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 #ifndef ART_LIBARTBASE_BASE_STRINGPIECE_H_
18 #define ART_LIBARTBASE_BASE_STRINGPIECE_H_
19 
20 #include <string.h>
21 #include <string>
22 
23 #include <android-base/logging.h>
24 
25 namespace art {
26 
27 // A string-like object that points to a sized piece of memory.
28 //
29 // Functions or methods may use const StringPiece& parameters to accept either
30 // a "const char*" or a "string" value that will be implicitly converted to
31 // a StringPiece.  The implicit conversion means that it is often appropriate
32 // to include this .h file in other files rather than forward-declaring
33 // StringPiece as would be appropriate for most other Google classes.
34 class StringPiece {
35  public:
36   // standard STL container boilerplate
37   typedef char value_type;
38   typedef const char* pointer;
39   typedef const char& reference;
40   typedef const char& const_reference;
41   typedef size_t size_type;
42   typedef ptrdiff_t difference_type;
43   static constexpr size_type npos = size_type(-1);
44   typedef const char* const_iterator;
45   typedef const char* iterator;
46   typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
47   typedef std::reverse_iterator<iterator> reverse_iterator;
48 
49   // We provide non-explicit singleton constructors so users can pass
50   // in a "const char*" or a "string" wherever a "StringPiece" is
51   // expected.
StringPiece()52   StringPiece() : ptr_(nullptr), length_(0) { }
StringPiece(const char * str)53   StringPiece(const char* str)  // NOLINT implicit constructor desired
54     : ptr_(str), length_((str == nullptr) ? 0 : strlen(str)) { }
StringPiece(const std::string & str)55   StringPiece(const std::string& str)  // NOLINT implicit constructor desired
56     : ptr_(str.data()), length_(str.size()) { }
StringPiece(const char * offset,size_t len)57   StringPiece(const char* offset, size_t len) : ptr_(offset), length_(len) { }
58 
59   // data() may return a pointer to a buffer with embedded NULs, and the
60   // returned buffer may or may not be null terminated.  Therefore it is
61   // typically a mistake to pass data() to a routine that expects a NUL
62   // terminated string.
data()63   const char* data() const { return ptr_; }
size()64   size_type size() const { return length_; }
length()65   size_type length() const { return length_; }
empty()66   bool empty() const { return length_ == 0; }
67 
clear()68   void clear() {
69     ptr_ = nullptr;
70     length_ = 0;
71   }
set(const char * data_in,size_type len)72   void set(const char* data_in, size_type len) {
73     ptr_ = data_in;
74     length_ = len;
75   }
set(const char * str)76   void set(const char* str) {
77     ptr_ = str;
78     if (str != nullptr) {
79       length_ = strlen(str);
80     } else {
81       length_ = 0;
82     }
83   }
set(const void * data_in,size_type len)84   void set(const void* data_in, size_type len) {
85     ptr_ = reinterpret_cast<const char*>(data_in);
86     length_ = len;
87   }
88 
89   char operator[](size_type i) const {
90     DCHECK_LT(i, length_);
91     return ptr_[i];
92   }
93 
remove_prefix(size_type n)94   void remove_prefix(size_type n) {
95     ptr_ += n;
96     length_ -= n;
97   }
98 
remove_suffix(size_type n)99   void remove_suffix(size_type n) {
100     length_ -= n;
101   }
102 
compare(const StringPiece & x)103   int compare(const StringPiece& x) const {
104     int r = memcmp(ptr_, x.ptr_, std::min(length_, x.length_));
105     if (r == 0) {
106       if (length_ < x.length_) r = -1;
107       else if (length_ > x.length_) r = +1;
108     }
109     return r;
110   }
111 
as_string()112   std::string as_string() const {
113     return std::string(data(), size());
114   }
115   // We also define ToString() here, since many other string-like
116   // interfaces name the routine that converts to a C++ string
117   // "ToString", and it's confusing to have the method that does that
118   // for a StringPiece be called "as_string()".  We also leave the
119   // "as_string()" method defined here for existing code.
