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backend/node_modules/restructure/src/Optional.js

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+class Optional {
+  constructor(type, condition = true) {
+    this.type = type;
+    this.condition = condition;
+  }
+
+  decode(stream, parent) {
+    let { condition } = this;
+    if (typeof condition === 'function') {
+      condition = condition.call(parent, parent);
+    }
+
+    if (condition) {
+      return this.type.decode(stream, parent);
+    }
+  }
+
+  size(val, parent) {
+    let { condition } = this;
+    if (typeof condition === 'function') {
+      condition = condition.call(parent, parent);
+    }
+
+    if (condition) {
+      return this.type.size(val, parent);
+    } else {
+      return 0;
+    }
+  }
+
+  encode(stream, val, parent) {
+    let { condition } = this;
+    if (typeof condition === 'function') {
+      condition = condition.call(parent, parent);
+    }
+
+    if (condition) {
+      return this.type.encode(stream, val, parent);
+    }
+  }
+}
+
+module.exports = Optional;