From 28efa80222d4329a01620dd84fd9673e2e0d2e0c Mon Sep 17 00:00:00 2001
From: Keichi Takahashi <hello@keichi.dev>
Date: Sun, 18 Oct 2026 22:46:22 +0900
Subject: [PATCH] Fix string with both length and zeroTerminated options

---
 lib/binary_parser.ts     | 11 ++++++-----
 test/primitive_parser.ts | 21 +++++++++++++++++++++
 2 files changed, 27 insertions(+), 5 deletions(-)

diff --git a/lib/binary_parser.ts b/lib/binary_parser.ts
index 785c62c..f0d78ef 100644
--- a/lib/binary_parser.ts
+++ b/lib/binary_parser.ts
@@ -1202,17 +1202,18 @@ export class Parser {
     const toHex = 'b => b.toString(16).padStart(2, "0")';
 
     if (this.options.length != null && this.options.zeroTerminated) {
-      const len = this.options.length;
+      const len = ctx.generateTmpVariable();
+      ctx.pushCode(`var ${len} = ${ctx.generateOption(this.options.length)};`);
       ctx.pushCode(`var ${start} = offset;`);
       ctx.pushCode(
-        `while(offset - ${start} < ${len} && dataView.getUint8(offset++) !== 0);`,
+        `while(offset - ${start} < ${len} && dataView.getUint8(offset) !== 0) offset++;`,
       );
-      const end = `offset - ${start} < ${len} ? offset - 1 : offset`;
       ctx.pushCode(
         isHex
-          ? `${name} = Array.from(buffer.subarray(${start}, ${end}), ${toHex}).join('');`
-          : `${name} = new TextDecoder('${encoding}').decode(buffer.subarray(${start}, ${end}));`,
+          ? `${name} = Array.from(buffer.subarray(${start}, offset), ${toHex}).join('');`
+          : `${name} = new TextDecoder('${encoding}').decode(buffer.subarray(${start}, offset));`,
       );
+      ctx.pushCode(`if (offset - ${start} < ${len}) offset++;`);
     } else if (this.options.length != null) {
       const len = ctx.generateOption(this.options.length);
       ctx.pushCode(
diff --git a/test/primitive_parser.ts b/test/primitive_parser.ts
index 0de578b..69f4854 100644
--- a/test/primitive_parser.ts
+++ b/test/primitive_parser.ts
@@ -382,6 +382,27 @@ function primitiveParserTests(
           c: "ij",
         });
       });
+      it("should exclude null terminator at the last byte of fixed-length string", () => {
+        const buffer = factory(new TextEncoder().encode("abc\u0000de"));
+        const parser = Parser.start()
+          .string("a", { length: 4, zeroTerminated: true })
+          .string("b", { length: 2 });
+
+        expect(parser.parse(buffer)).toStrictEqual({ a: "abc", b: "de" });
+      });
+      it("should parse zero terminated string with function/field length", () => {
+        const buffer = factory(new TextEncoder().encode("\u0004abcdef\u0000"));
+        const parser = Parser.start()
+          .uint8("len")
+          .string("a", { length: "len", zeroTerminated: true })
+          .string("b", { length: () => 4, zeroTerminated: true });
+
+        expect(parser.parse(buffer)).toStrictEqual({
+          len: 4,
+          a: "abcd",
+          b: "ef",
+        });
+      });
       it("should strip trailing null characters", () => {
         const buffer = hexToBuf("746573740000");
         const parser1 = Parser.start().string("str", {