--- /dev/null
+=====================
+Nanopb: API reference
+=====================
+
+.. include :: menu.rst
+
+.. contents ::
+
+
+
+
+Compilation options
+===================
+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.
+
+============================ ================================================
+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
+ 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.
+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
+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).
+
+.. _`overview page`: index.html#compiler-requirements
+
+
+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).
+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_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
+ 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
+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'. ::
+
+ # 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 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";
+
+ 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
+*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
+ }
+
+
+
+
+
+
+
+
+
+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
+---------
+Type used to store the type of each field, to control the encoder/decoder behaviour. ::
+
+ 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_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:
+
+==================== ===== ================================================
+HTYPE identifier Value Field handling
+==================== ===== ================================================
+PB_HTYPE_REQUIRED 0x00 Verify that field exists in decoded message.
+PB_HTYPE_OPTIONAL 0x10 Use separate *has_<field>* boolean to specify
+ whether the field is present.
+ (Unless it is a callback)
+PB_HTYPE_REPEATED 0x20 A repeated field with preallocated array.
+ Separate *<field>_count* for number of items.
+ (Unless it is a callback)
+==================== ===== ================================================
+
+The bits 6-7 define the how the storage for the field is allocated:
+
+==================== ===== ================================================
+ATYPE identifier Value Allocation method
+==================== ===== ================================================
+PB_ATYPE_STATIC 0x00 Statically allocated storage in the structure.
+PB_ATYPE_CALLBACK 0x40 A field with dynamic storage size. Struct field
+ actually contains a pointer to a callback
+ function.
+==================== ===== ================================================
+
+
+pb_field_t
+----------
+Describes a single structure field with memory position in relation to others. The descriptions are usually autogenerated. ::
+
+ typedef struct pb_field_s pb_field_t;
+ struct pb_field_s {
+ pb_size_t tag;
+ pb_type_t type;
+ 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;
+
+:tag: Tag number of the field or 0 to terminate a list of fields.
+:type: LTYPE, HTYPE and ATYPE of the field.
+:data_offset: Offset of field data, relative to the end of the previous field.
+:size_offset: Offset of *bool* flag for optional fields or *size_t* count for arrays, relative to field data.
+:data_size: Size of a single data entry, in bytes. For PB_LTYPE_BYTES, the size of the byte array inside the containing structure. For PB_HTYPE_CALLBACK, size of the C data type if known.
+:array_size: Maximum number of entries in an array, if it is an array type.
+:ptr: Pointer to default value for optional fields, or to submessage description for PB_LTYPE_SUBMESSAGE.
+
+The *uint8_t* datatypes limit the maximum size of a single item to 255 bytes and arrays to 255 items. Compiler will give error if the values are too large. The types can be changed to larger ones by defining *PB_FIELD_16BIT*.
+
+pb_bytes_array_t
+----------------
+An byte array with a field for storing the length::
+
+ typedef struct {
+ 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_callback_t
+-------------
+Part of a message structure, for fields with type PB_HTYPE_CALLBACK::
+
+ typedef struct _pb_callback_t pb_callback_t;
+ struct _pb_callback_t {
+ union {
+ bool (*decode)(pb_istream_t *stream, const pb_field_t *field, void **arg);
+ bool (*encode)(pb_ostream_t *stream, const pb_field_t *field, void * const *arg);
+ } funcs;
+
+ void *arg;
+ };
+
+A pointer to the *arg* is passed to the callback when calling. It can be used to store any information that the callback might need.
+
+Previously the function received just the value of *arg* instead of a pointer to it. This old behaviour can be enabled by defining *PB_OLD_CALLBACK_STYLE*.
+
+When calling `pb_encode`_, *funcs.encode* is used, and similarly when calling `pb_decode`_, *funcs.decode* is used. The function pointers are stored in the same memory location but are of incompatible types. You can set the function pointer to NULL to skip the field.
