1  // Copyright 2020 The Android Open Source Project
2  //
3  // Licensed under the Apache License, Version 2.0 (the "License");
4  // you may not use this file except in compliance with the License.
5  // You may obtain a copy of the License at
6  //
7  // http://www.apache.org/licenses/LICENSE-2.0
8  //
9  // Unless required by applicable law or agreed to in writing, software
10  // distributed under the License is distributed on an "AS IS" BASIS,
11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12  // See the License for the specific language governing permissions and
13  // limitations under the License.
14  
15  #include "aemu/base/StringFormat.h"
16  
17  #include <stdio.h>
18  
19  namespace android {
20  namespace base {
21  
StringFormatRaw(const char * format,...)22  std::string StringFormatRaw(const char* format, ...) {
23      va_list args;
24      va_start(args, format);
25      auto result = StringFormatWithArgs(format, args);
26      va_end(args);
27      return result;
28  }
29  
StringFormatWithArgs(const char * format,va_list args)30  std::string StringFormatWithArgs(const char* format, va_list args) {
31      std::string result;
32      StringAppendFormatWithArgs(&result, format, args);
33      return result;
34  }
35  
StringAppendFormatRaw(std::string * string,const char * format,...)36  void StringAppendFormatRaw(std::string* string, const char* format, ...) {
37      va_list args;
38      va_start(args, format);
39      StringAppendFormatWithArgs(string, format, args);
40      va_end(args);
41  }
42  
StringAppendFormatWithArgs(std::string * string,const char * format,va_list args)43  void StringAppendFormatWithArgs(std::string* string,
44                                  const char* format,
45                                  va_list args) {
46      size_t cur_size = string->size();
47      size_t extra = 0;
48      for (;;) {
49          va_list args2;
50          va_copy(args2, args);
51          int ret = vsnprintf(&(*string)[cur_size], extra, format, args2);
52          va_end(args2);
53  
54          if (ret == 0) {
55              // Nothing to do here.
56              break;
57          }
58  
59          if (ret > 0) {
60              size_t ret_sz = static_cast<size_t>(ret);
61              if (extra == 0) {
62                  // First pass, resize the string and try again.
63                  extra = ret_sz + 1;
64                  string->resize(cur_size + extra);
65                  continue;
66              }
67              if (ret_sz < extra) {
68                  // Second pass or later, success!
69                  string->resize(cur_size + ret_sz);
70                  return;
71              }
72          }
73  
74          // NOTE: The MSVCRT.DLL implementation of snprintf() is broken and
75          // will return -1 in case of truncation. This code path is taken
76          // when this happens, or when |ret_sz| is equal or larger than
77          // |extra|. Grow the buffer to allow for more room, then try again.
78          extra += (extra >> 1) + 32;
79          string->resize(cur_size + extra);
80      }
81  }
82  
83  }  // namespace base
84  }  // namespace android
85