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selectSource

From v4.2

The selectSource() function will make a "best effort" to select an appropriate source for a specific url or Blob. selectSource() is called internally by the createDataSource() and createDataSourceSync() functions, but can also be called directly from applications.

Source selection heuristics are based on:

  • Filename (or url) extensions
  • MIME types (from Response content-type headers or Blob.type/File.type fields)
  • Initial bytes - for certain inputs, the initial bytes in the supplied data can be compared against known "magic bytes" for various file formats.

Usage​

Select a source from a list of provided sources (best effort):

import {selectSourceSync} from '@loaders.gl/core';
import {PMTilesSource} from '@loaders.gl/pmtiles';
import {MVTSource} from '@loaders.gl/csv';

selectSourceSync('filename.pmtiles', [PMTilesSource, MVTSource]); // => PMTilesSource

Functions​

selectSource()​

selectSource(data: String | Blob, ..., sources?: Source[], options?): Promise<Source | null>`

Selects an appropriate source for a file from a list of candidate sources by examining the data parameter, looking at URL extension, mimeType ('Content-Type') and/or an initial data chunk.

Parameters:

  • data - data to perform autodetection against
  • sources - can be a single source or an array of sources, or null.
  • options.type - Force selection to a specific type of source (must still be provided in the source list).
  • options.nothrow=false - Return null instead of throwing exception if no source can be found

Returns:

  • A single source (or null if options.nothrow was set and no matching source was found).

Throws:

  • If no matching source was found, and options.nothrow was not set.

Regarding the sources parameter:

  • A single source object will be returned without matching.
  • a null source list will use the pre-registered list of sources.
  • A supplied list of sources will be searched for a matching source.

Supported Data Formats​

The acceptable types for data are inferred from the supplied loaders and may include:

  • strings / data urls
  • File and Blob objects:

MIME types​

If the standard MIME types for each format are not precise enough, sources.gl also supports unregistered MIME types. Each source will match the application/x.<id> where the <id> is the documented id of the source, e.g. application/x.ply/application/x.draco/etc ...

Remarks​

  • File extensions - An attempt will be made to extract a file extension by stripping away query parameters and base path before matching against known source extensions.