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[proxmark3-svn] / client / tinycbor / cborencoder.c
1 /****************************************************************************
2 **
3 ** Copyright (C) 2016 Intel Corporation
4 **
5 ** Permission is hereby granted, free of charge, to any person obtaining a copy
6 ** of this software and associated documentation files (the "Software"), to deal
7 ** in the Software without restriction, including without limitation the rights
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9 ** copies of the Software, and to permit persons to whom the Software is
10 ** furnished to do so, subject to the following conditions:
11 **
12 ** The above copyright notice and this permission notice shall be included in
13 ** all copies or substantial portions of the 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 THE
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19 ** LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
20 ** OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
21 ** THE SOFTWARE.
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23 ****************************************************************************/
24
25 #ifndef _BSD_SOURCE
26 #define _BSD_SOURCE 1
27 #endif
28 #ifndef _DEFAULT_SOURCE
29 #define _DEFAULT_SOURCE 1
30 #endif
31 #ifndef __STDC_LIMIT_MACROS
32 # define __STDC_LIMIT_MACROS 1
33 #endif
34
35 #include "cbor.h"
36 #include "cborinternal_p.h"
37 #include "compilersupport_p.h"
38
39 #include <stdlib.h>
40 #include <string.h>
41
42 /**
43 * \defgroup CborEncoding Encoding to CBOR
44 * \brief Group of functions used to encode data to CBOR.
45 *
46 * CborEncoder is used to encode data into a CBOR stream. The outermost
47 * CborEncoder is initialized by calling cbor_encoder_init(), with the buffer
48 * where the CBOR stream will be stored. The outermost CborEncoder is usually
49 * used to encode exactly one item, most often an array or map. It is possible
50 * to encode more than one item, but care must then be taken on the decoder
51 * side to ensure the state is reset after each item was decoded.
52 *
53 * Nested CborEncoder objects are created using cbor_encoder_create_array() and
54 * cbor_encoder_create_map(), later closed with cbor_encoder_close_container()
55 * or cbor_encoder_close_container_checked(). The pairs of creation and closing
56 * must be exactly matched and their parameters are always the same.
57 *
58 * CborEncoder writes directly to the user-supplied buffer, without extra
59 * buffering. CborEncoder does not allocate memory and CborEncoder objects are
60 * usually created on the stack of the encoding functions.
61 *
62 * The example below initializes a CborEncoder object with a buffer and encodes
63 * a single integer.
64 *
65 * \code
66 * uint8_t buf[16];
67 * CborEncoder encoder;
68 * cbor_encoder_init(&encoder, &buf, sizeof(buf), 0);
69 * cbor_encode_int(&encoder, some_value);
70 * \endcode
71 *
72 * As explained before, usually the outermost CborEncoder object is used to add
73 * one array or map, which in turn contains multiple elements. The example
74 * below creates a CBOR map with one element: a key "foo" and a boolean value.
75 *
76 * \code
77 * uint8_t buf[16];
78 * CborEncoder encoder, mapEncoder;
79 * cbor_encoder_init(&encoder, &buf, sizeof(buf), 0);
80 * cbor_encoder_create_map(&encoder, &mapEncoder, 1);
81 * cbor_encode_text_stringz(&mapEncoder, "foo");
82 * cbor_encode_boolean(&mapEncoder, some_value);
83 * cbor_encoder_close_container(&encoder, &mapEncoder);
84 * \endcode
85 *
86 * <h3 class="groupheader">Error checking and buffer size</h3>
87 *
88 * All functions operating on CborEncoder return a condition of type CborError.
89 * If the encoding was successful, they return CborNoError. Some functions do
90 * extra checking on the input provided and may return some other error
91 * conditions (for example, cbor_encode_simple_value() checks that the type is
92 * of the correct type).
93 *
94 * In addition, all functions check whether the buffer has enough bytes to
95 * encode the item being appended. If that is not possible, they return
96 * CborErrorOutOfMemory.
97 *
98 * It is possible to continue with the encoding of data past the first function
99 * that returns CborErrorOutOfMemory. CborEncoder functions will not overrun
100 * the buffer, but will instead count how many more bytes are needed to
101 * complete the encoding. At the end, you can obtain that count by calling
102 * cbor_encoder_get_extra_bytes_needed().
