14 The following options can be specified in one of two ways:
16 1. Using the -D switch on the C compiler command line.
17 2. By #defining them at the top of pb.h.
19 You must have the same settings for the nanopb library and all code that
22 ============================ ================================================
23 __BIG_ENDIAN__ Set this if your platform stores integers and
24 floats in big-endian format. Mixed-endian
25 systems (different layout for ints and floats)
26 are currently not supported.
27 PB_NO_PACKED_STRUCTS Disable packed structs. Increases RAM usage but
28 is necessary on some platforms that do not
29 support unaligned memory access.
30 PB_ENABLE_MALLOC Set this to enable dynamic allocation support
32 PB_MAX_REQUIRED_FIELDS Maximum number of required fields to check for
33 presence. Default value is 64. Increases stack
34 usage 1 byte per every 8 fields. Compiler
35 warning will tell if you need this.
36 PB_FIELD_16BIT Add support for tag numbers > 255 and fields
37 larger than 255 bytes or 255 array entries.
38 Increases code size 3 bytes per each field.
39 Compiler error will tell if you need this.
40 PB_FIELD_32BIT Add support for tag numbers > 65535 and fields
41 larger than 65535 bytes or 65535 array entries.
42 Increases code size 9 bytes per each field.
43 Compiler error will tell if you need this.
44 PB_NO_ERRMSG Disables the support for error messages; only
45 error information is the true/false return
46 value. Decreases the code size by a few hundred
48 PB_BUFFER_ONLY Disables the support for custom streams. Only
49 supports encoding and decoding with memory
50 buffers. Speeds up execution and decreases code
52 PB_OLD_CALLBACK_STYLE Use the old function signature (void\* instead
53 of void\*\*) for callback fields. This was the
54 default until nanopb-0.2.1.
55 PB_SYSTEM_HEADER Replace the standard header files with a single
56 header file. It should define all the required
57 functions and typedefs listed on the
58 `overview page`_. Value must include quotes,
59 for example *#define PB_SYSTEM_HEADER "foo.h"*.
60 ============================ ================================================
62 The PB_MAX_REQUIRED_FIELDS, PB_FIELD_16BIT and PB_FIELD_32BIT settings allow
63 raising some datatype limits to suit larger messages. Their need is recognized
64 automatically by C-preprocessor #if-directives in the generated .pb.h files.
65 The default setting is to use the smallest datatypes (least resources used).
67 .. _`overview page`: index.html#compiler-requirements
72 The generator behaviour can be adjusted using these options, defined in the
73 'nanopb.proto' file in the generator folder:
75 ============================ ================================================
76 max_size Allocated size for *bytes* and *string* fields.
77 max_count Allocated number of entries in arrays
79 type Type of the generated field. Default value
80 is *FT_DEFAULT*, which selects automatically.
81 You can use *FT_CALLBACK*, *FT_POINTER*,
82 *FT_STATIC* or *FT_IGNORE* to force a callback
83 field, a dynamically allocated field, a static
84 field or to completely ignore the field.
85 long_names Prefix the enum name to the enum value in
86 definitions, i.e. *EnumName_EnumValue*. Enabled
88 packed_struct Make the generated structures packed.
89 NOTE: This cannot be used on CPUs that break
90 on unaligned accesses to variables.
91 ============================ ================================================
93 These options can be defined for the .proto files before they are converted
94 using the nanopb-generatory.py. There are three ways to define the options:
96 1. Using a separate .options file.
97 This is the preferred way as of nanopb-0.2.1, because it has the best
98 compatibility with other protobuf libraries.
99 2. Defining the options on the command line of nanopb_generator.py.
100 This only makes sense for settings that apply to a whole file.
101 3. Defining the options in the .proto file using the nanopb extensions.
102 This is the way used in nanopb-0.1, and will remain supported in the
103 future. It however sometimes causes trouble when using the .proto file
104 with other protobuf libraries.
106 The effect of the options is the same no matter how they are given. The most
107 common purpose is to define maximum size for string fields in order to
108 statically allocate them.
