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bitvec_read_field(): indicate errors using errno 

This function returns an *unsigned* integer (uint64_t), so returning
a negative value on error is a bad idea.  A negative value turns into
a huge positive value, what was demonstrated in the bitvec_test:

  bitvec_read_field(idx=512, len=16) => ffffffffffffffea
  bitvec_read_field(idx=0, len=65) => ffffffffffffffea
  bitvec_read_field(idx=64, len=16) => ffffffffffffffea

The 0xffffffffffffffea above is basically:

  (uint64_t) -EINVAL, or
  (uint64_t) -22 + 1, or
  0xffffffffffffffff - 0x16 + 1.

Let's make use of the errno in order to indicate an error to the caller.

Change-Id: I2cc734caa3365d03c2ae2b3f2cd9544933c25e9e
Related: OS#4388
This commit is contained in:
Vadim Yanitskiy 2021-11-17 06:34:48 +03:00 committed by fixeria
parent 2768246e7a
commit de3549a234
3 changed files with 26 additions and 20 deletions
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11
src/bitvec.c
View File

@ -472,18 +472,23 @@ int bitvec_unhex(struct bitvec *bv, const char *src)
* \param[in] bv The boolean vector to work on
* \param[in,out] read_index Where reading supposed to start in the vector
* \param[in] len How many bits to read from vector
* \returns read bits or negative value on error
* \returns An integer made up of the bits read.
*
* In case of an error, errno is set to a non-zero value. Otherwise it holds 0.
*/
uint64_t bitvec_read_field(struct bitvec *bv, unsigned int *read_index, unsigned int len)
{
unsigned int i;
uint64_t ui = 0;
bv->cur_bit = *read_index;
errno = 0;
for (i = 0; i < len; i++) {
int bit = bitvec_get_bit_pos((const struct bitvec *)bv, bv->cur_bit);
if (bit < 0)
return bit;
if (bit < 0) {
errno = -bit;
break;
}
if (bit)
ui |= ((uint64_t)1 << (len - i - 1));
bv->cur_bit++;

3
tests/bitvec/bitvec_test.c
View File

@ -237,7 +237,8 @@ static void test_bitvec_read_field(void)
#define _bitvec_read_field(idx, len) \
readIndex = idx; \
field = bitvec_read_field(&bv, &readIndex, len); \
printf("bitvec_read_field(idx=%u, len=%u) => %" PRIx64 "\n", idx, len, field);
printf("bitvec_read_field(idx=%u, len=%u) => %" PRIx64 " (%s)\n", \
idx, len, field, errno == 0 ? "success" : "error");
_bitvec_read_field(0, 64);
_bitvec_read_field(0, 32);

32
tests/bitvec/bitvec_test.ok
View File

@ -171,21 +171,21 @@ bitvec_runlength....
bitvec bytes used.
test bitvec_read_field():
bitvec_read_field(idx=0, len=64) => deadbeeffeebdaed
bitvec_read_field(idx=0, len=32) => deadbeef
bitvec_read_field(idx=0, len=16) => dead
bitvec_read_field(idx=0, len=8) => de
bitvec_read_field(idx=0, len=0) => 0
bitvec_read_field(idx=8, len=8) => ad
bitvec_read_field(idx=8, len=4) => a
bitvec_read_field(idx=8, len=0) => 0
bitvec_read_field(idx=10, len=9) => 16d
bitvec_read_field(idx=10, len=7) => 5b
bitvec_read_field(idx=10, len=5) => 16
bitvec_read_field(idx=10, len=3) => 5
bitvec_read_field(idx=10, len=1) => 1
bitvec_read_field(idx=512, len=16) => ffffffffffffffea
bitvec_read_field(idx=0, len=65) => ffffffffffffffea
bitvec_read_field(idx=64, len=16) => ffffffffffffffea
bitvec_read_field(idx=0, len=64) => deadbeeffeebdaed (success)
bitvec_read_field(idx=0, len=32) => deadbeef (success)
bitvec_read_field(idx=0, len=16) => dead (success)
bitvec_read_field(idx=0, len=8) => de (success)
bitvec_read_field(idx=0, len=0) => 0 (success)
bitvec_read_field(idx=8, len=8) => ad (success)
bitvec_read_field(idx=8, len=4) => a (success)
bitvec_read_field(idx=8, len=0) => 0 (success)
bitvec_read_field(idx=10, len=9) => 16d (success)
bitvec_read_field(idx=10, len=7) => 5b (success)
bitvec_read_field(idx=10, len=5) => 16 (success)
bitvec_read_field(idx=10, len=3) => 5 (success)
bitvec_read_field(idx=10, len=1) => 1 (success)
bitvec_read_field(idx=512, len=16) => 0 (error)
bitvec_read_field(idx=0, len=65) => bd5b7ddffdd7b5db (error)
bitvec_read_field(idx=64, len=16) => 0 (error)
bitvec ok.