103 *
104 * \section1 Finalizing the encoding
105 *
106 * Once all items have been appended and the containers have all been properly
107 * closed, the user-supplied buffer will contain the CBOR stream and may be
108 * immediately used. To obtain the size of the buffer, call
109 * cbor_encoder_get_buffer_size() with the original buffer pointer.
110 *
111 * The example below illustrates how one can encode an item with error checking
112 * and then pass on the buffer for network sending.
113 *
114 * \code
115 * uint8_t buf[16];
116 * CborError err;
117 * CborEncoder encoder, mapEncoder;
118 * cbor_encoder_init(&encoder, &buf, sizeof(buf), 0);
119 * err = cbor_encoder_create_map(&encoder, &mapEncoder, 1);
120 * if (!err)
121 * return err;
122 * err = cbor_encode_text_stringz(&mapEncoder, "foo");
123 * if (!err)
124 * return err;
125 * err = cbor_encode_boolean(&mapEncoder, some_value);
126 * if (!err)
127 * return err;
128 * err = cbor_encoder_close_container_checked(&encoder, &mapEncoder);
129 * if (!err)
130 * return err;
131 *
132 * size_t len = cbor_encoder_get_buffer_size(&encoder, buf);
133 * send_payload(buf, len);
134 * return CborNoError;
135 * \endcode
136 *
137 * Finally, the example below expands on the one above and also
138 * deals with dynamically growing the buffer if the initial allocation wasn't
139 * big enough. Note the two places where the error checking was replaced with
140 * an cbor_assertion, showing where the author assumes no error can occur.
141 *
142 * \code
143 * uint8_t *encode_string_array(const char **strings, int n, size_t *bufsize)
144 * {
145 * CborError err;
146 * CborEncoder encoder, arrayEncoder;
147 * size_t size = 256;
148 * uint8_t *buf = NULL;
149 *
150 * while (1) {
151 * int i;
152 * size_t more_bytes;
153 * uint8_t *nbuf = realloc(buf, size);
154 * if (nbuf == NULL)
155 * goto error;
156 * buf = nbuf;
157 *
158 * cbor_encoder_init(&encoder, &buf, size, 0);
159 * err = cbor_encoder_create_array(&encoder, &arrayEncoder, n);
160 * cbor_assert(err); // can't fail, the buffer is always big enough
161 *
162 * for (i = 0; i < n; ++i) {
163 * err = cbor_encode_text_stringz(&arrayEncoder, strings[i]);
164 * if (err && err != CborErrorOutOfMemory)
165 * goto error;
166 * }
167 *
168 * err = cbor_encoder_close_container_checked(&encoder, &arrayEncoder);
169 * cbor_assert(err); // shouldn't fail!
170 *
171 * more_bytes = cbor_encoder_get_extra_bytes_needed(encoder);
172 * if (more_size) {
173 * // buffer wasn't big enough, try again
174 * size += more_bytes;
175 * continue;
176 * }
177 *
178 * *bufsize = cbor_encoder_get_buffer_size(encoder, buf);
179 * return buf;
180 * }
181 * error:
182 * free(buf);
183 * return NULL;
184 * }
185 * \endcode
186 */
187
188 /**
189 * \addtogroup CborEncoding
190 * @{
191 */
192
193 /**
194 * \struct CborEncoder
195 * Structure used to encode to CBOR.
196 */
197
198 /**
199 * Initializes a CborEncoder structure \a encoder by pointing it to buffer \a
200 * buffer of size \a size. The \a flags field is currently unused and must be
201 * zero.
