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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
12 extern "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  */
28 struct _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  */
68 bool 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  */
80 bool 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  */
86 bool 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  */
93 void 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  */
106 pb_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  */
111 bool 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. */
120 bool 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. */
123 bool 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. */
127 bool 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. */
131 bool 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. */
135 bool 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. */
139 bool pb_decode_fixed64(pb_istream_t *stream, void *dest);
140 
141 /* Make a limited-length substream for reading a PB_WT_STRING field. */
142 bool pb_make_string_substream(pb_istream_t *stream, pb_istream_t *substream);
143 void 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