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boot_serial: cbor_encode: Fix encoding data length 

Change fixes encoding data length and adds support for big endian
byte ordering. According to specification, data length can be
encoded either on 1, 2, 4 or 8 bytes.

Signed-off-by: Marek Pieta <Marek.Pieta@nordicsemi.no>
This commit is contained in:
Marek Pieta 2021-08-18 13:52:52 +02:00 committed by Andrzej Puzdrowski
parent 428d3ee78b
commit 4960d12cc1
1 changed files with 25 additions and 2 deletions
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27
boot/boot_serial/src/cbor_encode.c
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@ -86,12 +86,35 @@ static bool value_encode_len(cbor_state_t *state, cbor_major_type_t major_type,
static uint32_t get_result_len(const void *const input, uint32_t max_result_len)
{
uint8_t *u8_result = (uint8_t *)input;
size_t i;
for (; max_result_len > 0; max_result_len--) {
if (u8_result[max_result_len - 1] != 0) {
for (i = 0; i < max_result_len; i++) {
#ifdef CONFIG_BIG_ENDIAN
size_t idx = i;
#else
size_t idx = max_result_len - 1 - i;
#endif
if (u8_result[idx] != 0) {
break;
}
}
max_result_len -= i;
/* According to specification result length can be encoded on 1, 2, 4
* or 8 bytes.
*/
cbor_assert(max_result_len <= 8, "Up to 8 bytes can be used to encode length.\n");
size_t encode_byte_cnt = 1;
for (size_t i = 0; i <= 3; i++) {
if (max_result_len <= encode_byte_cnt) {
max_result_len = encode_byte_cnt;
break;
}
encode_byte_cnt *= 2;
}
if ((max_result_len == 1) && (u8_result[0] <= VALUE_IN_HEADER)) {
max_result_len = 0;
}