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This commit is contained in:
Petteri Aimonen
2014-03-16 15:52:19 +02:00
parent 108864963f
commit ab62402059
4 changed files with 63 additions and 8 deletions
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51
docs/reference.rst
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@@ -28,6 +28,8 @@ NANOPB_INTERNALS Set this to expose the field encoder functions
that are hidden since nanopb-0.1.3. Starting
with nanopb-0.2.4, this flag does nothing. Use
the newer functions that have better interface.
PB_ENABLE_MALLOC Set this to enable dynamic allocation support
in the decoder.
PB_MAX_REQUIRED_FIELDS Maximum number of required fields to check for
presence. Default value is 64. Increases stack
usage 1 byte per every 8 fields. Compiler
@@ -77,8 +79,9 @@ max_count Allocated number of entries in arrays
(*repeated* fields).
type Type of the generated field. Default value
is *FT_DEFAULT*, which selects automatically.
You can use *FT_CALLBACK*, *FT_STATIC* or
*FT_IGNORE* to force a callback field, a static
You can use *FT_CALLBACK*, *FT_POINTER*,
*FT_STATIC* or *FT_IGNORE* to force a callback
field, a dynamically allocated field, a static
field or to completely ignore the field.
long_names Prefix the enum name to the enum value in
definitions, i.e. *EnumName_EnumValue*. Enabled
@@ -417,6 +420,17 @@ Encodes the contents of a structure as a protocol buffers message and writes it
Normally pb_encode simply walks through the fields description array and serializes each field in turn. However, submessages must be serialized twice: first to calculate their size and then to actually write them to output. This causes some constraints for callback fields, which must return the same data on every call.
pb_encode_delimited
-------------------
Calculates the length of the message, encodes it as varint and then encodes the message. ::
bool pb_encode_delimited(pb_ostream_t *stream, const pb_field_t fields[], const void *src_struct);
(parameters are the same as for `pb_encode`_.)
A common way to indicate the message length in Protocol Buffers is to prefix it with a varint.
This function does this, and it is compatible with *parseDelimitedFrom* in Google's protobuf library.
.. sidebar:: Encoding fields manually
The functions with names *pb_encode_\** are used when dealing with callback fields. The typical reason for using callbacks is to have an array of unlimited size. In that case, `pb_encode`_ will call your callback function, which in turn will call *pb_encode_\** functions repeatedly to write out values.
@@ -579,6 +593,10 @@ In addition to EOF, the pb_decode implementation supports terminating a message
For optional fields, this function applies the default value and sets *has_<field>* to false if the field is not present.
If *PB_ENABLE_MALLOC* is defined, this function may allocate storage for any pointer type fields.
In this case, you have to call `pb_release`_ to release the memory after you are done with the message.
On error return `pb_decode` will release the memory itself.
pb_decode_noinit
----------------
Same as `pb_decode`_, except does not apply the default values to fields. ::
@@ -589,6 +607,35 @@ Same as `pb_decode`_, except does not apply the default values to fields. ::
The destination structure should be filled with zeros before calling this function. Doing a *memset* manually can be slightly faster than using `pb_decode`_ if you don't need any default values.
In addition to decoding a single message, this function can be used to merge two messages, so that
values from previous message will remain if the new message does not contain a field.
This function *will not* release the message even on error return. If you use *PB_ENABLE_MALLOC*,
you will need to call `pb_release`_ yourself.
pb_decode_delimited
-------------------
Same as `pb_decode`_, except that it first reads a varint with the length of the message. ::
bool pb_decode_delimited(pb_istream_t *stream, const pb_field_t fields[], void *dest_struct);
(parameters are the same as for `pb_decode`_.)
A common method to indicate message size in Protocol Buffers is to prefix it with a varint.
This function is compatible with *writeDelimitedTo* in the Google's Protocol Buffers library.
pb_release
----------
Releases any dynamically allocated fields.
void pb_release(const pb_field_t fields[], void *dest_struct);
:fields: A field description array. Usually autogenerated.
:dest_struct: Pointer to structure where data will be stored.
This function is only available if *PB_ENABLE_MALLOC* is defined. It will release any
pointer type fields in the structure and set the pointers to NULL.
pb_skip_varint
--------------
Skip a varint_ encoded integer without decoding it. ::