29 lines
768 B
TypeScript
29 lines
768 B
TypeScript
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// Buffer.byteLength polyfill in the Edge runtime, with only utf8 strings
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// supported at the moment.
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export function byteLength(payload: string): number {
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return new TextEncoder().encode(payload).buffer.byteLength
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}
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// Calculate the ETag for a payload.
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export async function generateETag(payload: string) {
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if (payload.length === 0) {
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// fast-path empty
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return '"0-2jmj7l5rSw0yVb/vlWAYkK/YBwk"'
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}
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// compute hash of entity
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const hash = btoa(
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String.fromCharCode.apply(
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null,
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new Uint8Array(
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await crypto.subtle.digest('SHA-1', new TextEncoder().encode(payload))
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) as any
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)
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).substring(0, 27)
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// compute length of entity
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const len = byteLength(payload)
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return '"' + len.toString(16) + '-' + hash + '"'
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}
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