110 Defining the options in a .options file
111 ---------------------------------------
112 The preferred way to define options is to have a separate file
113 'myproto.options' in the same directory as the 'myproto.proto'. ::
117 required string name = 1;
118 repeated int32 ids = 4;
124 MyMessage.name max_size:40
125 MyMessage.ids max_count:5
127 The generator will automatically search for this file and read the
128 options from it. The file format is as follows:
130 * Lines starting with '#' or '//' are regarded as comments.
131 * Blank lines are ignored.
132 * All other lines should start with a field name pattern, followed by one or
133 more options. For example: *"MyMessage.myfield max_size:5 max_count:10"*.
134 * The field name pattern is matched against a string of form *'Message.field'*.
135 For nested messages, the string is *'Message.SubMessage.field'*.
136 * The field name pattern may use the notation recognized by Python fnmatch():
138 - *\** matches any part of string, like 'Message.\*' for all fields
139 - *\?* matches any single character
140 - *[seq]* matches any of characters 's', 'e' and 'q'
141 - *[!seq]* matches any other character
143 * The options are written as *'option_name:option_value'* and several options
144 can be defined on same line, separated by whitespace.
145 * Options defined later in the file override the ones specified earlier, so
146 it makes sense to define wildcard options first in the file and more specific
149 If preferred, the name of the options file can be set using the command line
150 switch *-f* to nanopb_generator.py.
152 Defining the options on command line
153 ------------------------------------
154 The nanopb_generator.py has a simple command line option *-s OPTION:VALUE*.
155 The setting applies to the whole file that is being processed.
157 Defining the options in the .proto file
158 ---------------------------------------
159 The .proto file format allows defining custom options for the fields.
160 The nanopb library comes with *nanopb.proto* which does exactly that, allowing
161 you do define the options directly in the .proto file::
163 import "nanopb.proto";
166 required string name = 1 [(nanopb).max_size = 40];
167 repeated int32 ids = 4 [(nanopb).max_count = 5];
170 A small complication is that you have to set the include path of protoc so that
171 nanopb.proto can be found. This file, in turn, requires the file
172 *google/protobuf/descriptor.proto*. This is usually installed under
173 */usr/include*. Therefore, to compile a .proto file which uses options, use a
174 protoc command similar to::
176 protoc -I/usr/include -Inanopb/generator -I. -omessage.pb message.proto
178 The options can be defined in file, message and field scopes::
180 option (nanopb_fileopt).max_size = 20; // File scope
183 option (nanopb_msgopt).max_size = 30; // Message scope
184 required string fieldsize = 1 [(nanopb).max_size = 40]; // Field scope
200 Defines the encoder/decoder behaviour that should be used for a field. ::
202 typedef uint8_t pb_type_t;
204 The low-order nibble of the enumeration values defines the function that can be used for encoding and decoding the field data:
206 ==================== ===== ================================================
207 LTYPE identifier Value Storage format
208 ==================== ===== ================================================
209 PB_LTYPE_VARINT 0x00 Integer.
210 PB_LTYPE_SVARINT 0x01 Integer, zigzag encoded.
211 PB_LTYPE_FIXED32 0x02 32-bit integer or floating point.
212 PB_LTYPE_FIXED64 0x03 64-bit integer or floating point.
213 PB_LTYPE_BYTES 0x04 Structure with *size_t* field and byte array.
214 PB_LTYPE_STRING 0x05 Null-terminated string.
215 PB_LTYPE_SUBMESSAGE 0x06 Submessage structure.
216 ==================== ===== ================================================
218 The bits 4-5 define whether the field is required, optional or repeated:
220 ==================== ===== ================================================
221 HTYPE identifier Value Field handling
222 ==================== ===== ================================================
223 PB_HTYPE_REQUIRED 0x00 Verify that field exists in decoded message.
224 PB_HTYPE_OPTIONAL 0x10 Use separate *has_<field>* boolean to specify
225 whether the field is present.
