Courgette: Add static method QuickDetect() to optimize program detection.

courgette/program_detector.cc

 // Copyright 2016 The Chromium 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 "courgette/program_detector.h"
 
 #include <utility>
 
 #include "courgette/assembly_program.h"
 #include "courgette/disassembler.h"
 #include "courgette/disassembler_elf_32_arm.h"
 #include "courgette/disassembler_elf_32_x86.h"
 #include "courgette/disassembler_win32_x64.h"
 #include "courgette/disassembler_win32_x86.h"
 
 namespace courgette {
 
 namespace {
 
 // Returns a new instance of Disassembler subclass if binary data given in
 // |buffer| and |length| matches a known binary format, otherwise null.
-std::unique_ptr<Disassembler> DetectDisassembler(const void* buffer,
+std::unique_ptr<Disassembler> DetectDisassembler(const uint8_t* buffer,
                                                  size_t length) {
   std::unique_ptr<Disassembler> disassembler;
 
-  disassembler.reset(new DisassemblerWin32X86(buffer, length));
-  if (disassembler->ParseHeader())
-    return disassembler;
-
-  disassembler.reset(new DisassemblerWin32X64(buffer, length));
-  if (disassembler->ParseHeader())
-    return disassembler;
-
-  disassembler.reset(new DisassemblerElf32X86(buffer, length));
-  if (disassembler->ParseHeader())
-    return disassembler;
-
-  disassembler.reset(new DisassemblerElf32ARM(buffer, length));
-  if (disassembler->ParseHeader())
-    return disassembler;
-
+  if (DisassemblerWin32X86::QuickDetect(buffer, length)) {
+    disassembler.reset(new DisassemblerWin32X86(buffer, length));
+    if (disassembler->ParseHeader())
+      return disassembler;
+  }
+  if (DisassemblerWin32X64::QuickDetect(buffer, length)) {
+    disassembler.reset(new DisassemblerWin32X64(buffer, length));
+    if (disassembler->ParseHeader())
+      return disassembler;
+  }
+  if (DisassemblerElf32X86::QuickDetect(buffer, length)) {
+    disassembler.reset(new DisassemblerElf32X86(buffer, length));
+    if (disassembler->ParseHeader())
+      return disassembler;
+  }
+  if (DisassemblerElf32ARM::QuickDetect(buffer, length)) {
+    disassembler.reset(new DisassemblerElf32ARM(buffer, length));
+    if (disassembler->ParseHeader())
+      return disassembler;
+  }
   return nullptr;
 }
 
 }  // namespace
 
-Status DetectExecutableType(const void* buffer,
+Status DetectExecutableType(const uint8_t* buffer,
                             size_t length,
                             ExecutableType* type,
                             size_t* detected_length) {
   std::unique_ptr<Disassembler> disassembler(
       DetectDisassembler(buffer, length));
 
   if (!disassembler) {  // We failed to detect anything.
     *type = EXE_UNKNOWN;
     *detected_length = 0;
     return C_INPUT_NOT_RECOGNIZED;
   }
 
   *type = disassembler->kind();
   *detected_length = disassembler->length();
   return C_OK;
 }
 
-Status ParseDetectedExecutable(const void* buffer,
+Status ParseDetectedExecutable(const uint8_t* buffer,
                                size_t length,
                                std::unique_ptr<AssemblyProgram>* output) {
   output->reset();
 
   std::unique_ptr<Disassembler> disassembler(
       DetectDisassembler(buffer, length));
   if (!disassembler)
     return C_INPUT_NOT_RECOGNIZED;
 
   std::unique_ptr<AssemblyProgram> program(
       new AssemblyProgram(disassembler->kind()));
 
   if (!disassembler->Disassemble(program.get()))
     return C_DISASSEMBLY_FAILED;
 
   *output = std::move(program);
   return C_OK;
 }
 
 }  // namespace courgette