1 /* pb_encode.c -- encode a protobuf using minimal resources
3 * 2011 Petteri Aimonen <jpa@kapsi.fi>
11 /* Verify that we remember to check all return values for proper error propagation */
12 #define checkreturn __attribute__((warn_unused_result))
18 typedef bool (*pb_encoder_t)(pb_ostream_t *stream, const pb_field_t *field, const void *src) checkreturn;
20 /* --- Function pointers to field encoders ---
21 * Order in the array must match pb_action_t LTYPE numbering.
23 static const pb_encoder_t PB_ENCODERS[PB_LTYPES_COUNT] = {
34 /* pb_ostream_t implementation */
36 static bool checkreturn buf_write(pb_ostream_t *stream, const uint8_t *buf, size_t count)
38 uint8_t *dest = (uint8_t*)stream->state;
39 memcpy(dest, buf, count);
40 stream->state = dest + count;
44 pb_ostream_t pb_ostream_from_buffer(uint8_t *buf, size_t bufsize)
47 stream.callback = &buf_write;
49 stream.max_size = bufsize;
50 stream.bytes_written = 0;
54 bool checkreturn pb_write(pb_ostream_t *stream, const uint8_t *buf, size_t count)
56 if (stream->callback != NULL)
58 if (stream->bytes_written + count > stream->max_size)
61 if (!stream->callback(stream, buf, count))
65 stream->bytes_written += count;
69 /* Main encoding stuff */
71 /* Callbacks don't need this function because they usually know the data type
72 * without examining the field structure.
73 * Therefore it is static for now.
75 static bool checkreturn encode_array(pb_ostream_t *stream, const pb_field_t *field,
76 const void *pData, size_t count, pb_encoder_t func)
85 if (PB_LTYPE(field->type) <= PB_LTYPE_LAST_PACKABLE)
87 if (!pb_encode_tag(stream, PB_WT_STRING, field->tag))
90 /* Determine the total size of packed array. */
91 if (PB_LTYPE(field->type) == PB_LTYPE_FIXED32)
95 else if (PB_LTYPE(field->type) == PB_LTYPE_FIXED64)
101 pb_ostream_t sizestream = {0};
103 for (i = 0; i < count; i++)
105 if (!func(&sizestream, field, p))
107 p = (const char*)p + field->data_size;
109 size = sizestream.bytes_written;
112 if (!pb_encode_varint(stream, size))
115 if (stream->callback == NULL)
116 return pb_write(stream, NULL, size); /* Just sizing.. */
120 for (i = 0; i < count; i++)
122 if (!func(stream, field, p))
124 p = (const char*)p + field->data_size;
130 for (i = 0; i < count; i++)
132 if (!pb_encode_tag_for_field(stream, field))
134 if (!func(stream, field, p))
136 p = (const char*)p + field->data_size;
143 bool checkreturn pb_encode(pb_ostream_t *stream, const pb_field_t fields[], const void *src_struct)
145 const pb_field_t *field = fields;
146 const void *pData = src_struct;
148 size_t prev_size = 0;
150 while (field->tag != 0)
152 pData = (const char*)pData + prev_size + field->data_offset;
153 pSize = (const char*)pData + field->size_offset;
155 prev_size = field->data_size;
156 if (PB_HTYPE(field->type) == PB_HTYPE_ARRAY)
157 prev_size *= field->array_size;
159 pb_encoder_t func = PB_ENCODERS[PB_LTYPE(field->type)];
161 switch (PB_HTYPE(field->type))
163 case PB_HTYPE_REQUIRED:
164 if (!pb_encode_tag_for_field(stream, field))
166 if (!func(stream, field, pData))
170 case PB_HTYPE_OPTIONAL:
173 if (!pb_encode_tag_for_field(stream, field))
176 if (!func(stream, field, pData))
182 if (!encode_array(stream, field, pData, *(size_t*)pSize, func))
186 case PB_HTYPE_CALLBACK:
188 pb_callback_t *callback = (pb_callback_t*)pData;
189 if (callback->funcs.encode != NULL)
191 if (!callback->funcs.encode(stream, field, callback->arg))
204 /* Helper functions */
205 bool checkreturn pb_encode_varint(pb_ostream_t *stream, uint64_t value)
211 return pb_write(stream, (uint8_t*)&value, 1);
215 buffer[i] = (value & 0x7F) | 0x80;
219 buffer[i-1] &= 0x7F; /* Unset top bit on last byte */
221 return pb_write(stream, buffer, i);
224 bool checkreturn pb_encode_tag(pb_ostream_t *stream, pb_wire_type_t wiretype, int field_number)
226 int tag = wiretype | (field_number << 3);
227 return pb_encode_varint(stream, tag);
230 bool checkreturn pb_encode_tag_for_field(pb_ostream_t *stream, const pb_field_t *field)
232 pb_wire_type_t wiretype;
233 switch (PB_LTYPE(field->type))
235 case PB_LTYPE_VARINT:
236 case PB_LTYPE_SVARINT:
237 wiretype = PB_WT_VARINT;
240 case PB_LTYPE_FIXED32:
241 wiretype = PB_WT_32BIT;
244 case PB_LTYPE_FIXED64:
245 wiretype = PB_WT_64BIT;
249 case PB_LTYPE_STRING:
250 case PB_LTYPE_SUBMESSAGE:
251 wiretype = PB_WT_STRING;
258 return pb_encode_tag(stream, wiretype, field->tag);
261 bool checkreturn pb_encode_string(pb_ostream_t *stream, const uint8_t *buffer, size_t size)
263 if (!pb_encode_varint(stream, size))
266 return pb_write(stream, buffer, size);
271 /* Copy srcsize bytes from src so that values are casted properly.
