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 pb_encoder_t func = PB_ENCODERS[PB_LTYPE(field->type)];
153 pData = (const char*)pData + prev_size + field->data_offset;
154 pSize = (const char*)pData + field->size_offset;
156 prev_size = field->data_size;
157 if (PB_HTYPE(field->type) == PB_HTYPE_ARRAY)
158 prev_size *= field->array_size;
160 switch (PB_HTYPE(field->type))
162 case PB_HTYPE_REQUIRED:
163 if (!pb_encode_tag_for_field(stream, field))
165 if (!func(stream, field, pData))
169 case PB_HTYPE_OPTIONAL:
172 if (!pb_encode_tag_for_field(stream, field))
175 if (!func(stream, field, pData))
181 if (!encode_array(stream, field, pData, *(size_t*)pSize, func))
185 case PB_HTYPE_CALLBACK:
187 pb_callback_t *callback = (pb_callback_t*)pData;
188 if (callback->funcs.encode != NULL)
190 if (!callback->funcs.encode(stream, field, callback->arg))
203 /* Helper functions */
204 bool checkreturn pb_encode_varint(pb_ostream_t *stream, uint64_t value)
210 return pb_write(stream, (uint8_t*)&value, 1);
214 buffer[i] = (value & 0x7F) | 0x80;
218 buffer[i-1] &= 0x7F; /* Unset top bit on last byte */
220 return pb_write(stream, buffer, i);
223 bool checkreturn pb_encode_tag(pb_ostream_t *stream, pb_wire_type_t wiretype, int field_number)
225 int tag = wiretype | (field_number << 3);
226 return pb_encode_varint(stream, tag);
229 bool checkreturn pb_encode_tag_for_field(pb_ostream_t *stream, const pb_field_t *field)
231 pb_wire_type_t wiretype;
232 switch (PB_LTYPE(field->type))
234 case PB_LTYPE_VARINT:
235 case PB_LTYPE_SVARINT:
236 wiretype = PB_WT_VARINT;
239 case PB_LTYPE_FIXED32:
240 wiretype = PB_WT_32BIT;
243 case PB_LTYPE_FIXED64:
244 wiretype = PB_WT_64BIT;
248 case PB_LTYPE_STRING:
249 case PB_LTYPE_SUBMESSAGE:
250 wiretype = PB_WT_STRING;
257 return pb_encode_tag(stream, wiretype, field->tag);
260 bool checkreturn pb_encode_string(pb_ostream_t *stream, const uint8_t *buffer, size_t size)
262 if (!pb_encode_varint(stream, size))
265 return pb_write(stream, buffer, size);
270 /* Copy srcsize bytes from src so that values are casted properly.
271 * On little endian machine, copy to start of dest
272 * On big endian machine, copy to end of dest
273 * destsize must always be larger than srcsize
275 * Note: This is the reverse of the endian_copy in pb_decode.c.
277 static void endian_copy(void *dest, const void *src, size_t destsize, size_t srcsize)
279 #ifdef __BIG_ENDIAN__
280 memcpy((char*)dest + (destsize - srcsize), src, srcsize);
282 memcpy(dest, src, srcsize);
286 bool checkreturn pb_enc_varint(pb_ostream_t *stream, const pb_field_t *field, const void *src)
289 endian_copy(&value, src, sizeof(value), field->data_size);
290 return pb_encode_varint(stream, value);
293 bool checkreturn pb_enc_svarint(pb_ostream_t *stream, const pb_field_t *field, const void *src)
297 uint64_t signbitmask, xormask;
298 endian_copy(&value, src, sizeof(value), field->data_size);
300 signbitmask = (uint64_t)0x80 << (field->data_size * 8 - 8);
301 xormask = ((uint64_t)-1) >> (64 - field->data_size * 8);
302 if (value & signbitmask)
303 zigzagged = ((value ^ xormask) << 1) | 1;
305 zigzagged = value << 1;
307 return pb_encode_varint(stream, zigzagged);
310 bool checkreturn pb_enc_fixed64(pb_ostream_t *stream, const pb_field_t *field, const void *src)
312 #ifdef __BIG_ENDIAN__
313 uint8_t bytes[8] = {0};
314 memcpy(bytes, src, 8);
315 uint8_t lebytes[8] = {bytes[7], bytes[6], bytes[5], bytes[4],
316 bytes[3], bytes[2], bytes[1], bytes[0]};
317 return pb_write(stream, lebytes, 8);
319 return pb_write(stream, (uint8_t*)src, 8);
323 bool checkreturn pb_enc_fixed32(pb_ostream_t *stream, const pb_field_t *field, const void *src)
325 #ifdef __BIG_ENDIAN__
326 uint8_t bytes[4] = {0};
327 memcpy(bytes, src, 4);
328 uint8_t lebytes[4] = {bytes[3], bytes[2], bytes[1], bytes[0]};
329 return pb_write(stream, lebytes, 4);
331 return pb_write(stream, (uint8_t*)src, 4);
335 bool checkreturn pb_enc_bytes(pb_ostream_t *stream, const pb_field_t *field, const void *src)
337 pb_bytes_array_t *bytes = (pb_bytes_array_t*)src;
338 return pb_encode_string(stream, bytes->bytes, bytes->size);
341 bool checkreturn pb_enc_string(pb_ostream_t *stream, const pb_field_t *field, const void *src)
343 return pb_encode_string(stream, (uint8_t*)src, strlen((char*)src));
346 bool checkreturn pb_enc_submessage(pb_ostream_t *stream, const pb_field_t *field, const void *src)
348 pb_ostream_t substream = {0};
352 if (field->ptr == NULL)
355 if (!pb_encode(&substream, (pb_field_t*)field->ptr, src))
358 size = substream.bytes_written;
360 if (!pb_encode_varint(stream, size))
363 if (stream->callback == NULL)
364 return pb_write(stream, NULL, size); /* Just sizing */
366 if (stream->bytes_written + size > stream->max_size)
369 /* Use a substream to verify that a callback doesn't write more than
370 * what it did the first time. */
371 substream.callback = stream->callback;
372 substream.state = stream->state;
373 substream.max_size = size;
374 substream.bytes_written = 0;
376 status = pb_encode(&substream, (pb_field_t*)field->ptr, src);
378 stream->bytes_written += substream.bytes_written;
380 if (substream.bytes_written != size)