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pb_encode.h
1/* pb_encode.h: Functions to encode protocol buffers. Depends on pb_encode.c.
2 * The main function is pb_encode. You also need an output stream, and the
3 * field descriptions created by nanopb_generator.py.
4 */
5
6#ifndef PB_ENCODE_H_INCLUDED
7#define PB_ENCODE_H_INCLUDED
8
9#include "pb.h"
10
11#ifdef __cplusplus
12extern "C" {
13#endif
14
15/* Structure for defining custom output streams. You will need to provide
16 * a callback function to write the bytes to your storage, which can be
17 * for example a file or a network socket.
18 *
19 * The callback must conform to these rules:
20 *
21 * 1) Return false on IO errors. This will cause encoding to abort.
22 * 2) You can use state to store your own data (e.g. buffer pointer).
23 * 3) pb_write will update bytes_written after your callback runs.
24 * 4) Substreams will modify max_size and bytes_written. Don't use them
25 * to calculate any pointers.
26 */
28#ifdef PB_BUFFER_ONLY
29 /* Callback pointer is not used in buffer-only configuration.
30 * Having an int pointer here allows binary compatibility but
31 * gives an error if someone tries to assign callback function.
32 * Also, NULL pointer marks a 'sizing stream' that does not
33 * write anything.
34 */
35 const int * callback;
36#else
37 bool (*callback)(pb_ostream_t *stream, const pb_byte_t *buf, size_t count);
38#endif
39 void * state; /* Free field for use by callback implementation. */
40 size_t max_size; /* Limit number of output bytes written (or use SIZE_MAX). */
41 size_t bytes_written; /* Number of bytes written so far. */
42
43#ifndef PB_NO_ERRMSG
44 const char * errmsg;
45#endif
46};
47
48/***************************
49* Main encoding functions *
50***************************/
51
52/* Encode a single protocol buffers message from C structure into a stream.
53 * Returns true on success, false on any failure.
54 * The actual struct pointed to by src_struct must match the description in fields.
55 * All required fields in the struct are assumed to have been filled in.
56 *
57 * Example usage:
58 * MyMessage msg = {};
59 * uint8_t buffer[64];
60 * pb_ostream_t stream;
61 *
62 * msg.field1 = 42;
63 * stream = pb_ostream_from_buffer(buffer, sizeof(buffer));
64 * pb_encode(&stream, MyMessage_fields, &msg);
65 */
66bool pb_encode(pb_ostream_t *stream, const pb_msgdesc_t *fields, const void *src_struct);
67
68/* Extended version of pb_encode, with several options to control the
69 * encoding process:
70 *
71 * PB_ENCODE_DELIMITED: Prepend the length of message as a varint.
72 * Corresponds to writeDelimitedTo() in Google's
73 * protobuf API.
74 *
75 * PB_ENCODE_NULLTERMINATED: Append a null byte to the message for termination.
76 * NOTE: This behaviour is not supported in most other
77 * protobuf implementations, so PB_ENCODE_DELIMITED
78 * is a better option for compatibility.
79 */
80#define PB_ENCODE_DELIMITED 0x02U
81#define PB_ENCODE_NULLTERMINATED 0x04U
82bool pb_encode_ex(pb_ostream_t *stream, const pb_msgdesc_t *fields, const void *src_struct, unsigned int flags);
83
84/* Defines for backwards compatibility with code written before nanopb-0.4.0 */
85#define pb_encode_delimited(s, f, d) pb_encode_ex(s, f, d, PB_ENCODE_DELIMITED)
86#define pb_encode_nullterminated(s, f, d) pb_encode_ex(s, f, d, PB_ENCODE_NULLTERMINATED)
87
88/* Encode the message to get the size of the encoded data, but do not store
89 * the data. */
90bool pb_get_encoded_size(size_t *size, const pb_msgdesc_t *fields, const void *src_struct);
91
92/**************************************
93* Functions for manipulating streams *
94**************************************/
95
96/* Create an output stream for writing into a memory buffer.
