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1 | .\" -*-nroff-*- |
2 | .de VS |
3 | .sp 1 |
4 | .RS |
5 | .nf |
6 | .ft B |
7 | .. |
8 | .de VE |
9 | .ft R |
10 | .fi |
11 | .RE |
12 | .sp 1 |
13 | .. |
14 | .de hP |
15 | .IP |
16 | .ft B |
17 | \h'-\w'\\$1\ 'u'\\$1\ \c |
18 | .ft P |
19 | .. |
20 | .ie t .ds o \(bu |
21 | .el .ds o o |
22 | .TH buf 3 "23 September 2005" "Straylight/Edgeware" "mLib utilities library" |
23 | .SH NAME |
24 | buf \- reading and writing stuff in buffers |
25 | .\" @BBASE |
26 | .\" @BLIM |
27 | .\" @BCUR |
28 | .\" @BSZ |
29 | .\" @BLEN |
30 | .\" @BLEFT |
31 | .\" @BSTEP |
32 | .\" @BBAD |
33 | .\" @BOK |
34 | .\" @BENSURE |
35 | . |
36 | .\" @buf_init |
37 | .\" @buf_break |
38 | .\" @buf_flip |
39 | .\" @buf_ensure |
40 | .\" @buf_get |
41 | .\" @buf_put |
42 | . |
43 | .\" @buf_getbyte |
44 | .\" @buf_putbyte |
45 | . |
46 | .\" @buf_getu8 |
47 | .\" @buf_getu16 |
48 | .\" @buf_getu16b |
49 | .\" @buf_getu16l |
50 | .\" @buf_getu24 |
51 | .\" @buf_getu24b |
52 | .\" @buf_getu24l |
53 | .\" @buf_getu32 |
54 | .\" @buf_getu32b |
55 | .\" @buf_getu32l |
56 | . |
57 | .\" @buf_putu8 |
58 | .\" @buf_putu16 |
59 | .\" @buf_putu16b |
60 | .\" @buf_putu16l |
61 | .\" @buf_putu24 |
62 | .\" @buf_putu24b |
63 | .\" @buf_putu24l |
64 | .\" @buf_putu32 |
65 | .\" @buf_putu32b |
66 | .\" @buf_putu32l |
67 | . |
68 | .\" @buf_getbuf8 |
69 | .\" @buf_getbuf16 |
70 | .\" @buf_getbuf16b |
71 | .\" @buf_getbuf16l |
72 | .\" @buf_getbuf24 |
73 | .\" @buf_getbuf24b |
74 | .\" @buf_getbuf24l |
75 | .\" @buf_getbuf32 |
76 | .\" @buf_getbuf32b |
77 | .\" @buf_getbuf32l |
78 | .\" @buf_getbufz |
79 | . |
80 | .\" @buf_putbuf8 |
81 | .\" @buf_putbuf16 |
82 | .\" @buf_putbuf16b |
83 | .\" @buf_putbuf16l |
84 | .\" @buf_putbuf24 |
85 | .\" @buf_putbuf24b |
86 | .\" @buf_putbuf24l |
87 | .\" @buf_putbuf32 |
88 | .\" @buf_putbuf32b |
89 | .\" @buf_putbuf32l |
90 | .\" @buf_putbufz |
91 | . |
92 | .\" @buf_getmem16 |
93 | .\" @buf_getmem16b |
94 | .\" @buf_getmem16l |
95 | .\" @buf_getmem24 |
96 | .\" @buf_getmem24b |
97 | .\" @buf_getmem24l |
98 | .\" @buf_getmem32 |
99 | .\" @buf_getmem32b |
100 | .\" @buf_getmem32l |
101 | .\" @buf_getmem8 |
102 | .\" @buf_getmemz |
103 | . |
104 | .\" @buf_putmem8 |
105 | .\" @buf_putmem16 |
106 | .\" @buf_putmem16b |
107 | .\" @buf_putmem16l |
108 | .\" @buf_putmem24 |
109 | .\" @buf_putmem24b |
110 | .\" @buf_putmem24l |
111 | .\" @buf_putmem32 |
112 | .\" @buf_putmem32b |
113 | .\" @buf_putmem32l |
114 | .\" @buf_putmemz |
115 | . |
116 | .\" @buf_putstr8 |
117 | .\" @buf_putstr16 |
118 | .\" @buf_putstr16b |
119 | .\" @buf_putstr16l |
120 | .\" @buf_putstr24 |
121 | .\" @buf_putstr24b |
122 | .\" @buf_putstr24l |
123 | .\" @buf_putstr32 |
124 | .\" @buf_putstr32b |
125 | .\" @buf_putstr32l |
126 | .\" @buf_putstrz |
127 | . |
128 | .\" @buf_getdstr8 |
129 | .\" @buf_getdstr16 |
130 | .\" @buf_getdstr16b |
131 | .\" @buf_getdstr16l |
132 | .\" @buf_getdstr24 |
133 | .\" @buf_getdstr24b |
134 | .\" @buf_getdstr24l |
135 | .\" @buf_getdstr32 |
136 | .\" @buf_getdstr32b |
137 | .\" @buf_getdstr32l |
138 | .\" @buf_getdstrz |
139 | . |
140 | .\" @buf_putdstr8 |
141 | .\" @buf_putdstr16 |
142 | .\" @buf_putdstr16b |
143 | .\" @buf_putdstr16l |
144 | .\" @buf_putdstr24 |
145 | .\" @buf_putdstr24b |
146 | .\" @buf_putdstr24l |
147 | .\" @buf_putdstr32 |