+
+pb_wire_type_t
+--------------
+Protocol Buffers wire types. These are used with `pb_encode_tag`_. ::
+
+ typedef enum {
+ PB_WT_VARINT = 0,
+ PB_WT_64BIT = 1,
+ PB_WT_STRING = 2,
+ 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
+there is no error message::
+
+ #define PB_GET_ERROR(stream) (string expression)
+
+This should be used for printing errors, for example::
+
+ if (!pb_decode(...))
+ {
+ printf("Decode failed: %s\n", PB_GET_ERROR(stream));
+ }
+
+The macro only returns pointers to constant strings (in code memory),
+so that there is no need to release the returned pointer.
+
+PB_RETURN_ERROR
+---------------
+Set the error message and return false::
+
+ #define PB_RETURN_ERROR(stream,msg) (sets error and returns false)
+
+This should be used to handle error conditions inside nanopb functions
+and user callback functions::
+
+ if (error_condition)
+ {
+ PB_RETURN_ERROR(stream, "something went wrong");
+ }
+
+The *msg* parameter must be a constant string.
+
+
+
+pb_encode.h
+===========
+
+pb_ostream_from_buffer
+----------------------
+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(pb_byte_t *buf, size_t bufsize);
+
+:buf: Memory buffer to write into.
+:bufsize: Maximum number of bytes to write.
+:returns: An output stream.
+
+After writing, you can check *stream.bytes_written* to find out how much valid data there is in the buffer.
+
+pb_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 pb_byte_t *buf, size_t count);
+
+:stream: Output stream to write to.
+:buf: Pointer to buffer with the data to be written.
+:count: Number of bytes to write.
+:returns: True on success, false if maximum length is exceeded or an IO error happens.
+
+If an error happens, *bytes_written* is not incremented. Depending on the callback used, calling pb_write again after it has failed once may be dangerous. Nanopb itself never does this, instead it returns the error to user application. The builtin pb_ostream_from_buffer is safe to call again after failed write.
+
+pb_encode
+---------
+Encodes the contents of a structure as a protocol buffers message and writes it to output stream. ::
+
+ bool pb_encode(pb_ostream_t *stream, const pb_field_t fields[], const void *src_struct);
+
+:stream: Output stream to write to.
+:fields: A field description array, usually autogenerated.
+:src_struct: Pointer to the data that will be serialized.
+:returns: True on success, false on IO error, on detectable errors in field description, or if a field encoder returns false.
+
+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.
+
+ The tag of a field must be encoded separately with `pb_encode_tag_for_field`_. After that, you can call exactly one of the content-writing functions to encode the payload of the field. For repeated fields, you can repeat this process multiple times.
+
+ 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, 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
+:field_number: Identifier for the field, defined in the .proto file. You can get it from field->tag.
+:returns: True on success, false on IO error.
+
+pb_encode_tag_for_field
+-----------------------
+Same as `pb_encode_tag`_, except takes the parameters from a *pb_field_t* structure. ::
+
+ bool pb_encode_tag_for_field(pb_ostream_t *stream, const pb_field_t *field);
+
+:stream: Output stream to write to. 1-5 bytes will be written.
+:field: Field description structure. Usually autogenerated.
+:returns: True on success, false on IO error or unknown field type.
+
+This function only considers the LTYPE of the field. You can use it from your field callbacks, because the source generator writes correct LTYPE also for callback type fields.
+
+Wire type mapping is as follows:
+
+============================================= ============
+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
+----------------
+Encodes a signed or unsigned integer in the varint_ format. Works for fields of type `bool`, `enum`, `int32`, `int64`, `uint32` and `uint64`::
+
+ bool pb_encode_varint(pb_ostream_t *stream, uint64_t value);
+
+:stream: Output stream to write to. 1-10 bytes will be written.
+:value: Value to encode. Just cast e.g. int32_t directly to uint64_t.
+:returns: True on success, false on IO error.
