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