ToString()120   std::string ToString() const {
121     return std::string(data(), size());
122   }
123 
CopyToString(std::string * target)124   void CopyToString(std::string* target) const {
125     target->assign(ptr_, length_);
126   }
127 
128   void AppendToString(std::string* target) const;
129 
130   // Does "this" start with "x"
starts_with(const StringPiece & x)131   bool starts_with(const StringPiece& x) const {
132     return ((length_ >= x.length_) &&
133             (memcmp(ptr_, x.ptr_, x.length_) == 0));
134   }
135 
136   // Does "this" end with "x"
ends_with(const StringPiece & x)137   bool ends_with(const StringPiece& x) const {
138     return ((length_ >= x.length_) &&
139             (memcmp(ptr_ + (length_-x.length_), x.ptr_, x.length_) == 0));
140   }
141 
begin()142   iterator begin() const { return ptr_; }
end()143   iterator end() const { return ptr_ + length_; }
rbegin()144   const_reverse_iterator rbegin() const {
145     return const_reverse_iterator(ptr_ + length_);
146   }
rend()147   const_reverse_iterator rend() const {
148     return const_reverse_iterator(ptr_);
149   }
150 
151   size_type copy(char* buf, size_type n, size_type pos = 0) const {
152     size_type ret = std::min(length_ - pos, n);
153     memcpy(buf, ptr_ + pos, ret);
154     return ret;
155   }
156 
157   size_type find(const StringPiece& s, size_type pos = 0) const {
158     if (length_ == 0 || pos > static_cast<size_type>(length_)) {
159       return npos;
160     }
161     const char* result = std::search(ptr_ + pos, ptr_ + length_, s.ptr_, s.ptr_ + s.length_);
162     const size_type xpos = result - ptr_;
163     return xpos + s.length_ <= length_ ? xpos : npos;
164   }
165 
166   size_type find(char c, size_type pos = 0) const {
167     if (length_ == 0 || pos >= length_) {
168       return npos;
169     }
170     const char* result = std::find(ptr_ + pos, ptr_ + length_, c);
171     return result != ptr_ + length_ ? result - ptr_ : npos;
172   }
173 
174   size_type rfind(const StringPiece& s, size_type pos = npos) const {
175     if (length_ < s.length_) return npos;
176     const size_t ulen = length_;
177     if (s.length_ == 0) return std::min(ulen, pos);
178 
179     const char* last = ptr_ + std::min(ulen - s.length_, pos) + s.length_;
180     const char* result = std::find_end(ptr_, last, s.ptr_, s.ptr_ + s.length_);
181     return result != last ? result - ptr_ : npos;
182   }
183 
184   size_type rfind(char c, size_type pos = npos) const {
185     if (length_ == 0) return npos;
186     for (int i = std::min(pos, static_cast<size_type>(length_ - 1));
187          i >= 0; --i) {
188       if (ptr_[i] == c) {
189         return i;
190       }
191     }
192     return npos;
193   }
194 
195   StringPiece substr(size_type pos, size_type n = npos) const {
196     if (pos > static_cast<size_type>(length_)) pos = length_;
197     if (n > length_ - pos) n = length_ - pos;
198     return StringPiece(ptr_ + pos, n);
199   }
200 
Compare(const StringPiece & rhs)201   int Compare(const StringPiece& rhs) const {
202     const int r = memcmp(data(), rhs.data(), std::min(size(), rhs.size()));
203     if (r != 0) {
204       return r;
205     }
206     if (size() < rhs.size()) {
207       return -1;
208     } else if (size() > rhs.size()) {
209       return 1;
210     }
211     return 0;
212   }
213 
214  private:
215   // Pointer to char data, not necessarily zero terminated.
216   const char* ptr_;
217   // Length of data.
218   size_type length_;
219 };
220 
221 // This large function is defined inline so that in a fairly common case where
222 // one of the arguments is a literal, the compiler can elide a lot of the
223 // following comparisons.
224 inline bool operator==(const StringPiece& x, const StringPiece& y) {
225   StringPiece::size_type len = x.size();
226   if (len != y.size()) {
227     return false;
228   }
229 
230   const char* p1 = x.data();
231   const char* p2 = y.data();
232   if (p1 == p2) {
233     return true;
234   }
235   if (len == 0) {
236     return true;
237   }
238 
239   // Test last byte in case strings share large common prefix
240   if (p1[len-1] != p2[len-1]) return false;
241   if (len == 1) return true;
242 
243   // At this point we can, but don't have to, ignore the last byte.  We use
244   // this observation to fold the odd-length case into the even-length case.
245   len &= ~1;
246 
247   return memcmp(p1, p2, len) == 0;
248 }
249 
250 inline bool operator==(const StringPiece& x, const char* y) {
251   if (y == nullptr) {
252     return x.size() == 0;
253   } else {
254     return strncmp(x.data(), y, x.size()) == 0 && y[x.size()] == '\0';
255   }
256 }
257 
258 inline bool operator!=(const StringPiece& x, const StringPiece& y) {
259   return !(x == y);
260 }
261 
262 inline bool operator!=(const StringPiece& x, const char* y) {
263   return !(x == y);
264 }
265 
266 inline bool operator<(const StringPiece& x, const StringPiece& y) {
267   return x.Compare(y) < 0;
268 }
269 
270 inline bool operator>(const StringPiece& x, const StringPiece& y) {
271   return y < x;
272 }
273 
274 inline bool operator<=(const StringPiece& x, const StringPiece& y) {
275   return !(x > y);
276 }
277 
278 inline bool operator>=(const StringPiece& x, const StringPiece& y) {
279   return !(x < y);
280 }
281 
282 inline std::ostream& operator<<(std::ostream& o, const StringPiece& piece) {
283   o.write(piece.data(), piece.size());
284   return o;
285 }
286 
287 }  // namespace art
288 
289 #endif  // ART_LIBARTBASE_BASE_STRINGPIECE_H_
290