226 (Unless it is a callback)
227 PB_HTYPE_REPEATED 0x20 A repeated field with preallocated array.
228 Separate *<field>_count* for number of items.
229 (Unless it is a callback)
230 ==================== ===== ================================================
232 The bits 6-7 define the how the storage for the field is allocated:
234 ==================== ===== ================================================
235 ATYPE identifier Value Allocation method
236 ==================== ===== ================================================
237 PB_ATYPE_STATIC 0x00 Statically allocated storage in the structure.
238 PB_ATYPE_CALLBACK 0x40 A field with dynamic storage size. Struct field
239 actually contains a pointer to a callback
241 ==================== ===== ================================================
246 Describes a single structure field with memory position in relation to others. The descriptions are usually autogenerated. ::
248 typedef struct _pb_field_t pb_field_t;
259 :tag: Tag number of the field or 0 to terminate a list of fields.
260 :type: LTYPE, HTYPE and ATYPE of the field.
261 :data_offset: Offset of field data, relative to the end of the previous field.
262 :size_offset: Offset of *bool* flag for optional fields or *size_t* count for arrays, relative to field data.
263 :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.
264 :array_size: Maximum number of entries in an array, if it is an array type.
265 :ptr: Pointer to default value for optional fields, or to submessage description for PB_LTYPE_SUBMESSAGE.
267 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*.
271 An byte array with a field for storing the length::
278 In an actual array, the length of *bytes* may be different.
282 Part of a message structure, for fields with type PB_HTYPE_CALLBACK::
284 typedef struct _pb_callback_t pb_callback_t;
285 struct _pb_callback_t {
287 bool (*decode)(pb_istream_t *stream, const pb_field_t *field, void **arg);
288 bool (*encode)(pb_ostream_t *stream, const pb_field_t *field, void * const *arg);
294 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.
296 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*.
298 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.
302 Protocol Buffers wire types. These are used with `pb_encode_tag`_. ::
313 Defines the handler functions and auxiliary data for a field that extends
314 another message. Usually autogenerated by *nanopb_generator.py*::
317 bool (*decode)(pb_istream_t *stream, pb_extension_t *extension,
318 uint32_t tag, pb_wire_type_t wire_type);
319 bool (*encode)(pb_ostream_t *stream, const pb_extension_t *extension);
321 } pb_extension_type_t;
323 In the normal case, the function pointers are *NULL* and the decoder and
324 encoder use their internal implementations. The internal implementations
325 assume that *arg* points to a *pb_field_t* that describes the field in question.
327 To implement custom processing of unknown fields, you can provide pointers
328 to your own functions. Their functionality is mostly the same as for normal
329 callback fields, except that they get called for any unknown field when decoding.
333 Ties together the extension field type and the storage for the field value::
336 const pb_extension_type_t *type;
338 pb_extension_t *next;
341 :type: Pointer to the structure that defines the callback functions.
342 :dest: Pointer to the variable that stores the field value
343 (as used by the default extension callback functions.)
344 :next: Pointer to the next extension handler, or *NULL*.
348 Get the current error message from a stream, or a placeholder string if
349 there is no error message::
351 #define PB_GET_ERROR(stream) (string expression)
353 This should be used for printing errors, for example::
357 printf("Decode failed: %s\n", PB_GET_ERROR(stream));
360 The macro only returns pointers to constant strings (in code memory),
361 so that there is no need to release the returned pointer.
365 Set the error message and return false::
367 #define PB_RETURN_ERROR(stream,msg) (sets error and returns false)
369 This should be used to handle error conditions inside nanopb functions
370 and user callback functions::
374 PB_RETURN_ERROR(stream, "something went wrong");
377 The *msg* parameter must be a constant string.
384 pb_ostream_from_buffer
385 ----------------------
386 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. ::
388 pb_ostream_t pb_ostream_from_buffer(uint8_t *buf, size_t bufsize);
390 :buf: Memory buffer to write into.
391 :bufsize: Maximum number of bytes to write.
392 :returns: An output stream.
