GCC Code Coverage Report

Directory: cvmfs/
File: cvmfs/fd_table.h
Date: 2025-07-06 02:35:01
Exec Total Coverage
Lines: 62 63 98.4%
Branches: 40 59 67.8%
Line Branch Exec Source
1 /**
2 * This file is part of the CernVM File System.
3 */
4
5 #ifndef CVMFS_FD_TABLE_H_
6 #define CVMFS_FD_TABLE_H_
7
8 #include <errno.h>
9 #include <inttypes.h>
10 #include <stdint.h>
11
12 #include <cassert>
13 #include <vector>
14
15 #include "util/single_copy.h"
16
17 /**
18 * Maintains integers mapped to custom open file descriptors. File descriptors
19 * can be added, removed, and accessed. All operations take constant time. The
20 * maximum file descriptor number needs to be known upfront.
21 *
22 * Note that new file descriptors do not necessarily have the smallest available
23 * number but any number between 0..max_open_fds.
24 *
25 * This class is used by a couple of cache managers.
26 */
27 template<class HandleT>
28 class FdTable : SingleCopy {
29 public:
30 910 FdTable(unsigned max_open_fds, const HandleT &invalid_handle)
31 910 : invalid_handle_(invalid_handle)
32 910 , fd_pivot_(0)
33
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 910 , fd_index_(max_open_fds)
34
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 1820 , open_fds_(max_open_fds, FdWrapper(invalid_handle_, 0)) {
35
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 910 assert(max_open_fds > 0);
36
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 2548986 for (unsigned i = 0; i < max_open_fds; ++i) {
37 2548076 fd_index_[i] = i;
38 2548076 open_fds_[i].index = i;
39 }
40 910 }
41
42 /**
43 * Used to restore the state.
44 */
45 14 void AssignFrom(const FdTable<HandleT> &other) {
46 14 invalid_handle_ = other.invalid_handle_;
47 14 fd_pivot_ = other.fd_pivot_;
48 14 fd_index_.resize(other.fd_index_.size());
49
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 14 open_fds_.resize(other.open_fds_.size(), FdWrapper(invalid_handle_, 0));
50
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 1806 for (unsigned i = 0; i < fd_index_.size(); ++i) {
51 1792 fd_index_[i] = other.fd_index_[i];
52 1792 open_fds_[i] = other.open_fds_[i];
53 }
54 14 }
55
56 /**
57 * Used to save the state.
58 */
59 14 FdTable<HandleT> *Clone() {
60 14 FdTable<HandleT> *result = new FdTable<HandleT>(open_fds_.size(),
61
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 14 invalid_handle_);
62 14 result->fd_pivot_ = fd_pivot_;
63
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 1806 for (unsigned i = 0; i < fd_index_.size(); ++i) {
64 1792 result->fd_index_[i] = fd_index_[i];
65 1792 result->open_fds_[i] = open_fds_[i];
66 }
67 14 return result;
68 }
69
70
71 /**
72 * Registers fd with a currently unused number. If the table is full,
73 * returns -ENFILE;
74 */
75 15287255 int OpenFd(const HandleT &handle) {
76
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 15287255 if (handle == invalid_handle_)
77 ✗ return -EINVAL;
78
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 15287255 if (fd_pivot_ >= fd_index_.size())
79 2497899 return -ENFILE;
80
81 12789356 size_t next_fd = fd_index_[fd_pivot_];
82
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 12789356 assert(next_fd < open_fds_.size());
83
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 12789356 assert(open_fds_[next_fd].handle == invalid_handle_);
84
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 12789356 open_fds_[next_fd] = FdWrapper(handle, fd_pivot_);
85 12789356 ++fd_pivot_;
86 12789356 return next_fd;
87 }
88
89 /**
90 * For invalid and unused numbers, the invalid handle is returned.
91 */
92 15548482 HandleT GetHandle(int fd) {
93
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 15548482 return IsValid(fd) ? open_fds_[fd].handle : invalid_handle_;
94 }
95
96
97 /**
98 * Releases fd back to the set of available numbers. Gracefully handles
99 * invalid handles (-EBADFD)
100 */
101 15269396 int CloseFd(int fd) {
102
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 15269396 if (!IsValid(fd))
103 2480460 return -EBADF;
104
105 12788936 unsigned index = open_fds_[fd].index;
106
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 12788936 assert(index < fd_index_.size());
107
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 12788936 assert(fd_pivot_ <= fd_index_.size());
108
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 12788936 assert(fd_pivot_ > 0);
109 12788936 open_fds_[fd].handle = invalid_handle_;
110 12788936 --fd_pivot_;
111
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 12788936 if (index < fd_pivot_) {
112 7080241 unsigned other = fd_index_[fd_pivot_];
113
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 7080241 assert(other < open_fds_.size());
114
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 7080241 assert(open_fds_[other].handle != invalid_handle_);
115 7080241 open_fds_[other].index = index;
116 7080241 fd_index_[index] = other;
117 7080241 fd_index_[fd_pivot_] = fd;
118 }
119 12788936 return 0;
120 }
121
122 1792 unsigned GetMaxFds() const { return fd_index_.size(); }
123
124 private:
125 struct FdWrapper {
126 12790280 FdWrapper(HandleT h, unsigned i) : handle(h), index(i) { }
127
128 HandleT handle;
129 /**
130 * Back-pointer into fd_index_, which is needed when closing a file.
131 */
132 unsigned index;
133 };
134
135
136 30817878 inline bool IsValid(int fd) {
137
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 30817878 if ((fd < 0) || (static_cast<unsigned>(fd) >= open_fds_.size()))
138 120 return false;
139 30817758 return open_fds_[fd].handle != invalid_handle_;
140 }
141
142 /**
143 * An unused (available) file descriptor.
144 */
145 HandleT invalid_handle_;
146 /**
147 * The index of the first available file descriptor in fd_index_.
148 */
149 unsigned fd_pivot_;
150 /**
151 * Maps into open_fds_. Until fd_pivot_, file descriptors are used. As of
152 * fd_pivot_, points to free file descriptors. Used to acquire new file
153 * descriptors in constant time.
154 */
155 std::vector<unsigned> fd_index_;
156 /**
157 * The file descriptor number mapped to a user-defined file descriptor
158 * (struct). The fd integer passed to users of the file descriptor table
159 * points into this array.
160 */
161 std::vector<FdWrapper> open_fds_;
162 }; // class FdTable
163
164 #endif // CVMFS_FD_TABLE_H_
165