1 //===-- VASPrintf.cpp -------------------------------------------*- C++ -*-===//
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 #include "lldb/Utility/VASPrintf.h"
11 
12 #include "llvm/ADT/SmallString.h"
13 #include "llvm/ADT/SmallVector.h" // for SmallVectorImpl
14 #include "llvm/ADT/StringRef.h"   // for StringRef
15 
16 #include <assert.h> // for assert
17 #include <stdarg.h> // for va_end, va_list, va_copy
18 #include <stdio.h>  // for vsnprintf, size_t
19 
20 bool lldb_private::VASprintf(llvm::SmallVectorImpl<char> &buf, const char *fmt,
21                              va_list args) {
22   llvm::SmallString<16> error("<Encoding error>");
23   bool result = true;
24 
25   // Copy in case our first call to vsnprintf doesn't fit into our buffer
26   va_list copy_args;
27   va_copy(copy_args, args);
28 
29   buf.resize(buf.capacity());
30   // Write up to `capacity` bytes, ignoring the current size.
31   int length = ::vsnprintf(buf.data(), buf.size(), fmt, args);
32   if (length < 0) {
33     buf = error;
34     result = false;
35     goto finish;
36   }
37 
38   if (size_t(length) >= buf.size()) {
39     // The error formatted string didn't fit into our buffer, resize it
40     // to the exact needed size, and retry
41     buf.resize(length + 1);
42     length = ::vsnprintf(buf.data(), buf.size(), fmt, copy_args);
43     if (length < 0) {
44       buf = error;
45       result = false;
46       goto finish;
47     }
48     assert(size_t(length) < buf.size());
49   }
50   buf.resize(length);
51 
52 finish:
53   va_end(args);
54   va_end(copy_args);
55   return result;
56 }
57