97 * The number of bytes written can be found in stream.bytes_written after
98 * encoding the message.
99 *
100 * Alternatively, you can use a custom stream that writes directly to e.g.
101 * a file or a network socket.
102 */
103pb_ostream_t pb_ostream_from_buffer(pb_byte_t *buf, size_t bufsize);
104
105/* Pseudo-stream for measuring the size of a message without actually storing
106 * the encoded data.
107 *
108 * Example usage:
109 * MyMessage msg = {};
110 * pb_ostream_t stream = PB_OSTREAM_SIZING;
111 * pb_encode(&stream, MyMessage_fields, &msg);
112 * printf("Message size is %d\n", stream.bytes_written);
113 */
114#ifndef PB_NO_ERRMSG
115#define PB_OSTREAM_SIZING { 0, 0, 0, 0, 0 }
116#else
117#define PB_OSTREAM_SIZING { 0, 0, 0, 0 }
118#endif
119
120/* Function to write into a pb_ostream_t stream. You can use this if you need
121 * to append or prepend some custom headers to the message.
122 */
123bool pb_write(pb_ostream_t *stream, const pb_byte_t *buf, size_t count);
124
125
126/************************************************
127* Helper functions for writing field callbacks *
128************************************************/
129
130/* Encode field header based on type and field number defined in the field
131 * structure. Call this from the callback before writing out field contents. */
132bool pb_encode_tag_for_field(pb_ostream_t *stream, const pb_field_iter_t *field);
133
134/* Encode field header by manually specifying wire type. You need to use this
135 * if you want to write out packed arrays from a callback field. */
136bool pb_encode_tag(pb_ostream_t *stream, pb_wire_type_t wiretype, uint32_t field_number);
137
138/* Encode an integer in the varint format.
139 * This works for bool, enum, int32, int64, uint32 and uint64 field types. */
140#ifndef PB_WITHOUT_64BIT
141bool pb_encode_varint(pb_ostream_t *stream, uint64_t value);
142#else
143bool pb_encode_varint(pb_ostream_t *stream, uint32_t value);
144#endif
145
146/* Encode an integer in the zig-zagged svarint format.
147 * This works for sint32 and sint64. */
148#ifndef PB_WITHOUT_64BIT
149bool pb_encode_svarint(pb_ostream_t *stream, int64_t value);
150#else
151bool pb_encode_svarint(pb_ostream_t *stream, int32_t value);
152#endif
153
154/* Encode a string or bytes type field. For strings, pass strlen(s) as size. */
155bool pb_encode_string(pb_ostream_t *stream, const pb_byte_t *buffer, size_t size);
156
157/* Encode a fixed32, sfixed32 or float value.
158 * You need to pass a pointer to a 4-byte wide C variable. */
159bool pb_encode_fixed32(pb_ostream_t *stream, const void *value);
160
161#ifndef PB_WITHOUT_64BIT
162/* Encode a fixed64, sfixed64 or double value.
163 * You need to pass a pointer to a 8-byte wide C variable. */
164bool pb_encode_fixed64(pb_ostream_t *stream, const void *value);
165#endif
166
167#ifdef PB_CONVERT_DOUBLE_FLOAT
168/* Encode a float value so that it appears like a double in the encoded
169 * message. */
170bool pb_encode_float_as_double(pb_ostream_t *stream, float value);
171#endif
172
173/* Encode a submessage field.
174 * You need to pass the pb_field_t array and pointer to struct, just like
175 * with pb_encode(). This internally encodes the submessage twice, first to
176 * calculate message size and then to actually write it out.
177 */
178bool pb_encode_submessage(pb_ostream_t *stream, const pb_msgdesc_t *fields, const void *src_struct);
179
180#ifdef __cplusplus
181} /* extern "C" */
182#endif
183
184#endif
Definition: streams.h:14