1 | /* |
2 | * Copyright 2013-present Facebook, Inc. |
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 | #pragma once |
18 | |
19 | #include <cstddef> |
20 | |
21 | #include <boost/noncopyable.hpp> |
22 | |
23 | #include <folly/Range.h> |
24 | |
25 | namespace folly { |
26 | namespace symbolizer { |
27 | |
28 | /** |
29 | * Async-signal-safe line reader. |
30 | */ |
31 | class LineReader : private boost::noncopyable { |
32 | public: |
33 | /** |
34 | * Create a line reader that reads into a user-provided buffer (of size |
35 | * bufSize). |
36 | */ |
37 | LineReader(int fd, char* buf, size_t bufSize); |
38 | |
39 | enum State { |
40 | kReading, |
41 | kEof, |
42 | kError, |
43 | }; |
44 | /** |
45 | * Read the next line from the file. |
46 | * |
47 | * If the line is at most bufSize characters long, including the trailing |
48 | * newline, it will be returned (including the trailing newline). |
49 | * |
50 | * If the line is longer than bufSize, we return the first bufSize bytes |
51 | * (which won't include a trailing newline) and then continue from that |
52 | * point onwards. |
53 | * |
54 | * The lines returned are not null-terminated. |
55 | * |
56 | * Returns kReading with a valid line, kEof if at end of file, or kError |
57 | * if a read error was encountered. |
58 | * |
59 | * Example: |
60 | * bufSize = 10 |
61 | * input has "hello world\n" |
62 | * The first call returns "hello worl" |
63 | * The second call returns "d\n" |
64 | */ |
65 | State readLine(StringPiece& line); |
66 | |
67 | private: |
68 | int const fd_; |
69 | char* const buf_; |
70 | char* const bufEnd_; |
71 | |
72 | // buf_ <= bol_ <= eol_ <= end_ <= bufEnd_ |
73 | // |
74 | // [buf_, end_): current buffer contents (read from file) |
75 | // |
76 | // [buf_, bol_): free (already processed, can be discarded) |
77 | // [bol_, eol_): current line, including \n if it exists, eol_ points |
78 | // 1 character past the \n |
79 | // [eol_, end_): read, unprocessed |
80 | // [end_, bufEnd_): free |
81 | |
82 | char* bol_; |
83 | char* eol_; |
84 | char* end_; |
85 | State state_; |
86 | }; |
87 | } // namespace symbolizer |
88 | } // namespace folly |
89 | |