+
+.. _varint: http://code.google.com/apis/protocolbuffers/docs/encoding.html#varints
+
+pb_encode_svarint
+-----------------
+Encodes a signed integer in the 'zig-zagged' format. Works for fields of type `sint32` and `sint64`::
+
+ bool pb_encode_svarint(pb_ostream_t *stream, int64_t value);
+
+(parameters are the same as for `pb_encode_varint`_
+
+pb_encode_string
+----------------
+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 pb_byte_t *buffer, size_t size);
+
+:stream: Output stream to write to.
+:buffer: Pointer to string data.
+:size: Number of bytes in the string. Pass `strlen(s)` for strings.
+:returns: True on success, false on IO error.
+
+pb_encode_fixed32
+-----------------
+Writes 4 bytes to stream and swaps bytes on big-endian architectures. Works for fields of type `fixed32`, `sfixed32` and `float`::
+
+ bool pb_encode_fixed32(pb_ostream_t *stream, const void *value);
+
+:stream: Output stream to write to.
+:value: Pointer to a 4-bytes large C variable, for example `uint32_t foo;`.
+:returns: True on success, false on IO error.
+
+pb_encode_fixed64
+-----------------
+Writes 8 bytes to stream and swaps bytes on big-endian architecture. Works for fields of type `fixed64`, `sfixed64` and `double`::
+
+ bool pb_encode_fixed64(pb_ostream_t *stream, const void *value);
+
+:stream: Output stream to write to.
+:value: Pointer to a 8-bytes large C variable, for example `uint64_t foo;`.
+:returns: True on success, false on IO error.
+
+pb_encode_submessage
+--------------------
+Encodes a submessage field, including the size header for it. Works for fields of any message type::
+
+ bool pb_encode_submessage(pb_ostream_t *stream, const pb_field_t fields[], const void *src_struct);
+
+:stream: Output stream to write to.
+:fields: Pointer to the autogenerated field description array for the submessage type, e.g. `MyMessage_fields`.
+:src: Pointer to the structure where submessage data is.
+:returns: True on success, false on IO errors, pb_encode errors or if submessage size changes between calls.
+
+In Protocol Buffers format, the submessage size must be written before the submessage contents. Therefore, this function has to encode the submessage twice in order to know the size beforehand.
+
+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
+===========
+
+pb_istream_from_buffer
+----------------------
+Helper function for creating an input stream that reads data from a memory buffer. ::
+
+ 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.
+:returns: An input stream ready to use.
+
+pb_read
+-------
+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, 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.
+:count: Number of bytes to read.
+:returns: True on success, false if *stream->bytes_left* is less than *count* or if an IO error occurs.
+
+End of file is signalled by *stream->bytes_left* being zero after pb_read returns false.
+
+pb_decode
+---------
+Read and decode all fields of a structure. Reads until EOF on input stream. ::
+
+ bool pb_decode(pb_istream_t *stream, const pb_field_t fields[], void *dest_struct);
+
+:stream: Input stream to read from.
+:fields: A field description array. Usually autogenerated.
+:dest_struct: Pointer to structure where data will be stored.
+:returns: True on success, false on IO error, on detectable errors in field description, if a field encoder returns false or if a required field is missing.
+
+In Protocol Buffers binary format, EOF is only allowed between fields. If it happens anywhere else, pb_decode will return *false*. If pb_decode returns false, you cannot trust any of the data in the structure.
+
+In addition to EOF, the pb_decode implementation supports terminating a message with a 0 byte. This is compatible with the official Protocol Buffers because 0 is never a valid field tag.
+
+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. ::
+
+ bool pb_decode_noinit(pb_istream_t *stream, const pb_field_t fields[], void *dest_struct);
+
+(parameters are the same as for `pb_decode`_.)
+
+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 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, 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.
+:tag: Pointer to variable where to store the tag of the field.
+:eof: Pointer to variable where to store end-of-file status.
+:returns: True on success, false on error or EOF.
+
+When the message (stream) ends, this function will return false and set *eof* to true. On other
+errors, *eof* will be set to false.
