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Description
Suppose that the circular log buffer is of size 3 and has the following layout:
[<entry>, NULL, <entry>]
^ ^
back front
base index is 3 (so <entry> at front has index 3 and <entry> at back has index 4)
then it seems that a call to log_get_from_idx(3) instead of returning an array of 2 entries which includes entries 3 and 4, returns an array of just 1 entry which includes only entry 3.
This can be reproduced with the following (failing) test:
void TestLog_get_from_idx_with_wrapping(CuTest * tc)
{
void* queue = llqueue_new();
void *r = raft_new();
raft_cbs_t funcs = {
.log_pop = __log_pop,
.log_get_node_id = __logentry_get_node_id
};
raft_set_callbacks(r, &funcs, queue);
void *l;
raft_entry_t e1, e2, e3, e4;
memset(&e1, 0, sizeof(raft_entry_t));
memset(&e2, 0, sizeof(raft_entry_t));
memset(&e3, 0, sizeof(raft_entry_t));
memset(&e4, 0, sizeof(raft_entry_t));
e1.id = 1;
e2.id = 2;
e3.id = 3;
e4.id = 4;
l = log_alloc(3);
log_set_callbacks(l, &funcs, r);
raft_entry_t* ety;
/* append append append */
CuAssertIntEquals(tc, 0, log_append_entry(l, &e1));
CuAssertIntEquals(tc, 0, log_append_entry(l, &e2));
CuAssertIntEquals(tc, 0, log_append_entry(l, &e3));
CuAssertIntEquals(tc, 3, log_count(l));
/* poll poll */
CuAssertIntEquals(tc, log_poll(l, (void*)&ety), 0);
CuAssertIntEquals(tc, ety->id, 1);
CuAssertIntEquals(tc, log_poll(l, (void*)&ety), 0);
CuAssertIntEquals(tc, ety->id, 2);
CuAssertIntEquals(tc, 1, log_count(l));
/* append */
CuAssertIntEquals(tc, 0, log_append_entry(l, &e4));
CuAssertIntEquals(tc, 2, log_count(l));
/* get from index 3 */
int n_etys;
raft_entry_t* etys;
etys = log_get_from_idx(l, 3, &n_etys);
CuAssertPtrNotNull(tc, etys);
CuAssertIntEquals(tc, n_etys, 2);
CuAssertIntEquals(tc, etys[0].id, 3);
CuAssertIntEquals(tc, etys[1].id, 4);
}It seems the bug is log_get_from_idx() when it calculates the length of the array to be returned:
if (i < me->back)
logs_till_end_of_log = me->back - i;
else
logs_till_end_of_log = me->size - i;
In the else case the length should actually be me->size - i + me->back, to include the most recent entries that have wrapped around. However it's not clear how to return a pointer without performing some allocation, because of course pointers don't wrap around.
Does it make sense? Is this a bug?
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