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] = {
33 /* pb_ostream_t implementation */
35 static bool checkreturn buf_write(pb_ostream_t *stream, const uint8_t *buf, size_t count)
37 uint8_t *dest = (uint8_t*)stream->state;
38 memcpy(dest, buf, count);
39 stream->state = dest + count;
43 pb_ostream_t pb_ostream_from_buffer(uint8_t *buf, size_t bufsize)
46 stream.callback = &buf_write;
48 stream.max_size = bufsize;
49 stream.bytes_written = 0;
53 bool checkreturn pb_write(pb_ostream_t *stream, const uint8_t *buf, size_t count)
55 if (stream->callback != NULL)
57 if (stream->bytes_written + count > stream->max_size)
60 if (!stream->callback(stream, buf, count))
64 stream->bytes_written += count;
68 /* Main encoding stuff */
70 /* Callbacks don't need this function because they usually know the data type
71 * without examining the field structure.
72 * Therefore it is static for now.
74 static bool checkreturn encode_array(pb_ostream_t *stream, const pb_field_t *field,
75 const void *pData, size_t count, pb_encoder_t func)
84 if (PB_LTYPE(field->type) <= PB_LTYPE_LAST_PACKABLE)
86 if (!pb_encode_tag(stream, PB_WT_STRING, field->tag))
89 /* Determine the total size of packed array. */
90 if (PB_LTYPE(field->type) == PB_LTYPE_FIXED)
92 size = field->data_size * count;
96 pb_ostream_t sizestream = {0};
98 for (i = 0; i < count; i++)
100 if (!func(&sizestream, field, p))
102 p = (const char*)p + field->data_size;
104 size = sizestream.bytes_written;
107 if (!pb_encode_varint(stream, size))
110 if (stream->callback == NULL)
111 return pb_write(stream, NULL, size); /* Just sizing.. */
115 for (i = 0; i < count; i++)
117 if (!func(stream, field, p))
119 p = (const char*)p + field->data_size;
125 for (i = 0; i < count; i++)
127 if (!pb_encode_tag_for_field(stream, field))
129 if (!func(stream, field, p))
131 p = (const char*)p + field->data_size;
138 bool checkreturn pb_encode(pb_ostream_t *stream, const pb_field_t fields[], const void *src_struct)
140 const pb_field_t *field = fields;
141 const void *pData = src_struct;
143 size_t prev_size = 0;
145 while (field->tag != 0)
147 pData = (const char*)pData + prev_size + field->data_offset;
148 pSize = (const char*)pData + field->size_offset;
150 prev_size = field->data_size;
151 if (PB_HTYPE(field->type) == PB_HTYPE_ARRAY)
152 prev_size *= field->array_size;
154 pb_encoder_t func = PB_ENCODERS[PB_LTYPE(field->type)];
156 switch (PB_HTYPE(field->type))
158 case PB_HTYPE_REQUIRED:
159 if (!pb_encode_tag_for_field(stream, field))
161 if (!func(stream, field, pData))
165 case PB_HTYPE_OPTIONAL:
168 if (!pb_encode_tag_for_field(stream, field))
171 if (!func(stream, field, pData))
177 if (!encode_array(stream, field, pData, *(size_t*)pSize, func))
181 case PB_HTYPE_CALLBACK:
183 pb_callback_t *callback = (pb_callback_t*)pData;
184 if (callback->funcs.encode != NULL)
186 if (!callback->funcs.encode(stream, field, callback->arg))
199 /* Helper functions */
200 bool checkreturn pb_encode_varint(pb_ostream_t *stream, uint64_t value)
206 return pb_write(stream, (uint8_t*)&value, 1);
210 buffer[i] = (value & 0x7F) | 0x80;
214 buffer[i-1] &= 0x7F; /* Unset top bit on last byte */
216 return pb_write(stream, buffer, i);
219 bool checkreturn pb_encode_tag(pb_ostream_t *stream, pb_wire_type_t wiretype, int field_number)
221 int tag = wiretype | (field_number << 3);
222 return pb_encode_varint(stream, tag);
225 bool checkreturn pb_encode_tag_for_field(pb_ostream_t *stream, const pb_field_t *field)
227 pb_wire_type_t wiretype;
228 switch (PB_LTYPE(field->type))
230 case PB_LTYPE_VARINT:
231 case PB_LTYPE_SVARINT:
232 wiretype = PB_WT_VARINT;
236 if (field->data_size == 4)
237 wiretype = PB_WT_32BIT;
238 else if (field->data_size == 8)
239 wiretype = PB_WT_64BIT;
245 case PB_LTYPE_STRING:
246 case PB_LTYPE_SUBMESSAGE:
247 wiretype = PB_WT_STRING;
254 return pb_encode_tag(stream, wiretype, field->tag);
257 bool checkreturn pb_encode_string(pb_ostream_t *stream, const uint8_t *buffer, size_t size)
259 if (!pb_encode_varint(stream, size))
262 return pb_write(stream, buffer, size);
267 /* Copy srcsize bytes from src so that values are casted properly.
