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,

[huangs, 2016/06/10 21:10:22]

Replace "const void*" with "const uint8_t*" and propagate upwards, resolve as
needed?

[etiennep, 2016/06/13 17:50:22]

I did it up to Program detector. I will propagate in follow up cl.

                                                  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::QuickDetects(buffer, length)) {

[huangs, 2016/06/10 21:10:22]

NIT: Rename to QuickDetect() (verb).

[etiennep, 2016/06/13 17:50:22]

Done.

+    disassembler.reset(new DisassemblerWin32X86(buffer, length));
+    if (disassembler->ParseHeader())
+      return disassembler;
+  }
+  if (DisassemblerWin32X64::QuickDetects(buffer, length)) {
+    disassembler.reset(new DisassemblerWin32X64(buffer, length));
+    if (disassembler->ParseHeader())
+      return disassembler;
+  }
+  if (DisassemblerElf32X86::QuickDetects(buffer, length)) {
+    disassembler.reset(new DisassemblerElf32X86(buffer, length));
+    if (disassembler->ParseHeader())
+      return disassembler;
+  }
+  if (DisassemblerElf32ARM::QuickDetects(buffer, length)) {
+    disassembler.reset(new DisassemblerElf32ARM(buffer, length));
+    if (disassembler->ParseHeader())
+      return disassembler;
+  }
   return nullptr;
 }
 
 }  // namespace
 
 Status DetectExecutableType(const void* buffer,
                             size_t length,
                             ExecutableType* type,
                             size_t* detected_length) {
   std::unique_ptr<Disassembler> disassembler(
@@ skipping 24 matching lines @@
       new AssemblyProgram(disassembler->kind()));
 
   if (!disassembler->Disassemble(program.get()))
     return C_DISASSEMBLY_FAILED;
 
   *output = std::move(program);
   return C_OK;
 }
 
 }  // namespace courgette