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/*
* Copyright 2018 Google
*
* 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 "Firestore/core/src/firebase/firestore/util/string_printf.h"
#include <cstdio>
namespace firebase {
namespace firestore {
namespace util {
void StringAppendV(std::string* dst, const char* format, va_list ap) {
// First try with a small fixed size buffer
static const int kSpaceLength = 1024;
char space[kSpaceLength];
// It's possible for methods that use a va_list to invalidate
// the data in it upon use. The fix is to make a copy
// of the structure before using it and use that copy instead.
va_list backup_ap;
va_copy(backup_ap, ap);
int result = vsnprintf(space, kSpaceLength, format, backup_ap);
va_end(backup_ap);
if (result < kSpaceLength) {
if (result >= 0) {
// Normal case -- everything fit.
dst->append(space, static_cast<size_t>(result));
return;
}
#ifdef _MSC_VER
// Error or MSVC running out of space. MSVC 8.0 and higher
// can be asked about space needed with the special idiom below:
va_copy(backup_ap, ap);
result = vsnprintf(nullptr, 0, format, backup_ap);
va_end(backup_ap);
#endif
}
if (result < 0) {
// Just an error.
return;
}
size_t result_size = static_cast<size_t>(result);
// Increase the buffer size to the size requested by vsnprintf,
// plus one for the closing \0.
size_t initial_size = dst->size();
size_t target_size = initial_size + result_size;
dst->resize(target_size + 1);
char* buf = &(*dst)[initial_size];
size_t buf_remain = result_size + 1;
// Restore the va_list before we use it again
va_copy(backup_ap, ap);
result = vsnprintf(buf, buf_remain, format, backup_ap);
va_end(backup_ap);
if (result >= 0 && static_cast<size_t>(result) < buf_remain) {
// It fit and vsnprintf copied in directly. Resize down one to
// remove the trailing \0.
dst->resize(target_size);
} else {
// Didn't fit. Leave the original string unchanged.
dst->resize(initial_size);
}
}
std::string StringPrintf(const char* format, ...) {
va_list ap;
va_start(ap, format);
std::string result;
StringAppendV(&result, format, ap);
va_end(ap);
return result;
}
void StringAppendF(std::string* dst, const char* format, ...) {
va_list ap;
va_start(ap, format);
StringAppendV(dst, format, ap);
va_end(ap);
}
} // namespace util
} // namespace firestore
} // namespace firebase
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