Fix parallel stack bugs

src/coral/stack.zig

@@ -61,7 +61,10 @@ fn Generic(comptime Item: type, comptime Storage: type) type {
         pub fn pushAll(self: *Self, items: []const Item) bool {
             const new_len = self.items.len + items.len;
 
-            if (new_len < self.cap) {
+            if (new_len > self.items.cap) {
+                return false;
+            }
+
             const index = self.items.len;
 
             self.items.len = new_len;
@@ -71,9 +74,6 @@ fn Generic(comptime Item: type, comptime Storage: type) type {
             return true;
         }
 
-            return false;
-        }
-
         pub fn pushGrow(self: *Self, allocator: std.mem.Allocator, item: Item) std.mem.Allocator.Error!void {
             if (self.isFull()) {
                 try self.items.grow(allocator, @max(1, self.items.cap));
@@ -99,6 +99,16 @@ fn Generic(comptime Item: type, comptime Storage: type) type {
 
             return true;
         }
+
+        pub fn set(self: *Self, item: Item) bool {
+            if (self.isEmpty()) {
+                return false;
+            }
+
+            std.debug.assert(self.items.set(self.items.len - 1, item));
+
+            return true;
+        }
     };
 }
 
@@ -109,8 +119,7 @@ pub fn Parallel(comptime Item: type) type {
     };
 
     const item_align = @alignOf(Item);
-    const item_size = @sizeOf(usize);
+    const item_size = @sizeOf(Item);
-    const byte_size = @sizeOf(u8);
 
     return Generic(Item, struct {
         ptr: [*]align(item_align) u8 = undefined,
@@ -130,7 +139,7 @@ pub fn Parallel(comptime Item: type) type {
         }
 
         pub fn get(self: Self, index: usize) ?Item {
-            if (index >= self.cap) {
+            if (index >= self.len) {
                 return null;
             }
 
@@ -139,29 +148,52 @@ pub fn Parallel(comptime Item: type) type {
 
             inline for (item_fields) |item_field| {
                 @field(item, item_field.name) = @as([*]item_field.type, @ptrCast(@alignCast(ptr)))[index];
-                ptr += @sizeOf(item_field.type) * self.len;
+                ptr += @sizeOf(item_field.type) * self.cap;
             }
 
             return item;
         }
 
         pub fn grow(self: *Self, allocator: std.mem.Allocator, amount: usize) std.mem.Allocator.Error!void {
-            const new_cap = std.math.cast(u32, @as(usize, self.cap + amount)) orelse {
+            const old_cap = self.cap;
+
+            const new_cap = std.math.cast(u32, @as(usize, old_cap) + amount) orelse {
                 return error.OutOfMemory;
             };
 
-            const reallocation = try allocator.alignedAlloc(u8, item_align, byte_size * new_cap);
+            if (new_cap != 0) {
-            const len_in_bytes = byte_size * self.len;
+                const new_allocation = try allocator.alignedAlloc(u8, item_align, item_size * new_cap);
 
-            @memcpy(reallocation[0..len_in_bytes], self.ptr[0..len_in_bytes]);
+                errdefer {
-            allocator.free(self.ptr[0 .. byte_size * self.cap]);
+                    allocator.free(new_allocation);
+                }
 
-            self.ptr = reallocation.ptr;
+                if (old_cap != 0) {
-            self.cap = @intCast(new_cap);
+                    var old_ptr_offset: usize = 0;
+                    var new_ptr_offset: usize = 0;
+
+                    inline for (item_fields) |field| {
+                        const FieldType = field.type;
+                        const old_field_ptr: [*]const FieldType = @ptrCast(@alignCast(self.ptr + old_ptr_offset));
+                        const new_field_ptr: [*]FieldType = @ptrCast(@alignCast(new_allocation.ptr + new_ptr_offset));
+
+                        @memcpy(new_field_ptr[0..self.len], old_field_ptr[0..self.len]);
+
+                        old_ptr_offset += @sizeOf(FieldType) * old_cap;
+                        new_ptr_offset += @sizeOf(FieldType) * new_cap;
+                    }
+
+                    // Free the old allocation
+                    allocator.free(self.ptr[0 .. item_size * old_cap]);
+                }
+
+                self.ptr = new_allocation.ptr;
+                self.cap = new_cap;
+            }
         }
 
         pub fn set(self: Self, index: usize, item: Item) bool {
-            if (index >= self.cap) {
+            if (index >= self.len) {
                 return false;
             }
 
@@ -169,7 +201,7 @@ pub fn Parallel(comptime Item: type) type {
 
             inline for (item_fields) |item_field| {
                 @as([*]item_field.type, @ptrCast(@alignCast(ptr)))[index] = @field(item, item_field.name);
-                ptr += @sizeOf(item_field.type) * self.len;
+                ptr += @sizeOf(item_field.type) * self.cap;
             }
 
             return true;
@@ -180,7 +212,7 @@ pub fn Parallel(comptime Item: type) type {
             var ptr: [*]u8 = self.ptr;
 
             inline for (item_fields[0..field_index]) |item_field| {
-                ptr += @sizeOf(item_field.type) * self.len;
+                ptr += @sizeOf(item_field.type) * self.cap;
             }
 
             return @as([*]item_fields[field_index].type, @ptrCast(@alignCast(ptr)))[0..self.len];