2 * Copyright 2015 Facebook, Inc.
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
8 * http://www.apache.org/licenses/LICENSE-2.0
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.
18 #include <folly/io/Cursor.h>
21 #include <folly/ScopeGuard.h>
23 namespace folly { namespace io {
25 void Appender::printf(const char* fmt, ...) {
32 void Appender::vprintf(const char* fmt, va_list ap) {
33 // Make a copy of ap in case we need to retry.
34 // We use ap on the first attempt, so it always gets advanced
35 // passed the used arguments. We'll only use apCopy if we need to retry.
42 // First try writing into our available data space.
43 int ret = vsnprintf(reinterpret_cast<char*>(writableData()), length(),
46 throw std::runtime_error("error formatting printf() data");
48 // vsnprintf() returns the number of characters that would be printed,
49 // not including the terminating nul.
50 if (size_t(ret) < length()) {
51 // All of the data was successfully written.
56 // There wasn't enough room for the data.
57 // Allocate more room, and then retry.
59 ret = vsnprintf(reinterpret_cast<char*>(writableData()), length(),
62 throw std::runtime_error("error formatting printf() data");
64 if (size_t(ret) >= length()) {
65 // This shouldn't ever happen.
66 throw std::runtime_error("unexpectedly out of buffer space on second "
67 "vsnprintf() attmept");