1 /* pb_decode.c -- decode a protobuf using minimal resources
3 * 2011 Petteri Aimonen <jpa@kapsi.fi>
6 /* The warn_unused_result attribute appeared first in gcc-3.4.0 */
7 #if !defined(__GNUC__) || ( __GNUC__ < 3) || (__GNUC__ == 3 && __GNUC_MINOR__ < 4)
10 /* Verify that we remember to check all return values for proper error propagation */
11 #define checkreturn __attribute__((warn_unused_result))
15 #include "pb_decode.h"
18 typedef bool (*pb_decoder_t)(pb_istream_t *stream, const pb_field_t *field, void *dest) checkreturn;
20 /* --- Function pointers to field decoders ---
21 * Order in the array must match pb_action_t LTYPE numbering.
23 static const pb_decoder_t PB_DECODERS[PB_LTYPES_COUNT] = {
38 bool checkreturn pb_read(pb_istream_t *stream, uint8_t *buf, size_t count)
40 if (stream->bytes_left < count)
43 if (!stream->callback(stream, buf, count))
46 stream->bytes_left -= count;
50 static bool checkreturn buf_read(pb_istream_t *stream, uint8_t *buf, size_t count)
52 uint8_t *source = (uint8_t*)stream->state;
55 memcpy(buf, source, count);
57 stream->state = source + count;
61 pb_istream_t pb_istream_from_buffer(uint8_t *buf, size_t bufsize)
64 stream.callback = &buf_read;
66 stream.bytes_left = bufsize;
74 static bool checkreturn pb_decode_varint32(pb_istream_t *stream, uint32_t *dest)
77 bool status = pb_decode_varint(stream, &temp);
78 *dest = (uint32_t)temp;
82 bool checkreturn pb_decode_varint(pb_istream_t *stream, uint64_t *dest)
88 while (bitpos < 64 && pb_read(stream, &byte, 1))
90 *dest |= (uint64_t)(byte & 0x7F) << bitpos;
100 bool checkreturn pb_skip_varint(pb_istream_t *stream)
105 if (!pb_read(stream, &byte, 1))
107 } while (byte & 0x80);
111 bool checkreturn pb_skip_string(pb_istream_t *stream)
114 if (!pb_decode_varint32(stream, &length))
117 return pb_read(stream, NULL, length);
120 bool checkreturn pb_decode_tag(pb_istream_t *stream, pb_wire_type_t *wire_type, uint32_t *tag, bool *eof)
124 *wire_type = (pb_wire_type_t) 0;
127 if (!pb_decode_varint32(stream, &temp))
129 if (stream->bytes_left == 0)
137 *eof = true; /* Special feature: allow 0-terminated messages. */
142 *wire_type = (pb_wire_type_t)(temp & 7);
146 bool checkreturn pb_skip_field(pb_istream_t *stream, pb_wire_type_t wire_type)
150 case PB_WT_VARINT: return pb_skip_varint(stream);
151 case PB_WT_64BIT: return pb_read(stream, NULL, 8);
152 case PB_WT_STRING: return pb_skip_string(stream);
153 case PB_WT_32BIT: return pb_read(stream, NULL, 4);
154 default: return false;
158 /* Read a raw value to buffer, for the purpose of passing it to callback as
159 * a substream. Size is maximum size on call, and actual size on return.
161 static bool checkreturn read_raw_value(pb_istream_t *stream, pb_wire_type_t wire_type, uint8_t *buf, size_t *size)
163 size_t max_size = *size;
171 if (*size > max_size) return false;
172 if (!pb_read(stream, buf, 1)) return false;
173 } while (*buf++ & 0x80);
178 return pb_read(stream, buf, 8);
182 return pb_read(stream, buf, 4);
184 default: return false;
188 /* Decode string length from stream and return a substream with limited length.
