Docs update, remove malloc from limitations list

[apps/agl-service-can-low-level.git] / docs / reference.rst

diff --git a/docs/reference.rst b/docs/reference.rst
index 51556d3..ccbf0a4 100644 (file)
--- a/docs/reference.rst
+++ b/docs/reference.rst
@@ -24,8 +24,8 @@ __BIG_ENDIAN__                 Set this if your platform stores integers and
                                floats in big-endian format. Mixed-endian
                                systems (different layout for ints and floats)
                                are currently not supported.
-NANOPB_INTERNALS               Set this to expose the field encoder functions
-                               that are hidden since nanopb-0.1.3.
+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
@@ -75,8 +75,9 @@ 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
@@ -415,6 +416,17 @@ 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.
@@ -577,6 +589,10 @@ 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. ::
@@ -587,6 +603,35 @@ 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. ::