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changed resize_stack() slightly

partial-rewrite
Ben Blazak 2013-07-21 15:30:28 -07:00
parent 6727ed89b9
commit b5ffe83a38
1 changed files with 7 additions and 19 deletions
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26
firmware/lib/layout/layer-stack/layer-stack.c
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@ -102,30 +102,18 @@ static struct {
*/
static uint8_t resize_stack(void) {
int8_t unused = stack.allocated - stack.filled;
uint8_t unused_max = UINT8_MAX - stack.filled;
if (MIN_UNUSED <= unused && unused <= MAX_UNUSED)
return 0; // nothing to do
// calculate the amount of memory we'd like to have allocated
uint8_t new_allocated = stack.filled + (MIN_UNUSED + MAX_UNUSED) / 2;
// test whether `new_allocated` overflowed on assignment
if (new_allocated < stack.filled) {
// try using the maximum value
uint8_t new_allocated;
if (unused_max >= (MIN_UNUSED + MAX_UNUSED) / 2)
new_allocated = stack.filled + (MIN_UNUSED + MAX_UNUSED) / 2;
else if (unused_max >= MIN_UNUSED)
new_allocated = UINT8_MAX;
// test whether the maximum value is large enough
// - we know it's not too large, because the original value (which
// overflowed) would not have been too large, and this value is
// smaller
// - we know that `new_allocated - stack.filled >= 0`, because
// `new_allocated` is as large as the type can hold, at this point,
// and both variables are of the same type, so `stack.filled` cannot
// be larger than it
if (new_allocated - stack.filled < MIN_UNUSED)
return 1; // unable to count the required number of elements
}
else
return 1; // unable to count the required number of elements
void * new_data = realloc( stack.data, sizeof(element_t) * new_allocated );
if (!new_data)