generic-filehandle2
Version:
uniform interface for accessing binary data from local files, remote HTTP resources, and browser Blob data
47 lines • 1.6 kB
JavaScript
/**
* Blob of binary data fetched from a local file (with FileReader).
*
* Adapted by Robert Buels and Garrett Stevens from the BlobFetchable object in
* the Dalliance Genome Explorer, which is copyright Thomas Down 2006-2011.
*/
export default class BlobFile {
constructor(blob) {
this.blob = blob;
}
async read(length, position = 0) {
// short-circuit a read of 0 bytes here, because browsers actually sometimes
// crash if you try to read 0 bytes from a local file!
if (!length) {
return new Uint8Array(0);
}
const start = position;
const end = start + length;
const slice = this.blob.slice(start, end);
// eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
return slice.bytes
? slice.bytes()
: new Uint8Array(await slice.arrayBuffer());
}
async readFile(options) {
const encoding = typeof options === 'string' ? options : options?.encoding;
if (encoding === 'utf8') {
return this.blob.text();
}
else if (encoding) {
throw new Error(`unsupported encoding: ${encoding}`);
}
else {
// eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
return this.blob.bytes
? this.blob.bytes()
: new Uint8Array(await this.blob.arrayBuffer());
}
}
async stat() {
return { size: this.blob.size };
}
async close() {
return;
}
}
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