Introducing MemoryMappedExternalResource for creating an external...

src/platform-openbsd.cc

Index: src/platform-openbsd.cc
===================================================================
--- src/platform-openbsd.cc	(revision 6353)
+++ src/platform-openbsd.cc	(working copy)
@@ -213,6 +213,7 @@
     : file_(file), memory_(memory), size_(size) { }
   virtual ~PosixMemoryMappedFile();
   virtual void* memory() { return memory_; }
+  virtual int size() { return size_; }
  private:
   FILE* file_;
   void* memory_;
@@ -220,6 +221,19 @@
 };
 
 
+OS::MemoryMappedFile* OS::MemoryMappedFile::open(const char* name) {
+  FILE* file = fopen(name, "w+");
+  if (file == NULL) return NULL;
+
+  fseek(file, 0, SEEK_END);
+  int size = ftell(file);
+
+  void* memory =
+      mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, fileno(file), 0);
+  return new PosixMemoryMappedFile(file, memory, size);
+}
+
+
 OS::MemoryMappedFile* OS::MemoryMappedFile::create(const char* name, int size,
     void* initial) {
   FILE* file = fopen(name, "w+");