proto/codec

Protobuf encode/decode and browser file download utilities.

encodeMap

async function encodeMap(mapObj: ApolloMap): Promise<Uint8Array>

Encodes an ApolloMap JavaScript object to Protocol Buffer binary format.

1. Loads map.proto via loadProtoRoot
2. Looks up apollo.hdmap.Map
3. Calls MapType.verify(mapObj) — logs a warning if structure has issues
4. Returns MapType.encode(MapType.create(mapObj)).finish()

Example

const bytes = await encodeMap(apolloMap)
downloadBinary(bytes, 'base_map.bin')

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encodeGraph

async function encodeGraph(graphObj: TopoGraph): Promise<Uint8Array>

Encodes a TopoGraph object to binary using topo_graph.proto → apollo.routing.Graph.

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decodeMap

async function decodeMap(buffer: Uint8Array): Promise<ApolloMap>

Decodes a base_map.bin binary buffer back to a JavaScript object shaped as ApolloMap.

1. Loads map.proto
2. Calls MapType.decode(buffer)
3. Returns MapType.toObject(decoded, { longs: Number, enums: Number, defaults: true })

The { defaults: true } option ensures all optional fields have their zero/empty defaults present, which simplifies the import parser.

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downloadBinary

function downloadBinary(data: Uint8Array, filename: string): void

Triggers a browser file download for a binary blob:

const blob = new Blob([data.buffer as ArrayBuffer], { type: 'application/octet-stream' })
const url = URL.createObjectURL(blob)
const a = document.createElement('a')
a.href = url
a.download = filename
a.click()
URL.revokeObjectURL(url)

The data.buffer as ArrayBuffer cast is required because Uint8Array may have a SharedArrayBuffer backing in some environments, which Blob does not accept.