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);
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 /* Currently the wire type related stuff is kept hidden from
121 * callbacks. They shouldn't need it. It's better for performance
122 * to just assume the correct type and fail safely on corrupt message.
125 static bool checkreturn skip(pb_istream_t *stream, int wire_type)
129 case PB_WT_VARINT: return pb_skip_varint(stream);
130 case PB_WT_64BIT: return pb_read(stream, NULL, 8);
131 case PB_WT_STRING: return pb_skip_string(stream);
132 case PB_WT_32BIT: return pb_read(stream, NULL, 4);
133 default: return false;
137 /* Read a raw value to buffer, for the purpose of passing it to callback as
138 * a substream. Size is maximum size on call, and actual size on return.
140 static bool checkreturn read_raw_value(pb_istream_t *stream, pb_wire_type_t wire_type, uint8_t *buf, size_t *size)
142 size_t max_size = *size;
150 if (*size > max_size) return false;
151 if (!pb_read(stream, buf, 1)) return false;
152 } while (*buf++ & 0x80);
157 return pb_read(stream, buf, 8);
161 return pb_read(stream, buf, 4);
163 default: return false;
167 /* Decode string length from stream and return a substream with limited length.
168 * Before disposing the substream, remember to copy the substream->state back
171 static bool checkreturn make_string_substream(pb_istream_t *stream, pb_istream_t *substream)
174 if (!pb_decode_varint32(stream, &size))
177 *substream = *stream;
178 if (substream->bytes_left < size)
181 substream->bytes_left = size;
182 stream->bytes_left -= size;
186 /* Iterator for pb_field_t list */
188 const pb_field_t *start;
189 const pb_field_t *current;
194 } pb_field_iterator_t;
196 static void pb_field_init(pb_field_iterator_t *iter, const pb_field_t *fields, void *dest_struct)
198 iter->start = iter->current = fields;
199 iter->field_index = 0;
200 iter->pData = dest_struct + iter->current->data_offset;
201 iter->pSize = (char*)iter->pData + iter->current->size_offset;
202 iter->dest_struct = dest_struct;
205 static bool pb_field_next(pb_field_iterator_t *iter)
207 bool notwrapped = true;
208 size_t prev_size = iter->current->data_size;
210 if (PB_HTYPE(iter->current->type) == PB_HTYPE_ARRAY)
211 prev_size *= iter->current->array_size;
215 if (iter->current->tag == 0)
217 iter->current = iter->start;
218 iter->field_index = 0;
219 iter->pData = iter->dest_struct;
224 iter->pData = (char*)iter->pData + prev_size + iter->current->data_offset;
225 iter->pSize = (char*)iter->pData + iter->current->size_offset;
229 static bool checkreturn pb_field_find(pb_field_iterator_t *iter, int tag)
231 int start = iter->field_index;
234 if (iter->current->tag == tag)
237 } while (iter->field_index != start);
242 /*************************
243 * Decode a single field *
244 *************************/
246 static bool checkreturn decode_field(pb_istream_t *stream, int wire_type, pb_field_iterator_t *iter)
248 pb_decoder_t func = PB_DECODERS[PB_LTYPE(iter->current->type)];
250 switch (PB_HTYPE(iter->current->type))
252 case PB_HTYPE_REQUIRED:
253 return func(stream, iter->current, iter->pData);
255 case PB_HTYPE_OPTIONAL:
256 *(bool*)iter->pSize = true;
257 return func(stream, iter->current, iter->pData);
260 if (wire_type == PB_WT_STRING
261 && PB_LTYPE(iter->current->type) <= PB_LTYPE_LAST_PACKABLE)
264 size_t *size = (size_t*)iter->pSize;
265 pb_istream_t substream;
266 if (!make_string_substream(stream, &substream))
269 while (substream.bytes_left && *size < iter->current->array_size)
271 void *pItem = (uint8_t*)iter->pData + iter->current->data_size * (*size);
272 if (!func(&substream, iter->current, pItem))
276 return (substream.bytes_left == 0);
281 size_t *size = (size_t*)iter->pSize;
282 void *pItem = (uint8_t*)iter->pData + iter->current->data_size * (*size);
283 if (*size >= iter->current->array_size)
287 return func(stream, iter->current, pItem);
290 case PB_HTYPE_CALLBACK:
292 pb_callback_t *pCallback = (pb_callback_t*)iter->pData;
294 if (pCallback->funcs.decode == NULL)
295 return skip(stream, wire_type);
297 if (wire_type == PB_WT_STRING)
299 pb_istream_t substream;
301 if (!make_string_substream(stream, &substream))
304 while (substream.bytes_left)
306 if (!pCallback->funcs.decode(&substream, iter->current, pCallback->arg))
310 stream->state = substream.state;
315 /* Copy the single scalar value to stack.
