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import { Segment } from 'p2p-media-loader-core'
import { basename } from 'path'
type SegmentsJSON = { [filename: string]: string | { [byterange: string]: string } }
function segmentValidatorFactory (segmentsSha256Url: string) {
let segmentsJSON = fetchSha256Segments(segmentsSha256Url)
const regex = /bytes=(\d+)-(\d+)/
return async function segmentValidator (segment: Segment, canRefetchSegmentHashes = true) {
const filename = basename(segment.url)
const segmentValue = (await segmentsJSON)[filename]
if (!segmentValue && !canRefetchSegmentHashes) {
throw new Error(`Unknown segment name ${filename} in segment validator`)
}
if (!segmentValue) {
console.log('Refetching sha segments.')
// Refetch
segmentsJSON = fetchSha256Segments(segmentsSha256Url)
segmentValidator(segment, false)
return
}
let hashShouldBe: string
let range = ''
if (typeof segmentValue === 'string') {
hashShouldBe = segmentValue
} else {
const captured = regex.exec(segment.range)
range = captured[1] + '-' + captured[2]
hashShouldBe = segmentValue[range]
}
if (hashShouldBe === undefined) {
throw new Error(`Unknown segment name ${filename}/${range} in segment validator`)
}
const calculatedSha = bufferToEx(await sha256(segment.data))
if (calculatedSha !== hashShouldBe) {
throw new Error(
`Hashes does not correspond for segment ${filename}/${range}` +
`(expected: ${hashShouldBe} instead of ${calculatedSha})`
)
}
}
}
// ---------------------------------------------------------------------------
export {
segmentValidatorFactory
}
// ---------------------------------------------------------------------------
function fetchSha256Segments (url: string) {
return fetch(url)
.then(res => res.json() as Promise<SegmentsJSON>)
.catch(err => {
console.error('Cannot get sha256 segments', err)
return {}
})
}
function sha256 (data?: ArrayBuffer) {
if (!data) return undefined
return window.crypto.subtle.digest('SHA-256', data)
}
// Thanks: https://stackoverflow.com/a/53307879
function bufferToEx (buffer?: ArrayBuffer) {
if (!buffer) return ''
let s = ''
const h = '0123456789abcdef'
const o = new Uint8Array(buffer)
o.forEach((v: any) => s += h[ v >> 4 ] + h[ v & 15 ])
return s
}
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