344 lines
10 KiB
C++
344 lines
10 KiB
C++
// © 2016 and later: Unicode, Inc. and others.
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// License & terms of use: http://www.unicode.org/copyright.html
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// Copyright (C) 2009-2013, International Business Machines
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// Corporation and others. All Rights Reserved.
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//
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// Copyright 2001 and onwards Google Inc.
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// Author: Sanjay Ghemawat
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// This code is a contribution of Google code, and the style used here is
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// a compromise between the original Google code and the ICU coding guidelines.
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// For example, data types are ICU-ified (size_t,int->int32_t),
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// and API comments doxygen-ified, but function names and behavior are
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// as in the original, if possible.
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// Assertion-style error handling, not available in ICU, was changed to
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// parameter "pinning" similar to UnicodeString.
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//
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// In addition, this is only a partial port of the original Google code,
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// limited to what was needed so far. The (nearly) complete original code
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// is in the ICU svn repository at icuhtml/trunk/design/strings/contrib
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// (see ICU ticket 6765, r25517).
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#ifndef __STRINGPIECE_H__
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#define __STRINGPIECE_H__
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/**
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* \file
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* \brief C++ API: StringPiece: Read-only byte string wrapper class.
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*/
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#include "unicode/utypes.h"
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#if U_SHOW_CPLUSPLUS_API
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#include <cstddef>
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#include <type_traits>
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#include "unicode/uobject.h"
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#include "unicode/std_string.h"
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// Arghh! I wish C++ literals were "string".
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U_NAMESPACE_BEGIN
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/**
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* A string-like object that points to a sized piece of memory.
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*
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* We provide non-explicit singleton constructors so users can pass
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* in a "const char*" or a "string" wherever a "StringPiece" is
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* expected.
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*
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* Functions or methods may use StringPiece parameters to accept either a
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* "const char*" or a "string" value that will be implicitly converted to a
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* StringPiece.
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*
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* Systematic usage of StringPiece is encouraged as it will reduce unnecessary
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* conversions from "const char*" to "string" and back again.
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*
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* @stable ICU 4.2
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*/
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class U_COMMON_API StringPiece : public UMemory {
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private:
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const char* ptr_;
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int32_t length_;
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public:
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/**
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* Default constructor, creates an empty StringPiece.
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* @stable ICU 4.2
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*/
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StringPiece() : ptr_(nullptr), length_(0) { }
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/**
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* Constructs from a NUL-terminated const char * pointer.
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* @param str a NUL-terminated const char * pointer
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* @stable ICU 4.2
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*/
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StringPiece(const char* str);
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#if defined(__cpp_char8_t) || defined(U_IN_DOXYGEN)
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/**
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* Constructs from a NUL-terminated const char8_t * pointer.
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* @param str a NUL-terminated const char8_t * pointer
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* @stable ICU 67
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*/
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StringPiece(const char8_t* str) : StringPiece(reinterpret_cast<const char*>(str)) {}
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#endif
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/**
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* Constructs an empty StringPiece.
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* Needed for type disambiguation from multiple other overloads.
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* @param p nullptr
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* @stable ICU 67
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*/
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StringPiece(std::nullptr_t p) : ptr_(p), length_(0) {}
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/**
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* Constructs from a std::string.
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* @stable ICU 4.2
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*/
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StringPiece(const std::string& str)
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: ptr_(str.data()), length_(static_cast<int32_t>(str.size())) { }
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#if defined(__cpp_lib_char8_t) || defined(U_IN_DOXYGEN)
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/**
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* Constructs from a std::u8string.
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* @stable ICU 67
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*/
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StringPiece(const std::u8string& str)
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: ptr_(reinterpret_cast<const char*>(str.data())),
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length_(static_cast<int32_t>(str.size())) { }
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#endif
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/**
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* Constructs from some other implementation of a string piece class, from any
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* C++ record type that has these two methods:
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*
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* \code{.cpp}
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*
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* struct OtherStringPieceClass {
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* const char* data(); // or const char8_t*
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* size_t size();
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* };
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*
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* \endcode
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*
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* The other string piece class will typically be std::string_view from C++17
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* or absl::string_view from Abseil.
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*
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* Starting with C++20, data() may also return a const char8_t* pointer,
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* as from std::u8string_view.
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*
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* @param str the other string piece
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* @stable ICU 65
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*/
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template <typename T,
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typename = typename std::enable_if<
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(std::is_same<decltype(T().data()), const char*>::value
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#if defined(__cpp_char8_t)
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|| std::is_same<decltype(T().data()), const char8_t*>::value
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#endif
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) &&
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std::is_same<decltype(T().size()), size_t>::value>::type>
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StringPiece(T str)
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: ptr_(reinterpret_cast<const char*>(str.data())),
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length_(static_cast<int32_t>(str.size())) {}
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/**
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* Constructs from a const char * pointer and a specified length.
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* @param offset a const char * pointer (need not be terminated)
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* @param len the length of the string; must be non-negative
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* @stable ICU 4.2
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*/
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StringPiece(const char* offset, int32_t len) : ptr_(offset), length_(len) { }
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#if defined(__cpp_char8_t) || defined(U_IN_DOXYGEN)
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/**
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* Constructs from a const char8_t * pointer and a specified length.
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* @param str a const char8_t * pointer (need not be terminated)
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* @param len the length of the string; must be non-negative
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* @stable ICU 67
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*/
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StringPiece(const char8_t* str, int32_t len) :
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StringPiece(reinterpret_cast<const char*>(str), len) {}
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#endif
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/**
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* Substring of another StringPiece.
