[wasm] Enforce strict ordering of WASM module sections.

src/wasm/wasm-module.cc

Index: src/wasm/wasm-module.cc
diff --git a/src/wasm/wasm-module.cc b/src/wasm/wasm-module.cc
index 79b7c405fe2f3de4208c1bef5014d6a86964a9af..8b2caeec70951f8af60a241560a967d9d49913ad 100644
--- a/src/wasm/wasm-module.cc
+++ b/src/wasm/wasm-module.cc
@@ -20,13 +20,19 @@ 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

 };
@@ -49,6 +55,20 @@ 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";