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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 */
27struct pb_ostream_s
28{
29#ifdef PB_BUFFER_ONLY
30 /* Callback pointer is not used in buffer-only configuration.
31 * Having an int pointer here allows binary compatibility but
32 * gives an error if someone tries to assign callback function.
33 * Also, NULL pointer marks a 'sizing stream' that does not
34 * write anything.
35 */
36 const int *callback;
37#else
38 bool (*callback)(pb_ostream_t *stream, const pb_byte_t *buf, size_t count);
39#endif
40 void *state; /* Free field for use by callback implementation. */
41 size_t max_size; /* Limit number of output bytes written (or use SIZE_MAX). */
42 size_t bytes_written; /* Number of bytes written so far. */
43
44#ifndef PB_NO_ERRMSG
45 const char *errmsg;
46#endif
47};
48
49/***************************
50 * Main encoding functions *
51 ***************************/
52
53/* Encode a single protocol buffers message from C structure into a stream.
54 * Returns true on success, false on any failure.
55 * The actual struct pointed to by src_struct must match the description in fields.
56 * All required fields in the struct are assumed to have been filled in.
57 *
58 * Example usage:
59 * MyMessage msg = {};
60 * uint8_t buffer[64];
61 * pb_ostream_t stream;
62 *
63 * msg.field1 = 42;
64 * stream = pb_ostream_from_buffer(buffer, sizeof(buffer));
65 * pb_encode(&stream, MyMessage_fields, &msg);
66 */
67bool pb_encode(pb_ostream_t *stream, const pb_msgdesc_t *fields, const void *src_struct);
68
69/* Extended version of pb_encode, with several options to control the
70 * encoding process:
71 *
72 * PB_ENCODE_DELIMITED: Prepend the length of message as a varint.
73 * Corresponds to writeDelimitedTo() in Google's
74 * protobuf API.
75 *
76 * PB_ENCODE_NULLTERMINATED: Append a null byte to the message for termination.
77 * NOTE: This behaviour is not supported in most other
78 * protobuf implementations, so PB_ENCODE_DELIMITED
79 * is a better option for compatibility.
80 */
81#define PB_ENCODE_DELIMITED 0x02U
82#define PB_ENCODE_NULLTERMINATED 0x04U
83bool pb_encode_ex(pb_ostream_t *stream, const pb_msgdesc_t *fields, const void *src_struct, unsigned int flags);
84
85/* Defines for backwards compatibility with code written before nanopb-0.4.0 */
86#define pb_encode_delimited(s,f,d) pb_encode_ex(s,f,d, PB_ENCODE_DELIMITED)
87#define pb_encode_nullterminated(s,f,d) pb_encode_ex(s,f,d, PB_ENCODE_NULLTERMINATED)
88
89/* Encode the message to get the size of the encoded data, but do not store
90 * the data. */
91bool pb_get_encoded_size(size_t *size, const pb_msgdesc_t *fields, const void *src_struct);
92
93/**************************************
94 * Functions for manipulating streams *
95 **************************************/
96
97/* Create an output stream for writing into a memory buffer.
98 * The number of bytes written can be found in stream.bytes_written after
99 * encoding the message.
100 *
101 * Alternatively, you can use a custom stream that writes directly to e.g.
102 * a file or a network socket.
103 */
104pb_ostream_t pb_ostream_from_buffer(pb_byte_t *buf, size_t bufsize);
105
106/* Pseudo-stream for measuring the size of a message without actually storing
107 * the encoded data.
108 *
109 * Example usage:
110 * MyMessage msg = {};
111 * pb_ostream_t stream = PB_OSTREAM_SIZING;
112 * pb_encode(&stream, MyMessage_fields, &msg);
113 * printf("Message size is %d\n", stream.bytes_written);
114 */
115#ifndef PB_NO_ERRMSG
116#define PB_OSTREAM_SIZING {0,0,0,0,0}
117#else
118#define PB_OSTREAM_SIZING {0,0,0,0}
119#endif
120
121/* Function to write into a pb_ostream_t stream. You can use this if you need
122 * to append or prepend some custom headers to the message.
123 */
124bool pb_write(pb_ostream_t *stream, const pb_byte_t *buf, size_t count);
125
126
127/************************************************
128 * Helper functions for writing field callbacks *
129 ************************************************/
130
131/* Encode field header based on type and field number defined in the field
132 * structure. Call this from the callback before writing out field contents. */
133bool pb_encode_tag_for_field(pb_ostream_t *stream, const pb_field_iter_t *field);
134
135/* Encode field header by manually specifying wire type. You need to use this
136 * if you want to write out packed arrays from a callback field. */
137bool pb_encode_tag(pb_ostream_t *stream, pb_wire_type_t wiretype, uint32_t field_number);
138
139/* Encode an integer in the varint format.
140 * This works for bool, enum, int32, int64, uint32 and uint64 field types. */
141#ifndef PB_WITHOUT_64BIT
142bool pb_encode_varint(pb_ostream_t *stream, uint64_t value);
143#else
144bool pb_encode_varint(pb_ostream_t *stream, uint32_t value);
145#endif
146
147/* Encode an integer in the zig-zagged svarint format.
148 * This works for sint32 and sint64. */
149#ifndef PB_WITHOUT_64BIT
150bool pb_encode_svarint(pb_ostream_t *stream, int64_t value);
151#else
152bool pb_encode_svarint(pb_ostream_t *stream, int32_t value);
153#endif
154
155/* Encode a string or bytes type field. For strings, pass strlen(s) as size. */
156bool pb_encode_string(pb_ostream_t *stream, const pb_byte_t *buffer, size_t size);
157
158/* Encode a fixed32, sfixed32 or float value.
159 * You need to pass a pointer to a 4-byte wide C variable. */
160bool pb_encode_fixed32(pb_ostream_t *stream, const void *value);
161
162#ifndef PB_WITHOUT_64BIT
163/* Encode a fixed64, sfixed64 or double value.
164 * You need to pass a pointer to a 8-byte wide C variable. */
165bool pb_encode_fixed64(pb_ostream_t *stream, const void *value);
166#endif
167
168#ifdef PB_CONVERT_DOUBLE_FLOAT
169/* Encode a float value so that it appears like a double in the encoded
170 * message. */
171bool pb_encode_float_as_double(pb_ostream_t *stream, float value);
172#endif
173
174/* Encode a submessage field.
175 * You need to pass the pb_field_t array and pointer to struct, just like
176 * with pb_encode(). This internally encodes the submessage twice, first to
177 * calculate message size and then to actually write it out.
178 */
179bool pb_encode_submessage(pb_ostream_t *stream, const pb_msgdesc_t *fields, const void *src_struct);
180
181#ifdef __cplusplus
182} /* extern "C" */
183#endif
184
185#endif