202 */
203 void cbor_encoder_init(CborEncoder *encoder, uint8_t *buffer, size_t size, int flags)
204 {
205 encoder->data.ptr = buffer;
206 encoder->end = buffer + size;
207 encoder->remaining = 2;
208 encoder->flags = flags;
209 }
210
211 static inline void put16(void *where, uint16_t v)
212 {
213 v = cbor_htons(v);
214 memcpy(where, &v, sizeof(v));
215 }
216
217 /* Note: Since this is currently only used in situations where OOM is the only
218 * valid error, we KNOW this to be true. Thus, this function now returns just 'true',
219 * but if in the future, any function starts returning a non-OOM error, this will need
220 * to be changed to the test. At the moment, this is done to prevent more branches
221 * being created in the tinycbor output */
222 static inline bool isOomError(CborError err)
223 {
224 (void) err;
225 return true;
226 }
227
228 static inline void put32(void *where, uint32_t v)
229 {
230 v = cbor_htonl(v);
231 memcpy(where, &v, sizeof(v));
232 }
233
234 static inline void put64(void *where, uint64_t v)
235 {
236 v = cbor_htonll(v);
237 memcpy(where, &v, sizeof(v));
238 }
239
240 static inline bool would_overflow(CborEncoder *encoder, size_t len)
241 {
242 ptrdiff_t remaining = (ptrdiff_t)encoder->end;
243 remaining -= remaining ? (ptrdiff_t)encoder->data.ptr : encoder->data.bytes_needed;
244 remaining -= (ptrdiff_t)len;
245 return unlikely(remaining < 0);
246 }
247
248 static inline void advance_ptr(CborEncoder *encoder, size_t n)
249 {
250 if (encoder->end)
251 encoder->data.ptr += n;
252 else
253 encoder->data.bytes_needed += n;
254 }
255
256 static inline CborError append_to_buffer(CborEncoder *encoder, const void *data, size_t len)
257 {
258 if (would_overflow(encoder, len)) {
259 if (encoder->end != NULL) {
260 len -= encoder->end - encoder->data.ptr;
261 encoder->end = NULL;
262 encoder->data.bytes_needed = 0;
263 }
264
265 advance_ptr(encoder, len);
266 return CborErrorOutOfMemory;
267 }
268
269 memcpy(encoder->data.ptr, data, len);
270 encoder->data.ptr += len;
271 return CborNoError;
272 }
273
274 static inline CborError append_byte_to_buffer(CborEncoder *encoder, uint8_t byte)
275 {
276 return append_to_buffer(encoder, &byte, 1);
277 }
278
279 static inline CborError encode_number_no_update(CborEncoder *encoder, uint64_t ui, uint8_t shiftedMajorType)
280 {
281 /* Little-endian would have been so much more convenient here:
282 * We could just write at the beginning of buf but append_to_buffer
283 * only the necessary bytes.
284 * Since it has to be big endian, do it the other way around:
285 * write from the end. */
286 uint64_t buf[2];
287 uint8_t *const bufend = (uint8_t *)buf + sizeof(buf);
288 uint8_t *bufstart = bufend - 1;
289 put64(buf + 1, ui); /* we probably have a bunch of zeros in the beginning */
290
291 if (ui < Value8Bit) {
292 *bufstart += shiftedMajorType;
293 } else {
294 uint8_t more = 0;
295 if (ui > 0xffU)
296 ++more;
297 if (ui > 0xffffU)
298 ++more;
299 if (ui > 0xffffffffU)
300 ++more;
301 bufstart -= (size_t)1 << more;
302 *bufstart = shiftedMajorType + Value8Bit + more;
303 }
304
305 return append_to_buffer(encoder, bufstart, bufend - bufstart);
306 }
307
308 static inline void saturated_decrement(CborEncoder *encoder)
309 {
310 if (encoder->remaining)
311 --encoder->remaining;
312 }
313
314 static inline CborError encode_number(CborEncoder *encoder, uint64_t ui, uint8_t shiftedMajorType)
315 {
316 saturated_decrement(encoder);
317 return encode_number_no_update(encoder, ui, shiftedMajorType);
318 }
319
320 /**
321 * Appends the unsigned 64-bit integer \a value to the CBOR stream provided by
322 * \a encoder.
323 *
324 * \sa cbor_encode_negative_int, cbor_encode_int
325 */
326 CborError cbor_encode_uint(CborEncoder *encoder, uint64_t value)
327 {
328 return encode_number(encoder, value, UnsignedIntegerType << MajorTypeShift);
329 }
330
331 /**
332 * Appends the negative 64-bit integer whose absolute value is \a
333 * absolute_value to the CBOR stream provided by \a encoder.
334 *
335 * If the value \a absolute_value is zero, this function encodes -2^64.
336 *
337 * \sa cbor_encode_uint, cbor_encode_int
338 */
339 CborError cbor_encode_negative_int(CborEncoder *encoder, uint64_t absolute_value)
340 {
341 return encode_number(encoder, absolute_value - 1, NegativeIntegerType << MajorTypeShift);
342 }
343
344 /**
345 * Appends the signed 64-bit integer \a value to the CBOR stream provided by
346 * \a encoder.
