Compilation options
===================
-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.
+The following options can be specified in one of two ways:
+
+1. Using the -D switch on the C compiler command line.
+2. By #defining them at the top of pb.h.
+
+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_NO_PACKED_STRUCTS Disable packed structs. Increases RAM usage but
+ is necessary on some platforms that do not
+ support unaligned memory access.
+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
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.
+PB_SYSTEM_HEADER Replace the standard header files with a single
+ header file. It should define all the required
+ functions and typedefs listed on the
+ `overview page`_. Value must include quotes,
+ for example *#define PB_SYSTEM_HEADER "foo.h"*.
============================ ================================================
The PB_MAX_REQUIRED_FIELDS, PB_FIELD_16BIT and PB_FIELD_32BIT settings allow
automatically by C-preprocessor #if-directives in the generated .pb.h files.
The default setting is to use the smallest datatypes (least resources used).
-
+.. _`overview page`: index.html#compiler-requirements
Proto file options
'nanopb.proto' file in the generator folder:
============================ ================================================
-max_size Allocated size for 'bytes' and 'string' fields.
+max_size Allocated size for *bytes* and *string* fields.
max_count Allocated number of entries in arrays
- ('repeated' fields).
+ (*repeated* fields).
+int_size Override the integer type of a field.
+ (To use e.g. uint8_t to save RAM.)
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.
+ is *FT_DEFAULT*, which selects automatically.
+ 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
+ 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.
+skip_message Skip the whole message from generation.
+no_unions Generate 'oneof' fields as optional fields
+ instead of C unions.
+msgid Specifies a unique id for this message type.
+ Can be used by user code as an identifier.
+anonymous_oneof Generate 'oneof' fields as anonymous unions.
+fixed_length Generate 'bytes' fields with constant length.
============================ ================================================
These options can be defined for the .proto files before they are converted
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:
+'myproto.options' in the same directory as the 'myproto.proto'. ::
+
+ # myproto.proto
+ message MyMessage {
+ required string name = 1;
+ repeated int32 ids = 4;
+ }
+
+::
+
+ # myproto.options
+ MyMessage.name max_size:40
+ MyMessage.ids max_count:5
+
+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 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
+
+ - *\** 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.
+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 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:
+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];
+
+ message MyMessage {
+ required string name = 1 [(nanopb).max_size = 40];
+ repeated int32 ids = 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
pb.h
====
+pb_byte_t
+---------
+Type used for storing byte-sized data, such as raw binary input and bytes-type fields. ::
+
+ typedef uint_least8_t pb_byte_t;
+
+For most platforms this is equivalent to `uint8_t`. Some platforms however do not support
+8-bit variables, and on those platforms 16 or 32 bits need to be used for each byte.
+
pb_type_t
---------
-Defines the encoder/decoder behaviour that should be used for a field. ::
+Type used to store the type of each field, to control the encoder/decoder behaviour. ::
- typedef uint8_t pb_type_t;
+ typedef uint_least8_t pb_type_t;
The low-order nibble of the enumeration values defines the function that can be used for encoding and decoding the field data:
-==================== ===== ================================================
-LTYPE identifier Value Storage format
-==================== ===== ================================================
-PB_LTYPE_VARINT 0x00 Integer.
-PB_LTYPE_SVARINT 0x01 Integer, zigzag encoded.
-PB_LTYPE_FIXED32 0x02 32-bit integer or floating point.
-PB_LTYPE_FIXED64 0x03 64-bit integer or floating point.
-PB_LTYPE_BYTES 0x04 Structure with *size_t* field and byte array.
-PB_LTYPE_STRING 0x05 Null-terminated string.
-PB_LTYPE_SUBMESSAGE 0x06 Submessage structure.
-==================== ===== ================================================
+=========================== ===== ================================================
+LTYPE identifier Value Storage format
+=========================== ===== ================================================
+PB_LTYPE_VARINT 0x00 Integer.
+PB_LTYPE_UVARINT 0x01 Unsigned integer.
+PB_LTYPE_SVARINT 0x02 Integer, zigzag encoded.
+PB_LTYPE_FIXED32 0x03 32-bit integer or floating point.
+PB_LTYPE_FIXED64 0x04 64-bit integer or floating point.
+PB_LTYPE_BYTES 0x05 Structure with *size_t* field and byte array.
+PB_LTYPE_STRING 0x06 Null-terminated string.
