1 /* pb_decode.c -- decode a protobuf using minimal resources
3 * 2011 Petteri Aimonen <jpa@kapsi.fi>
10 typedef bool (*pb_decoder_t)(pb_istream_t *stream, const pb_field_t *field, void *dest);
12 /* --- Function pointers to field decoders ---
13 * Order in the array must match pb_action_t LTYPE numbering.
15 static const pb_decoder_t PB_DECODERS[PB_LTYPES_COUNT] = {
29 bool pb_read(pb_istream_t *stream, uint8_t *buf, size_t count)
31 if (stream->bytes_left < count)
34 if (!stream->callback(stream, buf, count))
37 stream->bytes_left -= count;
41 static bool buf_read(pb_istream_t *stream, uint8_t *buf, size_t count)
43 uint8_t *source = (uint8_t*)stream->state;
46 memcpy(buf, source, count);
48 stream->state = source + count;
52 pb_istream_t pb_istream_from_buffer(uint8_t *buf, size_t bufsize)
55 stream.callback = &buf_read;
57 stream.bytes_left = bufsize;
65 static bool pb_decode_varint32(pb_istream_t *stream, uint32_t *dest)
68 bool status = pb_decode_varint(stream, &temp);
73 bool pb_decode_varint(pb_istream_t *stream, uint64_t *dest)
79 while (bitpos < 64 && pb_read(stream, &byte, 1))
81 *dest |= (uint64_t)(byte & 0x7F) << bitpos;
91 bool pb_skip_varint(pb_istream_t *stream)
96 if (!pb_read(stream, &byte, 1))
98 } while (byte & 0x80);
102 bool pb_skip_string(pb_istream_t *stream)
105 if (!pb_decode_varint32(stream, &length))
108 return pb_read(stream, NULL, length);
111 /* Currently the wire type related stuff is kept hidden from
112 * callbacks. They shouldn't need it. It's better for performance
113 * to just assume the correct type and fail safely on corrupt message.
116 static bool skip(pb_istream_t *stream, int wire_type)
120 case PB_WT_VARINT: return pb_skip_varint(stream);
121 case PB_WT_64BIT: return pb_read(stream, NULL, 8);
122 case PB_WT_STRING: return pb_skip_string(stream);
123 case PB_WT_32BIT: return pb_read(stream, NULL, 4);
124 default: return false;
128 /* Read a raw value to buffer, for the purpose of passing it to callback as
129 * a substream. Size is maximum size on call, and actual size on return.
131 static bool read_raw_value(pb_istream_t *stream, pb_wire_type_t wire_type, uint8_t *buf, size_t *size)
133 size_t max_size = *size;
141 if (*size > max_size) return false;
142 if (!pb_read(stream, buf, 1)) return false;
143 } while (*buf++ & 0x80);
148 return pb_read(stream, buf, 8);
152 return pb_read(stream, buf, 4);
154 default: return false;
158 /* Decode string length from stream and return a substream with limited length */
159 static bool make_string_substream(pb_istream_t *stream, pb_istream_t *substream)
162 if (!pb_decode_varint32(stream, &size))
165 *substream = *stream;
166 if (substream->bytes_left < size)
169 substream->bytes_left = size;
170 stream->bytes_left -= size;
174 /* Iterator for pb_field_t list */
176 const pb_field_t *start;
177 const pb_field_t *current;
182 } pb_field_iterator_t;
184 static void pb_field_init(pb_field_iterator_t *iter, const pb_field_t *fields, void *dest_struct)
186 iter->start = iter->current = fields;
187 iter->field_index = 0;
188 iter->pData = dest_struct;
189 iter->dest_struct = dest_struct;
192 static bool pb_field_next(pb_field_iterator_t *iter)
194 bool notwrapped = true;
195 size_t prev_size = iter->current->data_size * iter->current->array_size;
198 if (iter->current->tag == 0)
200 iter->current = iter->start;
201 iter->field_index = 0;
202 iter->pData = iter->dest_struct;
207 iter->pData = (char*)iter->pData + prev_size + iter->current->data_offset;
208 iter->pSize = (char*)iter->pData + iter->current->size_offset;
212 static bool pb_field_find(pb_field_iterator_t *iter, int tag)
214 int start = iter->field_index;
217 if (iter->current->tag == tag)
220 } while (iter->field_index != start);
225 /*************************
226 * Decode a single field *
227 *************************/
229 static bool decode_field(pb_istream_t *stream, int wire_type, pb_field_iterator_t *iter)
231 pb_decoder_t func = PB_DECODERS[PB_LTYPE(iter->current->type)];
233 switch (PB_HTYPE(iter->current->type))
235 case PB_HTYPE_REQUIRED:
236 return func(stream, iter->current, iter->pData);
238 case PB_HTYPE_OPTIONAL:
239 *(bool*)iter->pSize = true;
240 return func(stream, iter->current, iter->pData);
243 if (wire_type == PB_WT_STRING
244 && PB_LTYPE(iter->current->type) <= PB_LTYPE_LAST_PACKABLE)
247 size_t *size = (size_t*)iter->pSize;
248 pb_istream_t substream;
249 if (!make_string_substream(stream, &substream))
252 while (substream.bytes_left && *size < iter->current->array_size)
254 void *pItem = (uint8_t*)iter->pData + iter->current->data_size * (*size);
255 if (!func(stream, iter->current, pItem))
259 return (substream.bytes_left == 0);
264 size_t *size = (size_t*)iter->pSize;
265 void *pItem = (uint8_t*)iter->pData + iter->current->data_size * (*size);
266 if (*size >= iter->current->array_size)
270 return func(stream, iter->current, pItem);
273 case PB_HTYPE_CALLBACK:
274 if (wire_type == PB_WT_STRING)
276 pb_callback_t *pCallback = (pb_callback_t*)iter->pData;
277 pb_istream_t substream;
279 if (!make_string_substream(stream, &substream))
282 while (substream.bytes_left)
284 if (!pCallback->funcs.decode(&substream, iter->current, pCallback->arg))
291 /* Copy the single scalar value to stack.
