1 /*
2 * Copyright © 2014 Intel Corporation
3 *
4 * Permission is hereby granted, free of charge, to any person obtaining a
5 * copy of this software and associated documentation files (the "Software"),
6 * to deal in the Software without restriction, including without limitation
7 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
8 * and/or sell copies of the Software, and to permit persons to whom the
9 * Software is furnished to do so, subject to the following conditions:
10 *
11 * The above copyright notice and this permission notice (including the next
12 * paragraph) shall be included in all copies or substantial portions of the
13 * Software.
14 *
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
18 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
20 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
21 * IN THE SOFTWARE.
22 */
23
24 #ifndef BLOB_H
25 #define BLOB_H
26
27 #include <stdbool.h>
28 #include <stddef.h>
29 #include <stdint.h>
30 #include <stdlib.h>
31
32 #ifdef __cplusplus
33 extern "C" {
34 #endif
35
36 /* The blob functions implement a simple, low-level API for serializing and
37 * deserializing.
38 *
39 * All objects written to a blob will be serialized directly, (without any
40 * additional meta-data to describe the data written). Therefore, it is the
41 * caller's responsibility to ensure that any data can be read later, (either
42 * by knowing exactly what data is expected, or by writing to the blob
43 * sufficient meta-data to describe what has been written).
44 *
45 * A blob is efficient in that it dynamically grows by doubling in size, so
46 * allocation costs are logarithmic.
47 */
48
49 struct blob {
50 /* The data actually written to the blob. Never read or write this directly
51 * when serializing, use blob_reserve_* and blob_overwrite_* instead which
52 * check for out_of_memory and handle fixed-size blobs correctly.
53 */
54 uint8_t *data;
55
56 /** Number of bytes that have been allocated for \c data. */
57 size_t allocated;
58
59 /** The number of bytes that have actual data written to them. */
60 size_t size;
61
62 /** True if \c data a fixed allocation that we cannot resize
63 *
64 * \see blob_init_fixed
65 */
66 bool fixed_allocation;
67
68 /**
69 * True if we've ever failed to realloc or if we go pas the end of a fixed
70 * allocation blob.
71 */
72 bool out_of_memory;
73 };
74
75 /* When done reading, the caller can ensure that everything was consumed by
76 * checking the following:
77 *
78 * 1. blob->current should be equal to blob->end, (if not, too little was
79 * read).
80 *
81 * 2. blob->overrun should be false, (otherwise, too much was read).
82 */
83 struct blob_reader {
84 const uint8_t *data;
85 const uint8_t *end;
86 const uint8_t *current;
87 bool overrun;
88 };
89
90 /**
91 * Init a new, empty blob.
92 */
93 void
94 blob_init(struct blob *blob);
95
96 /**
97 * Init a new, fixed-size blob.
98 *
99 * A fixed-size blob has a fixed block of data that will not be freed on
100 * blob_finish and will never be grown. If we hit the end, we simply start
101 * returning false from the write functions.
102 *
103 * If a fixed-size blob has a NULL data pointer then the data is written but
104 * it otherwise operates normally. This can be used to determine the size
105 * that will be required to write a given data structure.
106 */
107 void
108 blob_init_fixed(struct blob *blob, void *data, size_t size);
109
110 /**
111 * Finish a blob and free its memory.
112 *
113 * If \blob was initialized with blob_init_fixed, the data pointer is
114 * considered to be owned by the user and will not be freed.
115 */
116 static inline void
blob_finish(struct blob * blob)117 blob_finish(struct blob *blob)
118 {
119 if (!blob->fixed_allocation)
120 free(blob->data);
121 }
122
123 void
124 blob_finish_get_buffer(struct blob *blob, void **buffer, size_t *size);
125
126 /**
127 * Aligns the blob to the given alignment.
128 *
129 * \see blob_reader_align
130 *
131 * \return True unless allocation fails
132 */
133 bool
134 blob_align(struct blob *blob, size_t alignment);
135
136 /**
137 * Add some unstructured, fixed-size data to a blob.
138 *
139 * \return True unless allocation failed.
140 */
141 bool
142 blob_write_bytes(struct blob *blob, const void *bytes, size_t to_write);
143
144 /**
145 * Reserve space in \blob for a number of bytes.
146 *
147 * Space will be allocated within the blob for these byes, but the bytes will
148 * be left uninitialized. The caller is expected to use \sa
149 * blob_overwrite_bytes to write to these bytes.
150 *
151 * \return An offset to space allocated within \blob to which \to_write bytes
152 * can be written, (or -1 in case of any allocation error).
