// Copyright 2001, Google Inc.  All rights reserved.

// Maintainer: mec@google.com (Michael Chastain)

//

// A StringPiece points to part or all of a string, Cord, double-quoted string

// literal, or other string-like object.  A StringPiece does *not* own the

// string to which it points.  A StringPiece is not null-terminated.

//

// You can use StringPiece as a function or method parameter.  A StringPiece

// parameter can receive a double-quoted string literal argument, a "const

// char*" argument, a string argument, or a StringPiece argument with no data

// copying.  Systematic use of StringPiece for arguments reduces data

// copies and strlen() calls.

//

// You may pass a StringPiece argument by value or const reference.

// Passing by value generates slightly smaller code.

//   void MyFunction(const StringPiece& arg);

//   // Slightly better, but same lifetime requirements as const-ref parameter:

//   void MyFunction(StringPiece arg);

//

// StringPiece is also suitable for local variables if you know that

// the lifetime of the underlying object is longer than the lifetime

// of your StringPiece variable.

//

// Beware of binding a StringPiece to a temporary:

//   StringPiece sp = obj.MethodReturningString();  // BAD: lifetime problem

//

// This code is okay:

//   string str = obj.MethodReturningString();  // str owns its contents

//   StringPiece sp(str);  // GOOD, although you may not need sp at all

//

// StringPiece is sometimes a poor choice for a return value and usually a poor

// choice for a data member.  If you do use a StringPiece this way, it is your

// responsibility to ensure that the object pointed to by the StringPiece

// outlives the StringPiece.

//

// A StringPiece may represent just part of a string; thus the name "Piece".

// For example, when splitting a string, vector<StringPiece> is a natural data

// type for the output.  For another example, a Cord is a non-contiguous,

// potentially very long string-like object.  The Cord class has an interface

// that iteratively provides StringPiece objects that point to the

// successive pieces of a Cord object.

//

// A StringPiece is not null-terminated.  If you write code that scans a

// StringPiece, you must check its length before reading any characters.

// Common idioms that work on null-terminated strings do not work on

// StringPiece objects.

//

// There are several ways to create a null StringPiece:

//   StringPiece()

//   StringPiece(NULL)

//   StringPiece(NULL, 0)

// For all of the above, sp.data() == NULL, sp.length() == 0,

// and sp.empty() == true.  Also, if you create a StringPiece with

// a non-NULL pointer then sp.data() != non-NULL.  Once created,

// sp.data() will stay either NULL or not-NULL, except if you call

// sp.clear() or sp.set().

//

// Thus, you can use StringPiece(NULL) to signal an out-of-band value

// that is different from other StringPiece values.  This is similar

// to the way that const char* p1 = NULL; is different from

// const char* p2 = "";.

//

// There are many ways to create an empty StringPiece:

//   StringPiece()

//   StringPiece(NULL)

//   StringPiece(NULL, 0)

//   StringPiece("")

//   StringPiece("", 0)

//   StringPiece("abcdef", 0)

//   StringPiece("abcdef"+6, 0)

// For all of the above, sp.length() will be 0 and sp.empty() will be true.

// For some empty StringPiece values, sp.data() will be NULL.

// For some empty StringPiece values, sp.data() will not be NULL.

//

// Be careful not to confuse: null StringPiece and empty StringPiece.

// The set of empty StringPieces properly includes the set of null StringPieces.

// That is, every null StringPiece is an empty StringPiece,

// but some non-null StringPieces are empty Stringpieces too.

//

// All empty StringPiece values compare equal to each other.

// Even a null StringPieces compares equal to a non-null empty StringPiece:

//  StringPiece() == StringPiece("", 0)

//  StringPiece(NULL) == StringPiece("abc", 0)

//  StringPiece(NULL, 0) == StringPiece("abcdef"+6, 0)

//

// Look carefully at this example:

//   StringPiece("") == NULL

// True or false?  TRUE, because StringPiece::operator== converts

// the right-hand side from NULL to StringPiece(NULL),

// and then compares two zero-length spans of characters.