268 * On little endian machine, copy to start of dest
269 * On big endian machine, copy to end of dest
270 * destsize must always be larger than srcsize
272 * Note: This is the reverse of the endian_copy in pb_decode.c.
274 static void endian_copy(void *dest, const void *src, size_t destsize, size_t srcsize)
276 #ifdef __BIG_ENDIAN__
277 memcpy((char*)dest + (destsize - srcsize), src, srcsize);
279 memcpy(dest, src, srcsize);
283 bool checkreturn pb_enc_varint(pb_ostream_t *stream, const pb_field_t *field, const void *src)
286 endian_copy(&value, src, sizeof(value), field->data_size);
287 return pb_encode_varint(stream, value);
290 bool checkreturn pb_enc_svarint(pb_ostream_t *stream, const pb_field_t *field, const void *src)
294 uint64_t signbitmask, xormask;
295 endian_copy(&value, src, sizeof(value), field->data_size);
297 signbitmask = (uint64_t)0x80 << (field->data_size * 8 - 8);
298 xormask = ((uint64_t)-1) >> (64 - field->data_size * 8);
299 if (value & signbitmask)
300 zigzagged = ((value ^ xormask) << 1) | 1;
302 zigzagged = value << 1;
304 return pb_encode_varint(stream, zigzagged);
307 bool checkreturn pb_enc_fixed(pb_ostream_t *stream, const pb_field_t *field, const void *src)
309 #ifdef __BIG_ENDIAN__
310 uint8_t bytes[8] = {0};
311 endian_copy(bytes, src, sizeof(bytes), field->data_size);
312 uint8_t lebytes[8] = {bytes[7], bytes[6], bytes[5], bytes[4],
313 bytes[3], bytes[2], bytes[1], bytes[0]};
314 return pb_write(stream, lebytes, field->data_size);
316 return pb_write(stream, (uint8_t*)src, field->data_size);
320 bool checkreturn pb_enc_bytes(pb_ostream_t *stream, const pb_field_t *field, const void *src)
322 pb_bytes_array_t *bytes = (pb_bytes_array_t*)src;
323 return pb_encode_string(stream, bytes->bytes, bytes->size);
326 bool checkreturn pb_enc_string(pb_ostream_t *stream, const pb_field_t *field, const void *src)
328 return pb_encode_string(stream, (uint8_t*)src, strlen((char*)src));
331 bool checkreturn pb_enc_submessage(pb_ostream_t *stream, const pb_field_t *field, const void *src)
333 pb_ostream_t substream = {0};
337 if (field->ptr == NULL)
340 if (!pb_encode(&substream, (pb_field_t*)field->ptr, src))
343 size = substream.bytes_written;
345 if (!pb_encode_varint(stream, size))
348 if (stream->callback == NULL)
349 return pb_write(stream, NULL, size); /* Just sizing */
351 if (stream->bytes_written + size > stream->max_size)
354 /* Use a substream to verify that a callback doesn't write more than
355 * what it did the first time. */
356 substream.callback = stream->callback;
357 substream.state = stream->state;
358 substream.max_size = size;
359 substream.bytes_written = 0;
361 status = pb_encode(&substream, (pb_field_t*)field->ptr, src);
363 stream->bytes_written += substream.bytes_written;
365 if (substream.bytes_written != size)