sys/ubjson: Write missing marker for i64

[fhessel]

Contribution description

The UBJSON writer skips the marker for large integer values (64 bit) when writing them. This makes the resulting UBJSON document unparsable for the receiver.

UBJSON in general uses a <type-marker>[value] syntax, and for 64 bit integers, one would expect an literal L followed by the 8 data bytes (Reference).

Testing procedure

The following demo application can be run on native to examine the issue in isolation. It prints a 64 bit value within an object structure.

main.c

#include <ctype.h>
#include <stdio.h>
#include "ubjson.h"

/** Callback to print the data to the console. */
int write_cb(ubjson_cookie_t *cookie, const void *buf, size_t len);

int main(void)
{
    uint64_t big_number = 0x0123456789abcdef;
    ubjson_cookie_t cookie;
    ubjson_write_init(&cookie, write_cb);
    ubjson_open_object(&cookie);
    ubjson_write_key(&cookie, "big_number", 10);
    ubjson_write_i64(&cookie, big_number);
    ubjson_close_object(&cookie);
    return 0;
}

int write_cb(ubjson_cookie_t *cookie, const void *buf, size_t len)
{
    (void)cookie;
    const uint8_t *tbuf = buf;
    for(size_t idx = 0; idx < len; idx++) {
        printf("0x%02x ", tbuf[idx]);
        putchar(isprint(tbuf[idx]) ? tbuf[idx] : '.');
        printf("\n");
    }
    return len;
}

Makefile

APPLICATION = ubjson-test-bool
BOARD ?= native
RIOTBASE ?= $(CURDIR)/../..
DEVELHELP ?= 1
QUIET ?= 1
USEMODULE += ubjson
include $(RIOTBASE)/Makefile.include

Before applying the fix, it will output:

0x7b 0x69 0x0a 0x62 0x69 0x67 0x5f 0x6e 0x75 0x6d 0x62 0x65 0x72 0x01 0x23 0x45 0x67 0x89 0xab 0xcd 0xef 0x7d 
{    i    .    b    i    g    _    n    u    m    b    e    r    .    #    E    g    .    .    .    .    }

With the fix, the values will be correct (note the additional L):

0x7b 0x69 0x0a 0x62 0x69 0x67 0x5f 0x6e 0x75 0x6d 0x62 0x65 0x72 0x4c 0x01 0x23 0x45 0x67 0x89 0xab 0xcd 0xef 0x7d 
{    i    .    b    i    g    _    n    u    m    b    e    r    L    .    #    E    g    .    .    .    .    }

Issues/PRs references

None.

[leandrolanzieri]

One would think that this type of errors would be caught by the module's unit tests, it is not the case. : / Anyways, thanks for the fix! ACK.