+PB_LTYPE_SUBMESSAGE 0x07 Submessage structure.
+PB_LTYPE_EXTENSION 0x08 Point to *pb_extension_t*.
+PB_LTYPE_FIXED_LENGTH_BYTES 0x09 Inline *pb_byte_t* array of fixed size.
+=========================== ===== ================================================
The bits 4-5 define whether the field is required, optional or repeated:
----------
Describes a single structure field with memory position in relation to others. The descriptions are usually autogenerated. ::
- typedef struct _pb_field_t pb_field_t;
- struct _pb_field_t {
- uint8_t tag;
+ typedef struct pb_field_s pb_field_t;
+ struct pb_field_s {
+ pb_size_t tag;
pb_type_t type;
- uint8_t data_offset;
- int8_t size_offset;
- uint8_t data_size;
- uint8_t array_size;
+ pb_size_t data_offset;
+ pb_ssize_t size_offset;
+ pb_size_t data_size;
+ pb_size_t array_size;
const void *ptr;
} pb_packed;
An byte array with a field for storing the length::
typedef struct {
- size_t size;
- uint8_t bytes[1];
+ pb_size_t size;
+ pb_byte_t bytes[1];
} pb_bytes_array_t;
In an actual array, the length of *bytes* may be different.
PB_WT_32BIT = 5
} pb_wire_type_t;
+pb_extension_type_t
+-------------------
+Defines the handler functions and auxiliary data for a field that extends
+another message. Usually autogenerated by *nanopb_generator.py*::
+
+ typedef struct {
+ bool (*decode)(pb_istream_t *stream, pb_extension_t *extension,
+ uint32_t tag, pb_wire_type_t wire_type);
+ bool (*encode)(pb_ostream_t *stream, const pb_extension_t *extension);
+ const void *arg;
+ } pb_extension_type_t;
+
+In the normal case, the function pointers are *NULL* and the decoder and
+encoder use their internal implementations. The internal implementations
+assume that *arg* points to a *pb_field_t* that describes the field in question.
+
+To implement custom processing of unknown fields, you can provide pointers
+to your own functions. Their functionality is mostly the same as for normal
+callback fields, except that they get called for any unknown field when decoding.
+
+pb_extension_t
+--------------
+Ties together the extension field type and the storage for the field value::
+
+ typedef struct {
+ const pb_extension_type_t *type;
+ void *dest;
+ pb_extension_t *next;
+ bool found;
+ } pb_extension_t;
+
+:type: Pointer to the structure that defines the callback functions.
+:dest: Pointer to the variable that stores the field value
+ (as used by the default extension callback functions.)
+:next: Pointer to the next extension handler, or *NULL*.
+:found: Decoder sets this to true if the extension was found.
+
PB_GET_ERROR
------------
Get the current error message from a stream, or a placeholder string if
----------------------
Constructs an output stream for writing into a memory buffer. This is just a helper function, it doesn't do anything you couldn't do yourself in a callback function. It uses an internal callback that stores the pointer in stream *state* field. ::
- pb_ostream_t pb_ostream_from_buffer(uint8_t *buf, size_t bufsize);
+ pb_ostream_t pb_ostream_from_buffer(pb_byte_t *buf, size_t bufsize);
:buf: Memory buffer to write into.
:bufsize: Maximum number of bytes to write.
--------
Writes data to an output stream. Always use this function, instead of trying to call stream callback manually. ::
- bool pb_write(pb_ostream_t *stream, const uint8_t *buf, size_t count);
+ bool pb_write(pb_ostream_t *stream, const pb_byte_t *buf, size_t count);
:stream: Output stream to write to.
:buf: Pointer to buffer with the data to be written.
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.
Writing packed arrays is a little bit more involved: you need to use `pb_encode_tag` and specify `PB_WT_STRING` as the wire type. Then you need to know exactly how much data you are going to write, and use `pb_encode_varint`_ to write out the number of bytes before writing the actual data. Substreams can be used to determine the number of bytes beforehand; see `pb_encode_submessage`_ source code for an example.
+pb_get_encoded_size
+-------------------
+Calculates the length of the encoded message. ::
+
+ bool pb_get_encoded_size(size_t *size, const pb_field_t fields[], const void *src_struct);
+
+:size: Calculated size of the encoded message.
+:fields: A field description array, usually autogenerated.
+:src_struct: Pointer to the data that will be serialized.
