorNeedsFlush())
636     flush();
637   const char *colorcode = sys::Process::OutputReverse();
638   if (colorcode) {
639     size_t len = strlen(colorcode);
640     write(colorcode, len);
641     // don't account colors towards output characters
642     pos -= len;
643   }
644   return *this;
645 }
646 
is_displayed() const647 bool raw_fd_ostream::is_displayed() const {
648   return sys::Process::FileDescriptorIsDisplayed(FD);
649 }
650 
has_colors() const651 bool raw_fd_ostream::has_colors() const {
652   return sys::Process::FileDescriptorHasColors(FD);
653 }
654 
655 //===----------------------------------------------------------------------===//
656 //  outs(), errs(), nulls()
657 //===----------------------------------------------------------------------===//
658 
659 /// outs() - This returns a reference to a raw_ostream for standard output.
660 /// Use it like: outs() << "foo" << "bar";
outs()661 raw_ostream &llvm::outs() {
662   // Set buffer settings to model stdout behavior.
663   // Delete the file descriptor when the program exists, forcing error
664   // detection. If you don't want this behavior, don't use outs().
665   static raw_fd_ostream S(STDOUT_FILENO, true);
666   return S;
667 }
668 
669 /// errs() - This returns a reference to a raw_ostream for standard error.
670 /// Use it like: errs() << "foo" << "bar";
errs()671 raw_ostream &llvm::errs() {
672   // Set standard error to be unbuffered by default.
673   static raw_fd_ostream S(STDERR_FILENO, false, true);
674   return S;
675 }
676 
677 /// nulls() - This returns a reference to a raw_ostream which discards output.
nulls()678 raw_ostream &llvm::nulls() {
679   static raw_null_ostream S;
680   return S;
681 }
682 
683 
684 //===----------------------------------------------------------------------===//
685 //  raw_string_ostream
686 //===----------------------------------------------------------------------===//
687 
~raw_string_ostream()688 raw_string_ostream::~raw_string_ostream() {
689   flush();
690 }
691 
write_impl(const char * Ptr,size_t Size)692 void raw_string_ostream::write_impl(const char *Ptr, size_t Size) {
693   OS.append(Ptr, Size);
694 }
695 
696 //===----------------------------------------------------------------------===//
697 //  raw_svector_ostream
698 //===----------------------------------------------------------------------===//
699 
700 // The raw_svector_ostream implementation uses the SmallVector itself as the
701 // buffer for the raw_ostream. We guarantee that the raw_ostream buffer is
702 // always pointing past the end of the vector, but within the vector
703 // capacity. This allows raw_ostream to write directly into the correct place,
704 // and we only need to set the vector size when the data is flushed.
705 
raw_svector_ostream(SmallVectorImpl<char> & O)706 raw_svector_ostream::raw_svector_ostream(SmallVectorImpl<char> &O) : OS(O) {
707   // Set up the initial external buffer. We make sure that the buffer has at
708   // least 128 bytes free; raw_ostream itself only requires 64, but we want to
709   // make sure that we don't grow the buffer unnecessarily on destruction (when
710   // the data is flushed). See the FIXME below.
711   OS.reserve(OS.size() + 128);
712   SetBuffer(OS.end(), OS.capacity() - OS.size());
713 }
714 
~raw_svector_ostream()715 raw_svector_ostream::~raw_svector_ostream() {
716   // FIXME: Prevent resizing during this flush().
717   flush();
718 }
719 
720 /// resync - This is called when the SmallVector we're appending to is changed
721 /// outside of the raw_svector_ostream's control.  It is only safe to do this
722 /// if the raw_svector_ostream has previously been flushed.
resync()723 void raw_svector_ostream::resync() {
724   assert(GetNumBytesInBuffer() == 0 && "Didn't flush before mutating vector");
725 
726   if (OS.capacity() - OS.size() < 64)
727     OS.reserve(OS.capacity() * 2);
728   SetBuffer(OS.end(), OS.capacity() - OS.size());
729 }
730 
write_impl(const char * Ptr,size_t Size)731 void raw_svector_ostream::write_impl(const char *Ptr, size_t Size) {
732   // If we're writing bytes from the end of the buffer into the smallvector, we
733   // don't need to copy the bytes, just commit the bytes because they are
734   // already in the right place.
735   if (Ptr == OS.end()) {
736     assert(OS.size() + Size <= OS.capacity() && "Invalid write_impl() call!");
737     OS.set_size(OS.size() + Size);
738   } else {
739     assert(GetNumBytesInBuffer() == 0 &&
740            "Should be writing from buffer if some bytes in it");
741     // Otherwise, do copy the bytes.
742     OS.append(Ptr, Ptr+Size);
743   }
744 
745   // Grow the vector if necessary.
746   if (OS.capacity() - OS.size() < 64)
747     OS.reserve(OS.capacity() * 2);
748 
749   // Update the buffer position.
750   SetBuffer(OS.end(), OS.capacity() - OS.size());
751 }
752 
current_pos() const753 uint64_t raw_svector_ostream::current_pos() const {
754    return OS.size();
755 }
756 
str()757 StringRef raw_svector_ostream::str() {
758   flush();
759   return StringRef(OS.begin(), OS.size());
760 }
761 
762 //===----------------------------------------------------------------------===//
763 //  raw_null_ostream
764 //===----------------------------------------------------------------------===//
765 
~raw_null_ostream()766 raw_null_ostream::~raw_null_ostream() {
767 #ifndef NDEBUG
768   // ~raw_ostream asserts that the buffer is empty. This isn't necessary
769   // with raw_null_ostream, but it's better to have raw_null_ostream follow
770   // the rules than to change the rules just for raw_null_ostream.
771   flush();
772 #endif
773 }
774 
write_impl(const char * Ptr,size_t Size)775 void raw_null_ostream::write_impl(const char *Ptr, size_t Size) {
776 }
777 
current_pos() const778 uint64_t raw_null_ostream::current_pos() const {
779   return 0;
780 }
781