153 */
154 intptr_t
155 blob_reserve_bytes(struct blob *blob, size_t to_write);
156
157 /**
158 * Similar to \sa blob_reserve_bytes, but only reserves an uint32_t worth of
159 * space. Note that this must be used if later reading with \sa
160 * blob_read_uint32, since it aligns the offset correctly.
161 */
162 intptr_t
163 blob_reserve_uint32(struct blob *blob);
164
165 /**
166 * Similar to \sa blob_reserve_bytes, but only reserves an intptr_t worth of
167 * space. Note that this must be used if later reading with \sa
168 * blob_read_intptr, since it aligns the offset correctly.
169 */
170 intptr_t
171 blob_reserve_intptr(struct blob *blob);
172
173 /**
174 * Overwrite some data previously written to the blob.
175 *
176 * Writes data to an existing portion of the blob at an offset of \offset.
177 * This data range must have previously been written to the blob by one of the
178 * blob_write_* calls.
179 *
180 * For example usage, see blob_overwrite_uint32
181 *
182 * \return True unless the requested offset or offset+to_write lie outside
183 * the current blob's size.
184 */
185 bool
186 blob_overwrite_bytes(struct blob *blob,
187 size_t offset,
188 const void *bytes,
189 size_t to_write);
190
191 /**
192 * Add a uint8_t to a blob.
193 *
194 * \return True unless allocation failed.
195 */
196 bool
197 blob_write_uint8(struct blob *blob, uint8_t value);
198
199 /**
200 * Overwrite a uint8_t previously written to the blob.
201 *
202 * Writes a uint8_t value to an existing portion of the blob at an offset of
203 * \offset. This data range must have previously been written to the blob by
204 * one of the blob_write_* calls.
205 *
206 * \return True unless the requested position or position+to_write lie outside
207 * the current blob's size.
208 */
209 bool
210 blob_overwrite_uint8(struct blob *blob,
211 size_t offset,
212 uint8_t value);
213
214 /**
215 * Add a uint16_t to a blob.
216 *
217 * \note This function will only write to a uint16_t-aligned offset from the
218 * beginning of the blob's data, so some padding bytes may be added to the
219 * blob if this write follows some unaligned write (such as
220 * blob_write_string).
221 *
222 * \return True unless allocation failed.
223 */
224 bool
225 blob_write_uint16(struct blob *blob, uint16_t value);
226
227 /**
228 * Add a uint32_t to a blob.
229 *
230 * \note This function will only write to a uint32_t-aligned offset from the
231 * beginning of the blob's data, so some padding bytes may be added to the
232 * blob if this write follows some unaligned write (such as
233 * blob_write_string).
234 *
235 * \return True unless allocation failed.
236 */
237 bool
238 blob_write_uint32(struct blob *blob, uint32_t value);
239
240 /**
241 * Overwrite a uint32_t previously written to the blob.
242 *
243 * Writes a uint32_t value to an existing portion of the blob at an offset of
244 * \offset. This data range must have previously been written to the blob by
245 * one of the blob_write_* calls.
246 *
247 *
248 * The expected usage is something like the following pattern:
249 *
250 * size_t offset;
251 *
252 * offset = blob_reserve_uint32(blob);
253 * ... various blob write calls, writing N items ...
254 * blob_overwrite_uint32 (blob, offset, N);
255 *
256 * \return True unless the requested position or position+to_write lie outside
257 * the current blob's size.
258 */
259 bool
260 blob_overwrite_uint32(struct blob *blob,
261 size_t offset,
262 uint32_t value);
263
264 /**
265 * Add a uint64_t to a blob.
266 *
267 * \note This function will only write to a uint64_t-aligned offset from the
268 * beginning of the blob's data, so some padding bytes may be added to the
269 * blob if this write follows some unaligned write (such as
270 * blob_write_string).
271 *
272 * \return True unless allocation failed.
273 */
274 bool
275 blob_write_uint64(struct blob *blob, uint64_t value);
276
277 /**
278 * Add an intptr_t to a blob.
279 *
280 * \note This function will only write to an intptr_t-aligned offset from the
281 * beginning of the blob's data, so some padding bytes may be added to the
282 * blob if this write follows some unaligned write (such as
283 * blob_write_string).
284 *
285 * \return True unless allocation failed.
286 */
287 bool
288 blob_write_intptr(struct blob *blob, intptr_t value);
289
290 /**
291 * Overwrite an intptr_t previously written to the blob.
292 *
293 * Writes a intptr_t value to an existing portion of the blob at an offset of
294 * \offset. This data range must have previously been written to the blob by
295 * one of the blob_write_* calls.
296 *
297 * For example usage, see blob_overwrite_uint32
298 *
299 * \return True unless the requested position or position+to_write lie outside
300 * the current blob's size.
