string_piece.h revision 3345a6884c488ff3a535c2c9acdd33d74b37e311 
1// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4// Copied from strings/stringpiece.h with modifications
5//
6// A string-like object that points to a sized piece of memory.
7//
8// Functions or methods may use const StringPiece& parameters to accept either
9// a "const char*" or a "string" value that will be implicitly converted to
10// a StringPiece.  The implicit conversion means that it is often appropriate
11// to include this .h file in other files rather than forward-declaring
12// StringPiece as would be appropriate for most other Google classes.
13//
14// Systematic usage of StringPiece is encouraged as it will reduce unnecessary
15// conversions from "const char*" to "string" and back again.
16//
17
18#ifndef BASE_STRING_PIECE_H_
19#define BASE_STRING_PIECE_H_
20#pragma once
21
22#include <algorithm>
23#include <iosfwd>
24#include <string>
25
26#include "base/basictypes.h"
27
28namespace base {
29
30class StringPiece {
31 public:
32  typedef size_t size_type;
33
34 private:
35  const char*   ptr_;
36  size_type     length_;
37
38 public:
39  // We provide non-explicit singleton constructors so users can pass
40  // in a "const char*" or a "string" wherever a "StringPiece" is
41  // expected.
42  StringPiece() : ptr_(NULL), length_(0) { }
43  StringPiece(const char* str)
44    : ptr_(str), length_((str == NULL) ? 0 : strlen(str)) { }
45  StringPiece(const std::string& str)
46    : ptr_(str.data()), length_(str.size()) { }
47  StringPiece(const char* offset, size_type len)
48    : ptr_(offset), length_(len) { }
49
50  // data() may return a pointer to a buffer with embedded NULs, and the
51  // returned buffer may or may not be null terminated.  Therefore it is
52  // typically a mistake to pass data() to a routine that expects a NUL
53  // terminated string.
54  const char* data() const { return ptr_; }
55  size_type size() const { return length_; }
56  size_type length() const { return length_; }
57  bool empty() const { return length_ == 0; }
58
59  void clear() {
60    ptr_ = NULL;
61    length_ = 0;
62  }
63  void set(const char* data, size_type len) {
64    ptr_ = data;
65    length_ = len;
66  }
67  void set(const char* str) {
68    ptr_ = str;
69    length_ = str ? strlen(str) : 0;
70  }
71  void set(const void* data, size_type len) {
72    ptr_ = reinterpret_cast<const char*>(data);
73    length_ = len;
74  }
75
76  char operator[](size_type i) const { return ptr_[i]; }
77
78  void remove_prefix(size_type n) {
79    ptr_ += n;
80    length_ -= n;
81  }
82
83  void remove_suffix(size_type n) {
84    length_ -= n;
85  }
86
87  int compare(const StringPiece& x) const {
88    int r = wordmemcmp(ptr_, x.ptr_, std::min(length_, x.length_));
89    if (r == 0) {
90      if (length_ < x.length_) r = -1;
91      else if (length_ > x.length_) r = +1;
92    }
93    return r;
94  }
95
96  std::string as_string() const {
97    // std::string doesn't like to take a NULL pointer even with a 0 size.
98    return std::string(!empty() ? data() : "", size());
99  }
100
101  void CopyToString(std::string* target) const;
102  void AppendToString(std::string* target) const;
103
104  // Does "this" start with "x"
105  bool starts_with(const StringPiece& x) const {
106    return ((length_ >= x.length_) &&
107            (wordmemcmp(ptr_, x.ptr_, x.length_) == 0));
108  }
109
110  // Does "this" end with "x"
111  bool ends_with(const StringPiece& x) const {
112    return ((length_ >= x.length_) &&
113            (wordmemcmp(ptr_ + (length_-x.length_), x.ptr_, x.length_) == 0));
114  }
115
116  // standard STL container boilerplate
117  typedef char value_type;
118  typedef const char* pointer;
119  typedef const char& reference;
120  typedef const char& const_reference;
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
136  size_type max_size() const { return length_; }
137  size_type capacity() const { return length_; }
138
139  size_type copy(char* buf, size_type n, size_type pos = 0) const;
140
141  size_type find(const StringPiece& s, size_type pos = 0) const;
142  size_type find(char c, size_type pos = 0) const;
143  size_type rfind(const StringPiece& s, size_type pos = npos) const;
144  size_type rfind(char c, size_type pos = npos) const;
145
146  size_type find_first_of(const StringPiece& s, size_type pos = 0) const;
147  size_type find_first_of(char c, size_type pos = 0) const {
148    return find(c, pos);
149  }
150  size_type find_first_not_of(const StringPiece& s, size_type pos = 0) const;
151  size_type find_first_not_of(char c, size_type pos = 0) const;
152  size_type find_last_of(const StringPiece& s, size_type pos = npos) const;
153  size_type find_last_of(char c, size_type pos = npos) const {
154    return rfind(c, pos);
155  }
156  size_type find_last_not_of(const StringPiece& s, size_type pos = npos) const;
157  size_type find_last_not_of(char c, size_type pos = npos) const;
158
159  StringPiece substr(size_type pos, size_type n = npos) const;
160
161  static int wordmemcmp(const char* p, const char* p2, size_type N) {
162    return memcmp(p, p2, N);
163  }
164};
165
166bool operator==(const StringPiece& x, const StringPiece& y);
167
168inline bool operator!=(const StringPiece& x, const StringPiece& y) {
169  return !(x == y);
170}
171
172inline bool operator<(const StringPiece& x, const StringPiece& y) {
173  const int r = StringPiece::wordmemcmp(x.data(), y.data(),
174                                        std::min(x.size(), y.size()));
175  return ((r < 0) || ((r == 0) && (x.size() < y.size())));
176}
177
178inline bool operator>(const StringPiece& x, const StringPiece& y) {
179  return y < x;
180}
181
182inline bool operator<=(const StringPiece& x, const StringPiece& y) {
183  return !(x > y);
184}
185
186inline bool operator>=(const StringPiece& x, const StringPiece& y) {
187  return !(x < y);
188}
189
190// allow StringPiece to be logged (needed for unit testing).
191extern std::ostream& operator<<(std::ostream& o, const StringPiece& piece);
192
193}  // namespace base
194
195#endif  // BASE_STRING_PIECE_H_
196