148 | .\" @buf_putdstr32b |
149 | .\" @buf_putdstr32l |
150 | .\" @buf_putdstrz |
151 | .SH SYNOPSIS |
152 | .nf |
153 | .B "#include <mLib/dstr.h>" |
154 | |
155 | .BI "void buf_init(buf *" b ", void *" p ", size_t " sz ); |
156 | .BI "void buf_flip(buf *" b ); |
157 | .BI "octet *BBASE(buf *" b ); |
158 | .BI "octet *BLIM(buf *" b ); |
159 | .BI "octet *BCUR(buf *" b ); |
160 | .BI "ptrdiff_t BSZ(buf *" b ); |
161 | .BI "ptrdiff_t BLEN(buf *" b ); |
162 | .BI "ptrdiff_t BLEFT(buf *" b ); |
163 | |
164 | .BI "int buf_break(buf *" b ); |
165 | .BI "int BBAD(buf *" b ); |
166 | .BI "int BOK(buf *" b ); |
167 | |
168 | .BI "int buf_ensure(buf *" b ", size_t " sz ); |
169 | .BI "int BENSURE(buf *" b ", size_t " sz ); |
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170 | .BI "octet *BSTEP(buf *" b ", size_t " sz ); |
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171 | |
172 | .BI "void *buf_get(buf *" b ", size_t " sz ); |
173 | .BI "void *buf_put(buf *" b ", const void *" p ", size_t " sz ); |
174 | |
175 | .BI "int buf_getbyte(buf *" b ); |
176 | .BI "int buf_putbyte(buf *" b ", int ch" ); |
177 | .BI "int buf_getu" suff "(buf *" b ", uint" suff " *" w ); |
178 | .BI "int buf_putu" suff "(buf *" b ", uint" suff " " w ); |
179 | .BI "void *buf_getmem" suff "(buf *" b ", size_t *" sz ); |
180 | .BI "int buf_putmem" suff "(buf *" b ", const void *" p ", size_t " sz ); |
181 | .BI "int buf_getbuf" suff "(buf *" b ", buf *" bb ); |
182 | .BI "int buf_putbuf" suff "(buf *" b ", buf *" bb ); |
183 | .BI "int buf_getdstr" suff "(buf *" b ", dstr *" d ); |
184 | .BI "int buf_putdstr" suff "(buf *" b ", dstr *" d ); |
185 | .BI "int buf_putstr" suff "(buf *" b ", const char *" p ); |
186 | .fi |
187 | .SH DESCRIPTION |
188 | The |
189 | .B buf |
190 | interface allows relatively convenient reading and writing of structured |
191 | binary data from and to fixed-size memory buffers. It's useful for |
192 | formatting and parsing down network data packets, for example. |
193 | .SS "Buffer basics" |
194 | A buffer has three important pointers associated with it: |
195 | .TP |
196 | .I base |
197 | The base address of the buffer. |
198 | .TP |
199 | .I limit |
200 | Just past the last usable byte in the buffer |
201 | .TP |
202 | .I current |
203 | The position in the buffer at which the next read or write will occur. |
204 | .PP |
205 | A buffer is created using the |
206 | .B buf_init |
207 | function. You must pass it the buffer base address and size, and a |
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208 | pointer to a |
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209 | .B buf |
210 | structure to fill in. It doesn't allocate any memory, so you don't need |
211 | to dispose of the |
212 | .B buf |
213 | structure in any way before forgetting about it. |
214 | .PP |
215 | A collection of macros is provided for finding the positions of the |
216 | various interesting pointers known about a buffer, and the sizes of the |
217 | regions of memory they imply. |
218 | .TP |
219 | .B BBASE |
220 | The buffer's |
221 | .I base |
222 | pointer. |
223 | .TP |
224 | .B BLIM |
225 | The buffer's |
226 | .I limit |
227 | pointer. |
228 | .TP |
229 | .B BCUR |
230 | The buffer's |
231 | .I current |
232 | pointer. |
233 | .TP |
234 | .B BSZ |
235 | The size of the buffer; i.e., |
236 | .I limit |
237 | \- |
