1 // Copyright 2014 The Android Open Source Project 2 // 3 // This software is licensed under the terms of the GNU General Public 4 // License version 2, as published by the Free Software Foundation, and 5 // may be copied, distributed, and modified under those terms. 6 // 7 // This program is distributed in the hope that it will be useful, 8 // but WITHOUT ANY WARRANTY; without even the implied warranty of 9 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 10 // GNU General Public License for more details. 11 12 #pragma once 13 14 #include "android/base/StringView.h" 15 16 #include <string> 17 #include <type_traits> 18 #include <utility> 19 20 #include <stdarg.h> 21 22 namespace android { 23 namespace base { 24 25 // Create a new string instance that contains the printf-style formatted 26 // output from |format| and potentially any following arguments. 27 std::string StringFormatRaw(const char* format, ...); 28 29 // A variant of StringFormat() which uses a va_list to list formatting 30 // parameters instead. 31 std::string StringFormatWithArgs(const char* format, va_list args); 32 33 // Appends a formatted string at the end of an existing string. 34 // |string| is the target string instance, |format| the format string, 35 // followed by any formatting parameters. This is more efficient than 36 // appending the result of StringFormat(format,...) to |*string| directly. 37 void StringAppendFormatRaw(std::string* string, const char* format, ...); 38 39 // A variant of StringAppendFormat() that takes a va_list to list 40 // formatting parameters. 41 void StringAppendFormatWithArgs(std::string* string, 42 const char* format, 43 va_list args); 44 45 // unpackFormatArg() is a set of overloaded functions needed to unpack 46 // an argument of the formatting list to a POD value which can be passed 47 // into the sprintf()-like C function 48 49 // Anything which can be used to construct a string goes here and unpacks into 50 // a const char* 51 inline const char* unpackFormatArg(const std::string& str) { 52 return str.c_str(); 53 } 54 55 // Forward all PODs as-is 56 template <class T> 57 constexpr T&& unpackFormatArg(T&& t, 58 typename std::enable_if< 59 std::is_pod<typename std::decay<T>::type>::value 60 >::type* = nullptr) { 61 return std::forward<T>(t); 62 } 63 64 // These templated versions of StringFormat*() allow one to pass all kinds of 65 // string objects into the argument list 66 template <class... Args> 67 std::string StringFormat(const char* format, Args&&... args) { 68 return StringFormatRaw(format, unpackFormatArg(std::forward<Args>(args))...); 69 } 70 71 template <class... Args> 72 void StringAppendFormat(std::string* string, 73 const char* format, 74 Args&&... args) { 75 StringAppendFormatRaw(string, format, 76 unpackFormatArg(std::forward<Args>(args))...); 77 } 78 79 } // namespace base 80 } // namespace android 81
