overwriting a cbor map field result even though field is not decoded

Question

hello Nordic 
 i am using ncs 2.8.0 with nrf52832 and mrf52840 
 i am decoding a cbor file with the 'zcbor_map_decode_bulk' 
 LOG_INF("in func decode config - val_9 %d", result->val_9_placeholder);

ZCBOR_STATE_D(zsd, 2, config_file, config_file_len, 1, 0);
 struct zcbor_map_decode_key_val map_key_decode[] = {
 ZCBOR_MAP_DECODE_KEY_DECODER("..", zcbor_int32_decode, &result->..),
 ZCBOR_MAP_DECODE_KEY_DECODER("..", my_implementation_decode, &result->..),
 ZCBOR_MAP_DECODE_KEY_DECODER("..", my_implementation_decode, &result->..),
 ZCBOR_MAP_DECODE_KEY_DECODER("..", my_implementation_decode, &result->..),
 ZCBOR_MAP_DECODE_KEY_DECODER("..", my_implementation_decode, &result->..),
 ZCBOR_MAP_DECODE_KEY_DECODER("..", my_implementation_decode, &result->..),
 ZCBOR_MAP_DECODE_KEY_DECODER("..", zcbor_bool_decode, &result->..),
 ZCBOR_MAP_DECODE_KEY_DECODER("..", zcbor_bool_decode, &result->..),
 ZCBOR_MAP_DECODE_KEY_DECODER("val_9", zcbor_bool_decode, &result->val_9_placeholder),
 ZCBOR_MAP_DECODE_KEY_DECODER("..", zcbor_int32_decode, &result->battery_capacity),
 };

int rc = zcbor_map_decode_bulk(zsd, map_key_decode, ARRAY_SIZE(map_key_decode), &decoded);

LOG_INF("decode config - val_9 %d, rc %d", result->val_9_placeholder, rc); 
 the 'my_implementation_decode' is just a function that has map with all zcbor_decode.h function calls and the same 'zcbor_map_decode_bulk' at the end. 
 for some reason the value of the result->val9_placeholder changes from the default '1' it was before decoding, to '0' after, though there is no field 'val_9' in the cbor file i am decoding 
 and following the 'zcbor_map_decode_bulk' function, with log prints, shows that the val_9 never goes through 
 dptr -> decoder ( zsd , dptr -> value_ptr) ... it does not pass the condition 
 
 if ( key . len == dptr -> key . len && memcmp ( key . value , dptr -> key . value , key . len ) == 0 )

any idea why the result->val9_placeholder is changed anyway ? 
 p.s. it does not happen when there is a shorter cbor with less fields (the cbor with issues is 246 bytes, and the small cbor is 178) 
 
 hope to read from you soon 
 best regards 
 ZIv

ziv123 · Accepted Answer

the problem is that values of smaller size like uint8_t or uint16_t in the map, when decoded using zcbor_uint32_decode, cause over run of the other bytes, cause the function does a memset for 0 in the size of uint32 (4 bytes) so the values after the uint8_t, or uint16_t overrun with '0', if they are found in the cbor then they get new vals but else they get a '0' 
 anyways, the solution use zcbor_uint_decode api .. which also gets the size of the value in bytes .. the problem is that the macro does not get another value so i had to create a wrapper for that function like so: 
 static bool augu_uint16_decode(zcbor_state_t *state, uint16_t *result)
{
 return zcbor_uint_decode(state, result, sizeof(uint16_t));
}

static bool augu_uint8_decode(zcbor_state_t *state, uint8_t *result)
{
 return zcbor_uint_decode(state, result, sizeof(uint8_t));
} 
 best regards 
 Ziv

overwriting a cbor map field result even though field is not decoded

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