238 | .IR base . |
239 | .TP |
240 | .B BLEN |
241 | The length of data in the buffer (if writing) or the amount of data |
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242 | read (if reading); i.e., |
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243 | .I current |
244 | \- |
245 | .IR base . |
246 | .TP |
247 | .B BLEFT |
248 | The amount of space left in the buffer (if writing) or the amount of |
249 | data yet to read (if reading); i.e., |
250 | .I limit |
251 | \- |
252 | .IR current . |
253 | .PP |
254 | The function |
255 | .B buf_flip |
256 | takes a buffer which has been used for writing, and makes it suitable |
257 | for reading. This turns out to be useful when building packets in |
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258 | multi-layered networking software. Its precise behaviour is to preserve |
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259 | .IR base , |
260 | to set |
261 | .I limit |
262 | to |
263 | .IR current , |
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264 | and to set |
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265 | .I current |
266 | to |
267 | .IR base . |
268 | .PP |
269 | A buffer can be |
270 | .IR broken , |
271 | to indicate that it has overflowed or that its contents are otherwise |
272 | invalid. The various buffer access functions described below all fail |
273 | on a broken buffer, and any errors they encounter cause the buffer to |
274 | become broken. Most simple programs which only use the supplied buffer |
275 | access functions can avoid the tedium of error-checking every function |
276 | call and just check the brokenness state at the end of their run. |
277 | .PP |
278 | The function |
279 | .B buf_break |
280 | will break a buffer. The macro |
281 | .B BBAD |
282 | reports true (nonzero) if its buffer argument is broken, or false (zero) |
283 | otherwise; its counterpart |
284 | .B BOK |
285 | reports true if the buffer is OK, and false if it is broken. |
286 | .SS "Low-level buffer access" |
287 | Access to the data in the buffer is usually sequential. The |
288 | .B BENSURE |
289 | macro (or the equivalent |
290 | .B buf_ensure |
291 | function) checks that the buffer is OK and that there is enough space |
292 | remaining in the buffer for |
293 | .I sz |
294 | bytes: if so, it returns zero; otherwise it breaks the buffer and |
295 | returns \-1. |
296 | .PP |
297 | The |
298 | .B BSTEP |
299 | macro advances the buffer's |
300 | .I current |
301 | pointer by |
302 | .I sz |
303 | bytes. It does no bounds checking. Together with |
304 | .BR BENSURE , |
305 | this provides sequential access to the buffer's contents. |
306 | .PP |
307 | The |
308 | .B buf_get |
309 | function is the basis of most buffer access functions, whether for |
310 | reading or writing. If the buffer is OK, and there are |
311 | .I sz |
312 | or more bytes remaining, it steps the buffer's |
313 | .I current |
314 | pointer by |
315 | .I sz |
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316 | and returns the |
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317 | .I original |
318 | (pre-stepping) |
319 | .I current |
320 | pointer; otherwise it breaks the buffer if necessary, and returns a null |
321 | pointer. |
322 | .PP |
323 | The |
324 | .B buf_put |
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325 | function writes |
