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

courgette/disassembler_elf_32_arm.h

 // Copyright 2013 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_ELF_32_ARM_H_
 #define COURGETTE_DISASSEMBLER_ELF_32_ARM_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 10 matching lines @@
 enum ARM_RVA {
   ARM_OFF8,
   ARM_OFF11,
   ARM_OFF24,
   ARM_OFF25,
   ARM_OFF21,
 };
 
 class DisassemblerElf32ARM : public DisassemblerElf32 {
  public:
+  // Returns 'true' if an valid executable is detected using only quick checks.

[huangs, 2016/06/17 15:21:57]

NIT: true does not need ''
NIT: *a* valid executable.

+  static bool QuickDetect(const uint8_t* start, size_t length) {
+    return DisassemblerElf32::QuickDetect(start, length, EM_ARM);
+  }
+
   class TypedRVAARM : public TypedRVA {
    public:
     TypedRVAARM(ARM_RVA type, RVA rva) : TypedRVA(rva), type_(type) { }
     ~TypedRVAARM() override { }
 
     // TypedRVA interfaces.
     CheckBool ComputeRelativeTarget(const uint8_t* op_pointer) override;
     CheckBool EmitInstruction(AssemblyProgram* program,
                               Label* label) override;
     uint16_t op_size() const override;
 
     uint16_t c_op() const { return c_op_; }
 
    private:
     ARM_RVA type_;
     uint16_t c_op_;  // Set by ComputeRelativeTarget().
     const uint8_t* arm_op_;
   };
 
-  DisassemblerElf32ARM(const void* start, size_t length);
+  DisassemblerElf32ARM(const uint8_t* start, size_t length);
 
   ~DisassemblerElf32ARM() override { }
 
   // DisassemblerElf32 interfaces.
   ExecutableType kind() const override { return EXE_ELF_32_ARM; }
   e_machine_values ElfEM() const override { return EM_ARM; }
 
   // Takes an ARM or thumb opcode |arm_op| of specified |type| and located at
   // |rva|, extracts the instruction-relative target RVA into |*addr| and
   // encodes the corresponding Courgette opcode as |*c_op|.
@@ skipping 28 matching lines @@
 #if COURGETTE_HISTOGRAM_TARGETS
   std::map<RVA, int> rel32_target_rvas_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(DisassemblerElf32ARM);
 };
 
 }  // namespace courgette
 
 #endif  // COURGETTE_DISASSEMBLER_ELF_32_ARM_H_