189 * Before disposing the substream, remember to copy the substream->state back
192 static bool checkreturn make_string_substream(pb_istream_t *stream, pb_istream_t *substream)
195 if (!pb_decode_varint32(stream, &size))
198 *substream = *stream;
199 if (substream->bytes_left < size)
202 substream->bytes_left = size;
203 stream->bytes_left -= size;
207 /* Iterator for pb_field_t list */
209 const pb_field_t *start; /* Start of the pb_field_t array */
210 const pb_field_t *current; /* Current position of the iterator */
211 int field_index; /* Zero-based index of the field. */
212 int required_field_index; /* Zero-based index that counts only the required fields */
213 void *dest_struct; /* Pointer to the destination structure to decode to */
214 void *pData; /* Pointer where to store current field value */
215 void *pSize; /* Pointer where to store the size of current array field */
216 } pb_field_iterator_t;
218 static void pb_field_init(pb_field_iterator_t *iter, const pb_field_t *fields, void *dest_struct)
220 iter->start = iter->current = fields;
221 iter->field_index = 0;
222 iter->required_field_index = 0;
223 iter->pData = (char*)dest_struct + iter->current->data_offset;
224 iter->pSize = (char*)iter->pData + iter->current->size_offset;
225 iter->dest_struct = dest_struct;
228 static bool pb_field_next(pb_field_iterator_t *iter)
230 bool notwrapped = true;
231 size_t prev_size = iter->current->data_size;
233 if (PB_HTYPE(iter->current->type) == PB_HTYPE_ARRAY)
234 prev_size *= iter->current->array_size;
236 if (PB_HTYPE(iter->current->type) == PB_HTYPE_REQUIRED)
237 iter->required_field_index++;
241 if (iter->current->tag == 0)
243 iter->current = iter->start;
244 iter->field_index = 0;
245 iter->required_field_index = 0;
246 iter->pData = iter->dest_struct;
251 iter->pData = (char*)iter->pData + prev_size + iter->current->data_offset;
252 iter->pSize = (char*)iter->pData + iter->current->size_offset;
256 static bool checkreturn pb_field_find(pb_field_iterator_t *iter, uint32_t tag)
258 int start = iter->field_index;
261 if (iter->current->tag == tag)
264 } while (iter->field_index != start);
269 /*************************
270 * Decode a single field *
271 *************************/
273 static bool checkreturn decode_field(pb_istream_t *stream, pb_wire_type_t wire_type, pb_field_iterator_t *iter)
275 pb_decoder_t func = PB_DECODERS[PB_LTYPE(iter->current->type)];
277 switch (PB_HTYPE(iter->current->type))
279 case PB_HTYPE_REQUIRED:
280 return func(stream, iter->current, iter->pData);
282 case PB_HTYPE_OPTIONAL:
283 *(bool*)iter->pSize = true;
284 return func(stream, iter->current, iter->pData);
287 if (wire_type == PB_WT_STRING
288 && PB_LTYPE(iter->current->type) <= PB_LTYPE_LAST_PACKABLE)
292 size_t *size = (size_t*)iter->pSize;
293 pb_istream_t substream;
294 if (!make_string_substream(stream, &substream))
297 while (substream.bytes_left && *size < iter->current->array_size)
299 void *pItem = (uint8_t*)iter->pData + iter->current->data_size * (*size);
300 if (!func(&substream, iter->current, pItem))
304 status = (substream.bytes_left == 0);
305 stream->state = substream.state;
311 size_t *size = (size_t*)iter->pSize;
312 void *pItem = (uint8_t*)iter->pData + iter->current->data_size * (*size);
313 if (*size >= iter->current->array_size)
317 return func(stream, iter->current, pItem);
320 case PB_HTYPE_CALLBACK:
322 pb_callback_t *pCallback = (pb_callback_t*)iter->pData;
324 if (pCallback->funcs.decode == NULL)
325 return pb_skip_field(stream, wire_type);
327 if (wire_type == PB_WT_STRING)
329 pb_istream_t substream;
331 if (!make_string_substream(stream, &substream))
334 while (substream.bytes_left)
336 if (!pCallback->funcs.decode(&substream, iter->current, pCallback->arg))
340 stream->state = substream.state;
345 /* Copy the single scalar value to stack.
346 * This is required so that we can limit the stream length,
347 * which in turn allows to use same callback for packed and
348 * not-packed fields. */
349 pb_istream_t substream;
351 size_t size = sizeof(buffer);
353 if (!read_raw_value(stream, wire_type, buffer, &size))
355 substream = pb_istream_from_buffer(buffer, size);
357 return pCallback->funcs.decode(&substream, iter->current, pCallback->arg);
366 /* Initialize message fields to default values, recursively */
367 static void pb_message_set_to_defaults(const pb_field_t fields[], void *dest_struct)
369 pb_field_iterator_t iter;
370 pb_field_init(&iter, fields, dest_struct);
372 /* Initialize size/has fields and apply default values */
