1 /* pb_decode.c -- decode a protobuf using minimal resources
3 * 2011 Petteri Aimonen <jpa@kapsi.fi>
8 /* Verify that we remember to check all return values for proper error propagation */
9 #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)
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, int 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)
291 size_t *size = (size_t*)iter->pSize;
292 pb_istream_t substream;
293 if (!make_string_substream(stream, &substream))
296 while (substream.bytes_left && *size < iter->current->array_size)
298 void *pItem = (uint8_t*)iter->pData + iter->current->data_size * (*size);
299 if (!func(&substream, iter->current, pItem))
303 return (substream.bytes_left == 0);
308 size_t *size = (size_t*)iter->pSize;
309 void *pItem = (uint8_t*)iter->pData + iter->current->data_size * (*size);
310 if (*size >= iter->current->array_size)
314 return func(stream, iter->current, pItem);
317 case PB_HTYPE_CALLBACK:
319 pb_callback_t *pCallback = (pb_callback_t*)iter->pData;
321 if (pCallback->funcs.decode == NULL)
322 return pb_skip_field(stream, wire_type);
324 if (wire_type == PB_WT_STRING)
326 pb_istream_t substream;
328 if (!make_string_substream(stream, &substream))
331 while (substream.bytes_left)
333 if (!pCallback->funcs.decode(&substream, iter->current, pCallback->arg))
337 stream->state = substream.state;
342 /* Copy the single scalar value to stack.
343 * This is required so that we can limit the stream length,
344 * which in turn allows to use same callback for packed and
345 * not-packed fields. */
346 pb_istream_t substream;
348 size_t size = sizeof(buffer);
350 if (!read_raw_value(stream, wire_type, buffer, &size))
352 substream = pb_istream_from_buffer(buffer, size);
354 return pCallback->funcs.decode(&substream, iter->current, pCallback->arg);
363 /* Initialize message fields to default values, recursively */
364 static void pb_message_set_to_defaults(const pb_field_t fields[], void *dest_struct)
366 pb_field_iterator_t iter;
367 pb_field_init(&iter, fields, dest_struct);
369 /* Initialize size/has fields and apply default values */
372 if (iter.current->tag == 0)
375 /* Initialize the size field for optional/repeated fields to 0. */
376 if (PB_HTYPE(iter.current->type) == PB_HTYPE_OPTIONAL)
378 *(bool*)iter.pSize = false;
380 else if (PB_HTYPE(iter.current->type) == PB_HTYPE_ARRAY)
382 *(size_t*)iter.pSize = 0;
383 continue; /* Array is empty, no need to initialize contents */
386 /* Initialize field contents to default value */
387 if (PB_HTYPE(iter.current->type) == PB_HTYPE_CALLBACK)
389 continue; /* Don't overwrite callback */
391 else if (PB_LTYPE(iter.current->type) == PB_LTYPE_SUBMESSAGE)
393 pb_message_set_to_defaults(iter.current->ptr, iter.pData);
395 else if (iter.current->ptr != NULL)
397 memcpy(iter.pData, iter.current->ptr, iter.current->data_size);
401 memset(iter.pData, 0, iter.current->data_size);
403 } while (pb_field_next(&iter));
406 /*********************
407 * Decode all fields *
408 *********************/
410 bool checkreturn pb_decode(pb_istream_t *stream, const pb_field_t fields[], void *dest_struct)
412 uint8_t fields_seen[(PB_MAX_REQUIRED_FIELDS + 7) / 8] = {0}; /* Used to check for required fields */
413 pb_field_iterator_t iter;
415 pb_message_set_to_defaults(fields, dest_struct);
417 pb_field_init(&iter, fields, dest_struct);
419 while (stream->bytes_left)
422 pb_wire_type_t wire_type;
425 if (!pb_decode_tag(stream, &wire_type, &tag, &eof))
433 if (!pb_field_find(&iter, tag))
435 /* No match found, skip data */
436 if (!pb_skip_field(stream, wire_type))
441 if (PB_HTYPE(iter.current->type) == PB_HTYPE_REQUIRED
442 && iter.required_field_index < PB_MAX_REQUIRED_FIELDS)
444 fields_seen[iter.required_field_index >> 3] |= 1 << (iter.required_field_index & 7);
447 if (!decode_field(stream, wire_type, &iter))
451 /* Check that all required fields were present. */
452 pb_field_init(&iter, fields, dest_struct);
454 if (PB_HTYPE(iter.current->type) == PB_HTYPE_REQUIRED &&
455 iter.required_field_index < PB_MAX_REQUIRED_FIELDS &&
456 !(fields_seen[iter.required_field_index >> 3] & (1 << (iter.required_field_index & 7))))
460 } while (pb_field_next(&iter));
467 /* Copy destsize bytes from src so that values are casted properly.
