mutations fine-tuning

Author: Yevgeny Pats

examples/fuzzit/fuzz.js

@@ -0,0 +1,13 @@
+
+function fuzz(buf) {
+    const string = buf.toString();
+    if (string.length === 3) {
+        if (string[0] === 'f' && string[1] === 'u' && string[2] === 'z') {
+                    throw Error("error")
+        }
+    }
+}
+
+module.exports = {
+    fuzz
+};

src/corpus.ts

@@ -43,7 +43,9 @@ export class Corpus {
 
     generateInput() {
         if (this.inputs.length === 0) {
-            return this.mutate(Buffer.alloc(1, 0))
+            const buf = Buffer.alloc(0, 0)
+            this.putBuffer(buf);
+            return buf;
         }
         const buffer = this.inputs[this.rand(this.inputs.length)];
         return this.mutate(buffer);
@@ -84,7 +86,8 @@ export class Corpus {
     mutate(buf: Buffer) {
         let res = Buffer.allocUnsafe(buf.length);
         buf.copy(res, 0, 0, buf.length);
-        const nm = 1 + this.exp2();
+        // const nm = 1 + this.exp2();
+        const nm = 1 + this.rand(32);
         for (let i=0; i<nm; i++) {
             const x = this.rand(16);
             if ( x ===0 ) {
@@ -102,7 +105,7 @@ export class Corpus {
                 // Insert a range of random bytes.
                 const pos = this.rand(res.length + 1);
                 const n = this.chooseLen(10);
-                res = Buffer.concat([res, Buffer.alloc(n, 0)], res.length + n)
+                res = Buffer.concat([res, Buffer.alloc(n, 0)], res.length + n);
                 res.copy(res, pos + n, pos);
                 for (let k = 0; k < n; k++) {
                     res[pos + k] = this.rand(256)