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 if (stream->callback != NULL)
49 if (stream->bytes_written + count > stream->max_size)
52 if (!stream->callback(stream, buf, count))
56 stream->bytes_written += count;
60 /* Main encoding stuff */
62 static bool encode_array(pb_ostream_t *stream, const pb_field_t *field,
63 const void *pData, size_t count, pb_encoder_t func)
69 if (PB_LTYPE(field->type) < PB_LTYPE_LAST_PACKABLE)
71 if (!pb_encode_tag(stream, PB_WT_STRING, field->tag))
74 /* Determine the total size of packed array. */
75 if (PB_LTYPE(field->type) == PB_LTYPE_FIXED)
77 size = field->data_size * count;
81 pb_ostream_t sizestream = {0};
83 for (i = 0; i < count; i++)
85 if (!func(&sizestream, field, p))
87 p = (const char*)p + field->data_size;
89 size = sizestream.bytes_written;
92 pb_encode_varint(stream, size);
94 if (stream->callback == NULL)
95 return pb_write(stream, NULL, size); /* Just sizing.. */
99 for (i = 0; i < count; i++)
101 if (!func(stream, field, p))
103 p = (const char*)p + field->data_size;
109 for (i = 0; i < count; i++)
111 if (!pb_encode_tag_for_field(stream, field))
113 if (!func(stream, field, p))
115 p = (const char*)p + field->data_size;
122 bool pb_encode(pb_ostream_t *stream, const pb_field_t fields[], const void *src_struct)
124 const pb_field_t *field = fields;
125 const void *pData = src_struct;
127 size_t prev_size = 0;
129 while (field->tag != 0)
131 pData = (const char*)pData + prev_size + field->data_offset;
132 pSize = (const char*)pData + field->size_offset;
134 prev_size = field->data_size;
135 if (PB_HTYPE(field->type) == PB_HTYPE_ARRAY)
136 prev_size *= field->array_size;
138 pb_encoder_t func = PB_ENCODERS[PB_LTYPE(field->type)];
140 switch (PB_HTYPE(field->type))
142 case PB_HTYPE_REQUIRED:
143 if (!pb_encode_tag_for_field(stream, field))
145 if (!func(stream, field, pData))
149 case PB_HTYPE_OPTIONAL:
152 if (!pb_encode_tag_for_field(stream, field))
155 if (!func(stream, field, pData))
161 if (!encode_array(stream, field, pData, *(size_t*)pSize, func))
165 case PB_HTYPE_CALLBACK:
167 pb_callback_t *callback = (pb_callback_t*)pData;
168 if (callback->funcs.encode != NULL)
170 if (!callback->funcs.encode(stream, field, callback->arg))
183 /* Helper functions */
184 bool pb_encode_varint(pb_ostream_t *stream, uint64_t value)
190 return pb_write(stream, (uint8_t*)&value, 1);
194 buffer[i] = (value & 0x7F) | 0x80;
198 buffer[i-1] &= 0x7F; /* Unset top bit on last byte */
200 return pb_write(stream, buffer, i);
203 bool pb_encode_tag(pb_ostream_t *stream, pb_wire_type_t wiretype, int field_number)
205 int tag = wiretype | (field_number << 3);
206 return pb_encode_varint(stream, tag);
209 bool pb_encode_tag_for_field(pb_ostream_t *stream, const pb_field_t *field)
211 pb_wire_type_t wiretype;
212 switch (PB_LTYPE(field->type))
214 case PB_LTYPE_VARINT:
215 case PB_LTYPE_SVARINT:
216 wiretype = PB_WT_VARINT;
220 if (field->data_size == 4)
221 wiretype = PB_WT_32BIT;
222 else if (field->data_size == 8)
223 wiretype = PB_WT_64BIT;
229 case PB_LTYPE_STRING:
230 case PB_LTYPE_SUBMESSAGE:
231 wiretype = PB_WT_STRING;
238 return pb_encode_tag(stream, wiretype, field->tag);
241 bool pb_encode_string(pb_ostream_t *stream, const uint8_t *buffer, size_t size)
243 if (!pb_encode_varint(stream, size))
246 return pb_write(stream, buffer, size);
251 /* Copy srcsize bytes from src so that values are casted properly.
252 * On little endian machine, copy to start of dest
253 * On big endian machine, copy to end of dest
254 * destsize must always be larger than srcsize
256 * Note: This is the reverse of the endian_copy in pb_decode.c.
258 static void endian_copy(void *dest, const void *src, size_t destsize, size_t srcsize)
260 #ifdef __BIG_ENDIAN__
261 memcpy((char*)dest + (destsize - srcsize), src, srcsize);
263 memcpy(dest, src, srcsize);
267 bool pb_enc_varint(pb_ostream_t *stream, const pb_field_t *field, const void *src)
270 endian_copy(&value, src, sizeof(value), field->data_size);
271 return pb_encode_varint(stream, value);
274 bool pb_enc_svarint(pb_ostream_t *stream, const pb_field_t *field, const void *src)
278 uint64_t signbitmask, xormask;
279 endian_copy(&value, src, sizeof(value), field->data_size);
281 signbitmask = (uint64_t)0x80 << (field->data_size * 8 - 8);
282 xormask = ((uint64_t)-1) >> (64 - field->data_size * 8);
283 if (value & signbitmask)
284 zigzagged = ((value ^ xormask) << 1) | 1;
286 zigzagged = value << 1;
288 return pb_encode_varint(stream, zigzagged);
291 bool pb_enc_fixed(pb_ostream_t *stream, const pb_field_t *field, const void *src)
293 #ifdef __BIG_ENDIAN__
294 uint8_t bytes[8] = {0};
295 endian_copy(bytes, src, sizeof(bytes), field->data_size);
296 uint8_t lebytes[8] = {bytes[7], bytes[6], bytes[5], bytes[4],
297 bytes[3], bytes[2], bytes[1], bytes[0]};
298 return pb_write(stream, lebytes, field->data_size);
300 return pb_write(stream, (uint8_t*)src, field->data_size);
304 bool pb_enc_bytes(pb_ostream_t *stream, const pb_field_t *field, const void *src)
306 pb_bytes_array_t *bytes = (pb_bytes_array_t*)src;
307 return pb_encode_string(stream, bytes->bytes, bytes->size);
310 bool pb_enc_string(pb_ostream_t *stream, const pb_field_t *field, const void *src)
312 return pb_encode_string(stream, (uint8_t*)src, strlen((char*)src));
315 bool pb_enc_submessage(pb_ostream_t *stream, const pb_field_t *field, const void *src)
317 pb_ostream_t substream = {0};
321 if (field->ptr == NULL)
324 if (!pb_encode(&substream, (pb_field_t*)field->ptr, src))
327 size = substream.bytes_written;
329 if (!pb_encode_varint(stream, size))
332 if (stream->callback == NULL)
333 return pb_write(stream, NULL, size); /* Just sizing */
335 if (stream->bytes_written + size > stream->max_size)
338 /* Use a substream to verify that a callback doesn't write more than
339 * what it did the first time. */
340 substream.callback = stream->callback;
341 substream.state = stream->state;
342 substream.max_size = size;
343 substream.bytes_written = 0;
345 status = pb_encode(&substream, (pb_field_t*)field->ptr, src);
347 stream->bytes_written += substream.bytes_written;
349 if (substream.bytes_written != size)