Start refactoring to reduce executable type knowledge.

courgette/ensemble.cc

-// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// Copyright (c) 2011 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/ensemble.h"
 
 #include "base/basictypes.h"
 #include "base/string_number_conversions.h"
 
 #include "courgette/image_info.h"
 #include "courgette/region.h"
 #include "courgette/streams.h"
 #include "courgette/simple_delta.h"
 
 namespace courgette {
 
-Element::Element(Kind kind, Ensemble* ensemble, const Region& region)
-    : kind_(kind), ensemble_(ensemble), region_(region) {
+Element::Element(ExecutableType kind,
+                 Ensemble* ensemble,
+                 const Region& region,
+                 PEInfo* info)
+    : kind_(kind), ensemble_(ensemble), region_(region), info_(info) {
+}
+
+Element::~Element() {
+  delete info_;
 }
 
 std::string Element::Name() const {
   return ensemble_->name() + "("
       + base::IntToString(kind()) + ","
       + base::Uint64ToString(offset_in_ensemble()) + ","
       + base::Uint64ToString(region().length()) + ")";
 }
 
-// A subclass of Element that has a PEInfo.
-class ElementWinPE : public Element {
- public:
-  ElementWinPE(Kind kind, Ensemble* ensemble, const Region& region,
-               PEInfo* info)
-      : Element(kind, ensemble, region),
-        pe_info_(info) {
-  }
-
-  virtual PEInfo* GetPEInfo() const { return pe_info_; }
-
- protected:
-  ~ElementWinPE() { delete pe_info_; }
-
- private:
-  PEInfo* pe_info_;  // Owned by |this|.
-};
-
 // Scans the Ensemble's region, sniffing out Elements.  We assume that the
 // elements do not overlap.
 Status Ensemble::FindEmbeddedElements() {
+
   size_t length = region_.length();
   const uint8* start = region_.start();
 
   size_t position = 0;
   while (position < length) {
-    // Quick test; Windows executables begin with 'MZ'.
-    if (start[position] == 'M' &&
-        position + 1 < length && start[position + 1] == 'Z') {
-      courgette::PEInfo *info = new courgette::PEInfo();
-      info->Init(start + position, length - position);
-      if (info->ParseHeader()) {
+    ExecutableType type = DetectExecutableType(start + position,
+                                               length - position);
+
+    //
+    // TODO(dgarrett) This switch can go away totally after two things.
+    //
+    // Make ImageInfo generic for all executable types.
+    // Find a generic way to handle length detection for executables.
+    //
+    // When this switch is gone, that's one less piece of code that is
+    // executable type aware.
+    //
+    switch (type) {
+      case UNKNOWN: {
+        // No Element found at current position.
+        ++position;
+        break;
+      }
+      case WIN32_X86: {
+        // The Info is only created to detect the length of the executable
+        courgette::PEInfo* info(new courgette::PEInfo());
+        info->Init(start + position, length - position);
+        if (!info->ParseHeader()) {
+          delete info;
+          position++;
+          break;
+        }
         Region region(start + position, info->length());
 
-        if (info->has_text_section()) {
-          if (info->is_32bit()) {
-            Element* element = new ElementWinPE(Element::WIN32_X86_WITH_CODE,
-                                                this, region, info);
-            owned_elements_.push_back(element);
-            elements_.push_back(element);
-            position += region.length();
-            continue;
-          }
-          // TODO(sra): Extend to 64-bit executables.
-        }
-
-        // If we had a clever transformation for resource-only executables we
-        // should identify the suitable elements here:
-        if (!info->has_text_section() && false) {
-          Element* element = new ElementWinPE(Element::WIN32_NOCODE,
-                                              this, region, info);
-          owned_elements_.push_back(element);
-          elements_.push_back(element);
-          position += region.length();
-          continue;
-        }
+        Element* element = new Element(type, this, region, info);
+        owned_elements_.push_back(element);
+        elements_.push_back(element);
+        position += region.length();
+        break;
       }
-      delete info;
     }
-
-    // This is where to add new formats, e.g. Linux executables, Dalvik
-    // executables etc.
-
-    // No Element found at current position.
-    ++position;
   }
   return C_OK;
 }
 
 Ensemble::~Ensemble() {
   for (size_t i = 0;  i < owned_elements_.size();  ++i)
     delete owned_elements_[i];
 }
 
 }  // namespace