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
19bool 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
51finish:
52  va_end(args);
53  va_end(copy_args);
54  return result;
55}
56