347 *
348 * \sa cbor_encode_negative_int, cbor_encode_uint
349 */
350 CborError cbor_encode_int(CborEncoder *encoder, int64_t value)
351 {
352 /* adapted from code in RFC 7049 appendix C (pseudocode) */
353 uint64_t ui = value >> 63; /* extend sign to whole length */
354 uint8_t majorType = ui & 0x20; /* extract major type */
355 ui ^= value; /* complement negatives */
356 return encode_number(encoder, ui, majorType);
357 }
358
359 /**
360 * Appends the CBOR Simple Type of value \a value to the CBOR stream provided by
361 * \a encoder.
362 *
363 * This function may return error CborErrorIllegalSimpleType if the \a value
364 * variable contains a number that is not a valid simple type.
365 */
366 CborError cbor_encode_simple_value(CborEncoder *encoder, uint8_t value)
367 {
368 #ifndef CBOR_ENCODER_NO_CHECK_USER
369 /* check if this is a valid simple type */
370 if (value >= HalfPrecisionFloat && value <= Break)
371 return CborErrorIllegalSimpleType;
372 #endif
373 return encode_number(encoder, value, SimpleTypesType << MajorTypeShift);
374 }
375
376 /**
377 * Appends the floating-point value of type \a fpType and pointed to by \a
378 * value to the CBOR stream provided by \a encoder. The value of \a fpType must
379 * be one of CborHalfFloatType, CborFloatType or CborDoubleType, otherwise the
380 * behavior of this function is undefined.
381 *
382 * This function is useful for code that needs to pass through floating point
383 * values but does not wish to have the actual floating-point code.
384 *
385 * \sa cbor_encode_half_float, cbor_encode_float, cbor_encode_double
386 */
387 CborError cbor_encode_floating_point(CborEncoder *encoder, CborType fpType, const void *value)
388 {
389 unsigned size;
390 uint8_t buf[1 + sizeof(uint64_t)];
391 cbor_assert(fpType == CborHalfFloatType || fpType == CborFloatType || fpType == CborDoubleType);
392 buf[0] = fpType;
393
394 size = 2U << (fpType - CborHalfFloatType);
395 if (size == 8)
396 put64(buf + 1, *(const uint64_t*)value);
397 else if (size == 4)
398 put32(buf + 1, *(const uint32_t*)value);
399 else
400 put16(buf + 1, *(const uint16_t*)value);
401 saturated_decrement(encoder);
402 return append_to_buffer(encoder, buf, size + 1);
403 }
404
405 /**
406 * Appends the CBOR tag \a tag to the CBOR stream provided by \a encoder.
407 *
408 * \sa CborTag
409 */
410 CborError cbor_encode_tag(CborEncoder *encoder, CborTag tag)
411 {
412 /* tags don't count towards the number of elements in an array or map */
413 return encode_number_no_update(encoder, tag, TagType << MajorTypeShift);
414 }
415
416 static CborError encode_string(CborEncoder *encoder, size_t length, uint8_t shiftedMajorType, const void *string)
417 {
418 CborError err = encode_number(encoder, length, shiftedMajorType);
419 if (err && !isOomError(err))
420 return err;
421 return append_to_buffer(encoder, string, length);
422 }
423
424 /**
425 * \fn CborError cbor_encode_text_stringz(CborEncoder *encoder, const char *string)
426 *
427 * Appends the null-terminated text string \a string to the CBOR stream
428 * provided by \a encoder. CBOR requires that \a string be valid UTF-8, but
429 * TinyCBOR makes no verification of correctness. The terminating null is not
430 * included in the stream.
431 *
432 * \sa cbor_encode_text_string, cbor_encode_byte_string
433 */
434
435 /**
436 * Appends the text string \a string of length \a length to the CBOR stream
437 * provided by \a encoder. CBOR requires that \a string be valid UTF-8, but
438 * TinyCBOR makes no verification of correctness.
439 *
440 * \sa CborError cbor_encode_text_stringz, cbor_encode_byte_string
441 */
442 CborError cbor_encode_byte_string(CborEncoder *encoder, const uint8_t *string, size_t length)
443 {
444 return encode_string(encoder, length, ByteStringType << MajorTypeShift, string);
445 }
446
447 /**
448 * Appends the byte string \a string of length \a length to the CBOR stream
449 * provided by \a encoder. CBOR byte strings are arbitrary raw data.