292 * This is required so that we can limit the stream length,
293 * which in turn allows to use same callback for packed and
294 * not-packed fields. */
295 pb_istream_t substream;
296 pb_callback_t *pCallback = (pb_callback_t*)iter->pData;
298 size_t size = sizeof(buffer);
300 if (!read_raw_value(stream, wire_type, buffer, &size))
302 substream = pb_istream_from_buffer(buffer, size);
304 return pCallback->funcs.decode(&substream, iter->current, pCallback->arg);
312 /*********************
313 * Decode all fields *
314 *********************/
316 bool pb_decode(pb_istream_t *stream, const pb_field_t fields[], void *dest_struct)
318 uint32_t fields_seen = 0; /* Used to check for required fields */
319 pb_field_iterator_t iter;
322 if (fields[0].tag == 0)
324 /* No fields -> nothing to do */
325 return pb_read(stream, NULL, stream->bytes_left);
328 pb_field_init(&iter, fields, dest_struct);
330 /* Initialize size/has fields and apply default values */
333 if (PB_HTYPE(iter.current->type) == PB_HTYPE_OPTIONAL)
335 *(bool*)iter.pSize = false;
337 /* Initialize to default value */
338 if (iter.current->ptr != NULL)
339 memcpy(iter.pData, iter.current->ptr, iter.current->data_size);
341 memset(iter.pData, 0, iter.current->data_size);
343 else if (PB_HTYPE(iter.current->type) == PB_HTYPE_ARRAY)
345 *(size_t*)iter.pSize = 0;
347 } while (pb_field_next(&iter));
349 while (stream->bytes_left)
353 if (!pb_decode_varint32(stream, &temp))
354 return stream->bytes_left == 0; /* Was it EOF? */
357 return true; /* Special feature: allow 0-terminated messages. */
360 wire_type = temp & 7;
362 if (!pb_field_find(&iter, tag))
364 /* No match found, skip data */
365 skip(stream, wire_type);
369 fields_seen |= 1 << (iter.field_index & 31);
371 if (!decode_field(stream, wire_type, &iter))
375 /* Check that all required fields (mod 31) were present. */
376 for (i = 0; fields[i].tag != 0; i++)
378 if (PB_HTYPE(fields[i].type) == PB_HTYPE_REQUIRED &&
379 !(fields_seen & (1 << (i & 31))))
390 /* Copy destsize bytes from src so that values are casted properly.
391 * On little endian machine, copy first n bytes of src
392 * On big endian machine, copy last n bytes of src
393 * srcsize must always be larger than destsize
395 static void endian_copy(void *dest, void *src, size_t destsize, size_t srcsize)
397 #ifdef __BIG_ENDIAN__
398 memcpy(dest, (char*)src + (srcsize - destsize), destsize);
400 memcpy(dest, src, destsize);
404 bool pb_dec_varint(pb_istream_t *stream, const pb_field_t *field, void *dest)
407 bool status = pb_decode_varint(stream, &temp);
408 endian_copy(dest, &temp, field->data_size, sizeof(temp));
412 bool pb_dec_svarint(pb_istream_t *stream, const pb_field_t *field, void *dest)
415 bool status = pb_decode_varint(stream, &temp);
416 temp = (temp >> 1) ^ -(int64_t)(temp & 1);
417 endian_copy(dest, &temp, field->data_size, sizeof(temp));
421 bool pb_dec_fixed(pb_istream_t *stream, const pb_field_t *field, void *dest)
423 #ifdef __BIG_ENDIAN__
424 uint8_t bytes[8] = {0};
425 bool status = pb_read(stream, bytes, field->data_size);
426 uint8_t bebytes[8] = {bytes[7], bytes[6], bytes[5], bytes[4],
427 bytes[3], bytes[2], bytes[1], bytes[0]};
428 endian_copy(dest, lebytes, field->data_size, 8);
431 return pb_read(stream, (uint8_t*)dest, field->data_size);
435 bool pb_dec_bytes(pb_istream_t *stream, const pb_field_t *field, void *dest)
437 pb_bytes_array_t *x = (pb_bytes_array_t*)dest;
440 if (!pb_decode_varint32(stream, &temp))
444 /* Note: data_size includes the size of the x.size field, too.
445 * Calculate actual size starting from offset. */
446 if (x->size > field->data_size - offsetof(pb_bytes_array_t, bytes))
449 return pb_read(stream, x->bytes, x->size);
452 bool pb_dec_string(pb_istream_t *stream, const pb_field_t *field, void *dest)
456 if (!pb_decode_varint32(stream, &size))
459 if (size > field->data_size - 1)
462 status = pb_read(stream, (uint8_t*)dest, size);
463 *((uint8_t*)dest + size) = 0;
467 bool pb_dec_submessage(pb_istream_t *stream, const pb_field_t *field, void *dest)
469 pb_istream_t substream;
471 if (!make_string_substream(stream, &substream))
474 if (field->ptr == NULL)
477 return pb_decode(&substream, (pb_field_t*)field->ptr, dest);