Directory: | cvmfs/ |
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File: | cvmfs/shortstring.h |
Date: | 2025-09-28 02:35:26 |
Exec | Total | Coverage | |
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Lines: | 91 | 108 | 84.3% |
Branches: | 34 | 50 | 68.0% |
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1 | /** | ||
2 | * This file is part of the CernVM File System. | ||
3 | * | ||
4 | * Implements a string class that stores short strings on the stack and | ||
5 | * malloc's a std::string on the heap on overflow. Used for file names and | ||
6 | * path names that are usually small. | ||
7 | */ | ||
8 | |||
9 | #ifndef CVMFS_SHORTSTRING_H_ | ||
10 | #define CVMFS_SHORTSTRING_H_ | ||
11 | |||
12 | #include <algorithm> | ||
13 | #include <cstring> | ||
14 | #include <string> | ||
15 | |||
16 | #include "util/atomic.h" | ||
17 | |||
18 | #ifdef CVMFS_NAMESPACE_GUARD | ||
19 | namespace CVMFS_NAMESPACE_GUARD { | ||
20 | #endif | ||
21 | |||
22 | const unsigned char kDefaultMaxName = 25; | ||
23 | const unsigned char kDefaultMaxLink = 25; | ||
24 | const unsigned char kDefaultMaxPath = 200; | ||
25 | |||
26 | template<unsigned char StackSize, char Type> | ||
27 | class ShortString { | ||
28 | public: | ||
29 | 79265136 | ShortString() : long_string_(NULL), length_(0) { | |
30 | #ifdef DEBUGMSG | ||
31 | 79265136 | atomic_inc64(&num_instances_); | |
32 | #endif | ||
33 | 79265136 | } | |
34 | 93455070 | ShortString(const ShortString &other) : long_string_(NULL) { | |
35 | #ifdef DEBUGMSG | ||
36 | 186910140 | atomic_inc64(&num_instances_); | |
37 | #endif | ||
38 | 187510194 | Assign(other); | |
39 | 187007062 | } | |
40 | 32645 | ShortString(const char *chars, const unsigned length) : long_string_(NULL) { | |
41 | #ifdef DEBUGMSG | ||
42 | 32645 | atomic_inc64(&num_instances_); | |
43 | #endif | ||
44 | 32831 | Assign(chars, length); | |
45 | 32717 | } | |
46 | 74302706 | explicit ShortString(const std::string &std_string) : long_string_(NULL) { | |
47 | #ifdef DEBUGMSG | ||
48 | 74302706 | atomic_inc64(&num_instances_); | |
49 | #endif | ||
50 | 74403902 | Assign(std_string.data(), std_string.length()); | |
51 | 74299724 | } | |
52 | |||
53 | 38348568 | ShortString &operator=(const ShortString &other) { | |
54 |
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38348568 | if (this != &other) |
55 | 38349420 | Assign(other); | |
56 | 38291706 | return *this; | |
57 | } | ||
58 | |||
59 |
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305235544 | ~ShortString() { delete long_string_; } |
60 | |||
61 | 299798020 | void Assign(const char *chars, const unsigned length) { | |
62 |
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299798020 | delete long_string_; |
63 | 299724164 | long_string_ = NULL; | |
64 | 299724164 | this->length_ = length; | |
65 |
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299724164 | if (length > StackSize) { |
66 | #ifdef DEBUGMSG | ||
67 | ✗ | atomic_inc64(&num_overflows_); | |
68 | #endif | ||
69 | ✗ | long_string_ = new std::string(chars, length); | |
70 | } else { | ||
71 |
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299724164 | if (length) |
72 | 299263562 | memcpy(stack_, chars, length); | |
73 | } | ||
74 | 299724164 | } | |
75 | |||
76 | 225610504 | void Assign(const ShortString &other) { | |
77 | 225610504 | Assign(other.GetChars(), other.GetLength()); | |
78 | 225330402 | } | |
79 | |||
80 | 168424 | void Append(const char *chars, const unsigned length) { | |
81 |
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168424 | if (long_string_) { |
82 | ✗ | long_string_->append(chars, length); | |
83 | ✗ | return; | |
84 | } | ||
85 | |||
86 | 168424 | const unsigned new_length = this->length_ + length; | |
87 |
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168424 | if (new_length > StackSize) { |
88 | #ifdef DEBUGMSG | ||
89 | ✗ | atomic_inc64(&num_overflows_); | |
90 | #endif | ||
91 | ✗ | long_string_ = new std::string(); | |
92 | ✗ | long_string_->reserve(new_length); | |
93 | ✗ | long_string_->assign(stack_, length_); | |
94 | ✗ | long_string_->append(chars, length); | |
95 | ✗ | return; | |
96 | } | ||
97 |
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168424 | if (length > 0) |
98 | 166648 | memcpy(&stack_[this->length_], chars, length); | |
99 | 168424 | this->length_ = new_length; | |
100 | } | ||
101 | |||
102 | /** | ||
103 | * Truncates the current string to be of size smaller or equal to current size | ||
104 | * | ||
105 | * Note: Can lead to a heap allocated string that is shorter than | ||
106 | * the reserved stack space. | ||
107 | */ | ||
108 | 2646 | void Truncate(unsigned new_length) { | |
109 |
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2646 | assert(new_length <= this->GetLength()); |
110 |
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2646 | if (long_string_) { |
111 | ✗ | long_string_->erase(new_length); | |
112 | ✗ | return; | |
113 | } | ||
114 | 2646 | this->length_ = new_length; | |
115 | } | ||
116 | |||
117 | void Clear() { | ||
118 | delete long_string_; | ||
119 | long_string_ = NULL; | ||
120 | length_ = 0; | ||
121 | } | ||