450 *
451 * \sa cbor_encode_text_stringz, cbor_encode_text_string
452 */
453 CborError cbor_encode_text_string(CborEncoder *encoder, const char *string, size_t length)
454 {
455 return encode_string(encoder, length, TextStringType << MajorTypeShift, string);
456 }
457
458 #ifdef __GNUC__
459 __attribute__((noinline))
460 #endif
461 static CborError create_container(CborEncoder *encoder, CborEncoder *container, size_t length, uint8_t shiftedMajorType)
462 {
463 CborError err;
464 container->data.ptr = encoder->data.ptr;
465 container->end = encoder->end;
466 saturated_decrement(encoder);
467 container->remaining = length + 1; /* overflow ok on CborIndefiniteLength */
468
469 cbor_static_assert(((MapType << MajorTypeShift) & CborIteratorFlag_ContainerIsMap) == CborIteratorFlag_ContainerIsMap);
470 cbor_static_assert(((ArrayType << MajorTypeShift) & CborIteratorFlag_ContainerIsMap) == 0);
471 container->flags = shiftedMajorType & CborIteratorFlag_ContainerIsMap;
472
473 if (length == CborIndefiniteLength) {
474 container->flags |= CborIteratorFlag_UnknownLength;
475 err = append_byte_to_buffer(container, shiftedMajorType + IndefiniteLength);
476 } else {
477 if (shiftedMajorType & CborIteratorFlag_ContainerIsMap)
478 container->remaining += length;
479 err = encode_number_no_update(container, length, shiftedMajorType);
480 }
481 return err;
482 }
483
484 /**
485 * Creates a CBOR array in the CBOR stream provided by \a encoder and
486 * initializes \a arrayEncoder so that items can be added to the array using
487 * the CborEncoder functions. The array must be terminated by calling either
488 * cbor_encoder_close_container() or cbor_encoder_close_container_checked()
489 * with the same \a encoder and \a arrayEncoder parameters.
490 *
491 * The number of items inserted into the array must be exactly \a length items,
492 * otherwise the stream is invalid. If the number of items is not known when
493 * creating the array, the constant \ref CborIndefiniteLength may be passed as
494 * length instead.
495 *
496 * \sa cbor_encoder_create_map
497 */
498 CborError cbor_encoder_create_array(CborEncoder *encoder, CborEncoder *arrayEncoder, size_t length)
499 {
500 return create_container(encoder, arrayEncoder, length, ArrayType << MajorTypeShift);
501 }
502
503 /**
504 * Creates a CBOR map in the CBOR stream provided by \a encoder and
505 * initializes \a mapEncoder so that items can be added to the map using
506 * the CborEncoder functions. The map must be terminated by calling either
507 * cbor_encoder_close_container() or cbor_encoder_close_container_checked()
508 * with the same \a encoder and \a mapEncoder parameters.
509 *
510 * The number of pair of items inserted into the map must be exactly \a length
511 * items, otherwise the stream is invalid. If the number is not known
512 * when creating the map, the constant \ref CborIndefiniteLength may be passed as
513 * length instead.
514 *
515 * \b{Implementation limitation:} TinyCBOR cannot encode more than SIZE_MAX/2
516 * key-value pairs in the stream. If the length \a length is larger than this
517 * value (and is not \ref CborIndefiniteLength), this function returns error
518 * CborErrorDataTooLarge.
519 *
520 * \sa cbor_encoder_create_array
521 */
522 CborError cbor_encoder_create_map(CborEncoder *encoder, CborEncoder *mapEncoder, size_t length)
523 {
524 if (length != CborIndefiniteLength && length > SIZE_MAX / 2)
525 return CborErrorDataTooLarge;
526 return create_container(encoder, mapEncoder, length, MapType << MajorTypeShift);
527 }
528
529 /**
530 * Closes the CBOR container (array or map) provided by \a containerEncoder and
531 * updates the CBOR stream provided by \a encoder. Both parameters must be the
532 * same as were passed to cbor_encoder_create_array() or
533 * cbor_encoder_create_map().
534 *
535 * Since version 0.5, this function verifies that the number of items (or pairs
536 * of items, in the case of a map) was correct. It is no longer necessary to call
537 * cbor_encoder_close_container_checked() instead.
