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;
128 while (field->tag != 0)
130 pData = (const char*)pData + field->data_offset;
131 pSize = (const char*)pData + field->size_offset;
133 pb_encoder_t func = PB_ENCODERS[PB_LTYPE(field->type)];
135 switch (PB_HTYPE(field->type))
137 case PB_HTYPE_REQUIRED:
138 if (!pb_encode_tag_for_field(stream, field))
140 if (!func(stream, field, pData))
144 case PB_HTYPE_OPTIONAL:
147 if (!pb_encode_tag_for_field(stream, field))
150 if (!func(stream, field, pData))
156 if (!encode_array(stream, field, pData, *(size_t*)pSize, func))
160 case PB_HTYPE_CALLBACK:
162 pb_callback_t *callback = (pb_callback_t*)pData;
163 if (callback->funcs.encode != NULL)
165 if (!callback->funcs.encode(stream, field, callback->arg))
178 /* Helper functions */
179 bool pb_encode_varint(pb_ostream_t *stream, uint64_t value)
185 return pb_write(stream, (uint8_t*)&value, 1);
189 buffer[i] = (value & 0x7F) | 0x80;
193 buffer[i-1] &= 0x7F; /* Unset top bit on last byte */
195 return pb_write(stream, buffer, i);
198 bool pb_encode_tag(pb_ostream_t *stream, pb_wire_type_t wiretype, int field_number)
200 int tag = wiretype | (field_number << 3);
201 return pb_encode_varint(stream, tag);
204 bool pb_encode_tag_for_field(pb_ostream_t *stream, const pb_field_t *field)
206 pb_wire_type_t wiretype;
207 switch (PB_LTYPE(field->type))
209 case PB_LTYPE_VARINT:
210 case PB_LTYPE_SVARINT:
211 wiretype = PB_WT_VARINT;
215 if (field->data_size == 4)
216 wiretype = PB_WT_32BIT;
217 else if (field->data_size == 8)
218 wiretype = PB_WT_64BIT;
224 case PB_LTYPE_STRING:
225 case PB_LTYPE_SUBMESSAGE:
226 wiretype = PB_WT_STRING;
233 return pb_encode_tag(stream, wiretype, field->tag);
236 bool pb_encode_string(pb_ostream_t *stream, const uint8_t *buffer, size_t size)
238 if (!pb_encode_varint(stream, size))
241 return pb_write(stream, buffer, size);
246 /* Copy srcsize bytes from src so that values are casted properly.
247 * On little endian machine, copy to start of dest
248 * On big endian machine, copy to end of dest
249 * destsize must always be larger than srcsize
251 * Note: This is the reverse of the endian_copy in pb_decode.c.
253 static void endian_copy(void *dest, const void *src, size_t destsize, size_t srcsize)
255 #ifdef __BIG_ENDIAN__
256 memcpy((char*)dest + (destsize - srcsize), src, srcsize);
258 memcpy(dest, src, srcsize);
262 bool pb_enc_varint(pb_ostream_t *stream, const pb_field_t *field, const void *src)
265 endian_copy(&value, src, sizeof(value), field->data_size);
266 return pb_encode_varint(stream, value);
269 bool pb_enc_svarint(pb_ostream_t *stream, const pb_field_t *field, const void *src)
273 uint64_t signbitmask, xormask;
274 endian_copy(&value, src, sizeof(value), field->data_size);
276 signbitmask = (uint64_t)0x80 << (field->data_size * 8 - 8);
277 xormask = ((uint64_t)-1) >> (64 - field->data_size * 8);
278 if (value & signbitmask)
279 zigzagged = ((value ^ xormask) << 1) | 1;
281 zigzagged = value << 1;
283 return pb_encode_varint(stream, zigzagged);
286 bool pb_enc_fixed(pb_ostream_t *stream, const pb_field_t *field, const void *src)
288 #ifdef __BIG_ENDIAN__
289 uint8_t bytes[8] = {0};
290 endian_copy(bytes, src, sizeof(bytes), field->data_size);
291 uint8_t lebytes[8] = {bytes[7], bytes[6], bytes[5], bytes[4],
292 bytes[3], bytes[2], bytes[1], bytes[0]};
293 return pb_write(stream, lebytes, field->data_size);
295 return pb_write(stream, (uint8_t*)src, field->data_size);
299 bool pb_enc_bytes(pb_ostream_t *stream, const pb_field_t *field, const void *src)
301 pb_bytes_array_t *bytes = (pb_bytes_array_t*)src;
302 return pb_encode_string(stream, bytes->bytes, bytes->size);
305 bool pb_enc_string(pb_ostream_t *stream, const pb_field_t *field, const void *src)
307 return pb_encode_string(stream, (uint8_t*)src, strlen((char*)src));
310 bool pb_enc_submessage(pb_ostream_t *stream, const pb_field_t *field, const void *src)
312 pb_ostream_t sizestream = {0};
315 if (field->ptr == NULL)
318 if (!pb_encode(&sizestream, (pb_field_t*)field->ptr, src))
321 size = sizestream.bytes_written;
323 if (!pb_encode_varint(stream, size))
326 if (stream->callback == NULL)
327 return pb_write(stream, NULL, size); /* Just sizing */
329 return pb_encode(stream, (pb_field_t*)field->ptr, src);