1/* pb_decode.h: Functions to decode protocol buffers. Depends on pb_decode.c.
2 * The main function is pb_decode. You also need an input stream, and the
3 * field descriptions created by nanopb_generator.py.
4 */
5
6#ifndef _PB_DECODE_H_
7#define _PB_DECODE_H_
8
9#include "pb.h"
10
11#ifdef __cplusplus
12extern "C" {
13#endif
14
15/* Structure for defining custom input streams. You will need to provide
16 * a callback function to read the bytes from 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 decoding to abort.
22 * 2) You can use state to store your own data (e.g. buffer pointer),
23 *    and rely on pb_read to verify that no-body reads past bytes_left.
24 * 3) Your callback may be used with substreams, in which case bytes_left
25 *    is different than from the main stream. Don't use bytes_left to compute
26 *    any pointers.
27 */
28struct _pb_istream_t
29{
30#ifdef PB_BUFFER_ONLY
31    /* Callback pointer is not used in buffer-only configuration.
32     * Having an int pointer here allows binary compatibility but
33     * gives an error if someone tries to assign callback function.
34     */
35    int *callback;
36#else
37    bool (*callback)(pb_istream_t *stream, uint8_t *buf, size_t count);
38#endif
39
40    void *state; /* Free field for use by callback implementation */
41    size_t bytes_left;
42
43#ifndef PB_NO_ERRMSG
44    const char *errmsg;
45#endif
46};
47
48/***************************
49 * Main decoding functions *
50 ***************************/
51
52/* Decode a single protocol buffers message from input stream into a C structure.
53 * Returns true on success, false on any failure.
54 * The actual struct pointed to by dest must match the description in fields.
55 * Callback fields of the destination structure must be initialized by caller.
56 * All other fields will be initialized by this function.
57 *
58 * Example usage:
59 *    MyMessage msg = {};
60 *    uint8_t buffer[64];
61 *    pb_istream_t stream;
62 *
63 *    // ... read some data into buffer ...
64 *
65 *    stream = pb_istream_from_buffer(buffer, count);
66 *    pb_decode(&stream, MyMessage_fields, &msg);
67 */
68bool pb_decode(pb_istream_t *stream, const pb_field_t fields[], void *dest_struct);
69
70/* Same as pb_decode, except does not initialize the destination structure
71 * to default values. This is slightly faster if you need no default values
72 * and just do memset(struct, 0, sizeof(struct)) yourself.
73 *
74 * This can also be used for 'merging' two messages, i.e. update only the
75 * fields that exist in the new message.
76 *
77 * Note: If this function returns with an error, it will not release any
78 * dynamically allocated fields. You will need to call pb_release() yourself.
79 */
80bool pb_decode_noinit(pb_istream_t *stream, const pb_field_t fields[], void *dest_struct);
81
82/* Same as pb_decode, except expects the stream to start with the message size
83 * encoded as varint. Corresponds to parseDelimitedFrom() in Google's
84 * protobuf API.
85 */
86bool pb_decode_delimited(pb_istream_t *stream, const pb_field_t fields[], void *dest_struct);
87
88#ifdef PB_ENABLE_MALLOC
89/* Release any allocated pointer fields. If you use dynamic allocation, you should
90 * call this for any successfully decoded message when you are done with it. If
91 * pb_decode() returns with an error, the message is already released.
92 */
93void pb_release(const pb_field_t fields[], void *dest_struct);
94#endif
95
96
97/**************************************
98 * Functions for manipulating streams *
99 **************************************/
100
101/* Create an input stream for reading from a memory buffer.
102 *
103 * Alternatively, you can use a custom stream that reads directly from e.g.
104 * a file or a network socket.
105 */
106pb_istream_t pb_istream_from_buffer(uint8_t *buf, size_t bufsize);
107
108/* Function to read from a pb_istream_t. You can use this if you need to
109 * read some custom header data, or to read data in field callbacks.
110 */
111bool pb_read(pb_istream_t *stream, uint8_t *buf, size_t count);
112
113
114/************************************************
115 * Helper functions for writing field callbacks *
116 ************************************************/
117
118/* Decode the tag for the next field in the stream. Gives the wire type and
119 * field tag. At end of the message, returns false and sets eof to true. */
120bool pb_decode_tag(pb_istream_t *stream, pb_wire_type_t *wire_type, uint32_t *tag, bool *eof);
121
122/* Skip the field payload data, given the wire type. */
123bool pb_skip_field(pb_istream_t *stream, pb_wire_type_t wire_type);
124
125/* Decode an integer in the varint format. This works for bool, enum, int32,
126 * int64, uint32 and uint64 field types. */
127bool pb_decode_varint(pb_istream_t *stream, uint64_t *dest);
128
129/* Decode an integer in the zig-zagged svarint format. This works for sint32
130 * and sint64. */
131bool pb_decode_svarint(pb_istream_t *stream, int64_t *dest);
132
133/* Decode a fixed32, sfixed32 or float value. You need to pass a pointer to
134 * a 4-byte wide C variable. */
135bool pb_decode_fixed32(pb_istream_t *stream, void *dest);
136
137/* Decode a fixed64, sfixed64 or double value. You need to pass a pointer to
138 * a 8-byte wide C variable. */
139bool pb_decode_fixed64(pb_istream_t *stream, void *dest);
140
141/* Make a limited-length substream for reading a PB_WT_STRING field. */
142bool pb_make_string_substream(pb_istream_t *stream, pb_istream_t *substream);
143void pb_close_string_substream(pb_istream_t *stream, pb_istream_t *substream);
144
145#ifdef __cplusplus
146} /* extern "C" */
147#endif
148
149#endif
150