375 if (iter.current->tag == 0)
378 /* Initialize the size field for optional/repeated fields to 0. */
379 if (PB_HTYPE(iter.current->type) == PB_HTYPE_OPTIONAL)
381 *(bool*)iter.pSize = false;
383 else if (PB_HTYPE(iter.current->type) == PB_HTYPE_ARRAY)
385 *(size_t*)iter.pSize = 0;
386 continue; /* Array is empty, no need to initialize contents */
389 /* Initialize field contents to default value */
390 if (PB_HTYPE(iter.current->type) == PB_HTYPE_CALLBACK)
392 continue; /* Don't overwrite callback */
394 else if (PB_LTYPE(iter.current->type) == PB_LTYPE_SUBMESSAGE)
396 pb_message_set_to_defaults((const pb_field_t *) iter.current->ptr, iter.pData);
398 else if (iter.current->ptr != NULL)
400 memcpy(iter.pData, iter.current->ptr, iter.current->data_size);
404 memset(iter.pData, 0, iter.current->data_size);
406 } while (pb_field_next(&iter));
409 /*********************
410 * Decode all fields *
411 *********************/
413 bool checkreturn pb_decode(pb_istream_t *stream, const pb_field_t fields[], void *dest_struct)
415 uint8_t fields_seen[(PB_MAX_REQUIRED_FIELDS + 7) / 8] = {0}; /* Used to check for required fields */
416 pb_field_iterator_t iter;
418 pb_message_set_to_defaults(fields, dest_struct);
420 pb_field_init(&iter, fields, dest_struct);
422 while (stream->bytes_left)
425 pb_wire_type_t wire_type;
428 if (!pb_decode_tag(stream, &wire_type, &tag, &eof))
436 if (!pb_field_find(&iter, tag))
438 /* No match found, skip data */
439 if (!pb_skip_field(stream, wire_type))
444 if (PB_HTYPE(iter.current->type) == PB_HTYPE_REQUIRED
445 && iter.required_field_index < PB_MAX_REQUIRED_FIELDS)
447 fields_seen[iter.required_field_index >> 3] |= 1 << (iter.required_field_index & 7);
450 if (!decode_field(stream, wire_type, &iter))
454 /* Check that all required fields were present. */
455 pb_field_init(&iter, fields, dest_struct);
457 if (PB_HTYPE(iter.current->type) == PB_HTYPE_REQUIRED &&
458 iter.required_field_index < PB_MAX_REQUIRED_FIELDS &&
459 !(fields_seen[iter.required_field_index >> 3] & (1 << (iter.required_field_index & 7))))
463 } while (pb_field_next(&iter));
470 /* Copy destsize bytes from src so that values are casted properly.
471 * On little endian machine, copy first n bytes of src
472 * On big endian machine, copy last n bytes of src
473 * srcsize must always be larger than destsize
475 static void endian_copy(void *dest, void *src, size_t destsize, size_t srcsize)
477 #ifdef __BIG_ENDIAN__
478 memcpy(dest, (char*)src + (srcsize - destsize), destsize);
481 memcpy(dest, src, destsize);
485 bool checkreturn pb_dec_varint(pb_istream_t *stream, const pb_field_t *field, void *dest)
488 bool status = pb_decode_varint(stream, &temp);
489 endian_copy(dest, &temp, field->data_size, sizeof(temp));
493 bool checkreturn pb_dec_svarint(pb_istream_t *stream, const pb_field_t *field, void *dest)
496 bool status = pb_decode_varint(stream, &temp);
497 temp = (temp >> 1) ^ -(int64_t)(temp & 1);
498 endian_copy(dest, &temp, field->data_size, sizeof(temp));
502 bool checkreturn pb_dec_fixed32(pb_istream_t *stream, const pb_field_t *field, void *dest)
504 #ifdef __BIG_ENDIAN__
505 uint8_t bytes[4] = {0};
506 bool status = pb_read(stream, bytes, 4);
508 uint8_t *d = (uint8_t*)dest;
517 return pb_read(stream, (uint8_t*)dest, 4);
521 bool checkreturn pb_dec_fixed64(pb_istream_t *stream, const pb_field_t *field, void *dest)
523 #ifdef __BIG_ENDIAN__
524 uint8_t bytes[8] = {0};
525 bool status = pb_read(stream, bytes, 8);
527 uint8_t *d = (uint8_t*)dest;
540 return pb_read(stream, (uint8_t*)dest, 8);
544 bool checkreturn pb_dec_bytes(pb_istream_t *stream, const pb_field_t *field, void *dest)
546 pb_bytes_array_t *x = (pb_bytes_array_t*)dest;
549 if (!pb_decode_varint32(stream, &temp))
553 /* Check length, noting the space taken by the size_t header. */
554 if (x->size > field->data_size - offsetof(pb_bytes_array_t, bytes))
557 return pb_read(stream, x->bytes, x->size);
560 bool checkreturn pb_dec_string(pb_istream_t *stream, const pb_field_t *field, void *dest)
564 if (!pb_decode_varint32(stream, &size))
567 /* Check length, noting the null terminator */
568 if (size + 1 > field->data_size)
571 status = pb_read(stream, (uint8_t*)dest, size);
572 *((uint8_t*)dest + size) = 0;
576 bool checkreturn pb_dec_submessage(pb_istream_t *stream, const pb_field_t *field, void *dest)
579 pb_istream_t substream;
581 if (!make_string_substream(stream, &substream))
584 if (field->ptr == NULL)
587 status = pb_decode(&substream, (pb_field_t*)field->ptr, dest);
588 stream->state = substream.state;