feat: null terminated strings

types/string/fixed_length.ts

@@ -0,0 +1,25 @@
+import { SizedType } from "../types.ts";
+
+const encoder = new TextEncoder();
+const decoder = new TextDecoder();
+
+export class FixedLengthString implements SizedType<string> {
+  byteLength: number;
+
+  constructor(byteLength: number) {
+    this.byteLength = byteLength;
+  }
+
+  read(dataView: DataView, byteOffset = 0): string {
+    return decoder.decode(
+      new Uint8Array(dataView.buffer, byteOffset, byteOffset + this.byteLength),
+    );
+  }
+
+  write(value: string, dataView: DataView, byteOffset = 0) {
+    encoder.encodeInto(
+      value,
+      new Uint8Array(dataView.buffer, byteOffset, this.byteLength),
+    );
+  }
+}

types/string/mod.ts

@@ -1,25 +1,2 @@
-import { SizedType } from "../types.ts";
-
-const encoder = new TextEncoder();
-const decoder = new TextDecoder();
-
-export class FixedUTF8String implements SizedType<string> {
-  byteLength: number;
-
-  constructor(byteLength: number) {
-    this.byteLength = byteLength;
-  }
-
-  read(dataView: DataView, byteOffset = 0): string {
-    return decoder.decode(
-      new Uint8Array(dataView.buffer, byteOffset, byteOffset + this.byteLength),
-    );
-  }
-
-  write(value: string, dataView: DataView, byteOffset = 0) {
-    encoder.encodeInto(
-      value,
-      new Uint8Array(dataView.buffer, byteOffset, this.byteLength),
-    );
-  }
-}
+export * from "./fixed_length.ts";
+export * from "./null_terminated.ts";

types/string/null_terminated.ts

@@ -0,0 +1,37 @@
+import { Type } from "../types.ts";
+
+const encoder = new TextEncoder();
+const decoder = new TextDecoder();
+
+export class NullTerminatedString implements Type<string> {
+  read(dataView: DataView, byteOffset = 0): string {
+    let endByteLength;
+
+    for (let i = byteOffset; i < dataView.byteLength; i++) {
+      if (dataView.getUint8(i) === 0) {
+        endByteLength = i - byteOffset;
+        break;
+      }
+    }
+
+    if (endByteLength == null) {
+      throw new TypeError(
+        "Did not encounter null terminator when attempting to read null terminated string",
+      );
+    }
+
+    return decoder.decode(
+      new Uint8Array(dataView.buffer, byteOffset, endByteLength),
+    );
+  }
+
+  write(value: string, dataView: DataView, byteOffset = 0) {
+    value += "\0";
+    encoder.encodeInto(
+      value,
+      new Uint8Array(dataView.buffer, byteOffset, value.length),
+    );
+  }
+}
+
+export const nullTerminatedString = new NullTerminatedString();

types/string/null_terminated_test.ts

@@ -0,0 +1,47 @@
+import {
+  assertEquals,
+  assertThrows,
+} from "https://deno.land/[email protected]/testing/asserts.ts";
+import { nullTerminatedString } from "./null_terminated.ts";
+
+const encoder = new TextEncoder();
+
+Deno.test("NullTerminatedString", async ({ step }) => {
+  await step("read", () => {
+    assertEquals(
+      nullTerminatedString.read(
+        new DataView(encoder.encode("Hello world!\0").buffer),
+      ),
+      "Hello world!",
+    );
+
+    assertEquals(
+      nullTerminatedString.read(
+        new DataView(encoder.encode("Hello\0world!\0").buffer),
+      ),
+      "Hello",
+    );
+
+    assertEquals(
+      nullTerminatedString.read(
+        new DataView(encoder.encode("Hello\0world!\0").buffer),
+        6,
+      ),
+      "world!",
+    );
+
+    assertThrows(
+      () =>
+        nullTerminatedString.read(
+          new DataView(encoder.encode("Hello world!").buffer),
+        ),
+      "Did not encounter null terminator when attempting to read null terminated string",
+    );
+  });
+
+  await step("write", () => {
+    const dataView = new DataView(new Uint8Array(13).buffer);
+    nullTerminatedString.write("Hello world!", dataView);
+    assertEquals(dataView.buffer, encoder.encode("Hello world!\0").buffer);
+  });
+});