Added loading parameters from json to several emv commands (#686)
[proxmark3-svn] / HACKING.txt
1 "Coding styles are like assholes, everyone has one and no one likes anyone elses."
2 --Eric Warmenhoven
3
4 The Proxmark3 codebase is pretty messy and in the process of being cleaned up,
5 so we don't have clear guidelines on how to place new code just yet. However,
6 please don't make things worse.
7
8 However, we have established a set of coding style guidelines in order to
9 clean up the code consistently and keep it consistent in the future. Use common
10 sense and good taste. If breaking a rule leads to cleaner code, you can do so,
11 but laziness is not an excuse.
12
13 === INDENTATION ===
14
15 Use tabs for indentation, but use spaces for alignment:
16
17 if (foo(this, that, there)
18 && bar == baz)
19 {
20 dostuff();
21 }
22
23 Notice it's like this (T___ for tab, S for space, for a 4-char tab setting):
24
25 T___if (foo(this, that, there)
26 T___SSSS&& bar == baz)
27
28 Another example:
29
30 #define THIS 0x10
31 #define THAT_THING 0x20
32 #define SOMETHING_ELSE 0x80
33
34 These should look good no matter what your editor's tab setting is, so go nuts
35 and pick whatever you like best.
36
37 === WIDTH ===
38
39 Try to keep lines to a reasonable length. 80 characters is a good mark; using an
40 editor that shows a vertical line is a great idea. However, don't break a line
41 just because you're slightly over, it's not worth it. No 200-character lines,
42 though.
43
44 === MACROS ===
45
46 #defines, function-like or not, are all UPPERCASE unless you're emulating a
47 well-known function name.
48
49 === IDENTIFIERS ===
50
51 Functions, local variables, and arguments are all named using
52 underscores_as_spaces. Global variables are Evil and are prepended with g_ to
53 distinguish them. Avoid them.
54
55 Single-character variables are a bad idea. Exceptions: loop iterators and maybe
56 simple byte pointers (*p) in very obvious places. If you have more than one
57 such pointer, use a real name. If you have more than a couple nested loops,
58 complex logic, or indices that differ in interpretation or purpose, use real
59 names instead of i,j,k.
60
61 === DATA TYPES ===
62
63 Use stdint.h types (uint32_t and friends) unless you have a reason not to. Don't
64 use microsoft-style DWORD and the like, we're getting rid of those. Avoid char
65 for buffers, uint8_t is more obvious when you're not working with strings. Use
66 'const' where things are const. Try to use size_t for sizes.
67
68 Pointers are:
69 void *ptr;
70 not:
71 void* ptr;
72 otherwise you're tempted to write:
73 void* in, out;
74 and you'll fail.
75
76 === EXPRESSIONS ===
77
78 In general, use whitespace around binary operators - no unspaced blobs of an
79 expression. This rule may be broken if it makes things clearer. For example,
80
81 if (5*a < b && some_bool_var)
82
83 but not
84
85 if (5*a<b&&some_bool_var)
86
87 For equality with constants, use i == 0xF00, not 0xF00 == i. The compiler warns
88 you about = vs == anyway, and you shouldn't be screwing that one up by now
89 anyway.
90
91 === IF / FOR / WHILE / etc. ===
92
93 Put the opening brace on the same line, with a space before it. Exception: if
94 the if/for/while condition/whatever are split over several lines, it might be
95 more appealing to put the opening brace on its own line, so use your own
96 judgement there:
97
98 if (foo(this, that, there)
99 && bar == baz)
100 {
101 dostuff();
102 }
103
104 If you do split the condition, put the binary operators that join the lines at
105 the beginning of the following lines (as above), not at the end of the prior
106 lines.
107
108 There should be a space between the construct name (if/for/whatever) and the
109 opening parenthesis, and there should be a space between the closing parenthesis
110 and the opening brace.
111
112 For generic for() iterator variables, declare them in-line:
113
114 for (int i = 0; i < 10; i++) {
115 ...
116 }
117
118 Note the spaces after the semicolons.
119
120 if/else should be laid out as follows:
121
122 if (foo) {
123 ...
124 } else if (bar) {
125 ...
126 } else {
127 ...
128 }
129
130 or
131
132 if (foo)
133 ...
134 else if (bar)
135 ...
136 else
137 ...
138
139 Don't mix braces vs. no braces. If any of your bodies are > 1 line, put braces
140 around them all.
