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Diffstat (limited to 'docs')
| -rw-r--r-- | docs/reference.rst | 51 |
1 files changed, 49 insertions, 2 deletions
diff --git a/docs/reference.rst b/docs/reference.rst index 3228373..79fa733 100644 --- a/docs/reference.rst +++ b/docs/reference.rst @@ -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. :: |