1 /* pb_encode.c -- encode a protobuf using minimal resources
3 * 2011 Petteri Aimonen <jpa@kapsi.fi>
10 typedef bool (*pb_encoder_t)(pb_ostream_t *stream, const pb_field_t *field, const void *src);
12 /* --- Function pointers to field encoders ---
13 * Order in the array must match pb_action_t LTYPE numbering.
15 static const pb_encoder_t PB_ENCODERS[PB_LTYPES_COUNT] = {
25 /* pb_ostream_t implementation */
27 static bool buf_write(pb_ostream_t *stream, const uint8_t *buf, size_t count)
29 uint8_t *dest = (uint8_t*)stream->state;
30 memcpy(dest, buf, count);
31 stream->state = dest + count;
35 pb_ostream_t pb_ostream_from_buffer(uint8_t *buf, size_t bufsize)
38 stream.callback = &buf_write;
40 stream.max_size = bufsize;
41 stream.bytes_written = 0;
45 bool pb_write(pb_ostream_t *stream, const uint8_t *buf, size_t count)
47 stream->bytes_written += count;
49 if (stream->callback == NULL)
52 if (stream->bytes_written > stream->max_size)
55 return stream->callback(stream, buf, count);
58 /* Main encoding stuff */
60 static bool encode_array(pb_ostream_t *stream, const pb_field_t *field,
61 const void *pData, size_t count, pb_encoder_t func)
67 if (PB_LTYPE(field->type) < PB_LTYPE_LAST_PACKABLE)
69 if (!pb_encode_tag(stream, PB_WT_STRING, field->tag))
72 /* Determine the total size of packed array. */
73 if (PB_LTYPE(field->type) == PB_LTYPE_FIXED)
75 size = field->data_size * count;
79 pb_ostream_t sizestream = {0};
81 for (i = 0; i < count; i++)
83 if (!func(&sizestream, field, p))
85 p = (const char*)p + field->data_size;
87 size = sizestream.bytes_written;
90 pb_encode_varint(stream, size);
92 if (stream->callback == NULL)
93 return pb_write(stream, NULL, size); /* Just sizing.. */
97 for (i = 0; i < count; i++)
99 if (!func(stream, field, p))
101 p = (const char*)p + field->data_size;
107 for (i = 0; i < count; i++)
109 if (!pb_encode_tag_for_field(stream, field))
111 if (!func(stream, field, p))
113 p = (const char*)p + field->data_size;
120 bool pb_encode(pb_ostream_t *stream, const pb_field_t fields[], const void *src_struct)
122 const pb_field_t *field = fields;
123 const void *pData = src_struct;
126 while (field->tag != 0)
128 pData = (const char*)pData + field->data_offset;
129 pSize = (const char*)pData + field->size_offset;
131 pb_encoder_t func = PB_ENCODERS[PB_LTYPE(field->type)];
133 switch (PB_HTYPE(field->type))
135 case PB_HTYPE_REQUIRED:
136 if (!pb_encode_tag_for_field(stream, field))
138 if (!func(stream, field, pData))
142 case PB_HTYPE_OPTIONAL:
145 if (!pb_encode_tag_for_field(stream, field))
148 if (!func(stream, field, pData))
154 if (!encode_array(stream, field, pData, *(size_t*)pSize, func))
158 case PB_HTYPE_CALLBACK:
160 pb_callback_t *callback = (pb_callback_t*)pData;
161 if (callback->funcs.encode != NULL)
163 if (!callback->funcs.encode(stream, field, callback->arg))
176 /* Helper functions */
177 bool pb_encode_varint(pb_ostream_t *stream, uint64_t value)
183 return pb_write(stream, (uint8_t*)&value, 1);
187 buffer[i] = (value & 0x7F) | 0x80;
191 buffer[i-1] &= 0x7F; /* Unset top bit on last byte */
193 return pb_write(stream, buffer, i);
196 bool pb_encode_tag(pb_ostream_t *stream, pb_wire_type_t wiretype, int field_number)
198 int tag = wiretype | (field_number << 3);
199 return pb_encode_varint(stream, tag);
202 bool pb_encode_tag_for_field(pb_ostream_t *stream, const pb_field_t *field)
204 pb_wire_type_t wiretype;
205 switch (PB_LTYPE(field->type))
207 case PB_LTYPE_VARINT:
208 case PB_LTYPE_SVARINT:
209 wiretype = PB_WT_VARINT;
213 if (field->data_size == 4)
214 wiretype = PB_WT_32BIT;
215 else if (field->data_size == 8)
216 wiretype = PB_WT_64BIT;
222 case PB_LTYPE_STRING:
223 case PB_LTYPE_SUBMESSAGE:
224 wiretype = PB_WT_STRING;
231 return pb_encode_tag(stream, wiretype, field->tag);
234 bool pb_encode_string(pb_ostream_t *stream, uint8_t *buffer, size_t size)
236 if (!pb_encode_varint(stream, size))
239 return pb_write(stream, buffer, size);
244 /* Copy srcsize bytes from src so that values are casted properly.
245 * On little endian machine, copy to start of dest
246 * On big endian machine, copy to end of dest
247 * destsize must always be larger than srcsize
249 * Note: This is the reverse of the endian_copy in pb_decode.c.
251 static void endian_copy(void *dest, const void *src, size_t destsize, size_t srcsize)
253 #ifdef __BIG_ENDIAN__
254 memcpy((char*)dest + (destsize - srcsize), src, srcsize);
256 memcpy(dest, src, srcsize);
260 bool pb_enc_varint(pb_ostream_t *stream, const pb_field_t *field, const void *src)
263 endian_copy(&value, src, sizeof(value), field->data_size);
264 return pb_encode_varint(stream, value);
267 bool pb_enc_svarint(pb_ostream_t *stream, const pb_field_t *field, const void *src)
272 endian_copy(&value, src, sizeof(value), field->data_size);
274 mask = 0x80 << (field->data_size * 8);
275 zigzagged = (value & ~mask) << 1;
276 if (value & mask) zigzagged |= 1;
278 return pb_encode_varint(stream, value);
281 bool pb_enc_fixed(pb_ostream_t *stream, const pb_field_t *field, const void *src)
283 #ifdef __BIG_ENDIAN__
284 uint8_t bytes[8] = {0};
285 endian_copy(bytes, src, sizeof(bytes), field->data_size);
286 uint8_t lebytes[8] = {bytes[7], bytes[6], bytes[5], bytes[4],
287 bytes[3], bytes[2], bytes[1], bytes[0]};
288 return pb_write(stream, lebytes, field->data_size);
290 return pb_write(stream, (uint8_t*)src, field->data_size);
294 bool pb_enc_bytes(pb_ostream_t *stream, const pb_field_t *field, const void *src)
296 pb_bytes_array_t *bytes = (pb_bytes_array_t*)src;
297 return pb_encode_string(stream, bytes->bytes, bytes->size);
300 bool pb_enc_string(pb_ostream_t *stream, const pb_field_t *field, const void *src)
302 return pb_encode_string(stream, (uint8_t*)src, strlen((char*)src));
305 bool pb_enc_submessage(pb_ostream_t *stream, const pb_field_t *field, const void *src)
307 pb_ostream_t sizestream = {0};
310 if (field->ptr == NULL)
313 if (!pb_encode(&sizestream, (pb_field_t*)field->ptr, src))
316 size = sizestream.bytes_written;
318 if (!pb_encode_varint(stream, size))
321 if (stream->callback == NULL)
322 return pb_write(stream, NULL, size); /* Just sizing */
324 return pb_encode(stream, (pb_field_t*)field->ptr, src);