272 * On little endian machine, copy to start of dest
273 * On big endian machine, copy to end of dest
274 * destsize must always be larger than srcsize
276 * Note: This is the reverse of the endian_copy in pb_decode.c.
278 static void endian_copy(void *dest, const void *src, size_t destsize, size_t srcsize)
280 #ifdef __BIG_ENDIAN__
281 memcpy((char*)dest + (destsize - srcsize), src, srcsize);
283 memcpy(dest, src, srcsize);
287 bool checkreturn pb_enc_varint(pb_ostream_t *stream, const pb_field_t *field, const void *src)
290 endian_copy(&value, src, sizeof(value), field->data_size);
291 return pb_encode_varint(stream, value);
294 bool checkreturn pb_enc_svarint(pb_ostream_t *stream, const pb_field_t *field, const void *src)
298 uint64_t signbitmask, xormask;
299 endian_copy(&value, src, sizeof(value), field->data_size);
301 signbitmask = (uint64_t)0x80 << (field->data_size * 8 - 8);
302 xormask = ((uint64_t)-1) >> (64 - field->data_size * 8);
303 if (value & signbitmask)
304 zigzagged = ((value ^ xormask) << 1) | 1;
306 zigzagged = value << 1;
308 return pb_encode_varint(stream, zigzagged);
311 bool checkreturn pb_enc_fixed64(pb_ostream_t *stream, const pb_field_t *field, const void *src)
313 #ifdef __BIG_ENDIAN__
314 uint8_t bytes[8] = {0};
315 memcpy(bytes, src, 8);
316 uint8_t lebytes[8] = {bytes[7], bytes[6], bytes[5], bytes[4],
317 bytes[3], bytes[2], bytes[1], bytes[0]};
318 return pb_write(stream, lebytes, 8);
320 return pb_write(stream, (uint8_t*)src, 8);
324 bool checkreturn pb_enc_fixed32(pb_ostream_t *stream, const pb_field_t *field, const void *src)
326 #ifdef __BIG_ENDIAN__
327 uint8_t bytes[4] = {0};
328 memcpy(bytes, src, 4);
329 uint8_t lebytes[4] = {bytes[3], bytes[2], bytes[1], bytes[0]};
330 return pb_write(stream, lebytes, 4);
332 return pb_write(stream, (uint8_t*)src, 4);
336 bool checkreturn pb_enc_bytes(pb_ostream_t *stream, const pb_field_t *field, const void *src)
338 pb_bytes_array_t *bytes = (pb_bytes_array_t*)src;
339 return pb_encode_string(stream, bytes->bytes, bytes->size);
342 bool checkreturn pb_enc_string(pb_ostream_t *stream, const pb_field_t *field, const void *src)
344 return pb_encode_string(stream, (uint8_t*)src, strlen((char*)src));
347 bool checkreturn pb_enc_submessage(pb_ostream_t *stream, const pb_field_t *field, const void *src)
349 pb_ostream_t substream = {0};
353 if (field->ptr == NULL)
356 if (!pb_encode(&substream, (pb_field_t*)field->ptr, src))
359 size = substream.bytes_written;
361 if (!pb_encode_varint(stream, size))
364 if (stream->callback == NULL)
365 return pb_write(stream, NULL, size); /* Just sizing */
367 if (stream->bytes_written + size > stream->max_size)
370 /* Use a substream to verify that a callback doesn't write more than
371 * what it did the first time. */
372 substream.callback = stream->callback;
373 substream.state = stream->state;
374 substream.max_size = size;
375 substream.bytes_written = 0;
377 status = pb_encode(&substream, (pb_field_t*)field->ptr, src);
379 stream->bytes_written += substream.bytes_written;
381 if (substream.bytes_written != size)