Avoid Packer.makeDecoder choking on lengthy output.

index.js

@@ -835,7 +835,12 @@ export class Packer {
         // 0.
         // _: rANS output encoded in lowest 6 bits (higher bits are chosen to avoid backslash)
         // this should be isolated from other code for the best DEFLATE result
-        const firstLine = `_='${String.fromCharCode(...buf.map(c => c === 0x1c || c === 0x3f ? c : c | 0x40))}'`;
+        let firstLine = `_='`;
+        const CHUNK_SIZE = 8192;
+        for (let i = 0; i < buf.length; i += CHUNK_SIZE) {
+            firstLine += String.fromCharCode(...buf.slice(i, i + CHUNK_SIZE).map(c => c === 0x1c || c === 0x3f ? c : c | 0x40));
+        }
+        firstLine += `'`;
 
         let secondLine =
             // 1. initialize other variables

test.js

@@ -1,4 +1,5 @@
 import test from 'ava';
+import * as crypto from 'crypto';
 import {
     AnsEncoder, AnsDecoder, DefaultModel, Packer,
     compressWithModel, decompressWithModel
@@ -279,3 +280,14 @@ test('Packer with very high order context', t => {
     t.is(packAndEval('3 + 4 * 5', { sparseSelectors: [512] }), 23);
 });
 
+test('Packer with high entropy', t => {
+    let data = '';
+    for (let i = 0; i < (1 << 8); ++i) {
+        data += String.fromCharCode(...crypto.randomBytes(1 << 12));
+    }
+    // we've got 1 MB of random data, which can't be really compressed
+    const packer = new Packer([{ type: 'text', action: 'write', data }], { maxMemoryMB: 10, sparseSelectors: [0] });
+    packer.makeDecoder();
+    t.pass();
+});
+