[internal] Add a function for appending without growing extra data

1 files changed, 23 insertions, 0 deletions

diff --git a/src/string_mutable.zig b/src/string_mutable.zig
index 2849a4695..9d89ea9db 100644
--- a/src/string_mutable.zig
+++ b/src/string_mutable.zig
@@ -30,6 +30,20 @@ pub const MutableString = struct {
         }
     }
 
+    pub fn owns(this: *const MutableString, buffer: []const u8) bool {
+        if (this.list.capacity < buffer.len) {
+            return false;
+        }
+
+        if (@ptrToInt(this.list.items.ptr) <= @ptrToInt(buffer.ptr) and
+            @ptrToInt(buffer.ptr) + buffer.len <= @ptrToInt(this.list.items.ptr) + this.list.capacity)
+        {
+            return true;
+        }
+
+        return false;
+    }
+
     pub fn growIfNeeded(self: *MutableString, amount: usize) !void {
         try self.list.ensureUnusedCapacity(self.allocator, amount);
     }
@@ -156,6 +170,15 @@ pub const MutableString = struct {
         try self.list.appendSlice(self.allocator, slice);
     }
 
+    pub inline fn appendSliceExact(self: *MutableString, slice: []const u8) !void {
+        if (slice.len == 0) return;
+
+        try self.list.ensureTotalCapacityPrecise(self.allocator, self.list.items.len + slice.len);
+        var end = self.list.items.ptr + self.list.items.len;
+        self.list.items.len += slice.len;
+        @memcpy(end, slice.ptr, slice.len);
+    }
+
     pub inline fn reset(
         self: *MutableString,
     ) void {