394 After writing, you can check *stream.bytes_written* to find out how much valid data there is in the buffer.
398 Writes data to an output stream. Always use this function, instead of trying to call stream callback manually. ::
400 bool pb_write(pb_ostream_t *stream, const uint8_t *buf, size_t count);
402 :stream: Output stream to write to.
403 :buf: Pointer to buffer with the data to be written.
404 :count: Number of bytes to write.
405 :returns: True on success, false if maximum length is exceeded or an IO error happens.
407 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.
411 Encodes the contents of a structure as a protocol buffers message and writes it to output stream. ::
413 bool pb_encode(pb_ostream_t *stream, const pb_field_t fields[], const void *src_struct);
415 :stream: Output stream to write to.
416 :fields: A field description array, usually autogenerated.
417 :src_struct: Pointer to the data that will be serialized.
418 :returns: True on success, false on IO error, on detectable errors in field description, or if a field encoder returns false.
420 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.
424 Calculates the length of the message, encodes it as varint and then encodes the message. ::
426 bool pb_encode_delimited(pb_ostream_t *stream, const pb_field_t fields[], const void *src_struct);
428 (parameters are the same as for `pb_encode`_.)
430 A common way to indicate the message length in Protocol Buffers is to prefix it with a varint.
431 This function does this, and it is compatible with *parseDelimitedFrom* in Google's protobuf library.
433 .. sidebar:: Encoding fields manually
435 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.
437 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.
439 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.
443 Starts a field in the Protocol Buffers binary format: encodes the field number and the wire type of the data. ::
445 bool pb_encode_tag(pb_ostream_t *stream, pb_wire_type_t wiretype, int field_number);
447 :stream: Output stream to write to. 1-5 bytes will be written.
448 :wiretype: PB_WT_VARINT, PB_WT_64BIT, PB_WT_STRING or PB_WT_32BIT
449 :field_number: Identifier for the field, defined in the .proto file. You can get it from field->tag.
450 :returns: True on success, false on IO error.
452 pb_encode_tag_for_field
453 -----------------------
454 Same as `pb_encode_tag`_, except takes the parameters from a *pb_field_t* structure. ::
456 bool pb_encode_tag_for_field(pb_ostream_t *stream, const pb_field_t *field);
458 :stream: Output stream to write to. 1-5 bytes will be written.
459 :field: Field description structure. Usually autogenerated.
460 :returns: True on success, false on IO error or unknown field type.
462 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.
464 Wire type mapping is as follows:
466 ========================= ============
468 ========================= ============
469 VARINT, SVARINT PB_WT_VARINT
471 STRING, BYTES, SUBMESSAGE PB_WT_STRING
473 ========================= ============
477 Encodes a signed or unsigned integer in the varint_ format. Works for fields of type `bool`, `enum`, `int32`, `int64`, `uint32` and `uint64`::
479 bool pb_encode_varint(pb_ostream_t *stream, uint64_t value);
481 :stream: Output stream to write to. 1-10 bytes will be written.
482 :value: Value to encode. Just cast e.g. int32_t directly to uint64_t.
483 :returns: True on success, false on IO error.
485 .. _varint: http://code.google.com/apis/protocolbuffers/docs/encoding.html#varints
489 Encodes a signed integer in the 'zig-zagged' format. Works for fields of type `sint32` and `sint64`::
491 bool pb_encode_svarint(pb_ostream_t *stream, int64_t value);
493 (parameters are the same as for `pb_encode_varint`_
497 Writes the length of a string as varint and then contents of the string. Works for fields of type `bytes` and `string`::
499 bool pb_encode_string(pb_ostream_t *stream, const uint8_t *buffer, size_t size);
501 :stream: Output stream to write to.
502 :buffer: Pointer to string data.
503 :size: Number of bytes in the string. Pass `strlen(s)` for strings.
504 :returns: True on success, false on IO error.
508 Writes 4 bytes to stream and swaps bytes on big-endian architectures. Works for fields of type `fixed32`, `sfixed32` and `float`::
510 bool pb_encode_fixed32(pb_ostream_t *stream, const void *value);
512 :stream: Output stream to write to.
