stringpiece.h revision 7940e44f4517de5e2634a7e07d58d0fb26160513 
1/*
2 * Copyright (C) 2010 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17// A string-like object that points to a sized piece of memory.
18//
19// Functions or methods may use const StringPiece& parameters to accept either
20// a "const char*" or a "string" value that will be implicitly converted to
21// a StringPiece.  The implicit conversion means that it is often appropriate
22// to include this .h file in other files rather than forward-declaring
23// StringPiece as would be appropriate for most other Google classes.
24//
25// Systematic usage of StringPiece is encouraged as it will reduce unnecessary
26// conversions from "const char*" to "string" and back again.
27
28#ifndef ART_SRC_BASE_STRINGPIECE_H_
29#define ART_SRC_BASE_STRINGPIECE_H_
30
31#include <string.h>
32#include <algorithm>
33#include <cstddef>
34#include <iosfwd>
35#include <string>
36
37namespace art {
38
39class StringPiece {
40 private:
41  const char*   ptr_;
42  int           length_;
43
44 public:
45  // We provide non-explicit singleton constructors so users can pass
46  // in a "const char*" or a "string" wherever a "StringPiece" is
47  // expected.
48  StringPiece() : ptr_(NULL), length_(0) { }
49  StringPiece(const char* str)  // NOLINT
50    : ptr_(str), length_((str == NULL) ? 0 : static_cast<int>(strlen(str))) { }
51  StringPiece(const std::string& str)  // NOLINT
52    : ptr_(str.data()), length_(static_cast<int>(str.size())) { }
53  StringPiece(const char* offset, int len) : ptr_(offset), length_(len) { }
54
55  // data() may return a pointer to a buffer with embedded NULs, and the
56  // returned buffer may or may not be null terminated.  Therefore it is
57  // typically a mistake to pass data() to a routine that expects a NUL
58  // terminated string.
59  const char* data() const { return ptr_; }
60  int size() const { return length_; }
61  int length() const { return length_; }
62  bool empty() const { return length_ == 0; }
63
64  void clear() {
65    ptr_ = NULL;
66    length_ = 0;
67  }
68  void set(const char* data, int len) {
69    ptr_ = data;
70    length_ = len;
71  }
72  void set(const char* str) {
73    ptr_ = str;
74    if (str != NULL)
75      length_ = static_cast<int>(strlen(str));
76    else
77      length_ = 0;
78  }
79  void set(const void* data, int len) {
80    ptr_ = reinterpret_cast<const char*>(data);
81    length_ = len;
82  }
83
84  char operator[](int i) const { return ptr_[i]; }
85
86  void remove_prefix(int n) {
87    ptr_ += n;
88    length_ -= n;
89  }
90
91  void remove_suffix(int n) {
92    length_ -= n;
93  }
94
95  int compare(const StringPiece& x) const;
96
97  std::string as_string() const {
98    return std::string(data(), size());
99  }
100  // We also define ToString() here, since many other string-like
101  // interfaces name the routine that converts to a C++ string
102  // "ToString", and it's confusing to have the method that does that
103  // for a StringPiece be called "as_string()".  We also leave the
104  // "as_string()" method defined here for existing code.
105  std::string ToString() const {
106    return std::string(data(), size());
107  }
108
109  void CopyToString(std::string* target) const;
110  void AppendToString(std::string* target) const;
111
112  // Does "this" start with "x"
113  bool starts_with(const StringPiece& x) const {
114    return ((length_ >= x.length_) &&
115            (memcmp(ptr_, x.ptr_, x.length_) == 0));
116  }
117
118  // Does "this" end with "x"
119  bool ends_with(const StringPiece& x) const {
120    return ((length_ >= x.length_) &&
121            (memcmp(ptr_ + (length_-x.length_), x.ptr_, x.length_) == 0));
122  }
123
124  // standard STL container boilerplate
125  typedef char value_type;
126  typedef const char* pointer;
127  typedef const char& reference;
128  typedef const char& const_reference;
129  typedef size_t size_type;
130  typedef ptrdiff_t difference_type;
131  static const size_type npos;
132  typedef const char* const_iterator;
133  typedef const char* iterator;
134  typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
135  typedef std::reverse_iterator<iterator> reverse_iterator;
136  iterator begin() const { return ptr_; }
137  iterator end() const { return ptr_ + length_; }
138  const_reverse_iterator rbegin() const {
139    return const_reverse_iterator(ptr_ + length_);
140  }
141  const_reverse_iterator rend() const {
142    return const_reverse_iterator(ptr_);
143  }
144  // STLS says return size_type, but Google says return int
145  int max_size() const { return length_; }
146  int capacity() const { return length_; }
147
148  int copy(char* buf, size_type n, size_type pos = 0) const;
149
150  size_type find(const StringPiece& s, size_type pos = 0) const;
151  size_type find(char c, size_type pos = 0) const;
152  size_type rfind(const StringPiece& s, size_type pos = npos) const;
153  size_type rfind(char c, size_type pos = npos) const;
154
155  StringPiece substr(size_type pos, size_type n = npos) const;
156};
157
158// This large function is defined inline so that in a fairly common case where
159// one of the arguments is a literal, the compiler can elide a lot of the
160// following comparisons.
161inline bool operator==(const StringPiece& x, const StringPiece& y) {
162  int len = x.size();
163  if (len != y.size()) {
164    return false;
165  }
166
167  const char* p1 = x.data();
168  const char* p2 = y.data();
169  if (p1 == p2) {
170    return true;
171  }
172  if (len <= 0) {
173    return true;
174  }
175
176  // Test last byte in case strings share large common prefix
177  if (p1[len-1] != p2[len-1]) return false;
178  if (len == 1) return true;
179
180  // At this point we can, but don't have to, ignore the last byte.  We use
181  // this observation to fold the odd-length case into the even-length case.
182  len &= ~1;
183
184  return memcmp(p1, p2, len) == 0;
185}
186
187inline bool operator!=(const StringPiece& x, const StringPiece& y) {
188  return !(x == y);
189}
190
191inline bool operator<(const StringPiece& x, const StringPiece& y) {
192  const int r = memcmp(x.data(), y.data(),
193                       std::min(x.size(), y.size()));
194  return ((r < 0) || ((r == 0) && (x.size() < y.size())));
195}
196
197inline bool operator>(const StringPiece& x, const StringPiece& y) {
198  return y < x;
199}
200
201inline bool operator<=(const StringPiece& x, const StringPiece& y) {
202  return !(x > y);
203}
204
205inline bool operator>=(const StringPiece& x, const StringPiece& y) {
206  return !(x < y);
207}
208
209extern std::ostream& operator<<(std::ostream& o, const StringPiece& piece);
210
211struct StringPieceHash {
212  size_t operator()(const StringPiece& string_piece) const {
213    size_t string_size = string_piece.size();
214    const char* string_data = string_piece.data();
215    // This is the java.lang.String hashcode for convenience, not interoperability.
216    size_t hash = 0;
217    while (string_size--) {
218      hash = hash * 31 + *string_data++;
219    }
220    return hash;
221  }
222};
223
224}  // namespace art
225
226#endif  // ART_SRC_BASE_STRINGPIECE_H_
227