+:returns: True on success, false on detectable errors in field description or if a field encoder returns false.
+
pb_encode_tag
-------------
Starts a field in the Protocol Buffers binary format: encodes the field number and the wire type of the data. ::
- bool pb_encode_tag(pb_ostream_t *stream, pb_wire_type_t wiretype, int field_number);
+ bool pb_encode_tag(pb_ostream_t *stream, pb_wire_type_t wiretype, uint32_t field_number);
:stream: Output stream to write to. 1-5 bytes will be written.
:wiretype: PB_WT_VARINT, PB_WT_64BIT, PB_WT_STRING or PB_WT_32BIT
Wire type mapping is as follows:
-========================= ============
-LTYPEs Wire type
-========================= ============
-VARINT, SVARINT PB_WT_VARINT
-FIXED64 PB_WT_64BIT
-STRING, BYTES, SUBMESSAGE PB_WT_STRING
-FIXED32 PB_WT_32BIT
-========================= ============
+============================================= ============
+LTYPEs Wire type
+============================================= ============
+VARINT, UVARINT, SVARINT PB_WT_VARINT
+FIXED64 PB_WT_64BIT
+STRING, BYTES, SUBMESSAGE, FIXED_LENGTH_BYTES PB_WT_STRING
+FIXED32 PB_WT_32BIT
+============================================= ============
pb_encode_varint
----------------
----------------
Writes the length of a string as varint and then contents of the string. Works for fields of type `bytes` and `string`::
- bool pb_encode_string(pb_ostream_t *stream, const uint8_t *buffer, size_t size);
+ bool pb_encode_string(pb_ostream_t *stream, const pb_byte_t *buffer, size_t size);
:stream: Output stream to write to.
:buffer: Pointer to string data.
----------------------
Helper function for creating an input stream that reads data from a memory buffer. ::
- pb_istream_t pb_istream_from_buffer(uint8_t *buf, size_t bufsize);
+ pb_istream_t pb_istream_from_buffer(const pb_byte_t *buf, size_t bufsize);
:buf: Pointer to byte array to read from.
:bufsize: Size of the byte array.
-------
Read data from input stream. Always use this function, don't try to call the stream callback directly. ::
- bool pb_read(pb_istream_t *stream, uint8_t *buf, size_t count);
+ bool pb_read(pb_istream_t *stream, pb_byte_t *buf, size_t count);
:stream: Input stream to read from.
:buf: Buffer to store the data to, or NULL to just read data without storing it anywhere.
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. ::
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.
-pb_skip_varint
---------------
-Skip a varint_ encoded integer without decoding it. ::
+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.
- bool pb_skip_varint(pb_istream_t *stream);
+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.
-:stream: Input stream to read from. Will read 1 byte at a time until the MSB is clear.
-:returns: True on success, false on IO error.
+pb_decode_delimited
+-------------------
+Same as `pb_decode`_, except that it first reads a varint with the length of the message. ::
-pb_skip_string
---------------
-Skip a varint-length-prefixed string. This means skipping a value with wire type PB_WT_STRING. ::
+ bool pb_decode_delimited(pb_istream_t *stream, const pb_field_t fields[], void *dest_struct);
- bool pb_skip_string(pb_istream_t *stream);
+(parameters are the same as for `pb_decode`_.)
-:stream: Input stream to read from.
-:returns: True on success, false on IO error or length exceeding uint32_t.
+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 is stored. If NULL, function does nothing.
+
+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_decode_tag
-------------
Decode the tag that comes before field in the protobuf encoding::
- bool pb_decode_tag(pb_istream_t *stream, pb_wire_type_t *wire_type, int *tag, bool *eof);
+ bool pb_decode_tag(pb_istream_t *stream, pb_wire_type_t *wire_type, uint32_t *tag, bool *eof);
:stream: Input stream to read from.
:wire_type: Pointer to variable where to store the wire type of the field.
-----------------
Decode a *fixed64*, *sfixed64* or *double* value. ::
- bool pb_dec_fixed(pb_istream_t *stream, const pb_field_t *field, void *dest);
+ bool pb_decode_fixed64(pb_istream_t *stream, void *dest);
:stream: Input stream to read from. 8 bytes will be read.
-:field: Not used.
:dest: Pointer to destination *int64_t*, *uint64_t* or *double*.
:returns: True on success, false on IO errors.
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