When encoding, the callback should write out complete fields, including the wire type and field number tag. It can write as many or as few fields as it likes. For example, if you want to write out an array as *repeated* field, you should do it all in a single call.
-If the callback is used in a submessage, it will be called multiple times during a single call to `pb_encode`_. It must produce the same amount of data every time. If the callback is directly in the main message, it is called only once.
+Usually you can use `pb_encode_tag_for_field`_ to encode the wire type and tag number of the field. However, if you want to encode a repeated field as a packed array, you must call `pb_encode_tag`_ instead to specify a wire type of *PB_WT_STRING*.
+
+If the callback is used in a submessage, it will be called multiple times during a single call to `pb_encode`_. In this case, it must produce the same amount of data every time. If the callback is directly in the main message, it is called only once.
.. _`pb_encode`: reference.html#pb-encode
+.. _`pb_encode_tag_for_field`: reference.html#pb-encode-tag-for-field
+.. _`pb_encode_tag`: reference.html#pb-encode-tag
This callback writes out a dynamically sized string::
bool read_ints(pb_istream_t *stream, const pb_field_t *field, void *arg)
{
- while (stream.bytes_left)
+ while (stream->bytes_left)
{
uint64_t value;
if (!pb_decode_varint(stream, &value))
PB_HTYPE_OPTIONAL 0x10 Use separate *has_<field>* boolean to specify
whether the field is present.
PB_HTYPE_ARRAY 0x20 A repeated field with preallocated array.
+ Separate *<field>_count* for number of items.
PB_HTYPE_CALLBACK 0x30 A field with dynamic storage size, data is
actually a pointer to a structure containing a
callback function.
This function only considers the LTYPE of the field. You can use it from your field callbacks, because the source generator writes correct LTYPE also for callback type fields.
+Wire type mapping is as follows:
+
+========================= ============
+LTYPEs Wire type
+========================= ============
+VARINT, SVARINT PB_WT_VARINT
+FIXED with data_size == 8 PB_WT_64BIT
+STRING, BYTES, SUBMESSAGE PB_WT_STRING
+FIXED with data_size == 4 PB_WT_32BIT
+========================= ============
+
pb_encode_string
----------------
Writes the length of a string as varint and then contents of the string. Used for writing fields with wire type PB_WT_STRING. ::
return true;
}
+bool fieldcallback(pb_ostream_t *stream, const pb_field_t *field, const void *arg)
+{
+ int value = 0x55;
+ if (!pb_encode_tag_for_field(stream, field))
+ return false;
+ return pb_encode_varint(stream, value);
+}
+
+bool crazyfieldcallback(pb_ostream_t *stream, const pb_field_t *field, const void *arg)
+{
+ /* This callback writes different amount of data the second time. */
+ uint32_t *state = (uint32_t*)arg;
+ *state <<= 8;
+ if (!pb_encode_tag_for_field(stream, field))
+ return false;
+ return pb_encode_varint(stream, *state);
+}
+
/* Check that expression x writes data y.
* Y is a string, which may contain null bytes. Null terminator is ignored.
*/
COMMENT("Test pb_encode_tag_for_field")
TEST(WRITES(pb_encode_tag_for_field(&s, &field), "\x50"));
+
+ field.type = PB_LTYPE_FIXED;
+ field.data_size = 8;
+ TEST(WRITES(pb_encode_tag_for_field(&s, &field), "\x51"));
+
+ field.type = PB_LTYPE_STRING;
+ TEST(WRITES(pb_encode_tag_for_field(&s, &field), "\x52"));
+
+ field.type = PB_LTYPE_FIXED;
+ field.data_size = 4;
+ TEST(WRITES(pb_encode_tag_for_field(&s, &field), "\x55"));
}
{
}
{
+ uint8_t buffer[10];
+ pb_ostream_t s;
+ FloatArray msg = {1, {99.0f}};
+
+ COMMENT("Test pb_encode with float array")
+
+ TEST(WRITES(pb_encode(&s, FloatArray_fields, &msg),
+ "\x0A\x04\x00\x00\xc6\x42"))
+
+ msg.data_count = 0;
+ TEST(WRITES(pb_encode(&s, FloatArray_fields, &msg), ""))
+
+ msg.data_count = 3;
+ TEST(!pb_encode(&s, FloatArray_fields, &msg))
+ }
+
+ {
+ uint8_t buffer[10];
+ pb_ostream_t s;
+ CallbackArray msg;
+
+ msg.data.funcs.encode = &fieldcallback;
+
+ COMMENT("Test pb_encode with callback field.")
+ TEST(WRITES(pb_encode(&s, CallbackArray_fields, &msg), "\x08\x55"))
+ }
+
+ {
+ uint8_t buffer[10];
+ pb_ostream_t s;
+ IntegerContainer msg = {{5, {1,2,3,4,5}}};
+
+ COMMENT("Test pb_encode with packed array in a submessage.")
+ TEST(WRITES(pb_encode(&s, IntegerContainer_fields, &msg),
+ "\x0A\x07\x0A\x05\x01\x02\x03\x04\x05"))
+ }
+
+ {
+ uint8_t buffer[10];
+ pb_ostream_t s;
+ CallbackContainer msg;
+ CallbackContainerContainer msg2;
+ uint32_t state = 1;
+
+ msg.submsg.data.funcs.encode = &fieldcallback;
+ msg2.submsg.submsg.data.funcs.encode = &fieldcallback;
+
+ COMMENT("Test pb_encode with callback field in a submessage.")
+ TEST(WRITES(pb_encode(&s, CallbackContainer_fields, &msg), "\x0A\x02\x08\x55"))
+ TEST(WRITES(pb_encode(&s, CallbackContainerContainer_fields, &msg2),
+ "\x0A\x04\x0A\x02\x08\x55"))
+ /* Misbehaving callback */
+ msg.submsg.data.funcs.encode = &crazyfieldcallback;
+ msg.submsg.data.arg = &state;
+ msg2.submsg.submsg.data.funcs.encode = &crazyfieldcallback;
+ msg2.submsg.submsg.data.arg = &state;
+ TEST(!pb_encode(&s, CallbackContainer_fields, &msg))
+ state = 1;
+ TEST(!pb_encode(&s, CallbackContainerContainer_fields, &msg2))
}
if (status != 0)
Code Review / apps / low-level-can-service.git / commitdiff