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node_modules/crypto-es/lib/mode-cfb.js

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+import {
+  BlockCipherMode,
+} from './cipher-core.js';
+
+function generateKeystreamAndEncrypt(words, offset, blockSize, cipher) {
+  const _words = words;
+  let keystream;
+
+  // Shortcut
+  const iv = this._iv;
+
+  // Generate keystream
+  if (iv) {
+    keystream = iv.slice(0);
+
+    // Remove IV for subsequent blocks
+    this._iv = undefined;
+  } else {
+    keystream = this._prevBlock;
+  }
+  cipher.encryptBlock(keystream, 0);
+
+  // Encrypt
+  for (let i = 0; i < blockSize; i += 1) {
+    _words[offset + i] ^= keystream[i];
+  }
+}
+
+/**
+ * Cipher Feedback block mode.
+ */
+export class CFB extends BlockCipherMode {
+}
+CFB.Encryptor = class extends CFB {
+  processBlock(words, offset) {
+    // Shortcuts
+    const cipher = this._cipher;
+    const { blockSize } = cipher;
+
+    generateKeystreamAndEncrypt.call(this, words, offset, blockSize, cipher);
+
+    // Remember this block to use with next block
+    this._prevBlock = words.slice(offset, offset + blockSize);
+  }
+};
+CFB.Decryptor = class extends CFB {
+  processBlock(words, offset) {
+    // Shortcuts
+    const cipher = this._cipher;
+    const { blockSize } = cipher;
+
+    // Remember this block to use with next block
+    const thisBlock = words.slice(offset, offset + blockSize);
+
+    generateKeystreamAndEncrypt.call(this, words, offset, blockSize, cipher);
+
+    // This block becomes the previous block
+    this._prevBlock = thisBlock;
+  }
+};