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Planner: don't return static data in fake_dc()

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fake_dc() used to return a statically allocated dc with statically
allocated samples. This is of course a questionable practice in
the light of multi-threading / resource ownership. Once these
problems were recognized, the parameter "alloc" was added. If set
to true, the function would still return a statically allocated
dc, but heap-allocated samples, which could then be copied in
a different dc.

All in all an ownership nightmare and a recipie for disaster.
The returned static dc was only used as a pointer to the samples
anyway. There are four callers of fake_dc() and they all have access
to a dc-structure without samples. Therefore, change the semantics
of fake_dc() to fill out the passed in dc. If the caller does
not care about the samples, it can simply reset the sample number
to zero after work.

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
This commit is contained in:
Berthold Stoeger 2018-05-05 19:26:48 +02:00 • committed by Lubomir I. Ivanov
parent 450f0992a0
commit 920ff15f71
7 changed files with 39 additions and 40 deletions
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28
core/dive.c
View file

@ -714,22 +714,26 @@ void copy_samples(struct divecomputer *s, struct divecomputer *d)
memcpy(d->sample, s->sample, nr * sizeof(struct sample));
}
/* make room for num samples; if not enough space is available, the sample
* array is reallocated and the existing samples are copied. */
void alloc_samples(struct divecomputer *dc, int num)
{
if (num > dc->alloc_samples) {
dc->alloc_samples = (dc->alloc_samples * 3) / 2 + 10;
dc->sample = realloc(dc->sample, dc->alloc_samples * sizeof(struct sample));
if (!dc->sample)
dc->samples = dc->alloc_samples = 0;
}
}
struct sample *prepare_sample(struct divecomputer *dc)
{
if (dc) {
int nr = dc->samples;
int alloc_samples = dc->alloc_samples;
struct sample *sample;
if (nr >= alloc_samples) {
struct sample *newsamples;
alloc_samples = (alloc_samples * 3) / 2 + 10;
newsamples = realloc(dc->sample, alloc_samples * sizeof(struct sample));
if (!newsamples)
return NULL;
dc->alloc_samples = alloc_samples;
dc->sample = newsamples;
}
alloc_samples(dc, nr + 1);
if (!dc->sample)
return NULL;
sample = dc->sample + nr;
memset(sample, 0, sizeof(*sample));
@ -922,7 +926,7 @@ void per_cylinder_mean_depth(struct dive *dive, struct divecomputer *dc, int *me
return;
}
if (!dc->samples)
dc = fake_dc(dc, false);
fake_dc(dc);
struct event *ev = get_next_event(dc->events, "gaschange");
for (i = 0; i < dc->samples; i++) {
struct sample *sample = dc->sample + i;