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feat: add list clear and insert primitives with capacity growth and index validation

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Extract inline list growth logic into `ensureListCapacity` helper and add `validateIndex` function supporting negative indices. Implement `list_clear` primitive that resets count to zero without freeing memory, and `list_insert` primitive that shifts elements right and inserts at validated position. Add comprehensive test suites for both operations covering empty lists, normal/negative indices, and return values.
This commit is contained in:
Bob Nystrom
2013-11-27 07:11:11 +00:00
parent 91c675b28a
commit 3c3fa2bfd9
3 changed files with 126 additions and 28 deletions
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src/primitives.c
+75 -28
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@@ -64,52 +64,97 @@ DEF_FIBER_PRIMITIVE(fn_call6) { callFunction(fiber, AS_FN(args[0]), 7); }
DEF_FIBER_PRIMITIVE(fn_call7) { callFunction(fiber, AS_FN(args[0]), 8); }
DEF_FIBER_PRIMITIVE(fn_call8) { callFunction(fiber, AS_FN(args[0]), 9); }
// Grows [list] if needed to ensure it can hold [count] elements.
static void ensureListCapacity(WrenVM* vm, ObjList* list, int count)
{
if (list->capacity >= count) return;
int capacity = list->capacity * LIST_GROW_FACTOR;
if (capacity < LIST_MIN_CAPACITY) capacity = LIST_MIN_CAPACITY;
list->capacity *= 2;
list->elements = wrenReallocate(vm, list->elements,
list->capacity * sizeof(Value), capacity * sizeof(Value));
// TODO(bob): Handle allocation failure.
list->capacity = capacity;
}
// Validates that [index] is an integer within `[0, count)`. Also allows
// negative indices which map backwards from the end. Returns the valid positive
// index value, or -1 if the index wasn't valid (not a number, not an int, out
// of bounds).
static int validateIndex(Value index, int count)
{
if (!IS_NUM(index)) return -1;
double indexNum = AS_NUM(index);
int intIndex = (int)indexNum;
// Make sure the index is an integer.
if (indexNum != intIndex) return -1;
// Negative indices count from the end.
if (indexNum < 0) indexNum = count + indexNum;
// Check bounds.
if (indexNum < 0 || indexNum >= count) return -1;
return indexNum;
}
DEF_PRIMITIVE(list_add)
{
ObjList* list = AS_LIST(args[0]);
// TODO(bob): Move this into value or other module?
// Grow the list if needed.
if (list->capacity < list->count + 1)
{
int capacity = list->capacity * LIST_GROW_FACTOR;
if (capacity < LIST_MIN_CAPACITY) capacity = LIST_MIN_CAPACITY;
list->capacity *= 2;
list->elements = wrenReallocate(vm, list->elements,
list->capacity * sizeof(Value), capacity * sizeof(Value));
// TODO(bob): Handle allocation failure.
list->capacity = capacity;
}
ensureListCapacity(vm, list, list->count + 1);
list->elements[list->count++] = args[1];
return args[1];
}
DEF_PRIMITIVE(list_clear)
{
ObjList* list = AS_LIST(args[0]);
wrenReallocate(vm, list->elements, list->capacity * sizeof(Value), 0);
list->capacity = 0;
list->count = 0;
return NULL_VAL;
}
DEF_PRIMITIVE(list_count)
{
ObjList* list = AS_LIST(args[0]);
return NUM_VAL(list->count);
}
DEF_PRIMITIVE(list_subscript)
DEF_PRIMITIVE(list_insert)
{
// TODO(bob): Instead of returning null here, all of these failure cases
// should signal an error explicitly somehow.
if (!IS_NUM(args[1])) return NULL_VAL;
double indexNum = AS_NUM(args[1]);
int index = (int)indexNum;
// Make sure the index is an integer.
if (indexNum != index) return NULL_VAL;
ObjList* list = AS_LIST(args[0]);
// Negative indices count from the end.
if (index < 0) index = list->count + index;
int index = validateIndex(args[2], list->count + 1);
// TODO(bob): Instead of returning null here, should signal an error
// explicitly somehow.
if (index == -1) return NULL_VAL;
// Check bounds.
if (index < 0 || index >= list->count) return NULL_VAL;
ensureListCapacity(vm, list, list->count + 1);
// Shift items down.
for (int i = list->count; i > index; i--)
{
list->elements[i] = list->elements[i - 1];
}
list->elements[index] = args[1];
list->count++;
return args[1];
}
DEF_PRIMITIVE(list_subscript)
{
ObjList* list = AS_LIST(args[0]);
int index = validateIndex(args[1], list->count);
// TODO(bob): Instead of returning null here, should signal an error
// explicitly somehow.
if (index == -1) return NULL_VAL;
return list->elements[index];
}
@@ -351,7 +396,9 @@ void wrenLoadCore(WrenVM* vm)
vm->listClass = defineClass(vm, "List", vm->objectClass);
PRIMITIVE(vm->listClass, "add ", list_add);
PRIMITIVE(vm->listClass, "clear", list_clear);
PRIMITIVE(vm->listClass, "count", list_count);
PRIMITIVE(vm->listClass, "insert ", list_insert);
PRIMITIVE(vm->listClass, "[ ]", list_subscript);
vm->nullClass = defineClass(vm, "Null", vm->objectClass);