538 *
539 * \sa cbor_encoder_create_array(), cbor_encoder_create_map()
540 */
541 CborError cbor_encoder_close_container(CborEncoder *encoder, const CborEncoder *containerEncoder)
542 {
543 if (encoder->end)
544 encoder->data.ptr = containerEncoder->data.ptr;
545 else
546 encoder->data.bytes_needed = containerEncoder->data.bytes_needed;
547 encoder->end = containerEncoder->end;
548 if (containerEncoder->flags & CborIteratorFlag_UnknownLength)
549 return append_byte_to_buffer(encoder, BreakByte);
550
551 if (containerEncoder->remaining != 1)
552 return containerEncoder->remaining == 0 ? CborErrorTooManyItems : CborErrorTooFewItems;
553
554 if (!encoder->end)
555 return CborErrorOutOfMemory; /* keep the state */
556 return CborNoError;
557 }
558
559 /**
560 * \fn CborError cbor_encode_boolean(CborEncoder *encoder, bool value)
561 *
562 * Appends the boolean value \a value to the CBOR stream provided by \a encoder.
563 */
564
565 /**
566 * \fn CborError cbor_encode_null(CborEncoder *encoder)
567 *
568 * Appends the CBOR type representing a null value to the CBOR stream provided
569 * by \a encoder.
570 *
571 * \sa cbor_encode_undefined()
572 */
573
574 /**
575 * \fn CborError cbor_encode_undefined(CborEncoder *encoder)
576 *
577 * Appends the CBOR type representing an undefined value to the CBOR stream
578 * provided by \a encoder.
579 *
580 * \sa cbor_encode_null()
581 */
582
583 /**
584 * \fn CborError cbor_encode_half_float(CborEncoder *encoder, const void *value)
585 *
586 * Appends the IEEE 754 half-precision (16-bit) floating point value pointed to
587 * by \a value to the CBOR stream provided by \a encoder.
588 *
589 * \sa cbor_encode_floating_point(), cbor_encode_float(), cbor_encode_double()
590 */
591
592 /**
593 * \fn CborError cbor_encode_float(CborEncoder *encoder, float value)
594 *
595 * Appends the IEEE 754 single-precision (32-bit) floating point value \a value
596 * to the CBOR stream provided by \a encoder.
597 *
598 * \sa cbor_encode_floating_point(), cbor_encode_half_float(), cbor_encode_double()
599 */
600
601 /**
602 * \fn CborError cbor_encode_double(CborEncoder *encoder, double value)
603 *
604 * Appends the IEEE 754 double-precision (64-bit) floating point value \a value
605 * to the CBOR stream provided by \a encoder.
606 *
607 * \sa cbor_encode_floating_point(), cbor_encode_half_float(), cbor_encode_float()
608 */
609
610 /**
611 * \fn size_t cbor_encoder_get_buffer_size(const CborEncoder *encoder, const uint8_t *buffer)
612 *
613 * Returns the total size of the buffer starting at \a buffer after the
614 * encoding finished without errors. The \a encoder and \a buffer arguments
615 * must be the same as supplied to cbor_encoder_init().
616 *
617 * If the encoding process had errors, the return value of this function is
618 * meaningless. If the only errors were CborErrorOutOfMemory, instead use
619 * cbor_encoder_get_extra_bytes_needed() to find out by how much to grow the
620 * buffer before encoding again.
621 *
622 * See \ref CborEncoding for an example of using this function.
623 *
624 * \sa cbor_encoder_init(), cbor_encoder_get_extra_bytes_needed(), CborEncoding
625 */
626
627 /**
628 * \fn size_t cbor_encoder_get_extra_bytes_needed(const CborEncoder *encoder)
629 *
630 * Returns how many more bytes the original buffer supplied to
631 * cbor_encoder_init() needs to be extended by so that no CborErrorOutOfMemory
632 * condition will happen for the encoding. If the buffer was big enough, this
633 * function returns 0. The \a encoder must be the original argument as passed
634 * to cbor_encoder_init().
635 *
636 * This function is usually called after an encoding sequence ended with one or
637 * more CborErrorOutOfMemory errors, but no other error. If any other error
638 * happened, the return value of this function is meaningless.
639 *
640 * See \ref CborEncoding for an example of using this function.
641 *
642 * \sa cbor_encoder_init(), cbor_encoder_get_buffer_size(), CborEncoding
643 */
644
645 /** @} */
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