141
142 === FUNCTIONS ===
143
144 Functions with no arguments are declared as f(void), not f(). Put the return
145 type on the same line. Use static for functions that aren't exported, and put
146 exported functions in a header file (one header file per source file with
147 exported functions usually, no huge headers with all functions). Put a space
148 after a comma in argument lists.
149
150 void foo(int a_thing, int something_else)
151 {
152 ...
153 }
154
155 void baz(void)
156 {
157 foo(bluh, blah);
158 }
159
160 Function names should be separated_with_underscores(), except for standard
161 functions (memcpy, etc.). It may make sense to break this rule for very common,
162 generic functions that look like library functions (e.g. dprintf()).
163
164 Don't use single-character arguments. Exception: very short functions with one
165 argument that's really obvious:
166
167 static int ascii(char c)
168 {
169 if (c < 0x20 || c >= 0x7f)
170 return '.';
171 else
172 return c;
173 }
174
175 vs.
176
177 static void hexdump(void *buf, size_t len)
178 {
179 ...
180 }
181
182 As a general guideline, functions shouldn't usually be much more than 30-50
183 lines. Above, the general algorithm won't be easily apparent, and you're
184 probably missing some factoring/restructuring opportunity.
185
186 === STRUCTS / UNIONS / ENUMS ===
187
188 Use typedefs when defining structs. The type should be named something_t.
189
190 typedef struct {
191 blah blah;
192 } prox_cmd_t;
193
194 You can use anonymous enums to replace lots of sequential or mostly-sequential
195 #defines.
196
197 === SWITCH ===
198
199 Indent once for the case: labels, then again for the body. Like this:
200
201 switch(bar) {
202 case OPTION_A:
203 do_stuff();
204 break;
205 case OPTION_B:
206 do_other_stuff();
207 break;
208 }
209
210 If you fall through into another case, add an explicit comment; otherwise, it
211 can look confusing.
212
213 If your switch() is too long or has too many cases, it should be cleaned up.
214 Split off the cases into functions, break the switch() into parent and children
215 switches (e.g. command and subcommand), or use an array of function pointers or
216 the like. In other words, use common sense and your brain.
217
218 If you need local scope variables for a case, you can add braces:
219
220 switch(bar) {
221 case OPTION_A: {
222 int baz = 5*bar;
223 do_stuff(baz);
224 break;
225 }
226 ...
227
228 But at that point you should probably consider using a separate function.
229
230 === COMMENTS ===
231
232 Use //, it's shorter:
233
234 // this does foo
235 ...
236
237 // baz:
238 // This does blah blah blah .....
239 // blah blah...
240
241 /* */ can be used to comment blocks of code, but you should probably remove
242 them anyway - we have version control, it's easy to fetch old code if needed,
243 so avoid committing commented out chunks of code. The same goes for #if 0.
244
245 === FILE ===
246
247 Please use common sense and restrain yourself from having a thousands+++ line
248 file. Functions in a file should have something *specific* in common. Over time
249 sub-categories can arise and should therefore yield to file splitting.
250
251 For these reasons, vague and general filenames (e.g. util.*, global.*, misc.*,
252 main.*, and the like) should be very limited, if not prohibited.
253
254 === FILE HEADERS ===
255
256 License/description header first:
257
258 //-----------------------------------------------------------------------------
259 // YOUR COPYRIGHT LINE GOES HERE
260 //
261 // This code is licensed to you under the terms of the GNU GPL, version 2 or,
262 // at your option, any later version. See the LICENSE.txt file for the text of
263 // the license.
264 //-----------------------------------------------------------------------------
265 // FILE DESCRIPTION GOES HERE
266 //-----------------------------------------------------------------------------
267
268 If you modify a file in any non-trivial way (add code, etc.), add your copyright
269 to the top.
270
271 === HEADER FILES ===
272
273 Use the following include guard format:
274
275 #ifndef FOOBAR_H__
276 #define FOOBAR_H__
277
278 ...
279
280 #endif // FOOBAR_H__
281
282 Keep in mind that __FOOBAR_H would be reserved by the implementation and thus
283 you shouldn't use it (same for _FOOBAR_H).
284
285 === WHITESPACE ===
286
287 Avoid trailing whitespace (no line should end in tab or space). People forget
288 this all the time if their editor doesn't handle it, but don't be surprised if
289 you see someone fixing it from time to time.
290
291 Keep a newline (blank line) at the end of each file.
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