@gmod/jbrowse/src/JBrowse/Model/BlobFilehandleWrapper.js

JBrowse - client-side genome browser

const { Buffer } = cjsRequire('buffer')
/**
 * Wraps a XHRBlob or FileBlob in a new promise-based API (which is
 * the upcoming node fs.promises API) for use by newer code.
 */
class BlobFilehandleWrapper {
    constructor(oldStyleBlob) {
        this.blob = oldStyleBlob
    }

    async read(buffer, offset = 0, length, position) {
        const data = await this.blob.readBufferPromise(position, length)
        data.copy(buffer, offset)
        return {bytesRead: data.length, buffer}
    }

    async readFile() {
        return this.blob.fetchBufferPromise()
    }

    stat() {
        return this.blob.statPromise()
    }

    toString() {
        return ( this.blob.url  ? this.blob.url :
                 this.blob.blob ? this.blob.blob.name : undefined ) || undefined;
    }
}

module.exports = BlobFilehandleWrapper