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Data Access Proxies

To interact seamlessly with the ISC sandbox's regulated environment and facilitate smart contract data access, the WasmLib introduces data access proxies. Proxies are objects that can perform the underlying data transfers between the separate systems.

Overview​

The restrictive ISC sandbox environment requires an intermediary, or a library, to access sandbox functionalities — a role that the WasmLib fulfills through data access proxies. These entities stand as bridges, enabling data transfers between segregated systems, providing a streamlined pathway to interact with smart contract data stored on the ISC host.

The Role of Proxies​

Proxies refer to actual objects or values housed in the ISC host, essentially acting as data references that understand how to manipulate the data they represent. At the core, data is secured in maps on the ISC host with byte strings serving as both keys and values.

The WasmLib recognizes three predefined maps:

  • State Map: A repository for all state storage values.
  • Params Map: Holds the parameter values of the current function call.
  • Results Map: Returns the result values of the function call.

Through these maps, a complex, JSON-like data structure can be created with the aid of the Schema Tool, although, fundamentally, this structure is rooted in simple key-value access on the underlying map.

Proxy Varieties​

Proxies are segmented into various categories to facilitate different functionalities, including value proxies and container proxies.

Value Proxies​

Representing a single instance of a predetermined data type, value proxies are basic entities facilitating type conversion of the byte string representing the stored value.

The Schema Tool ensures type-safe code generation, always selecting the suitable proxy type.

Container Proxies​

Container proxies offer a virtual nesting system on the underlying map, creating paths leading to value proxies housed in a virtual container. They use JSON and YAML nesting patterns, and there are two primary types:

1. Map Proxies​

  • Root Maps: Encase any element type but restrict keys to human-readable strings, which are defined in the schema definition file.
  • Virtual Maps: Resides under a root map and accommodates values of a single associated data type.

2. Array Proxies​

  • Operate as a specialized map where the key is an Int32 value, forming a sequence from 0 to N-1 for an array harboring N elements.

Proxies in Action​

Proxies in WasmLib

In the illustration, we see the key-value combinations (Key 1 to Key 4) in the ISC state storage map. Key 4 directs us to an array containing indexed values ranging from 0 to N.

Notice the precise reflection of these elements in the WasmLib proxies, which maintain a container proxy for every container and a value proxy for each stored value. However, it is not obligatory for a smart contract function to define a proxy for every value or container in the ISC state storage.