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
41 /* state is a free field for use of the callback function defined above.
42 * Note that when pb_ostream_from_buffer() is used, it reserves this field
43 * for its own use.
44 */
45 void *state;
46
47 /* Limit number of output bytes written. Can be set to SIZE_MAX. */
48 size_t max_size;
49
50 /* Number of bytes written so far. */
51 size_t bytes_written;
52
53#ifndef PB_NO_ERRMSG
54 /* Pointer to constant (ROM) string when decoding function returns error */
55 const char *errmsg;
56#endif
57};
58
59/***************************
60 * Main encoding functions *
61 ***************************/
62
63/* Encode a single protocol buffers message from C structure into a stream.
64 * Returns true on success, false on any failure.
65 * The actual struct pointed to by src_struct must match the description in fields.
66 * All required fields in the struct are assumed to have been filled in.
67 *
68 * Example usage:
69 * MyMessage msg = {};
70 * uint8_t buffer[64];
71 * pb_ostream_t stream;
72 *
73 * msg.field1 = 42;
74 * stream = pb_ostream_from_buffer(buffer, sizeof(buffer));
75 * pb_encode(&stream, MyMessage_fields, &msg);
76 */
77bool pb_encode(pb_ostream_t *stream, const pb_msgdesc_t *fields, const void *src_struct);
78
79/* Extended version of pb_encode, with several options to control the
80 * encoding process:
81 *
82 * PB_ENCODE_DELIMITED: Prepend the length of message as a varint.
83 * Corresponds to writeDelimitedTo() in Google's
84 * protobuf API.
85 *
86 * PB_ENCODE_NULLTERMINATED: Append a null byte to the message for termination.
87 * NOTE: This behaviour is not supported in most other
88 * protobuf implementations, so PB_ENCODE_DELIMITED
89 * is a better option for compatibility.
90 */
91#define PB_ENCODE_DELIMITED 0x02U
92#define PB_ENCODE_NULLTERMINATED 0x04U
93bool pb_encode_ex(pb_ostream_t *stream, const pb_msgdesc_t *fields, const void *src_struct, unsigned int flags);
94
95/* Defines for backwards compatibility with code written before nanopb-0.4.0 */
96#define pb_encode_delimited(s,f,d) pb_encode_ex(s,f,d, PB_ENCODE_DELIMITED)
97#define pb_encode_nullterminated(s,f,d) pb_encode_ex(s,f,d, PB_ENCODE_NULLTERMINATED)
98
99/* Encode the message to get the size of the encoded data, but do not store
100 * the data. */
101bool pb_get_encoded_size(size_t *size, const pb_msgdesc_t *fields, const void *src_struct);
102
103/**************************************
104 * Functions for manipulating streams *
105 **************************************/
106
107/* Create an output stream for writing into a memory buffer.
108 * The number of bytes written can be found in stream.bytes_written after
109 * encoding the message.
110 *
111 * Alternatively, you can use a custom stream that writes directly to e.g.
112 * a file or a network socket.
113 */
114pb_ostream_t pb_ostream_from_buffer(pb_byte_t *buf, size_t bufsize);
115
116/* Pseudo-stream for measuring the size of a message without actually storing
117 * the encoded data.
118 *
119 * Example usage:
120 * MyMessage msg = {};
121 * pb_ostream_t stream = PB_OSTREAM_SIZING;
122 * pb_encode(&stream, MyMessage_fields, &msg);
123 * printf("Message size is %d\n", stream.bytes_written);
124 */
125#ifndef PB_NO_ERRMSG
126#define PB_OSTREAM_SIZING {0,0,0,0,0}
127#else
128#define PB_OSTREAM_SIZING {0,0,0,0}
129#endif
130
131/* Function to write into a pb_ostream_t stream. You can use this if you need
132 * to append or prepend some custom headers to the message.
133 */
134bool pb_write(pb_ostream_t *stream, const pb_byte_t *buf, size_t count);
135
136
137/************************************************
138 * Helper functions for writing field callbacks *
139 ************************************************/
140
141/* Encode field header based on type and field number defined in the field
142 * structure. Call this from the callback before writing out field contents. */
143bool pb_encode_tag_for_field(pb_ostream_t *stream, const pb_field_iter_t *field);
144
145/* Encode field header by manually specifying wire type. You need to use this
146 * if you want to write out packed arrays from a callback field. */
147bool pb_encode_tag(pb_ostream_t *stream, pb_wire_type_t wiretype, uint32_t field_number);
148
149/* Encode an integer in the varint format.
150 * This works for bool, enum, int32, int64, uint32 and uint64 field types. */
151#ifndef PB_WITHOUT_64BIT
152bool pb_encode_varint(pb_ostream_t *stream, uint64_t value);
153#else
154bool pb_encode_varint(pb_ostream_t *stream, uint32_t value);
155#endif
156
157/* Encode an integer in the zig-zagged svarint format.
158 * This works for sint32 and sint64. */
159#ifndef PB_WITHOUT_64BIT
160bool pb_encode_svarint(pb_ostream_t *stream, int64_t value);
161#else
162bool pb_encode_svarint(pb_ostream_t *stream, int32_t value);
163#endif
164
165/* Encode a string or bytes type field. For strings, pass strlen(s) as size. */
166bool pb_encode_string(pb_ostream_t *stream, const pb_byte_t *buffer, size_t size);
167
168/* Encode a fixed32, sfixed32 or float value.
169 * You need to pass a pointer to a 4-byte wide C variable. */
170bool pb_encode_fixed32(pb_ostream_t *stream, const void *value);
171
172#ifndef PB_WITHOUT_64BIT
173/* Encode a fixed64, sfixed64 or double value.
174 * You need to pass a pointer to a 8-byte wide C variable. */
175bool pb_encode_fixed64(pb_ostream_t *stream, const void *value);
176#endif
177
178#ifdef PB_CONVERT_DOUBLE_FLOAT
179/* Encode a float value so that it appears like a double in the encoded
180 * message. */
181bool pb_encode_float_as_double(pb_ostream_t *stream, float value);
182#endif
183
184/* Encode a submessage field.
185 * You need to pass the pb_field_t array and pointer to struct, just like
186 * with pb_encode(). This internally encodes the submessage twice, first to
187 * calculate message size and then to actually write it out.
188 */
189bool pb_encode_submessage(pb_ostream_t *stream, const pb_msgdesc_t *fields, const void *src_struct);
190
191#ifdef __cplusplus
192} /* extern "C" */
193#endif
194
195#endif
196