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
|
Decoding
=============================
Another way to decode data using libcbor is to specify a callbacks that will be invoked when upon finding certain items in the input. This service is provided by
.. doxygenfunction:: cbor_stream_decode
To get started, you might want to have a look at the simple streaming example:
.. code-block:: c
#include "cbor.h"
#include <stdio.h>
#include <string.h>
/*
* Illustrates how one might skim through a map (which is assumed to have
* string keys and values only), looking for the value of a specific key
*
* Use the examples/data/map.cbor input to test this.
*/
const char * key = "a secret key";
bool key_found = false;
void find_string(void * _ctx, cbor_data buffer, size_t len)
{
if (key_found) {
printf("Found the value: %*s\n", (int) len, buffer);
key_found = false;
} else if (len == strlen(key)) {
key_found = (memcmp(key, buffer, len) == 0);
}
}
int main(int argc, char * argv[])
{
FILE * f = fopen(argv[1], "rb");
fseek(f, 0, SEEK_END);
size_t length = (size_t)ftell(f);
fseek(f, 0, SEEK_SET);
unsigned char * buffer = malloc(length);
fread(buffer, length, 1, f);
struct cbor_callbacks callbacks = cbor_empty_callbacks;
struct cbor_decoder_result decode_result;
size_t bytes_read = 0;
callbacks.string = find_string;
while (bytes_read < length) {
decode_result = cbor_stream_decode(buffer + bytes_read,
length - bytes_read,
&callbacks, NULL);
bytes_read += decode_result.read;
}
free(buffer);
fclose(f);
}
The callbacks are defined by
.. doxygenstruct:: cbor_callbacks
:members:
When building custom sets of callbacks, feel free to start from
.. doxygenvariable:: cbor_empty_callbacks
Related structures
~~~~~~~~~~~~~~~~~~~~~
.. doxygenenum:: cbor_decoder_status
.. doxygenstruct:: cbor_decoder_result
:members:
Callback types definition
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.. doxygentypedef:: cbor_int8_callback
.. doxygentypedef:: cbor_int16_callback
.. doxygentypedef:: cbor_int32_callback
.. doxygentypedef:: cbor_int64_callback
.. doxygentypedef:: cbor_simple_callback
.. doxygentypedef:: cbor_string_callback
.. doxygentypedef:: cbor_collection_callback
.. doxygentypedef:: cbor_float_callback
.. doxygentypedef:: cbor_double_callback
.. doxygentypedef:: cbor_bool_callback
|
