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

courgette/disassembler_win32.h

 // 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.
 
 #ifndef COURGETTE_DISASSEMBLER_WIN32_H_
 #define COURGETTE_DISASSEMBLER_WIN32_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 31 matching lines @@
   // Output is a vector of the RVAs corresponding to locations within executable
   // that are listed in the base relocation table.
   bool ParseRelocs(std::vector<RVA>* addresses);
 
   // Returns Section containing the relative virtual address, or null if none.
   const Section* RVAToSection(RVA rva) const;
 
   static std::string SectionName(const Section* section);
 
  protected:
+  // Returns true if a valid executable is detected using only quick checks.
+  // Derived classes should inject |magic| corresponding to their architecture,
+  // which will be checked against the detected one.
+  static bool QuickDetect(const uint8_t* start, size_t length, uint16_t magic);
+
   // Disassembler interfaces.
   RvaVisitor* CreateAbs32TargetRvaVisitor() override;
   RvaVisitor* CreateRel32TargetRvaVisitor() override;
   void RemoveUnusedRel32Locations(AssemblyProgram* program) override;
 
-  DisassemblerWin32(const void* start, size_t length);
+  DisassemblerWin32(const uint8_t* start, size_t length);
 
   CheckBool ParseFile(AssemblyProgram* target) WARN_UNUSED_RESULT;
   bool ParseAbs32Relocs();
   void ParseRel32RelocsFromSections();
   virtual void ParseRel32RelocsFromSection(const Section* section) = 0;
 
   CheckBool ParseNonSectionFileRegion(FileOffset start_file_offset,
                                       FileOffset end_file_offset,
                                       AssemblyProgram* program)
       WARN_UNUSED_RESULT;
@@ skipping 71 matching lines @@
   std::map<RVA, int> rel32_target_rvas_;
 #endif
 
  private:
   DISALLOW_COPY_AND_ASSIGN(DisassemblerWin32);
 };
 
 }  // namespace courgette
 
 #endif  // COURGETTE_DISASSEMBLER_WIN32_H_