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;
133 prev_size = field->data_size * field->array_size;
135 pb_encoder_t func = PB_ENCODERS[PB_LTYPE(field->type)];
137 switch (PB_HTYPE(field->type))
139 case PB_HTYPE_REQUIRED:
140 if (!pb_encode_tag_for_field(stream, field))
142 if (!func(stream, field, pData))
146 case PB_HTYPE_OPTIONAL:
149 if (!pb_encode_tag_for_field(stream, field))
152 if (!func(stream, field, pData))
158 if (!encode_array(stream, field, pData, *(size_t*)pSize, func))
162 case PB_HTYPE_CALLBACK:
164 pb_callback_t *callback = (pb_callback_t*)pData;
165 if (callback->funcs.encode != NULL)
167 if (!callback->funcs.encode(stream, field, callback->arg))
180 /* Helper functions */
181 bool pb_encode_varint(pb_ostream_t *stream, uint64_t value)
187 return pb_write(stream, (uint8_t*)&value, 1);
191 buffer[i] = (value & 0x7F) | 0x80;
195 buffer[i-1] &= 0x7F; /* Unset top bit on last byte */
197 return pb_write(stream, buffer, i);
200 bool pb_encode_tag(pb_ostream_t *stream, pb_wire_type_t wiretype, int field_number)
202 int tag = wiretype | (field_number << 3);
203 return pb_encode_varint(stream, tag);
206 bool pb_encode_tag_for_field(pb_ostream_t *stream, const pb_field_t *field)
208 pb_wire_type_t wiretype;
209 switch (PB_LTYPE(field->type))
211 case PB_LTYPE_VARINT:
212 case PB_LTYPE_SVARINT:
213 wiretype = PB_WT_VARINT;
217 if (field->data_size == 4)
218 wiretype = PB_WT_32BIT;
219 else if (field->data_size == 8)
220 wiretype = PB_WT_64BIT;
226 case PB_LTYPE_STRING:
227 case PB_LTYPE_SUBMESSAGE:
228 wiretype = PB_WT_STRING;
235 return pb_encode_tag(stream, wiretype, field->tag);
238 bool pb_encode_string(pb_ostream_t *stream, const uint8_t *buffer, size_t size)
240 if (!pb_encode_varint(stream, size))
243 return pb_write(stream, buffer, size);
248 /* Copy srcsize bytes from src so that values are casted properly.
249 * On little endian machine, copy to start of dest
250 * On big endian machine, copy to end of dest
251 * destsize must always be larger than srcsize
253 * Note: This is the reverse of the endian_copy in pb_decode.c.
255 static void endian_copy(void *dest, const void *src, size_t destsize, size_t srcsize)
257 #ifdef __BIG_ENDIAN__
258 memcpy((char*)dest + (destsize - srcsize), src, srcsize);
260 memcpy(dest, src, srcsize);
264 bool pb_enc_varint(pb_ostream_t *stream, const pb_field_t *field, const void *src)
267 endian_copy(&value, src, sizeof(value), field->data_size);
268 return pb_encode_varint(stream, value);
271 bool pb_enc_svarint(pb_ostream_t *stream, const pb_field_t *field, const void *src)
275 uint64_t signbitmask, xormask;
276 endian_copy(&value, src, sizeof(value), field->data_size);
278 signbitmask = (uint64_t)0x80 << (field->data_size * 8 - 8);
279 xormask = ((uint64_t)-1) >> (64 - field->data_size * 8);
280 if (value & signbitmask)
281 zigzagged = ((value ^ xormask) << 1) | 1;
283 zigzagged = value << 1;
285 return pb_encode_varint(stream, zigzagged);
288 bool pb_enc_fixed(pb_ostream_t *stream, const pb_field_t *field, const void *src)
290 #ifdef __BIG_ENDIAN__
291 uint8_t bytes[8] = {0};
292 endian_copy(bytes, src, sizeof(bytes), field->data_size);
293 uint8_t lebytes[8] = {bytes[7], bytes[6], bytes[5], bytes[4],
294 bytes[3], bytes[2], bytes[1], bytes[0]};
295 return pb_write(stream, lebytes, field->data_size);
297 return pb_write(stream, (uint8_t*)src, field->data_size);
301 bool pb_enc_bytes(pb_ostream_t *stream, const pb_field_t *field, const void *src)
303 pb_bytes_array_t *bytes = (pb_bytes_array_t*)src;
304 return pb_encode_string(stream, bytes->bytes, bytes->size);
307 bool pb_enc_string(pb_ostream_t *stream, const pb_field_t *field, const void *src)
309 return pb_encode_string(stream, (uint8_t*)src, strlen((char*)src));
312 bool pb_enc_submessage(pb_ostream_t *stream, const pb_field_t *field, const void *src)
314 pb_ostream_t substream = {0};
318 if (field->ptr == NULL)
321 if (!pb_encode(&substream, (pb_field_t*)field->ptr, src))
324 size = substream.bytes_written;
326 if (!pb_encode_varint(stream, size))
329 if (stream->callback == NULL)
330 return pb_write(stream, NULL, size); /* Just sizing */
332 if (stream->bytes_written + size > stream->max_size)
335 /* Use a substream to verify that a callback doesn't write more than
336 * what it did the first time. */
337 substream.callback = stream->callback;
338 substream.state = stream->state;
339 substream.max_size = size;
340 substream.bytes_written = 0;
342 status = pb_encode(stream, (pb_field_t*)field->ptr, src);
344 stream->bytes_written += substream.bytes_written;
346 if (substream.bytes_written != size)