[wasm] Store function names in the wasm object

src/wasm/wasm-function-name-table.cc

+// Copyright 2016 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "src/wasm/wasm-function-name-table.h"
+
+#include "src/wasm/wasm-module.h"
+
+namespace v8 {
+namespace internal {
+namespace wasm {
+
+// Build an array with all function names. If there are N functions in the
+// module, then the first (kIntSize * (N+1)) bytes are integer entries.
+// The first integer entry encodes the number of functions in the module.
+// The entries 1 to N contain offsets into the second part of this array.
+// After these N+1 integer entries, the second part begins, which holds a
+// concatenation of all function names.
+//
+// Returns undefined if the array length would not fit in an integer value
+Handle<Object> BuildFunctionNamesTable(Isolate* isolate, WasmModule* module) {
+  uint64_t func_names_length = 0;
+  for (auto& func : module->functions) func_names_length += func.name_length;
+  int num_funcs_int = static_cast<int>(module->functions.size());
+  int current_offset = (num_funcs_int + 1) * kIntSize;
+  uint64_t total_array_length = current_offset + func_names_length;
+  int total_array_length_int = static_cast<int>(total_array_length);
+  // Check for overflow. Just skip function names if it happens.
+  if (total_array_length_int != total_array_length || num_funcs_int < 0 ||
+      num_funcs_int != module->functions.size())
+    return isolate->factory()->undefined_value();
+  Handle<ByteArray> func_names_array =
+      isolate->factory()->NewByteArray(total_array_length_int, TENURED);
+  if (func_names_array.is_null()) return isolate->factory()->undefined_value();
+  func_names_array->set_int(0, num_funcs_int);
+  int func_index = 0;
+  for (WasmFunction& fun : module->functions) {
+    WasmName name = module->GetNameOrNull(&fun);
+    func_names_array->copy_in(current_offset,
+                              reinterpret_cast<const byte*>(name.start()),
+                              name.length());
+    func_names_array->set_int(func_index + 1, current_offset);
+    current_offset += name.length();
+    ++func_index;
+  }
+  return func_names_array;
+}
+
+Handle<Object> GetWasmFunctionNameFromTable(Handle<ByteArray> func_names_array,
+                                            uint32_t func_index) {
+  uint32_t num_funcs = static_cast<uint32_t>(func_names_array->get_int(0));
+  DCHECK(static_cast<int>(num_funcs) >= 0);
+  auto undefined = [&func_names_array]() -> Handle<Object> {
+    return func_names_array->GetIsolate()->factory()->undefined_value();
+  };
+  if (func_index >= num_funcs) return undefined();
+  int offset = func_names_array->get_int(func_index + 1);
+  int next_offset = func_index == num_funcs - 1
+                        ? func_names_array->length()
+                        : func_names_array->get_int(func_index + 2);
+  ScopedVector<byte> buffer(next_offset - offset);
+  func_names_array->copy_out(offset, buffer.start(), next_offset - offset);
+  MaybeHandle<Object> maybe_name =
+      func_names_array->GetIsolate()->factory()->NewStringFromUtf8(
+          Vector<const char>::cast(buffer));
+  return maybe_name.is_null() ? undefined() : maybe_name.ToHandleChecked();
+}
+
+}  // namespace wasm
+}  // namespace internal
+}  // namespace v8