Guidelines for API documentation » History » Version 14
neels, 12/11/2018 04:16 PM
1 | 1 | neels | h1. Guidelines for API documentation |
---|---|---|---|
2 | |||
3 | 12 | neels | Find the current API doc in HTML form here: http://ftp.osmocom.org/api/latest/ |
4 | |||
5 | 13 | neels | We use doxygen for API documentation, for an overview see http://www.doxygen.nl/manual/docblocks.html. Please follow these guidelines: |
6 | 1 | neels | |
7 | 14 | neels | h2. Marker style |
8 | |||
9 | 1 | neels | Use the @/*!@ (Qt-style) doxygen markers. |
10 | 14 | neels | <pre> |
11 | /*! Item summary. |
||
12 | * Details follow. */ |
||
13 | struct item { |
||
14 | int member; /*!< Member summary. */ |
||
15 | }; |
||
16 | </pre> |
||
17 | 1 | neels | |
18 | 14 | neels | h2. Summary |
19 | |||
20 | Since we are using the AUTOBRIEF feature, omit '\brief', and always end the first sentence with a full-stop "." to mark the end of the short description. |
||
21 | |||
22 | To have a dot in a summary, use an escaped space like |
||
23 | 1 | neels | <pre>/*! Brief description (e.g.\ using only a few words). Details follow. */</pre> |
24 | |||
25 | Never rely on line breaks as semantic separation or to end a sentence, always use proper punctuation. The API doc may be rendered with different line breaks than in the source file. |
||
26 | 4 | neels | |
27 | h2. Locations |
||
28 | |||
29 | Header files usually contain merely function declarations bare of any API docs. The API doc comment should be in a @.c@ file at the definition of a function. |
||
30 | |||
31 | Structs and enums defined in a header file, though, also have their API doc comments in that @.h@ file. |
||
32 | 10 | neels | |
33 | Comments for single-line items like enum values or struct members can be placed on the same line using @/*!< Description */@. |
||
34 | 4 | neels | |
35 | h2. Grammar |
||
36 | |||
37 | Always use the imperative form, i.e. omit wording like "This function does", and avoid writing documentation that merely mirrors a function's name. For example: |
||
38 | |||
39 | <pre> |
||
40 | /*! Return a (static) buffer containing a hexdump of the msg. |
||
41 | * \param[in] msg message buffer |
||
42 | * \returns a pointer to a static char array |
||
43 | */ |
||
44 | const char *msgb_hexdump(const struct msgb *msg) |
||
45 | { |
||
46 | ... |
||
47 | </pre> |
||
48 | |||
49 | 1 | neels | h2. Parameters |
50 | 12 | neels | |
51 | 4 | neels | All parameters of a function should be documented. Input params are documented with @\param[in]@, where out-parameters (pointers to which returned data is written) are documented with @\param[out]@. Rarely, a param is both: @\param[in,out]@. |
52 | |||
53 | <pre> |
||
54 | /*! Apply nifty algorithm. |
||
55 | * \param[in] x0 First factor. |
||
56 | * \param[in] n Amount of values to calculate. |
||
57 | * \param[out] buf Write calculated values to this buffer. |
||
58 | * |
||
59 | 1 | neels | * Optional longer function description. */ |
60 | 7 | neels | </pre> |
61 | 8 | neels | |
62 | 4 | neels | It is also possible to document parameters without a direction, using merely @\param param_name Description@, however, it is desirable to always indicate @[in]@, @[out]@ or @[inout]@. |
63 | 1 | neels | |
64 | h2. File comments |
||
65 | |||
66 | If a file contains a descriptive comment, this comment should be right at the start of the file, as a doxygen @\file@ section. |
||
67 | The first sentence must be ended by a full stop "." to mark the end of the short description. |
||
68 | The copyright notice shall not be part of such API doc file comment. |
||
69 | |||
70 | <pre> |
||
71 | /*! \file foo.c |
||
72 | * Short description. */ |
||
73 | /* |
||
74 | * (C) 2017 ... Copyright not in a doxygen comment |
||
75 | * license information |
||
76 | */ |
||
77 | </pre> |
||
78 | |||
79 | or |
||
80 | |||
81 | <pre> |
||
82 | /*! \file foo.c |
||
83 | * Short description. |
||
84 | * |
||
85 | * More information in multiple lines. |
||
86 | */ |
||
