1 /* Copyright 2015 The TensorFlow Authors. All Rights Reserved.
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
16 #include "tensorflow/core/platform/stringprintf.h"
17
18 #include <errno.h>
19 #include <stdarg.h> // For va_list and related operations
20 #include <stdio.h> // MSVC requires this for _vsnprintf
21
22 namespace tensorflow {
23 namespace strings {
24
Appendv(string * dst,const char * format,va_list ap)25 void Appendv(string* dst, const char* format, va_list ap) {
26 // First try with a small fixed size buffer
27 static const int kSpaceLength = 1024;
28 char space[kSpaceLength];
29
30 // It's possible for methods that use a va_list to invalidate
31 // the data in it upon use. The fix is to make a copy
32 // of the structure before using it and use that copy instead.
33 va_list backup_ap;
34 va_copy(backup_ap, ap);
35 int result = vsnprintf(space, kSpaceLength, format, backup_ap);
36 va_end(backup_ap);
37
38 if (result < kSpaceLength) {
39 if (result >= 0) {
40 // Normal case -- everything fit.
41 dst->append(space, result);
42 return;
43 }
44
45 #ifdef _MSC_VER
46 // Error or MSVC running out of space. MSVC 8.0 and higher
47 // can be asked about space needed with the special idiom below:
48 va_copy(backup_ap, ap);
49 result = vsnprintf(nullptr, 0, format, backup_ap);
50 va_end(backup_ap);
51 #endif
52
53 if (result < 0) {
54 // Just an error.
55 return;
56 }
57 }
58
59 // Increase the buffer size to the size requested by vsnprintf,
60 // plus one for the closing \0.
61 int length = result + 1;
62 char* buf = new char[length];
63
64 // Restore the va_list before we use it again
65 va_copy(backup_ap, ap);
66 result = vsnprintf(buf, length, format, backup_ap);
67 va_end(backup_ap);
68
69 if (result >= 0 && result < length) {
70 // It fit
71 dst->append(buf, result);
72 }
73 delete[] buf;
74 }
75
Printf(const char * format,...)76 string Printf(const char* format, ...) {
77 va_list ap;
78 va_start(ap, format);
79 string result;
80 Appendv(&result, format, ap);
81 va_end(ap);
82 return result;
83 }
84
Appendf(string * dst,const char * format,...)85 void Appendf(string* dst, const char* format, ...) {
86 va_list ap;
87 va_start(ap, format);
88 Appendv(dst, format, ap);
89 va_end(ap);
90 }
91
92 } // namespace strings
93 } // namespace tensorflow
94