513 :value: Pointer to a 4-bytes large C variable, for example `uint32_t foo;`.
514 :returns: True on success, false on IO error.
518 Writes 8 bytes to stream and swaps bytes on big-endian architecture. Works for fields of type `fixed64`, `sfixed64` and `double`::
520 bool pb_encode_fixed64(pb_ostream_t *stream, const void *value);
522 :stream: Output stream to write to.
523 :value: Pointer to a 8-bytes large C variable, for example `uint64_t foo;`.
524 :returns: True on success, false on IO error.
528 Encodes a submessage field, including the size header for it. Works for fields of any message type::
530 bool pb_encode_submessage(pb_ostream_t *stream, const pb_field_t fields[], const void *src_struct);
532 :stream: Output stream to write to.
533 :fields: Pointer to the autogenerated field description array for the submessage type, e.g. `MyMessage_fields`.
534 :src: Pointer to the structure where submessage data is.
535 :returns: True on success, false on IO errors, pb_encode errors or if submessage size changes between calls.
537 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.
539 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.
555 pb_istream_from_buffer
556 ----------------------
557 Helper function for creating an input stream that reads data from a memory buffer. ::
559 pb_istream_t pb_istream_from_buffer(uint8_t *buf, size_t bufsize);
561 :buf: Pointer to byte array to read from.
562 :bufsize: Size of the byte array.
563 :returns: An input stream ready to use.
567 Read data from input stream. Always use this function, don't try to call the stream callback directly. ::
569 bool pb_read(pb_istream_t *stream, uint8_t *buf, size_t count);
571 :stream: Input stream to read from.
572 :buf: Buffer to store the data to, or NULL to just read data without storing it anywhere.
573 :count: Number of bytes to read.
574 :returns: True on success, false if *stream->bytes_left* is less than *count* or if an IO error occurs.
576 End of file is signalled by *stream->bytes_left* being zero after pb_read returns false.
580 Read and decode all fields of a structure. Reads until EOF on input stream. ::
582 bool pb_decode(pb_istream_t *stream, const pb_field_t fields[], void *dest_struct);
584 :stream: Input stream to read from.
585 :fields: A field description array. Usually autogenerated.
586 :dest_struct: Pointer to structure where data will be stored.
587 :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.
589 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.
591 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.
593 For optional fields, this function applies the default value and sets *has_<field>* to false if the field is not present.
595 If *PB_ENABLE_MALLOC* is defined, this function may allocate storage for any pointer type fields.
596 In this case, you have to call `pb_release`_ to release the memory after you are done with the message.
597 On error return `pb_decode` will release the memory itself.
601 Same as `pb_decode`_, except does not apply the default values to fields. ::
603 bool pb_decode_noinit(pb_istream_t *stream, const pb_field_t fields[], void *dest_struct);
605 (parameters are the same as for `pb_decode`_.)
607 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.
609 In addition to decoding a single message, this function can be used to merge two messages, so that
610 values from previous message will remain if the new message does not contain a field.
612 This function *will not* release the message even on error return. If you use *PB_ENABLE_MALLOC*,
613 you will need to call `pb_release`_ yourself.
617 Same as `pb_decode`_, except that it first reads a varint with the length of the message. ::
619 bool pb_decode_delimited(pb_istream_t *stream, const pb_field_t fields[], void *dest_struct);
621 (parameters are the same as for `pb_decode`_.)
623 A common method to indicate message size in Protocol Buffers is to prefix it with a varint.
624 This function is compatible with *writeDelimitedTo* in the Google's Protocol Buffers library.
628 Releases any dynamically allocated fields.
630 void pb_release(const pb_field_t fields[], void *dest_struct);
632 :fields: A field description array. Usually autogenerated.
633 :dest_struct: Pointer to structure where data will be stored.
635 This function is only available if *PB_ENABLE_MALLOC* is defined. It will release any
636 pointer type fields in the structure and set the pointers to NULL.
