pkarr: PK_ARR_MOVE_IN_PLACE shift correct byte range

1 files changed, 41 insertions, 4 deletions

diff --git a/pkarr.h b/pkarr.h
index 3d05e77..fa2d88a 100644
--- a/pkarr.h
+++ b/pkarr.h
@@ -80,14 +80,39 @@ pk_arr_move_to_back(struct pk_arr *arr, uint32_t index)
 	if (arr->next <= 1) return;
 #ifdef PK_ARR_MOVE_IN_PLACE
 	uint32_t i, ii;
-	uint8_t *target = (uint8_t *)pk_new(arr->stride, arr->alignment, arr->bkt);
-	uint8_t *buffer = (uint8_t *)arr->data;
+	char *target = (char *)pk_new(arr->stride, arr->alignment, arr->bkt);
+	char *buffer = (char *)arr->data;
+	// copy bytes to temp buffer
 	for (ii = 0, i = arr->stride * index; ii < arr->stride; ++ii, ++i) {
 		target[ii] = buffer[i];
 	}
+	// shift everything forward
+	// arr->stride = 8
+	// arr->next = 2
+	// index = 0
+	//
+	// for (i = 0; i < 8; ++i) {
+	//   b[i] = b[i + 8]
+	// }
+	// b[00] = b[08]
+	// b[01] = b[09]
+	// ...
+	// b[07] = b[15]
 	for (i = arr->stride * index; i < (arr->stride * (arr->next - 1)); ++i) {
 		buffer[i] = buffer[i + arr->stride];
 	}
+	// copy temp buffer back into arr
+	// arr->stride = 8
+	// arr->next = 2
+	// index = 0
+	//
+	// for (ii = 0, i = 8; ii < 8; ++ii, ++i) {
+	//   b[i] = t[ii]
+	// }
+	// b[08] = t[00]
+	// b[09] = t[01]
+	// ...
+	// b[15] = t[07]
 	for (ii = 0, i = arr->stride * (arr->next - 1); ii < arr->stride; ++ii, ++i) {
 		buffer[i] = target[ii];
 	}
@@ -138,8 +163,20 @@ pk_arr_remove_at(struct pk_arr *arr, uint32_t index)
 	}
 #ifdef PK_ARR_MOVE_IN_PLACE
 	uint32_t i;
-	uint8_t *buffer = (uint8_t *)arr->data;
-	for (i = arr->stride * index; i < (arr->stride * (arr->next - 1)); ++i) {
+	char *buffer = (char *)arr->data;
+	// shift everything forward
+	// arr->stride = 8
+	// arr->next = 3
+	// index = 0
+	//
+	// for (i = 0; i < 16; ++i) {
+	//   b[i] = b[i + 8]
+	// }
+	// b[00] = b[08]
+	// b[01] = b[09]
+	// ...
+	// b[15] = b[23]
+	for (i = arr->stride * index; i < arr->stride * arr->next; ++i) {
 		buffer[i] = buffer[i + arr->stride];
 	}
 #else