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. */
51 uint8_t *data;
52
53 /** Number of bytes that have been allocated for \c data. */
54 size_t allocated;
55
56 /** The number of bytes that have actual data written to them. */
57 size_t size;
58
59 /** True if \c data a fixed allocation that we cannot resize
60 *
61 * \see blob_init_fixed
62 */
63 bool fixed_allocation;
64
65 /**
66 * True if we've ever failed to realloc or if we go pas the end of a fixed
67 * allocation blob.
68 */
69 bool out_of_memory;
70 };
71
72 /* When done reading, the caller can ensure that everything was consumed by
73 * checking the following:
74 *
75 * 1. blob->current should be equal to blob->end, (if not, too little was
76 * read).
77 *
78 * 2. blob->overrun should be false, (otherwise, too much was read).
79 */
80 struct blob_reader {
81 const uint8_t *data;
82 const uint8_t *end;
83 const uint8_t *current;
84 bool overrun;
85 };
86
87 /**
88 * Init a new, empty blob.
89 */
90 void
91 blob_init(struct blob *blob);
92
93 /**
94 * Init a new, fixed-size blob.
95 *
96 * A fixed-size blob has a fixed block of data that will not be freed on
97 * blob_finish and will never be grown. If we hit the end, we simply start
98 * returning false from the write functions.
99 *
100 * If a fixed-size blob has a NULL data pointer then the data is written but
101 * it otherwise operates normally. This can be used to determine the size
102 * that will be required to write a given data structure.
103 */
104 void
105 blob_init_fixed(struct blob *blob, void *data, size_t size);
106
107 /**
108 * Finish a blob and free its memory.
109 *
110 * If \blob was initialized with blob_init_fixed, the data pointer is
111 * considered to be owned by the user and will not be freed.
112 */
113 static inline void
blob_finish(struct blob * blob)114 blob_finish(struct blob *blob)
115 {
116 if (!blob->fixed_allocation)
117 free(blob->data);
118 }
119
120 /**
121 * Add some unstructured, fixed-size data to a blob.
122 *
123 * \return True unless allocation failed.
124 */
125 bool
126 blob_write_bytes(struct blob *blob, const void *bytes, size_t to_write);
127
128 /**
129 * Reserve space in \blob for a number of bytes.
130 *
131 * Space will be allocated within the blob for these byes, but the bytes will
132 * be left uninitialized. The caller is expected to use \sa
133 * blob_overwrite_bytes to write to these bytes.
134 *
135 * \return An offset to space allocated within \blob to which \to_write bytes
136 * can be written, (or -1 in case of any allocation error).
137 */
138 intptr_t
139 blob_reserve_bytes(struct blob *blob, size_t to_write);
140
141 /**
142 * Similar to \sa blob_reserve_bytes, but only reserves an uint32_t worth of
143 * space. Note that this must be used if later reading with \sa
144 * blob_read_uint32, since it aligns the offset correctly.
145 */
146 intptr_t
147 blob_reserve_uint32(struct blob *blob);
148
149 /**
150 * Similar to \sa blob_reserve_bytes, but only reserves an intptr_t worth of
151 * space. Note that this must be used if later reading with \sa
152 * blob_read_intptr, since it aligns the offset correctly.
153 */
154 intptr_t
155 blob_reserve_intptr(struct blob *blob);
156
157 /**
158 * Overwrite some data previously written to the blob.
159 *
160 * Writes data to an existing portion of the blob at an offset of \offset.
161 * This data range must have previously been written to the blob by one of the
162 * blob_write_* calls.
163 *
164 * For example usage, see blob_overwrite_uint32
165 *
166 * \return True unless the requested offset or offset+to_write lie outside
167 * the current blob's size.
168 */
169 bool
170 blob_overwrite_bytes(struct blob *blob,
171 size_t offset,
172 const void *bytes,
173 size_t to_write);
174
175 /**
176 * Add a uint32_t to a blob.
177 *
178 * \note This function will only write to a uint32_t-aligned offset from the
179 * beginning of the blob's data, so some padding bytes may be added to the
180 * blob if this write follows some unaligned write (such as
181 * blob_write_string).
182 *
183 * \return True unless allocation failed.
184 */
185 bool
186 blob_write_uint32(struct blob *blob, uint32_t value);
187
188 /**
189 * Overwrite a uint32_t previously written to the blob.
190 *
191 * Writes a uint32_t value to an existing portion of the blob at an offset of
192 * \offset. This data range must have previously been written to the blob by
193 * one of the blob_write_* calls.
194 *
195 *
196 * The expected usage is something like the following pattern:
197 *
198 * size_t offset;
199 *
200 * offset = blob_reserve_uint32(blob);
201 * ... various blob write calls, writing N items ...
