1 | /* |
2 | * Copyright 2014-present Facebook, Inc. |
3 | * |
4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
5 | * you may not use this file except in compliance with the License. |
6 | * You may obtain a copy of the License at |
7 | * |
8 | * http://www.apache.org/licenses/LICENSE-2.0 |
9 | * |
10 | * Unless required by applicable law or agreed to in writing, software |
11 | * distributed under the License is distributed on an "AS IS" BASIS, |
12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
13 | * See the License for the specific language governing permissions and |
14 | * limitations under the License. |
15 | */ |
16 | |
17 | #include <folly/io/Cursor.h> |
18 | |
19 | #include <cstdio> |
20 | |
21 | #include <folly/ScopeGuard.h> |
22 | |
23 | namespace folly { |
24 | namespace io { |
25 | |
26 | void Appender::printf(const char* fmt, ...) { |
27 | va_list ap; |
28 | va_start(ap, fmt); |
29 | vprintf(fmt, ap); |
30 | va_end(ap); |
31 | } |
32 | |
33 | void Appender::vprintf(const char* fmt, va_list ap) { |
34 | // Make a copy of ap in case we need to retry. |
35 | // We use ap on the first attempt, so it always gets advanced |
36 | // passed the used arguments. We'll only use apCopy if we need to retry. |
37 | va_list apCopy; |
38 | va_copy(apCopy, ap); |
39 | SCOPE_EXIT { |
40 | va_end(apCopy); |
41 | }; |
42 | |
43 | // First try writing into our available data space. |
44 | int ret = |
45 | vsnprintf(reinterpret_cast<char*>(writableData()), length(), fmt, ap); |
46 | if (ret < 0) { |
47 | throw std::runtime_error("error formatting printf() data" ); |
48 | } |
49 | auto len = size_t(ret); |
50 | // vsnprintf() returns the number of characters that would be printed, |
51 | // not including the terminating nul. |
52 | if (len < length()) { |
53 | // All of the data was successfully written. |
54 | append(len); |
55 | return; |
56 | } |
57 | |
58 | // There wasn't enough room for the data. |
59 | // Allocate more room, and then retry. |
60 | ensure(len + 1); |
61 | ret = |
62 | vsnprintf(reinterpret_cast<char*>(writableData()), length(), fmt, apCopy); |
63 | if (ret < 0) { |
64 | throw std::runtime_error("error formatting printf() data" ); |
65 | } |
66 | len = size_t(ret); |
67 | if (len >= length()) { |
68 | // This shouldn't ever happen. |
69 | throw std::runtime_error( |
70 | "unexpectedly out of buffer space on second " |
71 | "vsnprintf() attmept" ); |
72 | } |
73 | append(len); |
74 | } |
75 | } // namespace io |
76 | } // namespace folly |
77 | |