1 files changed, 75 insertions, 0 deletions
diff --git a/devtools/client/debugger/test/mochitest/examples/wasm-sourcemaps/utils.js b/devtools/client/debugger/test/mochitest/examples/wasm-sourcemaps/utils.js
new file mode 100644
index 0000000000..906ae02165
--- /dev/null
+++ b/devtools/client/debugger/test/mochitest/examples/wasm-sourcemaps/utils.js
@@ -0,0 +1,75 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+// Simple wasm parser to replace "sourceMappingURL" section.
+
+function updateSourceMappingURLSection(buffer, sourceMapUrl) {
+  function readVarUint8(buf, pos) {
+    let b = buf[pos++];
+    let shift = 0;
+    let result = 0;
+    while (b & 0x80) {
+      result |= (b & 0x7f) << shift;
+      shift += 7;
+      b = buf[pos++];
+    }
+    return {
+      value: result | (b << shift),
+      pos
+    };
+  }
+  function readWasmString(buf, pos) {
+    const { pos: next, value: len } = readVarUint8(buf, pos);
+    const result = String.fromCharCode.apply(
+      null,
+      buf.subarray(next, next + len)
+    );
+    return { value: result, pos: next + len };
+  }
+  function toVarUint(n) {
+    const buf = [];
+    while (n > 127) {
+      buf.push((n & 0x7f) | 0x80);
+      n >>>= 7;
+    }
+    buf.push(n);
+    return buf;
+  }
+  function toWasmString(s) {
+    const buf = toVarUint(s.length);
+    for (let i = 0; i < s.length; i++) {
+      buf.push(s.charCodeAt(i));
+    }
+    return buf;
+  }
+
+  // Appending/replacing sourceMappingURL section based on
+  // https://github.com/WebAssembly/design/pull/1051
+  const mappingSectionBody = toWasmString("sourceMappingURL").concat(
+    toWasmString(sourceMapUrl)
+  );
+  const mappingSection = toVarUint(0).concat(
+    toVarUint(mappingSectionBody.length),
+    mappingSectionBody
+  );
+  const data = new Uint8Array(buffer);
+  let start = data.length,
+    end = data.length;
+  for (let i = 8; i < data.length; ) {
+    const { pos: next, value: id } = readVarUint8(data, i);
+    const { pos: next2, value: size } = readVarUint8(data, next);
+    if (id == 0 && readWasmString(data, next2).value === "sourceMappingURL") {
+      start = i;
+      end = next2 + size;
+      break;
+    }
+    i = next2 + size;
+  }
+  const result = new Uint8Array(
+    start + (data.length - end) + mappingSection.length
+  );
+  result.set(data.subarray(0, start));
+  result.set(new Uint8Array(mappingSection), start);
+  result.set(data.subarray(end), start + mappingSection.length);
+  return result.buffer;
+}