tor-browser

stringpiece.h (10532B)

---

// © 2016 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html
// Copyright (C) 2009-2013, International Business Machines
// Corporation and others. All Rights Reserved.
//
// Copyright 2001 and onwards Google Inc.
// Author: Sanjay Ghemawat

// This code is a contribution of Google code, and the style used here is
// a compromise between the original Google code and the ICU coding guidelines.
// For example, data types are ICU-ified (size_t,int->int32_t),
// and API comments doxygen-ified, but function names and behavior are
// as in the original, if possible.
// Assertion-style error handling, not available in ICU, was changed to
// parameter "pinning" similar to UnicodeString.
//
// In addition, this is only a partial port of the original Google code,
// limited to what was needed so far. The (nearly) complete original code
// is in the ICU svn repository at icuhtml/trunk/design/strings/contrib
// (see ICU ticket 6765, r25517).

#ifndef __STRINGPIECE_H__
#define __STRINGPIECE_H__

/**
* \file 
* \brief C++ API: StringPiece: Read-only byte string wrapper class.
*/

#include "unicode/utypes.h"

#if U_SHOW_CPLUSPLUS_API

#include <cstddef>
#include <string_view>
#include <type_traits>

#include "unicode/uobject.h"
#include "unicode/std_string.h"

// Arghh!  I wish C++ literals were "string".

U_NAMESPACE_BEGIN

/**
* A string-like object that points to a sized piece of memory.
*
* We provide non-explicit singleton constructors so users can pass
* in a "const char*" or a "string" wherever a "StringPiece" is
* expected.
*
* Functions or methods may use StringPiece parameters to accept either a
* "const char*" or a "string" value that will be implicitly converted to a
* StringPiece.
*
* Systematic usage of StringPiece is encouraged as it will reduce unnecessary
* conversions from "const char*" to "string" and back again.
*
* @stable ICU 4.2
*/
class U_COMMON_API StringPiece : public UMemory {
private:
 const char*   ptr_;
 int32_t       length_;

public:
 /**
  * Default constructor, creates an empty StringPiece.
  * @stable ICU 4.2
  */
 StringPiece() : ptr_(nullptr), length_(0) { }

 /**
  * Constructs from a NUL-terminated const char * pointer.
  * @param str a NUL-terminated const char * pointer
  * @stable ICU 4.2
  */
 StringPiece(const char* str);
#if defined(__cpp_char8_t) || defined(U_IN_DOXYGEN)
 /**
  * Constructs from a NUL-terminated const char8_t * pointer.
  * @param str a NUL-terminated const char8_t * pointer
  * @stable ICU 67
  */
 StringPiece(const char8_t* str) : StringPiece(reinterpret_cast<const char*>(str)) {}
#endif
 /**
  * Constructs an empty StringPiece.
  * Needed for type disambiguation from multiple other overloads.
  * @param p nullptr
  * @stable ICU 67
  */
 StringPiece(std::nullptr_t p) : ptr_(p), length_(0) {}

 /**
  * Constructs from a std::string.
  * @stable ICU 4.2
  */
 StringPiece(const std::string& str)
   : ptr_(str.data()), length_(static_cast<int32_t>(str.size())) { }
#if defined(__cpp_lib_char8_t) || defined(U_IN_DOXYGEN)
 /**
  * Constructs from a std::u8string.
  * @stable ICU 67
  */
 StringPiece(const std::u8string& str)
   : ptr_(reinterpret_cast<const char*>(str.data())),
     length_(static_cast<int32_t>(str.size())) { }
#endif

 /**
  * Constructs from some other implementation of a string piece class, from any
  * C++ record type that has these two methods:
  *
  * \code{.cpp}
  *
  *   struct OtherStringPieceClass {
  *     const char* data();  // or const char8_t*
  *     size_t size();
  *   };
  *
  * \endcode
  *
  * The other string piece class will typically be std::string_view from C++17
  * or absl::string_view from Abseil.
  *
  * Starting with C++20, data() may also return a const char8_t* pointer,
  * as from std::u8string_view.
  *
  * @param str the other string piece
  * @stable ICU 65
  */
 template <typename T,
           typename = std::enable_if_t<
               (std::is_same_v<decltype(T().data()), const char*>
#if defined(__cpp_char8_t)
                   || std::is_same_v<decltype(T().data()), const char8_t*>
#endif
               ) &&
               std::is_same_v<decltype(T().size()), size_t>>>
 StringPiece(T str)
     : ptr_(reinterpret_cast<const char*>(str.data())),
       length_(static_cast<int32_t>(str.size())) {}

 /**
  * Constructs from a const char * pointer and a specified length.
  * @param offset a const char * pointer (need not be terminated)
  * @param len the length of the string; must be non-negative
  * @stable ICU 4.2
  */
 StringPiece(const char* offset, int32_t len) : ptr_(offset), length_(len) { }
#if defined(__cpp_char8_t) || defined(U_IN_DOXYGEN)
 /**
  * Constructs from a const char8_t * pointer and a specified length.
  * @param str a const char8_t * pointer (need not be terminated)
  * @param len the length of the string; must be non-negative
  * @stable ICU 67
  */
 StringPiece(const char8_t* str, int32_t len) :
     StringPiece(reinterpret_cast<const char*>(str), len) {}
#endif