87 | /* |
||
88 | * (C) 2017 ... |
||
89 | */ |
||
90 | </pre> |
||
91 | 11 | neels | |
92 | 9 | neels | If a file needs no description, it is ok to omit the @\file@ tag entirely. Since we are using EXTRACT_ALL = YES, files lacking a @\file@ tag are still listed in the API docs. |
93 | 1 | neels | |
94 | h2. Groups |
||
95 | |||
96 | Doxygen allows grouping elements: a group can include code elements and also entire files. |
||
97 | |||
98 | This works by enclosing the items to be grouped between an opening and a closing marker: |
||
99 | |||
100 | * A @\defgroup@ initially defines a group, this shall exist only once. |
||
101 | * More items can be added using an @\addtogroup@ marker. |
||
102 | * Both have to be closed by "@}". |
||
103 | |||
104 | For example: |
||
105 | |||
106 | <pre> |
||
107 | /*! \defgroup groupname Short description of the group. |
||
108 | * @{ |
||
109 | */ |
||
110 | |||
111 | struct type_that_belongs_to_group { |
||
112 | ... |
||
113 | }; |
||
114 | |||
115 | void func_that_belongs_to_group() |
||
116 | { |
||
117 | ... |
||
118 | } |
||
119 | |||
120 | /*! @} */ |
||
121 | </pre> |
||
122 | |||
123 | and |
||
124 | |||
125 | <pre> |
||
126 | /*! \addtogroup groupname |
||
127 | * @{ |
||
128 | */ |
||
129 | 3 | neels | |
130 | 1 | neels | ... |
131 | |||
132 | /*! @} */ |
||
133 | </pre> |
||
134 | 5 | neels | |
135 | 1 | neels | If a *file* should be added to a group, add a (possibly second) short descriptionless @\file@ tag to the group start. To clearly mark that the purpose is to add to the group, do so within the same comment block: |
136 | |||
137 | <pre> |
||
138 | 2 | neels | /*! \file foo.c |
139 | 1 | neels | * File's description. */ |
140 | /* |
||
141 | * (C) ... |
||
142 | */ |
||
143 | |||
144 | /*! \addtogroup groupname |
||
145 | * @{ |
||
146 | * \file foo.c */ |
||
147 | |||
148 | ... |
||
149 | |||
150 | /*! @} */ |
||
151 | </pre> |
||
152 | |||
153 | The point is that we like to have a file's short description near the start of the file, to also serve us well when we're reading only the .h file. But to be included in a group, the doxygen group start must precede the @\file@ tag. Also, the doxygen group should rather not enclose @#include@ directives, to clearly exclude those from the group. Hence, the best way is to keep the file's actual description at the top of the file, and add a second descriptionless @\file@ with the group opening. |
||
154 | |||
155 | A group may contain a short as well as a longer description. We often @\defgroup@ in a @.h@ file but keep the longer description in an @\addtogroup@ in a @.c@ file. Any @\file@ tags must follow *after* such description, or the description will be associated with the file instead of the group: |
||
156 | |||
157 | @.h@ file: |
||
158 | <pre> |
||
159 | /*! \defgroup groupname Short description of the group. |
||
160 | * @{ |
||
161 | */ |
||
162 | |||
163 | ... |
||
164 | |||
165 | /*! @} */ |
||
166 | </pre> |
||
167 | |||
168 | @.c file: |
||
169 | |||
170 | <pre> |
||
171 | /*! \addtogroup groupname |
||
172 | * @{ |
||
173 | * Longer description of the group. |
||
174 | * - contains a |
||
175 | * - bullet list |
||
176 | * |
||
177 | * As well as a |
||
178 | * |
||
179 | * Code example |
||
180 | * block |
||
181 | 6 | neels | * |
182 | 1 | neels | * All of which must not be below the directive adding this file to the group... |
183 | * |
||
184 | * \file foo.c */ |
||
185 | |||
186 | [...] |
||
187 | |||
188 | /*! @} */ |
||
189 | </pre> |
||
190 | |||
191 | Often, a file's description matches or is identical with a group's description. In that case, the file's description header comment can be omitted to avoid duplicating identical descriptions. |
||
192 | |||
193 | <pre> |
||
194 | /* |
||
195 | * (C) 2017 ... |
||
196 | */ |
||
197 | |||
198 | /* \addtogroup group |
||
199 | * @{ |
||
200 | * Description... |
||
201 | * |
||
202 | * \file foo.c */ |
||
203 | |||
204 | ... |
||
205 | |||
206 | /* @} */ |
||
207 | </pre> |