stringpiece.h revision 2ee91b4af4353b9e6a9d591c32fedfc58fd4ef35
1// Copyright 2001-2010 The RE2 Authors.  All Rights Reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5// A string-like object that points to a sized piece of memory.
6//
7// Functions or methods may use const StringPiece& parameters to accept either
8// a "const char*" or a "string" value that will be implicitly converted to
9// a StringPiece.  The implicit conversion means that it is often appropriate
10// to include this .h file in other files rather than forward-declaring
11// StringPiece as would be appropriate for most other Google classes.
12//
13// Systematic usage of StringPiece is encouraged as it will reduce unnecessary
14// conversions from "const char*" to "string" and back again.
15//
16//
17// Arghh!  I wish C++ literals were "string".
18
19#ifndef STRINGS_STRINGPIECE_H__
20#define STRINGS_STRINGPIECE_H__
21
22#include <string.h>
23#include <cstddef>
24#include <iosfwd>
25#include <string>
26
27namespace re2 {
28
29class StringPiece {
30 private:
31  const char*   ptr_;
32  int           length_;
33
34 public:
35  // We provide non-explicit singleton constructors so users can pass
36  // in a "const char*" or a "string" wherever a "StringPiece" is
37  // expected.
38  StringPiece() : ptr_(NULL), length_(0) { }
39  StringPiece(const char* str)
40    : ptr_(str), length_((str == NULL) ? 0 : static_cast<int>(strlen(str))) { }
41  StringPiece(const std::string& str)
42    : ptr_(str.data()), length_(static_cast<int>(str.size())) { }
43  StringPiece(const char* offset, int len) : ptr_(offset), length_(len) { }
44
45  // data() may return a pointer to a buffer with embedded NULs, and the
46  // returned buffer may or may not be null terminated.  Therefore it is
47  // typically a mistake to pass data() to a routine that expects a NUL
48  // terminated string.
49  const char* data() const { return ptr_; }
50  int size() const { return length_; }
51  int length() const { return length_; }
52  bool empty() const { return length_ == 0; }
53
54  void clear() { ptr_ = NULL; length_ = 0; }
55  void set(const char* data, int len) { ptr_ = data; length_ = len; }
56  void set(const char* str) {
57    ptr_ = str;
58    if (str != NULL)
59      length_ = static_cast<int>(strlen(str));
60    else
61      length_ = 0;
62  }
63  void set(const void* data, int len) {
64    ptr_ = reinterpret_cast<const char*>(data);
65    length_ = len;
66  }
67
68  char operator[](int i) const { return ptr_[i]; }
69
70  void remove_prefix(int n) {
71    ptr_ += n;
72    length_ -= n;
73  }
74
75  void remove_suffix(int n) {
76    length_ -= n;
77  }
78
79  int compare(const StringPiece& x) const {
80    int r = memcmp(ptr_, x.ptr_, std::min(length_, x.length_));
81    if (r == 0) {
82      if (length_ < x.length_) r = -1;
83      else if (length_ > x.length_) r = +1;
84    }
85    return r;
86  }
87
88  std::string as_string() const {
89    return std::string(data(), size());
90  }
91  // We also define ToString() here, since many other string-like
92  // interfaces name the routine that converts to a C++ string
93  // "ToString", and it's confusing to have the method that does that
94  // for a StringPiece be called "as_string()".  We also leave the
95  // "as_string()" method defined here for existing code.
96  std::string ToString() const {
97    return std::string(data(), size());
98  }
99
100  void CopyToString(std::string* target) const;
101  void AppendToString(std::string* target) const;
102
103  // Does "this" start with "x"
104  bool starts_with(const StringPiece& x) const {
105    return ((length_ >= x.length_) &&
106            (memcmp(ptr_, x.ptr_, x.length_) == 0));
107  }
108
109  // Does "this" end with "x"
110  bool ends_with(const StringPiece& x) const {
111    return ((length_ >= x.length_) &&
112            (memcmp(ptr_ + (length_-x.length_), x.ptr_, x.length_) == 0));
113  }
114
115  // standard STL container boilerplate
116  typedef char value_type;
117  typedef const char* pointer;
118  typedef const char& reference;
119  typedef const char& const_reference;
120  typedef size_t size_type;
121  typedef ptrdiff_t difference_type;
122  static const size_type npos;
123  typedef const char* const_iterator;
124  typedef const char* iterator;
125  typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
126  typedef std::reverse_iterator<iterator> reverse_iterator;
127  iterator begin() const { return ptr_; }
128  iterator end() const { return ptr_ + length_; }
129  const_reverse_iterator rbegin() const {
130    return const_reverse_iterator(ptr_ + length_);
131  }
132  const_reverse_iterator rend() const {
133    return const_reverse_iterator(ptr_);
134  }
135  // STLS says return size_type, but Google says return int
136  int max_size() const { return length_; }
137  int capacity() const { return length_; }
138
139  int copy(char* buf, size_type n, size_type pos = 0) const;
140
141  int find(const StringPiece& s, size_type pos = 0) const;
142  int find(char c, size_type pos = 0) const;
143  int rfind(const StringPiece& s, size_type pos = npos) const;
144  int rfind(char c, size_type pos = npos) const;
145
146  StringPiece substr(size_type pos, size_type n = npos) const;
147
148  static bool _equal(const StringPiece&, const StringPiece&);
149};
150
151inline bool operator==(const StringPiece& x, const StringPiece& y) {
152  return StringPiece::_equal(x, y);
153}
154
155inline bool operator!=(const StringPiece& x, const StringPiece& y) {
156  return !(x == y);
157}
158
159inline bool operator<(const StringPiece& x, const StringPiece& y) {
160  const int r = memcmp(x.data(), y.data(),
161                       std::min(x.size(), y.size()));
162  return ((r < 0) || ((r == 0) && (x.size() < y.size())));
163}
164
165inline bool operator>(const StringPiece& x, const StringPiece& y) {
166  return y < x;
167}
168
169inline bool operator<=(const StringPiece& x, const StringPiece& y) {
170  return !(x > y);
171}
172
173inline bool operator>=(const StringPiece& x, const StringPiece& y) {
174  return !(x < y);
175}
176
177}  // namespace re2
178
179// allow StringPiece to be logged
180extern std::ostream& operator<<(std::ostream& o, const re2::StringPiece& piece);
181
182#endif  // STRINGS_STRINGPIECE_H__
183