Initial

resources/app/node_modules/@smithy/eventstream-codec/dist-es/splitMessage.js

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+import { Crc32 } from "@aws-crypto/crc32";
+const PRELUDE_MEMBER_LENGTH = 4;
+const PRELUDE_LENGTH = PRELUDE_MEMBER_LENGTH * 2;
+const CHECKSUM_LENGTH = 4;
+const MINIMUM_MESSAGE_LENGTH = PRELUDE_LENGTH + CHECKSUM_LENGTH * 2;
+export function splitMessage({ byteLength, byteOffset, buffer }) {
+    if (byteLength < MINIMUM_MESSAGE_LENGTH) {
+        throw new Error("Provided message too short to accommodate event stream message overhead");
+    }
+    const view = new DataView(buffer, byteOffset, byteLength);
+    const messageLength = view.getUint32(0, false);
+    if (byteLength !== messageLength) {
+        throw new Error("Reported message length does not match received message length");
+    }
+    const headerLength = view.getUint32(PRELUDE_MEMBER_LENGTH, false);
+    const expectedPreludeChecksum = view.getUint32(PRELUDE_LENGTH, false);
+    const expectedMessageChecksum = view.getUint32(byteLength - CHECKSUM_LENGTH, false);
+    const checksummer = new Crc32().update(new Uint8Array(buffer, byteOffset, PRELUDE_LENGTH));
+    if (expectedPreludeChecksum !== checksummer.digest()) {
+        throw new Error(`The prelude checksum specified in the message (${expectedPreludeChecksum}) does not match the calculated CRC32 checksum (${checksummer.digest()})`);
+    }
+    checksummer.update(new Uint8Array(buffer, byteOffset + PRELUDE_LENGTH, byteLength - (PRELUDE_LENGTH + CHECKSUM_LENGTH)));
+    if (expectedMessageChecksum !== checksummer.digest()) {
+        throw new Error(`The message checksum (${checksummer.digest()}) did not match the expected value of ${expectedMessageChecksum}`);
+    }
+    return {
+        headers: new DataView(buffer, byteOffset + PRELUDE_LENGTH + CHECKSUM_LENGTH, headerLength),
+        body: new Uint8Array(buffer, byteOffset + PRELUDE_LENGTH + CHECKSUM_LENGTH + headerLength, messageLength - headerLength - (PRELUDE_LENGTH + CHECKSUM_LENGTH + CHECKSUM_LENGTH)),
+    };
+}