202 * blob_overwrite_uint32 (blob, offset, N);
203 *
204 * \return True unless the requested position or position+to_write lie outside
205 * the current blob's size.
206 */
207 bool
208 blob_overwrite_uint32(struct blob *blob,
209 size_t offset,
210 uint32_t value);
211
212 /**
213 * Add a uint64_t to a blob.
214 *
215 * \note This function will only write to a uint64_t-aligned offset from the
216 * beginning of the blob's data, so some padding bytes may be added to the
217 * blob if this write follows some unaligned write (such as
218 * blob_write_string).
219 *
220 * \return True unless allocation failed.
221 */
222 bool
223 blob_write_uint64(struct blob *blob, uint64_t value);
224
225 /**
226 * Add an intptr_t to a blob.
227 *
228 * \note This function will only write to an intptr_t-aligned offset from the
229 * beginning of the blob's data, so some padding bytes may be added to the
230 * blob if this write follows some unaligned write (such as
231 * blob_write_string).
232 *
233 * \return True unless allocation failed.
234 */
235 bool
236 blob_write_intptr(struct blob *blob, intptr_t value);
237
238 /**
239 * Overwrite an intptr_t previously written to the blob.
240 *
241 * Writes a intptr_t value to an existing portion of the blob at an offset of
242 * \offset. This data range must have previously been written to the blob by
243 * one of the blob_write_* calls.
244 *
245 * For example usage, see blob_overwrite_uint32
246 *
247 * \return True unless the requested position or position+to_write lie outside
248 * the current blob's size.
249 */
250 bool
251 blob_overwrite_intptr(struct blob *blob,
252 size_t offset,
253 intptr_t value);
254
255 /**
256 * Add a NULL-terminated string to a blob, (including the NULL terminator).
257 *
258 * \return True unless allocation failed.
259 */
260 bool
261 blob_write_string(struct blob *blob, const char *str);
262
263 /**
264 * Start reading a blob, (initializing the contents of \blob for reading).
265 *
266 * After this call, the caller can use the various blob_read_* functions to
267 * read elements from the data array.
268 *
269 * For all of the blob_read_* functions, if there is insufficient data
270 * remaining, the functions will do nothing, (perhaps returning default values
271 * such as 0). The caller can detect this by noting that the blob_reader's
272 * current value is unchanged before and after the call.
273 */
274 void
275 blob_reader_init(struct blob_reader *blob, const void *data, size_t size);
276
277 /**
278 * Read some unstructured, fixed-size data from the current location, (and
279 * update the current location to just past this data).
280 *
281 * \note The memory returned belongs to the data underlying the blob reader. The
282 * caller must copy the data in order to use it after the lifetime of the data
283 * underlying the blob reader.
284 *
285 * \return The bytes read (see note above about memory lifetime).
286 */
287 const void *
288 blob_read_bytes(struct blob_reader *blob, size_t size);
289
290 /**
291 * Read some unstructured, fixed-size data from the current location, copying
292 * it to \dest (and update the current location to just past this data)
293 */
294 void
295 blob_copy_bytes(struct blob_reader *blob, void *dest, size_t size);
296
297 /**
298 * Read a uint32_t from the current location, (and update the current location
299 * to just past this uint32_t).
300 *
301 * \note This function will only read from a uint32_t-aligned offset from the
302 * beginning of the blob's data, so some padding bytes may be skipped.
303 *
304 * \return The uint32_t read
305 */
306 uint32_t
307 blob_read_uint32(struct blob_reader *blob);
308
309 /**
310 * Read a uint64_t from the current location, (and update the current location
311 * to just past this uint64_t).
312 *
313 * \note This function will only read from a uint64_t-aligned offset from the
314 * beginning of the blob's data, so some padding bytes may be skipped.
315 *
316 * \return The uint64_t read
317 */
318 uint64_t
319 blob_read_uint64(struct blob_reader *blob);
320
321 /**
322 * Read an intptr_t value from the current location, (and update the
323 * current location to just past this intptr_t).
324 *
325 * \note This function will only read from an intptr_t-aligned offset from the
326 * beginning of the blob's data, so some padding bytes may be skipped.
327 *
328 * \return The intptr_t read
329 */
330 intptr_t
331 blob_read_intptr(struct blob_reader *blob);
332
333 /**
334 * Read a NULL-terminated string from the current location, (and update the
335 * current location to just past this string).
336 *
337 * \note The memory returned belongs to the data underlying the blob reader. The
338 * caller must copy the string in order to use the string after the lifetime
339 * of the data underlying the blob reader.
340 *
341 * \return The string read (see note above about memory lifetime). However, if
342 * there is no NULL byte remaining within the blob, this function returns
343 * NULL.
344 */
345 char *
346 blob_read_string(struct blob_reader *blob);
347
348 #ifdef __cplusplus
349 }
350 #endif
351
352 #endif /* BLOB_H */
353