+
+pb_skip_field
+-------------
+Remove the data for a field from the stream, without actually decoding it::
+
+ bool pb_skip_field(pb_istream_t *stream, pb_wire_type_t wire_type);
+
+:stream: Input stream to read from.
+:wire_type: Type of field to skip.
+:returns: True on success, false on IO error.
+
+.. sidebar:: Decoding fields manually
+
+ The functions with names beginning with *pb_decode_* 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_decode`_ will call your callback function repeatedly, which can then store the values into e.g. filesystem in the order received in.
+
+ For decoding numeric (including enumerated and boolean) values, use `pb_decode_varint`_, `pb_decode_svarint`_, `pb_decode_fixed32`_ and `pb_decode_fixed64`_. They take a pointer to a 32- or 64-bit C variable, which you may then cast to smaller datatype for storage.
+
+ For decoding strings and bytes fields, the length has already been decoded. You can therefore check the total length in *stream->bytes_left* and read the data using `pb_read`_.
+
+ Finally, for decoding submessages in a callback, simply use `pb_decode`_ and pass it the *SubMessage_fields* descriptor array.
+
+pb_decode_varint
+----------------
+Read and decode a varint_ encoded integer. ::
+
+ bool pb_decode_varint(pb_istream_t *stream, uint64_t *dest);
+
+:stream: Input stream to read from. 1-10 bytes will be read.
+:dest: Storage for the decoded integer. Value is undefined on error.
+:returns: True on success, false if value exceeds uint64_t range or an IO error happens.
+
+pb_decode_svarint
+-----------------
+Similar to `pb_decode_varint`_, except that it performs zigzag-decoding on the value. This corresponds to the Protocol Buffers *sint32* and *sint64* datatypes. ::
+
+ bool pb_decode_svarint(pb_istream_t *stream, int64_t *dest);
+
+(parameters are the same as `pb_decode_varint`_)
+
+pb_decode_fixed32
+-----------------
+Decode a *fixed32*, *sfixed32* or *float* value. ::
+
+ bool pb_decode_fixed32(pb_istream_t *stream, void *dest);
+
+:stream: Input stream to read from. 4 bytes will be read.
+:dest: Pointer to destination *int32_t*, *uint32_t* or *float*.
+:returns: True on success, false on IO errors.
+
+This function reads 4 bytes from the input stream.
+On big endian architectures, it then reverses the order of the bytes.
+Finally, it writes the bytes to *dest*.
+
+pb_decode_fixed64
+-----------------
+Decode a *fixed64*, *sfixed64* or *double* value. ::
+
+ bool pb_decode_fixed64(pb_istream_t *stream, void *dest);
+
+:stream: Input stream to read from. 8 bytes will be read.
+:dest: Pointer to destination *int64_t*, *uint64_t* or *double*.
+:returns: True on success, false on IO errors.
+
+Same as `pb_decode_fixed32`_, except this reads 8 bytes.
+
+pb_make_string_substream
+------------------------
+Decode the length for a field with wire type *PB_WT_STRING* and create a substream for reading the data. ::
+
+ bool pb_make_string_substream(pb_istream_t *stream, pb_istream_t *substream);
+
+:stream: Original input stream to read the length and data from.
+:substream: New substream that has limited length. Filled in by the function.
+:returns: True on success, false if reading the length fails.
+
+This function uses `pb_decode_varint`_ to read an integer from the stream. This is interpreted as a number of bytes, and the substream is set up so that its `bytes_left` is initially the same as the length, and its callback function and state the same as the parent stream.
+
+pb_close_string_substream
+-------------------------
+Close the substream created with `pb_make_string_substream`_. ::
+
+ void pb_close_string_substream(pb_istream_t *stream, pb_istream_t *substream);
+
+:stream: Original input stream to read the length and data from.
+:substream: Substream to close
+
+This function copies back the state from the substream to the parent stream.
+It must be called after done with the substream.
Code Review / apps / low-level-can-service.git / blobdiff