316 * This is required so that we can limit the stream length,
317 * which in turn allows to use same callback for packed and
318 * not-packed fields. */
319 pb_istream_t substream;
321 size_t size = sizeof(buffer);
323 if (!read_raw_value(stream, wire_type, buffer, &size))
325 substream = pb_istream_from_buffer(buffer, size);
327 return pCallback->funcs.decode(&substream, iter->current, pCallback->arg);
336 /* Initialize message fields to default values, recursively */
337 static void pb_message_set_to_defaults(const pb_field_t fields[], void *dest_struct)
339 pb_field_iterator_t iter;
340 pb_field_init(&iter, fields, dest_struct);
342 /* Initialize size/has fields and apply default values */
345 if (iter.current->tag == 0)
348 /* Initialize the size field for optional/repeated fields to 0. */
349 if (PB_HTYPE(iter.current->type) == PB_HTYPE_OPTIONAL)
351 *(bool*)iter.pSize = false;
353 else if (PB_HTYPE(iter.current->type) == PB_HTYPE_ARRAY)
355 *(size_t*)iter.pSize = 0;
356 continue; /* Array is empty, no need to initialize contents */
359 /* Initialize field contents to default value */
360 if (PB_HTYPE(iter.current->type) == PB_HTYPE_CALLBACK)
362 continue; /* Don't overwrite callback */
364 else if (PB_LTYPE(iter.current->type) == PB_LTYPE_SUBMESSAGE)
366 pb_message_set_to_defaults(iter.current->ptr, iter.pData);
368 else if (iter.current->ptr != NULL)
370 memcpy(iter.pData, iter.current->ptr, iter.current->data_size);
374 memset(iter.pData, 0, iter.current->data_size);
376 } while (pb_field_next(&iter));
379 /*********************
380 * Decode all fields *
381 *********************/
383 bool checkreturn pb_decode(pb_istream_t *stream, const pb_field_t fields[], void *dest_struct)
385 uint32_t fields_seen = 0; /* Used to check for required fields */
386 pb_field_iterator_t iter;
389 pb_message_set_to_defaults(fields, dest_struct);
391 pb_field_init(&iter, fields, dest_struct);
393 while (stream->bytes_left)
397 if (!pb_decode_varint32(stream, &temp))
399 if (stream->bytes_left == 0)
400 break; /* It was EOF */
402 return false; /* It was error */
406 break; /* Special feature: allow 0-terminated messages. */
409 wire_type = temp & 7;
411 if (!pb_field_find(&iter, tag))
413 /* No match found, skip data */
414 if (!skip(stream, wire_type))
419 fields_seen |= 1 << (iter.field_index & 31);
421 if (!decode_field(stream, wire_type, &iter))
425 /* Check that all required fields (mod 31) were present. */
426 for (i = 0; fields[i].tag != 0; i++)
428 if (PB_HTYPE(fields[i].type) == PB_HTYPE_REQUIRED &&
429 !(fields_seen & (1 << (i & 31))))
440 /* Copy destsize bytes from src so that values are casted properly.
441 * On little endian machine, copy first n bytes of src
442 * On big endian machine, copy last n bytes of src
443 * srcsize must always be larger than destsize
445 static void endian_copy(void *dest, void *src, size_t destsize, size_t srcsize)
447 #ifdef __BIG_ENDIAN__
448 memcpy(dest, (char*)src + (srcsize - destsize), destsize);
450 memcpy(dest, src, destsize);
454 bool checkreturn pb_dec_varint(pb_istream_t *stream, const pb_field_t *field, void *dest)
457 bool status = pb_decode_varint(stream, &temp);
458 endian_copy(dest, &temp, field->data_size, sizeof(temp));
462 bool checkreturn pb_dec_svarint(pb_istream_t *stream, const pb_field_t *field, void *dest)
465 bool status = pb_decode_varint(stream, &temp);
466 temp = (temp >> 1) ^ -(int64_t)(temp & 1);
467 endian_copy(dest, &temp, field->data_size, sizeof(temp));
471 bool checkreturn pb_dec_fixed32(pb_istream_t *stream, const pb_field_t *field, void *dest)
473 #ifdef __BIG_ENDIAN__
474 uint8_t bytes[4] = {0};
475 bool status = pb_read(stream, bytes, 4);
476 uint8_t bebytes[4] = {bytes[3], bytes[2], bytes[1], bytes[0]};
477 memcpy(dest, bebytes, 4);
480 return pb_read(stream, (uint8_t*)dest, 4);
484 bool checkreturn pb_dec_fixed64(pb_istream_t *stream, const pb_field_t *field, void *dest)
486 #ifdef __BIG_ENDIAN__
487 uint8_t bytes[8] = {0};
488 bool status = pb_read(stream, bytes, 8);
489 uint8_t bebytes[8] = {bytes[7], bytes[6], bytes[5], bytes[4],
490 bytes[3], bytes[2], bytes[1], bytes[0]};
491 memcpy(dest, bebytes, 8);
494 return pb_read(stream, (uint8_t*)dest, 8);
498 bool checkreturn pb_dec_bytes(pb_istream_t *stream, const pb_field_t *field, void *dest)
500 pb_bytes_array_t *x = (pb_bytes_array_t*)dest;
503 if (!pb_decode_varint32(stream, &temp))
507 if (x->size > field->data_size)
510 return pb_read(stream, x->bytes, x->size);
513 bool checkreturn pb_dec_string(pb_istream_t *stream, const pb_field_t *field, void *dest)
517 if (!pb_decode_varint32(stream, &size))
520 if (size > field->data_size - 1)
523 status = pb_read(stream, (uint8_t*)dest, size);
524 *((uint8_t*)dest + size) = 0;
528 bool checkreturn pb_dec_submessage(pb_istream_t *stream, const pb_field_t *field, void *dest)
531 pb_istream_t substream;
533 if (!make_string_substream(stream, &substream))
536 if (field->ptr == NULL)
539 status = pb_decode(&substream, (pb_field_t*)field->ptr, dest);
540 stream->state = substream.state;