mirror of
https://github.com/klzgrad/naiveproxy.git
synced 2024-11-28 00:06:09 +03:00
101 lines
3.9 KiB
C++
101 lines
3.9 KiB
C++
// Copyright 2017 The Chromium Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style license that can be
|
|
// found in the LICENSE file.
|
|
|
|
#ifndef BASE_STRINGS_STRCAT_H_
|
|
#define BASE_STRINGS_STRCAT_H_
|
|
|
|
#include <initializer_list>
|
|
|
|
#include "base/base_export.h"
|
|
#include "base/compiler_specific.h"
|
|
#include "base/containers/span.h"
|
|
#include "base/strings/string_piece.h"
|
|
#include "build/build_config.h"
|
|
|
|
#if defined(OS_WIN)
|
|
// Guard against conflict with Win32 API StrCat macro:
|
|
// check StrCat wasn't and will not be redefined.
|
|
#define StrCat StrCat
|
|
#endif
|
|
|
|
namespace base {
|
|
|
|
// StrCat ----------------------------------------------------------------------
|
|
//
|
|
// StrCat is a function to perform concatenation on a sequence of strings.
|
|
// It is preferrable to a sequence of "a + b + c" because it is both faster and
|
|
// generates less code.
|
|
//
|
|
// std::string result = base::StrCat({"foo ", result, "\nfoo ", bar});
|
|
//
|
|
// To join an array of strings with a separator, see base::JoinString in
|
|
// base/strings/string_util.h.
|
|
//
|
|
// MORE INFO
|
|
//
|
|
// StrCat can see all arguments at once, so it can allocate one return buffer
|
|
// of exactly the right size and copy once, as opposed to a sequence of
|
|
// operator+ which generates a series of temporary strings, copying as it goes.
|
|
// And by using StringPiece arguments, StrCat can avoid creating temporary
|
|
// string objects for char* constants.
|
|
//
|
|
// ALTERNATIVES
|
|
//
|
|
// Internal Google / Abseil has a similar StrCat function. That version takes
|
|
// an overloaded number of arguments instead of initializer list (overflowing
|
|
// to initializer list for many arguments). We don't have any legacy
|
|
// requirements and using only initializer_list is simpler and generates
|
|
// roughly the same amount of code at the call sites.
|
|
//
|
|
// Abseil's StrCat also allows numbers by using an intermediate class that can
|
|
// be implicitly constructed from either a string or various number types. This
|
|
// class formats the numbers into a static buffer for increased performance,
|
|
// and the call sites look nice.
|
|
//
|
|
// As-written Abseil's helper class for numbers generates slightly more code
|
|
// than the raw StringPiece version. We can de-inline the helper class'
|
|
// constructors which will cause the StringPiece constructors to be de-inlined
|
|
// for this call and generate slightly less code. This is something we can
|
|
// explore more in the future.
|
|
|
|
BASE_EXPORT std::string StrCat(span<const StringPiece> pieces);
|
|
BASE_EXPORT string16 StrCat(span<const StringPiece16> pieces);
|
|
BASE_EXPORT std::string StrCat(span<const std::string> pieces);
|
|
BASE_EXPORT string16 StrCat(span<const string16> pieces);
|
|
|
|
// Initializer list forwards to the array version.
|
|
inline std::string StrCat(std::initializer_list<StringPiece> pieces) {
|
|
return StrCat(make_span(pieces.begin(), pieces.size()));
|
|
}
|
|
inline string16 StrCat(std::initializer_list<StringPiece16> pieces) {
|
|
return StrCat(make_span(pieces.begin(), pieces.size()));
|
|
}
|
|
|
|
// StrAppend -------------------------------------------------------------------
|
|
//
|
|
// Appends a sequence of strings to a destination. Prefer:
|
|
// StrAppend(&foo, ...);
|
|
// over:
|
|
// foo += StrCat(...);
|
|
// because it avoids a temporary string allocation and copy.
|
|
|
|
BASE_EXPORT void StrAppend(std::string* dest, span<const StringPiece> pieces);
|
|
BASE_EXPORT void StrAppend(string16* dest, span<const StringPiece16> pieces);
|
|
BASE_EXPORT void StrAppend(std::string* dest, span<const std::string> pieces);
|
|
BASE_EXPORT void StrAppend(string16* dest, span<const string16> pieces);
|
|
|
|
// Initializer list forwards to the array version.
|
|
inline void StrAppend(std::string* dest,
|
|
std::initializer_list<StringPiece> pieces) {
|
|
return StrAppend(dest, make_span(pieces.begin(), pieces.size()));
|
|
}
|
|
inline void StrAppend(string16* dest,
|
|
std::initializer_list<StringPiece16> pieces) {
|
|
return StrAppend(dest, make_span(pieces.begin(), pieces.size()));
|
|
}
|
|
|
|
} // namespace base
|
|
|
|
#endif // BASE_STRINGS_STRCAT_H_
|