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 28  
 29  #ifndef COMMON_STRING_VIEW_H__
 30  #define COMMON_STRING_VIEW_H__
 31  
 32  #include <cassert>
 33  #include <cstring>
 34  #include <ostream>
 35  #include "common/using_std_string.h"
 36  
 37  namespace google_breakpad {
 38  
 39  // A StringView is a string reference to a string object, but not own the
 40  // string object. It's a compatibile layer until we can use std::string_view in
 41  // C++17.
 42  class StringView {
 43   private:
 44    // The start of the string, in an external buffer. It doesn't have to be
 45    // null-terminated.
 46    const char* data_ = "";
 47  
 48    size_t length_ = 0;
 49  
 50   public:
 51    // Construct an empty StringView.
 52    StringView() = default;
 53  
 54    // Disallow construct StringView from nullptr.
 55    StringView(std::nullptr_t) = delete;
 56  
 57    // Construct a StringView from a cstring.
 58    StringView(const char* str) : data_(str) {
 59      assert(str);
 60      length_ = strlen(str);
 61    }
 62  
 63    // Construct a StringView from a cstring with fixed length.
 64    StringView(const char* str, size_t length) : data_(str), length_(length) {
 65      assert(str);
 66    }
 67  
 68    // Construct a StringView from an std::string.
 69    StringView(const string& str) : data_(str.data()), length_(str.length()) {}
 70  
 71    string str() const { return string(data_, length_); }
 72  
 73    const char* data() const { return data_; }
 74  
 75    bool empty() const { return length_ == 0; }
 76  
 77    size_t size() const { return length_; }
 78  
 79    int compare(StringView rhs) const {
 80      size_t min_len = std::min(size(), rhs.size());
 81      int res = memcmp(data_, rhs.data(), min_len);
 82      if (res != 0)
 83        return res;
 84      if (size() == rhs.size())
 85        return 0;
 86      return size() < rhs.size() ? -1 : 1;
 87    }
 88  };
 89  
 90  inline bool operator==(StringView lhs, StringView rhs) {
 91    return lhs.compare(rhs) == 0;
 92  }
 93  
 94  inline bool operator!=(StringView lhs, StringView rhs) {
 95    return lhs.compare(rhs) != 0;
 96  }
 97  
 98  inline bool operator<(StringView lhs, StringView rhs) {
 99    return lhs.compare(rhs) < 0;
100  }
101  
102  inline bool operator>(StringView lhs, StringView rhs) {
103    return lhs.compare(rhs) > 0;
104  }
105  
106  inline std::ostream& operator<<(std::ostream& os, StringView s) {
107    os << s.str();
108    return os;
109  }
110  
111  }  // namespace google_breakpad
112  
113  #endif  // COMMON_STRING_VIEW_H__