122 | |||
123 | 300204202 | const char *GetChars() const { | |
124 |
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300204202 | if (long_string_) { |
125 | ✗ | return long_string_->data(); | |
126 | } else { | ||
127 | 300204202 | return stack_; | |
128 | } | ||
129 | } | ||
130 | |||
131 | 300816006 | unsigned GetLength() const { | |
132 |
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300816006 | if (long_string_) |
133 | ✗ | return long_string_->length(); | |
134 | 300816006 | return length_; | |
135 | } | ||
136 | |||
137 | 5834 | bool IsEmpty() const { return GetLength() == 0; } | |
138 | |||
139 | 37217029 | std::string ToString() const { | |
140 |
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37217029 | return std::string(this->GetChars(), this->GetLength()); |
141 | } | ||
142 | |||
143 | 35960 | const char *c_str() const { | |
144 |
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35960 | if (long_string_) |
145 | ✗ | return long_string_->c_str(); | |
146 | |||
147 | 35960 | char *c = const_cast<char *>(stack_) + length_; | |
148 | 35960 | *c = '\0'; | |
149 | 35960 | return stack_; | |
150 | } | ||
151 | |||
152 | 31970 | bool operator==(const ShortString &other) const { | |
153 | 31970 | const unsigned this_length = this->GetLength(); | |
154 | 31970 | const unsigned other_length = other.GetLength(); | |
155 |
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31970 | if (this_length != other_length) |
156 | 20048 | return false; | |
157 |
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11922 | if (this_length == 0) |
158 | 6649 | return true; | |
159 | |||
160 | 5273 | return memcmp(this->GetChars(), other.GetChars(), this_length) == 0; | |
161 | } | ||
162 | |||
163 | 23141 | bool operator!=(const ShortString &other) const { return !(*this == other); } | |
164 | |||
165 | 39649 | bool operator<(const ShortString &other) const { | |
166 | 39649 | const unsigned this_length = this->GetLength(); | |
167 | 39649 | const unsigned other_length = other.GetLength(); | |
168 | |||
169 |
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39649 | if (this_length < other_length) |
170 | 10765 | return true; | |
171 |
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28884 | if (this_length > other_length) |
172 | 7969 | return false; | |
173 | |||
174 | 20915 | const char *this_chars = this->GetChars(); | |
175 | 20915 | const char *other_chars = other.GetChars(); | |
176 |
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273989 | for (unsigned i = 0; i < this_length; ++i) { |
177 |
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256673 | if (this_chars[i] < other_chars[i]) |
178 | 2772 | return true; | |
179 |
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253901 | if (this_chars[i] > other_chars[i]) |
180 | 827 | return false; | |
181 | } | ||
182 | 17316 | return false; | |
183 | } | ||
184 | |||
185 | 34669 | bool StartsWith(const ShortString &other) const { | |
186 | 34669 | const unsigned this_length = this->GetLength(); | |
187 | 34669 | const unsigned other_length = other.GetLength(); | |
188 |
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34669 | if (this_length < other_length) |
189 | 2380 | return false; | |
190 | |||
191 | 32289 | return memcmp(this->GetChars(), other.GetChars(), other_length) == 0; | |
192 | } | ||
193 | |||
194 | 14607 | ShortString Suffix(const unsigned start_at) const { | |
195 | 14607 | const unsigned length = this->GetLength(); | |
196 |
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14607 | if (start_at >= length) |
197 | 12 | return ShortString("", 0); | |
198 | |||
199 | 14595 | return ShortString(this->GetChars() + start_at, length - start_at); | |
200 | } | ||
201 | |||
202 | ✗ | static uint64_t num_instances() { return atomic_read64(&num_instances_); } | |
203 | ✗ | static uint64_t num_overflows() { return atomic_read64(&num_overflows_); } | |
204 | |||
205 | private: | ||
206 | std::string *long_string_; | ||
207 | char stack_[StackSize + 1]; // +1 to add a final '\0' if necessary | ||
208 | unsigned char length_; | ||
209 | static atomic_int64 num_overflows_; | ||
210 | static atomic_int64 num_instances_; | ||
211 | }; // class ShortString | ||
212 | |||
213 | typedef ShortString<kDefaultMaxPath, 0> PathString; | ||
214 | typedef ShortString<kDefaultMaxName, 1> NameString; | ||
215 | typedef ShortString<kDefaultMaxLink, 2> LinkString; | ||
216 | |||
217 | template<unsigned char StackSize, char Type> | ||
218 | atomic_int64 ShortString<StackSize, Type>::num_overflows_ = 0; | ||
219 | template<unsigned char StackSize, char Type> | ||
220 | atomic_int64 ShortString<StackSize, Type>::num_instances_ = 0; | ||
221 | |||
222 | // See posix.cc for the std::string counterparts | ||
223 | PathString GetParentPath(const PathString &path); | ||
224 | NameString GetFileName(const PathString &path); | ||
225 | |||
226 | bool IsSubPath(const PathString &parent, const PathString &path); | ||
227 | |||
228 | |||
229 | #ifdef CVMFS_NAMESPACE_GUARD | ||
230 | } // namespace CVMFS_NAMESPACE_GUARD | ||
231 | #endif | ||
232 | |||
233 | #endif // CVMFS_SHORTSTRING_H_ | ||
234 |