summaryrefslogtreecommitdiffstats
path: root/docs/reference.rst
diff options
context:
space:
mode:
Diffstat (limited to 'docs/reference.rst')
-rw-r--r--docs/reference.rst192
1 files changed, 171 insertions, 21 deletions
diff --git a/docs/reference.rst b/docs/reference.rst
index 0db8e43e..6094e13c 100644
--- a/docs/reference.rst
+++ b/docs/reference.rst
@@ -6,31 +6,160 @@ Nanopb: API reference
.. contents ::
+
+
+
Compilation options
===================
-The following options can be specified using -D switch given to the C compiler:
-
-============================ ================================================================================================
-__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_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 warning will tell if you need this.
-PB_FIELD_16BIT Add support for tag numbers > 255 and fields larger than 255 bytes or 255 array entries.
- Increases code size 3 bytes per each field. Compiler error will tell if you need this.
-PB_FIELD_32BIT Add support for tag numbers > 65535 and fields larger than 65535 bytes or 65535 array entries.
- Increases code size 9 bytes per each field. Compiler error will tell if you need this.
-PB_NO_ERRMSG Disables the support for error messages; only error information is the true/false return value.
- Decreases the code size by a few hundred bytes.
-PB_BUFFER_ONLY Disables the support for custom streams. Only supports encoding to memory buffers.
- Speeds up execution and decreases code size slightly.
-PB_OLD_CALLBACK_STYLE Use the old function signature (void\* instead of void\*\*) for callback fields. This was the
+The following options can be specified using -D switch given to the C compiler
+when compiling the nanopb library and applications using it. You must have the
+same settings for the nanopb library and all code that includes pb.h.
+
+============================ ================================================
+__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_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
+ warning will tell if you need this.
+PB_FIELD_16BIT Add support for tag numbers > 255 and fields
+ larger than 255 bytes or 255 array entries.
+ Increases code size 3 bytes per each field.
+ Compiler error will tell if you need this.
+PB_FIELD_32BIT Add support for tag numbers > 65535 and fields
+ larger than 65535 bytes or 65535 array entries.
+ Increases code size 9 bytes per each field.
+ Compiler error will tell if you need this.
+PB_NO_ERRMSG Disables the support for error messages; only
+ error information is the true/false return
+ value. Decreases the code size by a few hundred
+ bytes.
+PB_BUFFER_ONLY Disables the support for custom streams. Only
+ supports encoding and decoding with memory
+ buffers. Speeds up execution and decreases code
+ size slightly.
+PB_OLD_CALLBACK_STYLE Use the old function signature (void\* instead
+ of void\*\*) for callback fields. This was the
default until nanopb-0.2.1.
-============================ ================================================================================================
+============================ ================================================
+
+The PB_MAX_REQUIRED_FIELDS, PB_FIELD_16BIT and PB_FIELD_32BIT settings allow
+raising some datatype limits to suit larger messages. Their need is recognized
+automatically by C-preprocessor #if-directives in the generated .pb.h files.
+The default setting is to use the smallest datatypes (least resources used).
+
+
+
+
+Proto file options
+==================
+The generator behaviour can be adjusted using these options, defined in the
+'nanopb.proto' file in the generator folder:
+
+============================ ================================================
+max_size Allocated size for 'bytes' and 'string' fields.
+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 field or
+ to completely ignore the field.
+long_names Prefix the enum name to the enum value in
+ definitions, i.e. 'EnumName_EnumValue'. Enabled
+ by default.
+packed_struct Make the generated structures packed.
+ NOTE: This cannot be used on CPUs that break
+ on unaligned accesses to variables.
+============================ ================================================
+
+These options can be defined for the .proto files before they are converted
+using the nanopb-generatory.py. There are three ways to define the options:
+
+1. Using a separate .options file.
+ This is the preferred way as of nanopb-0.2.1, because it has the best
+ compatibility with other protobuf libraries.
