Add JSON utils for returning kinds, and valid utf8

Author: davekay100

index.ts

@@ -1108,6 +1108,92 @@ export class JSONValue {
     assert(this.kind == JSONValueKind.OBJECT, 'JSON value is not an object.')
     return changetype<TypedMap<string, JSONValue>>(this.data as u32)
   }
+
+  /**
+   * Make sure the given JSONValue is a string and returns string it contains.
+   * Returns `null` or a blank string otherwise, depending on returnNull value.
+   */
+  asStringOrNull(val: JSONValue | null, returnNull: boolean): string | null {
+    if (val != null && val.kind === JSONValueKind.STRING) {
+      return val.toString()
+    }
+    if (returnNull) {
+      return null
+    } else {
+      return ''
+    }
+  }
+
+  /**
+   * Makes sure the given JSONValue is an object and return the object it contains.
+   * Returns `null` otherwise.
+   */
+  asObject(val: JSONValue | null): TypedMap<string, JSONValue> | null {
+    if (val != null && val.kind === JSONValueKind.OBJECT) {
+      return val.toObject()
+    }
+    return null
+  }
+
+  /**
+   * Make sure the given JSONValue is an array and returns that array it contains.
+   * Returns `null` otherwise.
+   */
+  asArray(val: JSONValue | null): Array<JSONValue> | null {
+    if (val != null && val.kind === JSONValueKind.ARRAY) {
+      return val.toArray()
+    }
+    return null
+  }
+
+  /**
+   * This function checks if the given byte array contains a valid
+   * UTF-8 sequence and can be successfully parsed into a string.
+   */
+  isValidUtf8(bytes: Bytes): boolean {
+    let pending = 0
+    for (let i = 0; i < bytes.length; i++) {
+      let b = bytes[i]
+      if (pending === 0) {
+        let m = 0b10000000
+        while ((m & b) !== 0) {
+          pending += 1
+          m = m >> 1
+        }
+        if (pending === 0) {
+          continue
+        }
+        if (pending === 1 || pending > 4) {
+          return false
+        }
+      } else {
+        if ((b & 0b11000000) !== 0b10000000) {
+          return false
+        }
+      }
+      pending -= 1
+    }
+    return pending === 0
+  }
+
+  kindToString(kind: JSONValueKind): string {
+    switch (kind) {
+      case JSONValueKind.ARRAY:
+        return 'ARRAY'
+      case JSONValueKind.OBJECT:
+        return 'OBJECT'
+      case JSONValueKind.STRING:
+        return 'STRING'
+      case JSONValueKind.NUMBER:
+        return 'NUMBER'
+      case JSONValueKind.BOOL:
+        return 'BOOL'
+      case JSONValueKind.NULL:
+        return 'NULL'
+      default:
+        return '?'
+    }
+  }
 }
 
 /**