301 */
302 bool
303 blob_overwrite_intptr(struct blob *blob,
304 size_t offset,
305 intptr_t value);
306
307 /**
308 * Add a NULL-terminated string to a blob, (including the NULL terminator).
309 *
310 * \return True unless allocation failed.
311 */
312 bool
313 blob_write_string(struct blob *blob, const char *str);
314
315 /**
316 * Start reading a blob, (initializing the contents of \blob for reading).
317 *
318 * After this call, the caller can use the various blob_read_* functions to
319 * read elements from the data array.
320 *
321 * For all of the blob_read_* functions, if there is insufficient data
322 * remaining, the functions will do nothing, (perhaps returning default values
323 * such as 0). The caller can detect this by noting that the blob_reader's
324 * current value is unchanged before and after the call.
325 */
326 void
327 blob_reader_init(struct blob_reader *blob, const void *data, size_t size);
328
329 /**
330 * Align the current offset of the blob reader to the given alignment.
331 *
332 * This may be useful if you need the result of blob_read_bytes to have a
333 * particular alignment. Note that this only aligns relative to blob->data
334 * and the alignment of the resulting pointer is only guaranteed if blob->data
335 * is also aligned to the requested alignment.
336 */
337 void
338 blob_reader_align(struct blob_reader *blob, size_t alignment);
339
340 /**
341 * Read some unstructured, fixed-size data from the current location, (and
342 * update the current location to just past this data).
343 *
344 * \note The memory returned belongs to the data underlying the blob reader. The
345 * caller must copy the data in order to use it after the lifetime of the data
346 * underlying the blob reader.
347 *
348 * \return The bytes read (see note above about memory lifetime).
349 */
350 const void *
351 blob_read_bytes(struct blob_reader *blob, size_t size);
352
353 /**
354 * Read some unstructured, fixed-size data from the current location, copying
355 * it to \dest (and update the current location to just past this data)
356 */
357 void
358 blob_copy_bytes(struct blob_reader *blob, void *dest, size_t size);
359
360 /**
361 * Skip \size bytes within the blob.
362 */
363 void
364 blob_skip_bytes(struct blob_reader *blob, size_t size);
365
366 /**
367 * Read a uint8_t from the current location, (and update the current location
368 * to just past this uint8_t).
369 *
370 * \return The uint8_t read
371 */
372 uint8_t
373 blob_read_uint8(struct blob_reader *blob);
374
375 /**
376 * Read a uint16_t from the current location, (and update the current location
377 * to just past this uint16_t).
378 *
379 * \note This function will only read from a uint16_t-aligned offset from the
380 * beginning of the blob's data, so some padding bytes may be skipped.
381 *
382 * \return The uint16_t read
383 */
384 uint16_t
385 blob_read_uint16(struct blob_reader *blob);
386
387 /**
388 * Read a uint32_t from the current location, (and update the current location
389 * to just past this uint32_t).
390 *
391 * \note This function will only read from a uint32_t-aligned offset from the
392 * beginning of the blob's data, so some padding bytes may be skipped.
393 *
394 * \return The uint32_t read
395 */
396 uint32_t
397 blob_read_uint32(struct blob_reader *blob);
398
399 /**
400 * Read a uint64_t from the current location, (and update the current location
401 * to just past this uint64_t).
402 *
403 * \note This function will only read from a uint64_t-aligned offset from the
404 * beginning of the blob's data, so some padding bytes may be skipped.
405 *
406 * \return The uint64_t read
407 */
408 uint64_t
409 blob_read_uint64(struct blob_reader *blob);
410
411 /**
412 * Read an intptr_t value from the current location, (and update the
413 * current location to just past this intptr_t).
414 *
415 * \note This function will only read from an intptr_t-aligned offset from the
416 * beginning of the blob's data, so some padding bytes may be skipped.
417 *
418 * \return The intptr_t read
419 */
420 intptr_t
421 blob_read_intptr(struct blob_reader *blob);
422
423 /**
424 * Read a NULL-terminated string from the current location, (and update the
425 * current location to just past this string).
426 *
427 * \note The memory returned belongs to the data underlying the blob reader. The
428 * caller must copy the string in order to use the string after the lifetime
429 * of the data underlying the blob reader.
430 *
431 * \return The string read (see note above about memory lifetime). However, if
432 * there is no NULL byte remaining within the blob, this function returns
433 * NULL.
434 */
435 char *
436 blob_read_string(struct blob_reader *blob);
437
438 #ifdef __cplusplus
439 }
440 #endif
441
442 #endif /* BLOB_H */
443