| 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 ); |
| 170 | .BI "octet *BSTEP(buf *" b ", size_t " sz ); |
| 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 |
| 208 | pointer to a |
| 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 |
| 242 | read (if reading); i.e., |
| 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 |
| 258 | multi-layered networking software. Its precise behaviour is to preserve |
| 259 | .IR base , |
| 260 | to set |
| 261 | .I limit |
| 262 | to |
| 263 | .IR current , |
| 264 | and to set |
| 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 |
| 316 | and returns the |
| 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 |
| 325 | function writes |
| 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> |