468 * On little endian machine, copy first n bytes of src
469 * On big endian machine, copy last n bytes of src
470 * srcsize must always be larger than destsize
472 static void endian_copy(void *dest, void *src, size_t destsize, size_t srcsize)
474 #ifdef __BIG_ENDIAN__
475 memcpy(dest, (char*)src + (srcsize - destsize), destsize);
478 memcpy(dest, src, destsize);
482 bool checkreturn pb_dec_varint(pb_istream_t *stream, const pb_field_t *field, void *dest)
485 bool status = pb_decode_varint(stream, &temp);
486 endian_copy(dest, &temp, field->data_size, sizeof(temp));
490 bool checkreturn pb_dec_svarint(pb_istream_t *stream, const pb_field_t *field, void *dest)
493 bool status = pb_decode_varint(stream, &temp);
494 temp = (temp >> 1) ^ -(int64_t)(temp & 1);
495 endian_copy(dest, &temp, field->data_size, sizeof(temp));
499 bool checkreturn pb_dec_fixed32(pb_istream_t *stream, const pb_field_t *field, void *dest)
501 #ifdef __BIG_ENDIAN__
502 uint8_t bytes[4] = {0};
503 bool status = pb_read(stream, bytes, 4);
505 uint8_t *d = (uint8_t*)dest;
514 return pb_read(stream, (uint8_t*)dest, 4);
518 bool checkreturn pb_dec_fixed64(pb_istream_t *stream, const pb_field_t *field, void *dest)
520 #ifdef __BIG_ENDIAN__
521 uint8_t bytes[8] = {0};
522 bool status = pb_read(stream, bytes, 8);
524 uint8_t *d = (uint8_t*)dest;
537 return pb_read(stream, (uint8_t*)dest, 8);
541 bool checkreturn pb_dec_bytes(pb_istream_t *stream, const pb_field_t *field, void *dest)
543 pb_bytes_array_t *x = (pb_bytes_array_t*)dest;
546 if (!pb_decode_varint32(stream, &temp))
550 /* Check length, noting the space taken by the size_t header. */
551 if (x->size > field->data_size - offsetof(pb_bytes_array_t, bytes))
554 return pb_read(stream, x->bytes, x->size);
557 bool checkreturn pb_dec_string(pb_istream_t *stream, const pb_field_t *field, void *dest)
561 if (!pb_decode_varint32(stream, &size))
564 /* Check length, noting the null terminator */
565 if (size + 1 > field->data_size)
568 status = pb_read(stream, (uint8_t*)dest, size);
569 *((uint8_t*)dest + size) = 0;
573 bool checkreturn pb_dec_submessage(pb_istream_t *stream, const pb_field_t *field, void *dest)
576 pb_istream_t substream;
578 if (!make_string_substream(stream, &substream))
581 if (field->ptr == NULL)
584 status = pb_decode(&substream, (pb_field_t*)field->ptr, dest);
585 stream->state = substream.state;