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Diffstat (limited to 'docs/reference.rst')
| -rw-r--r-- | docs/reference.rst | 175 |
1 files changed, 100 insertions, 75 deletions
diff --git a/docs/reference.rst b/docs/reference.rst index ccbf0a4..40a69ad 100644 --- a/docs/reference.rst +++ b/docs/reference.rst @@ -20,10 +20,9 @@ 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. +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 @@ -54,6 +53,8 @@ PB_SYSTEM_HEADER Replace the standard header files with a single functions and typedefs listed on the `overview page`_. Value must include quotes, for example *#define PB_SYSTEM_HEADER "foo.h"*. +PB_WITHOUT_64BIT Disable 64-bit support, for old compilers or + for a slight speedup on 8-bit platforms. ============================ ================================================ The PB_MAX_REQUIRED_FIELDS, PB_FIELD_16BIT and PB_FIELD_32BIT settings allow @@ -73,18 +74,31 @@ The generator behaviour can be adjusted using these options, defined in the 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. + *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 + (max_size must also be defined). +fixed_count Generate arrays with constant length + (max_count must also be defined). ============================ ================================================ These options can be defined for the .proto files before they are converted @@ -143,8 +157,20 @@ options from it. The file format is as follows: 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. +To debug problems in applying the options, you can use the *-v* option for the +plugin. Plugin options are specified in front of the output path: + + protoc ... --nanopb_out=-v:. message.proto + +Protoc doesn't currently pass include path into plugins. Therefore if your +*.proto* is in a subdirectory, nanopb may have trouble finding the associated +*.options* file. A workaround is to specify include path separately to the +nanopb plugin, like: + + protoc -Isubdir --nanopb_out=-Isubdir:. message.proto + +If preferred, the name of the options file can be set using plugin argument +*-f*. Defining the options on command line ------------------------------------ @@ -170,7 +196,7 @@ nanopb.proto can be found. This file, in turn, requires the file */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 + protoc -I/usr/include -Inanopb/generator -I. --nanopb_out=. message.proto The options can be defined in file, message and field scopes:: @@ -182,35 +208,40 @@ The options can be defined in file, message and field scopes:: } +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; - - - - -pb.h -==== +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: @@ -242,14 +273,14 @@ pb_field_t ---------- 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; @@ -268,8 +299,8 @@ pb_bytes_array_t 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. @@ -333,12 +364,14 @@ Ties together the extension field type and the storage for the field value:: 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 ------------ @@ -382,7 +415,7 @@ 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(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. @@ -394,7 +427,7 @@ 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 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. @@ -435,11 +468,22 @@ This function does this, and it is compatible with *parseDelimitedFrom* in Googl 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 @@ -460,14 +504,14 @@ This function only considers the LTYPE of the field. You can use it from your fi 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 ---------------- @@ -493,7 +537,7 @@ 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 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. @@ -553,7 +597,7 @@ 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(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. @@ -563,7 +607,7 @@ 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, 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. @@ -622,39 +666,21 @@ This function is compatible with *writeDelimitedTo* in the Google's Protocol Buf pb_release ---------- -Releases any dynamically allocated fields. +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. +: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_skip_varint --------------- -Skip a varint_ encoded integer without decoding it. :: - - bool pb_skip_varint(pb_istream_t *stream); - -: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_skip_string --------------- -Skip a varint-length-prefixed string. This means skipping a value with wire type PB_WT_STRING. :: - - bool pb_skip_string(pb_istream_t *stream); - -:stream: Input stream to read from. -:returns: True on success, false on IO error or length exceeding uint32_t. - 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. @@ -721,10 +747,9 @@ pb_decode_fixed64 ----------------- 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. |