// However, we are working to make this example produce a compile error.

//

// Suppose you want to write:

//   bool TestWhat?(StringPiece sp) { return sp == NULL; }  // BAD

// Do not do that.  Write one of these instead:

//   bool TestNull(StringPiece sp) { return sp.data() == NULL; }

//   bool TestEmpty(StringPiece sp) { return sp.empty(); }

// The intent of TestWhat? is unclear.  Did you mean TestNull or TestEmpty?

// Right now, TestWhat? behaves likes TestEmpty.

// We are working to make TestWhat? produce a compile error.

// TestNull is good to test for an out-of-band signal.

// TestEmpty is good to test for an empty StringPiece.

//

// Caveats (again):

// (1) The lifetime of the pointed-to string (or piece of a string)

//     must be longer than the lifetime of the StringPiece.

// (2) There may or may not be a '\0' character after the end of

//     StringPiece data.

// (3) A null StringPiece is empty.

//     An empty StringPiece may or may not be a null StringPiece.

#pragma once

#include <assert.h>

#include <stddef.h>

#include <string.h>

#include <cstddef>

#include <iosfwd>

#include <iterator>

#include <limits> // IWYU pragma: keep

#include <string>

#include <string_view>

class StringPiece {

private:

    const char* ptr_ = nullptr;

    int length_;

public:

    // We provide non-explicit singleton constructors so users can pass

    // in a "const char*" or a "string" wherever a "StringPiece" is

    // expected.

    //

    // Style guide exception granted:

    // http://goto/style-guide-exception-20978288

    StringPiece() : ptr_(NULL), length_(0) {}

    StringPiece(const char* str) // NOLINT(runtime/explicit)

            : ptr_(str), length_(0) {

        if (str != NULL) {

            size_t length = strlen(str);

            assert(length <= static_cast<size_t>(std::numeric_limits<int>::max()));

            length_ = static_cast<int>(length);

        }

    }

    StringPiece(const std::string& str) // NOLINT(runtime/explicit)

            : ptr_(str.data()), length_(0) {

        size_t length = str.size();

        assert(length <= static_cast<size_t>(std::numeric_limits<int>::max()));

        length_ = static_cast<int>(length);

    }

    StringPiece(const char* offset, int len) : ptr_(offset), length_(len) { assert(len >= 0); }

    // Substring of another StringPiece.

    // pos must be non-negative and <= x.length().

    StringPiece(StringPiece x, int pos);

    // Substring of another StringPiece.

    // pos must be non-negative and <= x.length().

    // len must be non-negative and will be pinned to at most x.length() - pos.

    StringPiece(StringPiece x, int pos, int len);

    // 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.

    const char* data() const { return ptr_; }

    int size() const { return length_; }

    int length() const { return length_; }

    bool empty() const { return length_ == 0; }

    void clear() {

        ptr_ = NULL;

        length_ = 0;

    }

    void set(const char* data, int len) {

        assert(len >= 0);

        ptr_ = data;

        length_ = len;

    }

    void set(const char* str) {

        ptr_ = str;

        if (str != NULL)

            length_ = static_cast<int>(strlen(str));

        else

            length_ = 0;

    }

    void set(const void* data, int len) {

        ptr_ = reinterpret_cast<const char*>(data);

        length_ = len;

    }

    char operator[](int i) const {

        assert(0 <= i);

        assert(i < length_);

        return ptr_[i];

    }

    void remove_prefix(int n) {

        assert(length_ >= n);

        ptr_ += n;

        length_ -= n;

    }

    void remove_suffix(int n) {

        assert(length_ >= n);

        length_ -= n;

    }

    // returns {-1, 0, 1}

    int compare(StringPiece x) const {

        const int min_size = length_ < x.length_ ? length_ : x.length_;

        int r = memcmp(ptr_, x.ptr_, min_size);

        if (r < 0) return -1;

        if (r > 0) return 1;

        if (length_ < x.length_) return -1;

        if (length_ > x.length_) return 1;

        return 0;

