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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Non-compliant handling of shared array buffers/views in web APIs","articleBody":"In the web specification, an ArrayBufferView is explicitly a TypedArray/DataView that views an ArrayBuffer. Unless marked as AllowShared, an ArrayBufferView cannot be backed by a SharedArrayBuffer, nor can a BufferSource be a SharedArrayBuffer itself (whatwg/webidl#353), and compliant implementations will consider these invalid. This impacts many APIs that interact with byte sources.\n\nThe compliance with this in Node.js's various web API implementations is really hit-and-miss, and there's no indication that any divergence is deliberate. (WPT does not cover these cases.)\n\n\u003ctable\u003e\n\u003cthead\u003e\n\u003cth\u003eAPI\u003c/th\u003e\n\u003cth\u003ecomponent\u003c/th\u003e\n\u003cth\u003ecompliance\u003c/th\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eFetch\u003c/td\u003e\n\u003ctd\u003e\u003ccode\u003eBodyInit\u003c/code\u003e\u003c/td\u003e\n\u003ctd\u003e\u003ca href=\"https://github.com/nodejs/undici/blob/4eddf5a08f4271b7f545c0dfeb3e79c745d6e3eb/lib/web/fetch/body.js#L39-L271\"\u003ePartial\u003c/a\u003e.\u003cbr\u003e✅ SharedArrayBuffers are rejected as invalid sources.\u003cbr\u003e❌ Views on SharedArrayBuffers are accepted, and result in the source being copied into a new SharedArrayBuffer internally.\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eWebSockets\u003c/td\u003e\n\u003ctd\u003e\u003ccode\u003eWebSocket#send()\u003c/code\u003e\u003c/td\u003e\n\u003ctd\u003e\u003ca href=\"https://github.com/nodejs/undici/blob/4eddf5a08f4271b7f545c0dfeb3e79c745d6e3eb/lib/web/websocket/websocket.js#L215-L311\"\u003ePartial\u003c/a\u003e.\u003cbr\u003e✅ The \u003ccode\u003edata\u003c/code\u003e parameter rejects SharedArrayBuffers.\u003cbr\u003e❌ Views on SharedArrayBuffers are accepted.\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFile\u003c/td\u003e\n\u003ctd\u003e\u003ccode\u003eBlobPart\u003c/code\u003e\u003c/td\u003e\n\u003ctd\u003e❌ Both SharedArrayBuffers and views on SharedArrayBuffers are accepted as valid sources.\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd rowspan=\"2\"\u003eStreams\u003c/td\u003e\n\u003ctd\u003e\u003ccode\u003eReadableStreamBYOBReader#read()\u003c/code\u003e\u003c/td\u003e\n\u003ctd\u003e❌ The \u003ccode\u003eview\u003c/code\u003e argument accepts views on SharedArrayBuffers.\u003cbr\u003eThis will result in delayed errors, as the underlying SharedArrayBuffer cannot be transferred.\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003ccode\u003eReadableByteStreamController#enqueue()\u003c/code\u003e\u003c/td\u003e\n\u003ctd\u003e❌ The \u003ccode\u003echunk\u003c/code\u003e argument accepts views on SharedArrayBuffers.\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCompression Streams\u003c/td\u003e\n\u003ctd\u003e\u003ccode\u003eCompressionStream\u003c/code\u003e and \u003ccode\u003eDecompressionStream\u003c/code\u003e chunk type\u003c/td\u003e\n\u003ctd\u003e❌ Does not accept ArrayBuffers at all, as the webstream wraps an underlying Duplex. (#43433)\u003cbr\u003e❌ Accepts views over SharedArrayBuffers.\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eEncoding\u003c/td\u003e\n\u003ctd\u003e\u003ccode\u003eTextDecoder#decode()\u003c/code\u003e\u003c/td\u003e\n\u003ctd\u003e✅ The API specifies AllowSharedBufferSource.\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eWeb Cryptography\u003c/td\u003e\n\u003ctd\u003e\u003ccode\u003edata\u003c/code\u003e parameters\u003c/td\u003e\n\u003ctd\u003e✅ Validates input to be an ArrayBuffer or non-shared ArrayBufferView.\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\n`internal/crypto/webidl` already defines compatible validators for non-shared BufferSource and ArrayBufferView types. These should probably be moved into the `internal/webidl` namespace and used more widely across the various web API implementations.\n\ncc: @nodejs/web-standards","author":{"url":"https://github.com/Renegade334","@type":"Person","name":"Renegade334"},"datePublished":"2025-08-30T18:56:32.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":6},"url":"https://github.com/59688/node/issues/59688"}