[wasm] Enforce strict ordering of WASM module sections.

src/wasm/wasm-module.cc

 // Copyright 2015 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/macro-assembler.h"
 #include "src/objects.h"
 #include "src/v8.h"
 
 #include "src/simulator.h"
 
 #include "src/wasm/ast-decoder.h"
 #include "src/wasm/module-decoder.h"
 #include "src/wasm/wasm-module.h"
 #include "src/wasm/wasm-result.h"
 
 #include "src/compiler/wasm-compiler.h"
 
 namespace v8 {
 namespace internal {
 namespace wasm {
 
 static const char* wasmSections[] = {
-#define F(enumerator, string) string,
+#define F(enumerator, order, string) string,
     FOR_EACH_WASM_SECTION_TYPE(F)
 #undef F

[JF, 2016/04/20 17:59:54]

Need an entry for Code::Max. Should probably make it clear that it's an unknown
section.

[titzer, 2016/04/21 10:59:22]

done.

 };
 
 static uint8_t wasmSectionsLengths[]{
-#define F(enumerator, string) sizeof(string) - 1,
+#define F(enumerator, order, string) sizeof(string) - 1,
     FOR_EACH_WASM_SECTION_TYPE(F)
 #undef F

[JF, 2016/04/20 17:59:54]

Same, but this one's weird.

[titzer, 2016/04/21 10:59:22]

done

 };
+
+static uint8_t wasmSectionsOrders[]{
+#define F(enumerator, order, string) order,
+    FOR_EACH_WASM_SECTION_TYPE(F)
+#undef F

[JF, 2016/04/20 17:59:54]

Need a 0 at the end for Code::Max?

[titzer, 2016/04/21 10:59:22]

done

+};
 
 static_assert(sizeof(wasmSections) / sizeof(wasmSections[0]) ==
                   (size_t)WasmSection::Code::Max,
               "expected enum WasmSection::Code to be monotonic from 0");
 
 WasmSection::Code WasmSection::begin() { return (WasmSection::Code)0; }
 WasmSection::Code WasmSection::end() { return WasmSection::Code::Max; }
 WasmSection::Code WasmSection::next(WasmSection::Code code) {
   return (WasmSection::Code)(1 + (uint32_t)code);
 }
 
 const char* WasmSection::getName(WasmSection::Code code) {
   return wasmSections[(size_t)code];
 }
 
 size_t WasmSection::getNameLength(WasmSection::Code code) {
   return wasmSectionsLengths[(size_t)code];
 }
 
+int WasmSection::getOrder(WasmSection::Code code) {
+  return wasmSectionsOrders[(size_t)code];
+}
+
+WasmSection::Code WasmSection::lookup(const byte* string, uint32_t length) {
+  // TODO(jfb) Linear search, it may be better to do a common-prefix search.
+  for (Code i = begin(); i != end(); i = next(i)) {
+    if (getNameLength(i) == length && 0 == memcmp(getName(i), string, length)) {
+      return i;
+    }
+  }
+  return Code::Max;
+}
+
 std::ostream& operator<<(std::ostream& os, const WasmModule& module) {
   os << "WASM module with ";
   os << (module.min_mem_pages * module.kPageSize) << " min mem";
   os << (module.max_mem_pages * module.kPageSize) << " max mem";
   os << module.functions.size() << " functions";
   os << module.functions.size() << " globals";
   os << module.functions.size() << " data segments";
   return os;
 }
 
@@ skipping 643 matching lines @@
   }
   if (result->IsHeapNumber()) {
     return static_cast<int32_t>(HeapNumber::cast(*result)->value());
   }
   thrower.Error("WASM.compileRun() failed: Return value should be number");
   return -1;
 }
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8