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326 | .I sz |
327 | bytes of data starting at |
328 | .I p |
329 | to the buffer. If it succeeded, it returns 0; otherwise it returns \-1. |
330 | .SS "Formatted buffer access" |
331 | The function |
332 | .B buf_getbyte |
333 | returns the next byte from a buffer as a nonnegative integer, or \-1 on |
334 | error. The function |
335 | .B buf_putbyte |
336 | writes its argument to a buffer, and returns 0 on succes; it returns \-1 |
337 | if it failed. |
338 | .PP |
339 | Many of the remaining functions deal with integer formatting and buffer |
340 | lengths. The functions support 8-, 16-, 24- and 32-bit integers, in |
341 | big- or little-endian order; on platforms with 64-bit integers, these |
342 | are supported too. The functions' names carry a suffix which is the |
343 | width in bits of the integers they deal with and an optional |
344 | .RB ` l ' |
345 | for little- or |
346 | .RB ` b ' |
347 | for big-endian byte order. (The variant with no letter uses big-endian |
348 | order. Use of these variants tends to mean `I don't really care, but be |
349 | consistent,' and is not recommended if you have an externally-defined |
350 | spec you're meant to be compatible with.) |
351 | .PP |
352 | The function |
353 | .BI buf_getu suff |
354 | reads an integer. On success, it stores the integer it read at the |
355 | address |
356 | .I w |
357 | given, and returns zero; on failure, it returns \-1. The function |
358 | .BI buf_putu suff |
359 | write an integer. It returns zero on success or \-1 on failure. |
360 | .PP |
361 | Functions which deal with block lengths assume the length is prefixed to |
362 | the data, and don't include themselves. They also have an additional |
363 | .RB ` z ' |
364 | variant, which deals with zero-terminated data. No checks are done on |
365 | writing that the data written contains no zero bytes. |
366 | .PP |
367 | The function |
368 | .BI buf_getmem suff |
369 | fetches a block of data. On success, it returns its base address and |
370 | stores its length at the given address; on failure, it returns null. |
371 | The function |
372 | .BI buf_putmem suff |
373 | writes a block of data; it return zero on success or \-1 on failure. |
374 | .PP |
375 | The functon |
376 | .BI buf_getbuf suff |
377 | fetches a block of data and makes a second buffer point to it, i.e., |
378 | setting its |
379 | .I base |
380 | and |
381 | .I current |
382 | pointers to the start of the block and its |
383 | .I limit |
384 | pointer to just past the end. No copying of bulk data is performed. |
385 | The function |
386 | .BI buf_putbuf suff |
387 | writes the contents of a buffer (i.e., between its |
388 | .I base |
389 | and |
390 | .I current |
391 | pointers). The function |
392 | .BI buf_getdstr suff |
393 | fetches a block of data and append it to a dynamic string (see |
394 | .BR dstr (3)). |
395 | The function |
396 | .BI buf_putdstr suff |
397 | writes the contents of a dynamic string to a buffer. Finally, the |
398 | function |
399 | .BI buf_putstr suff |
400 | writes a standard C null-terminated string to a buffer. All these |
401 | functions return zero on success or \-1 on failure. |
402 | .SH "SEE ALSO" |
403 | .BR dstr (3), |
404 | .BR mLib (3). |
405 | .SH AUTHOR |
406 | Mark Wooding, <mdw@distorted.org.uk> |