640 Skip a varint_ encoded integer without decoding it. ::
642 bool pb_skip_varint(pb_istream_t *stream);
644 :stream: Input stream to read from. Will read 1 byte at a time until the MSB is clear.
645 :returns: True on success, false on IO error.
649 Skip a varint-length-prefixed string. This means skipping a value with wire type PB_WT_STRING. ::
651 bool pb_skip_string(pb_istream_t *stream);
653 :stream: Input stream to read from.
654 :returns: True on success, false on IO error or length exceeding uint32_t.
658 Decode the tag that comes before field in the protobuf encoding::
660 bool pb_decode_tag(pb_istream_t *stream, pb_wire_type_t *wire_type, int *tag, bool *eof);
662 :stream: Input stream to read from.
663 :wire_type: Pointer to variable where to store the wire type of the field.
664 :tag: Pointer to variable where to store the tag of the field.
665 :eof: Pointer to variable where to store end-of-file status.
666 :returns: True on success, false on error or EOF.
668 When the message (stream) ends, this function will return false and set *eof* to true. On other
669 errors, *eof* will be set to false.
673 Remove the data for a field from the stream, without actually decoding it::
675 bool pb_skip_field(pb_istream_t *stream, pb_wire_type_t wire_type);
677 :stream: Input stream to read from.
678 :wire_type: Type of field to skip.
679 :returns: True on success, false on IO error.
681 .. sidebar:: Decoding fields manually
683 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.
685 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.
687 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`_.
689 Finally, for decoding submessages in a callback, simply use `pb_decode`_ and pass it the *SubMessage_fields* descriptor array.
693 Read and decode a varint_ encoded integer. ::
695 bool pb_decode_varint(pb_istream_t *stream, uint64_t *dest);
697 :stream: Input stream to read from. 1-10 bytes will be read.
698 :dest: Storage for the decoded integer. Value is undefined on error.
699 :returns: True on success, false if value exceeds uint64_t range or an IO error happens.
703 Similar to `pb_decode_varint`_, except that it performs zigzag-decoding on the value. This corresponds to the Protocol Buffers *sint32* and *sint64* datatypes. ::
705 bool pb_decode_svarint(pb_istream_t *stream, int64_t *dest);
707 (parameters are the same as `pb_decode_varint`_)
711 Decode a *fixed32*, *sfixed32* or *float* value. ::
713 bool pb_decode_fixed32(pb_istream_t *stream, void *dest);
715 :stream: Input stream to read from. 4 bytes will be read.
716 :dest: Pointer to destination *int32_t*, *uint32_t* or *float*.
717 :returns: True on success, false on IO errors.
719 This function reads 4 bytes from the input stream.
720 On big endian architectures, it then reverses the order of the bytes.
721 Finally, it writes the bytes to *dest*.
725 Decode a *fixed64*, *sfixed64* or *double* value. ::
727 bool pb_dec_fixed(pb_istream_t *stream, const pb_field_t *field, void *dest);
729 :stream: Input stream to read from. 8 bytes will be read.
731 :dest: Pointer to destination *int64_t*, *uint64_t* or *double*.
732 :returns: True on success, false on IO errors.
734 Same as `pb_decode_fixed32`_, except this reads 8 bytes.
736 pb_make_string_substream
737 ------------------------
738 Decode the length for a field with wire type *PB_WT_STRING* and create a substream for reading the data. ::
740 bool pb_make_string_substream(pb_istream_t *stream, pb_istream_t *substream);
742 :stream: Original input stream to read the length and data from.
743 :substream: New substream that has limited length. Filled in by the function.
744 :returns: True on success, false if reading the length fails.
746 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.
748 pb_close_string_substream
749 -------------------------
750 Close the substream created with `pb_make_string_substream`_. ::
752 void pb_close_string_substream(pb_istream_t *stream, pb_istream_t *substream);
754 :stream: Original input stream to read the length and data from.
755 :substream: Substream to close
757 This function copies back the state from the substream to the parent stream.
758 It must be called after done with the substream.