    }

    std::string as_string() const { return ToString(); }

    // We also define ToString() here, since many other string-like

    // interfaces name the routine that converts to a C++ string

    // "ToString", and it's confusing to have the method that does that

    // for a StringPiece be called "as_string()".  We also leave the

    // "as_string()" method defined here for existing code.

    std::string ToString() const {

        if (ptr_ == NULL) return std::string();

        return std::string(data(), size());

    }

    void CopyToString(std::string* target) const;

    void AppendToString(std::string* target) const;

    bool starts_with(StringPiece x) const {

        return (length_ >= x.length_) && (memcmp(ptr_, x.ptr_, x.length_) == 0);

    }

    bool ends_with(StringPiece x) const {

        return ((length_ >= x.length_) &&

                (memcmp(ptr_ + (length_ - x.length_), x.ptr_, x.length_) == 0));

    }

    // standard STL container boilerplate

    typedef char value_type;

    typedef const char* pointer;

    typedef const char& reference;

    typedef const char& const_reference;

    typedef size_t size_type;

    typedef ptrdiff_t difference_type;

    static const size_type npos;

    typedef const char* const_iterator;

    typedef const char* iterator;

    typedef std::reverse_iterator<const_iterator> const_reverse_iterator;

    typedef std::reverse_iterator<iterator> reverse_iterator;

    iterator begin() const { return ptr_; }

    iterator end() const { return ptr_ + length_; }

    const_reverse_iterator rbegin() const { return const_reverse_iterator(ptr_ + length_); }

    const_reverse_iterator rend() const { return const_reverse_iterator(ptr_); }

    // STLS says return size_type, but Google says return int

    int max_size() const { return length_; }

    int capacity() const { return length_; }

    // cpplint.py emits a false positive [build/include_what_you_use]

    int copy(char* buf, size_type n, size_type pos = 0) const; // NOLINT

    bool contains(StringPiece s) const;

    int find(StringPiece s, size_type pos = 0) const;

    int find(char c, size_type pos = 0) const;

    int rfind(StringPiece s, size_type pos = npos) const;

    int rfind(char c, size_type pos = npos) const;

    int find_first_of(StringPiece s, size_type pos = 0) const;

    int find_first_of(char c, size_type pos = 0) const { return find(c, pos); }

    int find_first_not_of(StringPiece s, size_type pos = 0) const;

    int find_first_not_of(char c, size_type pos = 0) const;

    int find_last_of(StringPiece s, size_type pos = npos) const;

    int find_last_of(char c, size_type pos = npos) const { return rfind(c, pos); }

    int find_last_not_of(StringPiece s, size_type pos = npos) const;

    int find_last_not_of(char c, size_type pos = npos) const;

    StringPiece substr(size_type pos, size_type n = npos) const;

};

// This large function is defined inline so that in a fairly common case where

// one of the arguments is a literal, the compiler can elide a lot of the

// following comparisons.

inline bool operator==(StringPiece x, StringPiece y) {

    int len = x.size();

    if (len != y.size()) {

        return false;

    }

    return x.data() == y.data() || len <= 0 || 0 == memcmp(x.data(), y.data(), len);

}

inline bool operator!=(StringPiece x, StringPiece y) {

    return !(x == y);

}

inline bool operator<(StringPiece x, StringPiece y) {

    const int min_size = x.size() < y.size() ? x.size() : y.size();

    const int r = memcmp(x.data(), y.data(), min_size);

    return (r < 0) || (r == 0 && x.size() < y.size());

}

inline bool operator>(StringPiece x, StringPiece y) {

    return y < x;

}

inline bool operator<=(StringPiece x, StringPiece y) {

    return !(x > y);

}

inline bool operator>=(StringPiece x, StringPiece y) {

    return !(x < y);

}

// allow StringPiece to be logged

extern std::ostream& operator<<(std::ostream& o, StringPiece piece);