@jridgewell/sourcemap-codec provides fast, lossless encoding and decoding of base64 VLQ mappings, the core data structure within Source Maps. It offers efficient algorithms for converting between the array-of-array structure commonly used in Source Maps and the compact, encoded string representation. This package is essential for tools that consume, generate, or manipulate Source Maps, ensuring optimal performance when dealing with large mapping datasets. Its focus is solely on codec functionality, avoiding any IO or higher-level Source Map operations.