summaryrefslogtreecommitdiffstats
path: root/pb_decode.h
blob: 1d9bb1945c1f5289261b36cf62a68d6ca06faa76 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
/* pb_decode.h: Functions to decode protocol buffers. Depends on pb_decode.c.
 * The main function is pb_decode. You also need an input stream, and the
 * field descriptions created by nanopb_generator.py.
 */

#ifndef PB_DECODE_H_INCLUDED
#define PB_DECODE_H_INCLUDED

#include "pb.h"

#ifdef __cplusplus
extern "C" {
#endif

/* Structure for defining custom input streams. You will need to provide
 * a callback function to read the bytes from your storage, which can be
 * for example a file or a network socket.
 * 
 * The callback must conform to these rules:
 *
 * 1) Return false on IO errors. This will cause decoding to abort.
 * 2) You can use state to store your own data (e.g. buffer pointer),
 *    and rely on pb_read to verify that no-body reads past bytes_left.
 * 3) Your callback may be used with substreams, in which case bytes_left
 *    is different than from the main stream. Don't use bytes_left to compute
 *    any pointers.
 */
struct pb_istream_s
{
#ifdef PB_BUFFER_ONLY
    /* Callback pointer is not used in buffer-only configuration.
     * Having an int pointer here allows binary compatibility but
     * gives an error if someone tries to assign callback function.
     */
    int *callback;
#else
    bool (*callback)(pb_istream_t *stream, pb_byte_t *buf, size_t count);
#endif

    void *state; /* Free field for use by callback implementation */
    size_t bytes_left;
    
#ifndef PB_NO_ERRMSG
    const char *errmsg;
#endif
};

/***************************
 * Main decoding functions *
 ***************************/
 
/* Decode a single protocol buffers message from input stream into a C structure.
 * Returns true on success, false on any failure.
 * The actual struct pointed to by dest must match the description in fields.
 * Callback fields of the destination structure must be initialized by caller.
 * All other fields will be initialized by this function.
 *
 * Example usage:
 *    MyMessage msg = {};
 *    uint8_t buffer[64];
 *    pb_istream_t stream;
 *    
 *    // ... read some data into buffer ...
 *
 *    stream = pb_istream_from_buffer(buffer, count);
 *    pb_decode(&stream, MyMessage_fields, &msg);
 */
bool pb_decode(pb_istream_t *stream, const pb_field_t fields[], void *dest_struct);

/* Same as pb_decode, except does not initialize the destination structure
 * to default values. This is slightly faster if you need no default values
 * and just do memset(struct, 0, sizeof(struct)) yourself.
 *
 * This can also be used for 'merging' two messages, i.e. update only the
 * fields that exist in the new message.
 *
 * Note: If this function returns with an error, it will not release any
 * dynamically allocated fields. You will need to call pb_release() yourself.
 */
bool pb_decode_noinit(pb_istream_t *stream, const pb_field_t fields[], void *dest_struct);

/* Same as pb_decode, except expects the stream to start with the message size
 * encoded as varint. Corresponds to parseDelimitedFrom() in Google's
 * protobuf API.
 */
bool pb_decode_delimited(pb_istream_t *stream, const pb_field_t fields[], void *dest_struct);

#ifdef PB_ENABLE_MALLOC
/* Release any allocated pointer fields. If you use dynamic allocation, you should
 * call this for any successfully decoded message when you are done with it. If
 * pb_decode() returns with an error, the message is already released.
 */
void pb_release(const pb_field_t fields[], void *dest_struct);
#endif


/**************************************
 * Functions for manipulating streams *
 **************************************/

/* Create an input stream for reading from a memory buffer.
 *
 * Alternatively, you can use a custom stream that reads directly from e.g.
 * a file or a network socket.
 */
pb_istream_t pb_istream_from_buffer(const pb_byte_t *buf, size_t bufsize);

/* Function to read from a pb_istream_t. You can use this if you need to
 * read some custom header data, or to read data in field callbacks.
 */
bool pb_read(pb_istream_t *stream, pb_byte_t *buf, size_t count);


/************************************************
 * Helper functions for writing field callbacks *
 ************************************************/

/* Decode the tag for the next field in the stream. Gives the wire type and
 * field tag. At end of the message, returns false and sets eof to true. */
bool pb_decode_tag(pb_istream_t *stream, pb_wire_type_t *wire_type, uint32_t *tag, bool *eof);

/* Skip the field payload data, given the wire type. */
bool pb_skip_field(pb_istream_t *stream, pb_wire_type_t wire_type);

/* Decode an integer in the varint format. This works for bool, enum, int32,
 * int64, uint32 and uint64 field types. */
bool pb_decode_varint(pb_istream_t *stream, uint64_t *dest);

/* Decode an integer in the zig-zagged svarint format. This works for sint32
 * and sint64. */
bool pb_decode_svarint(pb_istream_t *stream, int64_t *dest);

/* Decode a fixed32, sfixed32 or float value. You need to pass a pointer to
 * a 4-byte wide C variable. */
bool pb_decode_fixed32(pb_istream_t *stream, void *dest);

/* Decode a fixed64, sfixed64 or double value. You need to pass a pointer to
 * a 8-byte wide C variable. */
bool pb_decode_fixed64(pb_istream_t *stream, void *dest);

/* Make a limited-length substream for reading a PB_WT_STRING field. */
bool pb_make_string_substream(pb_istream_t *stream, pb_istream_t *substream);
void pb_close_string_substream(pb_istream_t *stream, pb_istream_t *substream);

#ifdef __cplusplus
} /* extern "C" */
#endif

#endif