lldb/source/Utility/VASprintf.cpp

   1 //===-- VASprintf.cpp -----------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "lldb/Utility/VASPrintf.h"
  10
  11 #include "llvm/ADT/SmallString.h"
  12 #include "llvm/ADT/SmallVector.h"
  13 #include "llvm/ADT/StringRef.h"
  14
  15 #include <cassert>
  16 #include <cstdarg>
  17 #include <cstdio>
  18
  19 bool lldb_private::VASprintf(llvm::SmallVectorImpl<char> &buf, const char *fmt,
  20                              va_list args) {
  21   llvm::SmallString<16> error("<Encoding error>");
  22   bool result = true;
  23
  24   // Copy in case our first call to vsnprintf doesn't fit into our buffer
  25   va_list copy_args;
  26   va_copy(copy_args, args);
  27
  28   buf.resize(buf.capacity());
  29   // Write up to `capacity` bytes, ignoring the current size.
  30   int length = ::vsnprintf(buf.data(), buf.size(), fmt, args);
  31   if (length < 0) {
  32     buf = error;
  33     result = false;
  34     goto finish;
  35   }
  36
  37   if (size_t(length) >= buf.size()) {
  38     // The error formatted string didn't fit into our buffer, resize it to the
  39     // exact needed size, and retry
  40     buf.resize(length + 1);
  41     length = ::vsnprintf(buf.data(), buf.size(), fmt, copy_args);
  42     if (length < 0) {
  43       buf = error;
  44       result = false;
  45       goto finish;
  46     }
  47     assert(size_t(length) < buf.size());
  48   }
  49   buf.resize(length);
  50
  51 finish:
  52   va_end(args);
  53   va_end(copy_args);
  54   return result;
  55 }