/* * Copyright 2018 The WebRTC Project Authors. All rights reserved. * * Use of this source code is governed by a BSD-style license * that can be found in the LICENSE file in the root of the source * tree. An additional intellectual property rights grant can be found * in the file PATENTS. All contributing project authors may * be found in the AUTHORS file in the root of the source tree. */ #ifndef RTC_BASE_STRINGS_STRING_BUILDER_H_ #define RTC_BASE_STRINGS_STRING_BUILDER_H_ #include #include #include #include "api/array_view.h" #include "rtc_base/checks.h" #include "rtc_base/numerics/safe_minmax.h" #include "rtc_base/stringutils.h" namespace rtc { // This is a minimalistic string builder class meant to cover the most cases of // when you might otherwise be tempted to use a stringstream (discouraged for // anything except logging). It uses a fixed-size buffer provided by the caller // and concatenates strings and numbers into it, allowing the results to be // read via |str()|. class SimpleStringBuilder { public: explicit SimpleStringBuilder(rtc::ArrayView buffer); SimpleStringBuilder(const SimpleStringBuilder&) = delete; SimpleStringBuilder& operator=(const SimpleStringBuilder&) = delete; SimpleStringBuilder& operator<<(const char* str); SimpleStringBuilder& operator<<(char ch); SimpleStringBuilder& operator<<(const std::string& str); SimpleStringBuilder& operator<<(int i); SimpleStringBuilder& operator<<(unsigned i); SimpleStringBuilder& operator<<(long i); // NOLINT SimpleStringBuilder& operator<<(long long i); // NOLINT SimpleStringBuilder& operator<<(unsigned long i); // NOLINT SimpleStringBuilder& operator<<(unsigned long long i); // NOLINT SimpleStringBuilder& operator<<(float f); SimpleStringBuilder& operator<<(double f); SimpleStringBuilder& operator<<(long double f); // Returns a pointer to the built string. The name |str()| is borrowed for // compatibility reasons as we replace usage of stringstream throughout the // code base. const char* str() const { return buffer_.data(); } // Returns the length of the string. The name |size()| is picked for STL // compatibility reasons. size_t size() const { return size_; } // Allows appending a printf style formatted string. #if defined(__GNUC__) __attribute__((__format__(__printf__, 2, 3))) #endif SimpleStringBuilder& AppendFormat(const char* fmt, ...); // An alternate way from operator<<() to append a string. This variant is // slightly more efficient when the length of the string to append, is known. SimpleStringBuilder& Append(const char* str, size_t length = SIZE_UNKNOWN); private: bool IsConsistent() const { return size_ <= buffer_.size() - 1 && buffer_[size_] == '\0'; } // An always-zero-terminated fixed-size buffer that we write to. The fixed // size allows the buffer to be stack allocated, which helps performance. // Having a fixed size is furthermore useful to avoid unnecessary resizing // while building it. const rtc::ArrayView buffer_; // Represents the number of characters written to the buffer. // This does not include the terminating '\0'. size_t size_ = 0; }; } // namespace rtc #endif // RTC_BASE_STRINGS_STRING_BUILDER_H_