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* @param x the other StringPiece
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* @param pos start position in x; must be non-negative and <= x.length().
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* @stable ICU 4.2
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*/
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StringPiece(const StringPiece& x, int32_t pos);
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/**
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* Substring of another StringPiece.
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* @param x the other StringPiece
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* @param pos start position in x; must be non-negative and <= x.length().
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* @param len length of the substring;
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* must be non-negative and will be pinned to at most x.length() - pos.
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* @stable ICU 4.2
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*/
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StringPiece(const StringPiece& x, int32_t pos, int32_t len);
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/**
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* Returns the string pointer. May be nullptr if it is empty.
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*
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* data() may return a pointer to a buffer with embedded NULs, and the
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* returned buffer may or may not be null terminated. Therefore it is
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* typically a mistake to pass data() to a routine that expects a NUL
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* terminated string.
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* @return the string pointer
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* @stable ICU 4.2
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*/
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const char* data() const { return ptr_; }
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/**
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* Returns the string length. Same as length().
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* @return the string length
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* @stable ICU 4.2
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*/
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int32_t size() const { return length_; }
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/**
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* Returns the string length. Same as size().
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* @return the string length
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* @stable ICU 4.2
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*/
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int32_t length() const { return length_; }
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/**
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* Returns whether the string is empty.
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* @return true if the string is empty
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* @stable ICU 4.2
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*/
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UBool empty() const { return length_ == 0; }
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/**
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* Sets to an empty string.
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* @stable ICU 4.2
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*/
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void clear() { ptr_ = nullptr; length_ = 0; }
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/**
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* Reset the stringpiece to refer to new data.
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* @param xdata pointer the new string data. Need not be nul terminated.
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* @param len the length of the new data
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* @stable ICU 4.8
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*/
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void set(const char* xdata, int32_t len) { ptr_ = xdata; length_ = len; }
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/**
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* Reset the stringpiece to refer to new data.
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* @param str a pointer to a NUL-terminated string.
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* @stable ICU 4.8
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*/
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void set(const char* str);
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#if defined(__cpp_char8_t) || defined(U_IN_DOXYGEN)
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/**
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* Resets the stringpiece to refer to new data.
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* @param xdata pointer the new string data. Need not be NUL-terminated.
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* @param len the length of the new data
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* @stable ICU 67
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*/
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inline void set(const char8_t* xdata, int32_t len) {
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set(reinterpret_cast<const char*>(xdata), len);
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}
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/**
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* Resets the stringpiece to refer to new data.
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* @param str a pointer to a NUL-terminated string.
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* @stable ICU 67
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*/
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inline void set(const char8_t* str) {
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set(reinterpret_cast<const char*>(str));
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}
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#endif
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/**
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* Removes the first n string units.
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* @param n prefix length, must be non-negative and <=length()
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* @stable ICU 4.2
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*/
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void remove_prefix(int32_t n) {
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if (n >= 0) {
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if (n > length_) {
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n = length_;
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}
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ptr_ += n;
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length_ -= n;
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}
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}
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/**
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* Removes the last n string units.
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* @param n suffix length, must be non-negative and <=length()
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* @stable ICU 4.2
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*/
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void remove_suffix(int32_t n) {
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if (n >= 0) {
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if (n <= length_) {
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length_ -= n;
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} else {
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length_ = 0;
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}
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}
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}
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/**
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* Searches the StringPiece for the given search string (needle);
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* @param needle The string for which to search.
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* @param offset Where to start searching within this string (haystack).
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* @return The offset of needle in haystack, or -1 if not found.
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* @stable ICU 67
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*/
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int32_t find(StringPiece needle, int32_t offset);
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/**
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* Compares this StringPiece with the other StringPiece, with semantics
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* similar to std::string::compare().
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* @param other The string to compare to.
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* @return below zero if this < other; above zero if this > other; 0 if this == other.
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* @stable ICU 67
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*/
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int32_t compare(StringPiece other);
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/**
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* Maximum integer, used as a default value for substring methods.
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* @stable ICU 4.2
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*/
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static const int32_t npos; // = 0x7fffffff;
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/**
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* Returns a substring of this StringPiece.
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* @param pos start position; must be non-negative and <= length().
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* @param len length of the substring;
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* must be non-negative and will be pinned to at most length() - pos.
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* @return the substring StringPiece
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* @stable ICU 4.2
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*/
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StringPiece substr(int32_t pos, int32_t len = npos) const {
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return StringPiece(*this, pos, len);
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}
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};
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/**
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* Global operator == for StringPiece
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* @param x The first StringPiece to compare.
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* @param y The second StringPiece to compare.
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* @return true if the string data is equal
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* @stable ICU 4.8
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*/
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U_EXPORT UBool U_EXPORT2
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operator==(const StringPiece& x, const StringPiece& y);
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/**
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* Global operator != for StringPiece
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* @param x The first StringPiece to compare.
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* @param y The second StringPiece to compare.
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* @return true if the string data is not equal
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* @stable ICU 4.8
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*/
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inline bool operator!=(const StringPiece& x, const StringPiece& y) {
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return !(x == y);
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}
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U_NAMESPACE_END
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#endif /* U_SHOW_CPLUSPLUS_API */
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#endif // __STRINGPIECE_H__
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