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History_Stack :: struct(
Action_Type : Type,
destructor : (obj : Action_Type) = default_destructor
){
BUF_SIZE :: 100;
buffer : [BUF_SIZE]Action_Type;
offset, current, saved : int;
}
deinit :: (using history_stack : *History_Stack) {
guard(history);
for i : 0..saved-1 {
j := (i + offset) % BUF_SIZE;
destructor(buffer[offset]);
}
offset, current, saved = 0;
}
write :: (using history : *History_Stack, action : Edit_Action) {
guard(history);
for i : current..saved-1 {
j := (i + offset) % BUF_SIZE;
destructor(buffer[j]);
}
i0 := (offset + current) % BUF_SIZE;
if current == BUF_SIZE {
destructor(buffer[offset]);
saved = current;
offset = (offset + 1) % BUF_SIZE;
} else {
current += 1;
saved = current;
}
i1 := (offset + current) % BUF_SIZE;
assert(i0 == i1);
buffer[i0] = action;
}
undo :: (using history : *History) -> bool, Action_Type {
guard(history);
action : Action_Type = ---;
if current == 0 return false, action;
current -= 1;
action = buffer[(current + offset) % BUF_SIZE];
return true, action;
}
redo :: (using history : *History) -> bool, Action_Type {
guard(history);
action : Action_Type = ---;
if current == saved return false, action;
action = buffer[(current + offset) % BUF_SIZE];
current += 1;
return true, action;
}
#scope_file
default_destructor :: (obj : $T) { }
guard :: (using history : *History) #expand {
check :: (using history : *History) {
assert(0 <= current && current <= saved && saved <= BUF_SIZE);
assert(0 <= offset && offset <= BUF_SIZE);
}
check(history); defer check(history);
}
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