// © 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_EXPORT 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__