+2. Defining the options on the command line of nanopb_generator.py.
+ This only makes sense for settings that apply to a whole file.
+3. Defining the options in the .proto file using the nanopb extensions.
+ This is the way used in nanopb-0.1, and will remain supported in the
+ future. It however sometimes causes trouble when using the .proto file
+ with other protobuf libraries.
+
+The effect of the options is the same no matter how they are given. The most
+common purpose is to define maximum size for string fields in order to
+statically allocate them.
+
+Defining the options in a .options file
+---------------------------------------
+The preferred way to define options is to have a separate file
+'myproto.options' in the same directory as the 'myproto.proto'. The
+generator will automatically search for this file and read the options from
+it. The file format is as follows:
+
+* Lines starting with '#' or '//' are regarded as comments.
+* Blank lines are ignored.
+* All other lines should start with a field name pattern, followed by one or
+ more options. For example: *"MyMessage.myfield max_size:5 max_count:10"*.
+* The field name pattern is matched against a string of form 'Message.field'.
+ For nested messages, the string is 'Message.SubMessage.field'.
+* The field name pattern may use the notation recognized by Python fnmatch():
+ - \* matches any part of string, like 'Message.\*' for all fields
+ - \? matches any single character
+ - [seq] matches any of characters 's', 'e' and 'q'
+ - [!seq] matches any other character
+* The options are written as 'option_name:option_value' and several options
+ can be defined on same line, separated by whitespace.
+* Options defined later in the file override the ones specified earlier, so
+ it makes sense to define wildcard options first in the file and more specific
+ ones later.
+
+If preferred, the name of the options file can be set using the command line
+switch '-f' to nanopb_generator.py.
+
+Defining the options on command line
+------------------------------------
+The nanopb_generator.py has a simple command line option '-s OPTION:VALUE'.
+The setting applies to the whole file that is being processed.
+
+Defining the options in the .proto file
+---------------------------------------
+The .proto file format allows defining custom options for the fields.
+The nanopb library comes with 'nanopb.proto' which does exactly that, allowing
+you do define the options directly in the .proto file:
+
+ import "nanopb.proto";
+ required string name = 1 [(nanopb).max_size = 40];
+ repeated PhoneNumber phone = 4 [(nanopb).max_count = 5];
+
+A small complication is that you have to set the include path of protoc so that
+nanopb.proto can be found. This file, in turn, requires the file
+*google/protobuf/descriptor.proto*. This is usually installed under
+*/usr/include*. Therefore, to compile a .proto file which uses options, use a
+protoc command similar to::
+
+ protoc -I/usr/include -Inanopb/generator -I. -omessage.pb message.proto
+
+The options can be defined in file, message and field scopes::
+
+ option (nanopb_fileopt).max_size = 20; // File scope
+ message Message
+ {
+ option (nanopb_msgopt).max_size = 30; // Message scope
+ required string fieldsize = 1 [(nanopb).max_size = 40]; // Field scope
+ }
+
+
+
+
+
+
+
-The PB_MAX_REQUIRED_FIELDS, PB_FIELD_16BIT and PB_FIELD_32BIT settings allow raising some datatype limits to suit larger messages.
-Their need is recognized automatically by C-preprocessor #if-directives in the generated .pb.h files. The default setting is to use
-the smallest datatypes (least resources used).
pb.h
====
@@ -148,6 +277,16 @@ Protocol Buffers wire types. These are used with `pb_encode_tag`_. ::
PB_WT_32BIT = 5
} pb_wire_type_t;
+
+
+
+
+
+
+
+
+
+
pb_encode.h
===========
@@ -297,6 +436,17 @@ In Protocol Buffers format, the submessage size must be written before the subme
If the submessage contains callback fields, the callback function might misbehave and write out a different amount of data on the second call. This situation is recognized and *false* is returned, but garbage will be written to the output before the problem is detected.
+
+
+
+
+
+
+
+
+
+
+
pb_decode.h
===========