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- /*
- * Copyright 2014-present Facebook, Inc.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
- #include <folly/io/Cursor.h>
- #include <cstdio>
- #include <folly/ScopeGuard.h>
- namespace folly {
- namespace io {
- void Appender::printf(const char* fmt, ...) {
- va_list ap;
- va_start(ap, fmt);
- vprintf(fmt, ap);
- va_end(ap);
- }
- void Appender::vprintf(const char* fmt, va_list ap) {
- // Make a copy of ap in case we need to retry.
- // We use ap on the first attempt, so it always gets advanced
- // passed the used arguments. We'll only use apCopy if we need to retry.
- va_list apCopy;
- va_copy(apCopy, ap);
- SCOPE_EXIT {
- va_end(apCopy);
- };
- // First try writing into our available data space.
- int ret =
- vsnprintf(reinterpret_cast<char*>(writableData()), length(), fmt, ap);
- if (ret < 0) {
- throw std::runtime_error("error formatting printf() data");
- }
- auto len = size_t(ret);
- // vsnprintf() returns the number of characters that would be printed,
- // not including the terminating nul.
- if (len < length()) {
- // All of the data was successfully written.
- append(len);
- return;
- }
- // There wasn't enough room for the data.
- // Allocate more room, and then retry.
- ensure(len + 1);
- ret =
- vsnprintf(reinterpret_cast<char*>(writableData()), length(), fmt, apCopy);
- if (ret < 0) {
- throw std::runtime_error("error formatting printf() data");
- }
- len = size_t(ret);
- if (len >= length()) {
- // This shouldn't ever happen.
- throw std::runtime_error(
- "unexpectedly out of buffer space on second "
- "vsnprintf() attmept");
- }
- append(len);
- }
- } // namespace io
- } // namespace folly
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