 /**
  * Substring of another StringPiece.
  * @param x the other StringPiece
  * @param pos start position in x; must be non-negative and <= x.length().
  * @stable ICU 4.2
  */
 StringPiece(const StringPiece& x, int32_t pos);
 /**
  * Substring of another StringPiece.
  * @param x the other StringPiece
  * @param pos start position in x; must be non-negative and <= x.length().
  * @param len length of the substring;
  *            must be non-negative and will be pinned to at most x.length() - pos.
  * @stable ICU 4.2
  */
 StringPiece(const StringPiece& x, int32_t pos, int32_t len);

#ifndef U_HIDE_INTERNAL_API
 /**
  * Converts to a std::string_view().
  * @internal
  */
 inline operator std::string_view() const {
   return {data(), static_cast<std::string_view::size_type>(size())};
 }
#endif  // U_HIDE_INTERNAL_API

 /**
  * Returns the string pointer. May be nullptr if it is empty.
  *
  * data() may return a pointer to a buffer with embedded NULs, and the
  * returned buffer may or may not be null terminated.  Therefore it is
  * typically a mistake to pass data() to a routine that expects a NUL
  * terminated string.
  * @return the string pointer
  * @stable ICU 4.2
  */
 const char* data() const { return ptr_; }
 /**
  * Returns the string length. Same as length().
  * @return the string length
  * @stable ICU 4.2
  */
 int32_t size() const { return length_; }
 /**
  * Returns the string length. Same as size().
  * @return the string length
  * @stable ICU 4.2
  */
 int32_t length() const { return length_; }
 /**
  * Returns whether the string is empty.
  * @return true if the string is empty
  * @stable ICU 4.2
  */
 UBool empty() const { return length_ == 0; }

 /**
  * Sets to an empty string.
  * @stable ICU 4.2
  */
 void clear() { ptr_ = nullptr; length_ = 0; }

 /**
  * Reset the stringpiece to refer to new data.
  * @param xdata pointer the new string data.  Need not be nul terminated.
  * @param len the length of the new data
  * @stable ICU 4.8
  */
 void set(const char* xdata, int32_t len) { ptr_ = xdata; length_ = len; }

 /**
  * Reset the stringpiece to refer to new data.
  * @param str a pointer to a NUL-terminated string. 
  * @stable ICU 4.8
  */
 void set(const char* str);

#if defined(__cpp_char8_t) || defined(U_IN_DOXYGEN)
 /**
  * Resets the stringpiece to refer to new data.
  * @param xdata pointer the new string data. Need not be NUL-terminated.
  * @param len the length of the new data
  * @stable ICU 67
  */
 inline void set(const char8_t* xdata, int32_t len) {
     set(reinterpret_cast<const char*>(xdata), len);
 }

 /**
  * Resets the stringpiece to refer to new data.
  * @param str a pointer to a NUL-terminated string.
  * @stable ICU 67
  */
 inline void set(const char8_t* str) {
     set(reinterpret_cast<const char*>(str));
 }
#endif

 /**
  * Removes the first n string units.
  * @param n prefix length, must be non-negative and <=length()
  * @stable ICU 4.2
  */
 void remove_prefix(int32_t n) {
   if (n >= 0) {
     if (n > length_) {
       n = length_;
     }
     ptr_ += n;
     length_ -= n;
   }
 }

 /**
  * Removes the last n string units.
  * @param n suffix length, must be non-negative and <=length()
  * @stable ICU 4.2
  */
 void remove_suffix(int32_t n) {
   if (n >= 0) {
     if (n <= length_) {
       length_ -= n;
     } else {
       length_ = 0;
     }
   }
 }

 /**
  * Searches the StringPiece for the given search string (needle);
  * @param needle The string for which to search.
  * @param offset Where to start searching within this string (haystack).
  * @return The offset of needle in haystack, or -1 if not found.
  * @stable ICU 67
  */
 int32_t find(StringPiece needle, int32_t offset);

 /**
  * Compares this StringPiece with the other StringPiece, with semantics
  * similar to std::string::compare().
  * @param other The string to compare to.
  * @return below zero if this < other; above zero if this > other; 0 if this == other.
  * @stable ICU 67
  */
 int32_t compare(StringPiece other);

 /**
  * Maximum integer, used as a default value for substring methods.
  * @stable ICU 4.2
  */
 static const int32_t npos; // = 0x7fffffff;

 /**
  * Returns a substring of this StringPiece.
  * @param pos start position; must be non-negative and <= length().
  * @param len length of the substring;
  *            must be non-negative and will be pinned to at most length() - pos.
  * @return the substring StringPiece
  * @stable ICU 4.2
  */
 StringPiece substr(int32_t pos, int32_t len = npos) const {
   return StringPiece(*this, pos, len);
 }
};

/**
* Global operator == for StringPiece
* @param x The first StringPiece to compare.
* @param y The second StringPiece to compare.
* @return true if the string data is equal
* @stable ICU 4.8
*/
U_COMMON_API UBool U_EXPORT2 
operator==(const StringPiece& x, const StringPiece& y);

/**
* Global operator != for StringPiece
* @param x The first StringPiece to compare.
* @param y The second StringPiece to compare.
* @return true if the string data is not equal
* @stable ICU 4.8
*/
inline bool operator!=(const StringPiece& x, const StringPiece& y) {
 return !(x == y);
}

U_NAMESPACE_END

#endif /* U_SHOW_CPLUSPLUS_API */

#endif  // __STRINGPIECE_H__