diff --git a/src/oat.cc b/src/oat.cc
new file mode 100644
index 0000000..191f26f
--- /dev/null
+++ b/src/oat.cc
@@ -0,0 +1,68 @@
+// Copyright 2011 Google Inc. All Rights Reserved.
+
+#include "oat.h"
+
+#include <zlib.h>
+
+namespace art {
+
+const uint8_t OatHeader::kOatMagic[] = { 'o', 'a', 't', '\n' };
+const uint8_t OatHeader::kOatVersion[] = { '0', '0', '1', '\0' };
+
+OatHeader::OatHeader(const std::vector<const DexFile*>* dex_files) {
+  memcpy(magic_, kOatMagic, sizeof(kOatMagic));
+  memcpy(version_, kOatVersion, sizeof(kOatVersion));
+  adler32_checksum_ = adler32(0L, Z_NULL, 0);
+  dex_file_count_ = dex_files->size();
+  UpdateChecksum(&dex_file_count_, sizeof(dex_file_count_));
+  executable_offset_ = 0;
+}
+
+bool OatHeader::IsValid() const {
+  if (memcmp(magic_, kOatMagic, sizeof(kOatMagic) != 0)) {
+    return false;
+  }
+  if (memcmp(version_, kOatVersion, sizeof(kOatVersion) != 0)) {
+    return false;
+  }
+  return true;
+}
+
+const char* OatHeader::GetMagic() const {
+  CHECK(IsValid());
+  return reinterpret_cast<const char*>(magic_);
+}
+
+uint32_t OatHeader::GetDexFileCount() const {
+  DCHECK(IsValid());
+  return dex_file_count_;
+}
+
+uint32_t OatHeader::GetChecksum() const {
+  CHECK(IsValid());
+  return adler32_checksum_;
+}
+
+void OatHeader::UpdateChecksum(const void* data, size_t length) {
+  DCHECK(IsValid());
+  const uint8_t* bytes = reinterpret_cast<const uint8_t*>(data);
+  adler32_checksum_ = adler32(adler32_checksum_, bytes, length);
+}
+
+uint32_t OatHeader::GetExecutableOffset() const {
+  DCHECK(IsValid());
+  DCHECK(IsAligned(executable_offset_, kPageSize));
+  CHECK_GT(executable_offset_, sizeof(OatHeader));
+  return executable_offset_;
+}
+
+void OatHeader::SetExecutableOffset(uint32_t executable_offset) {
+  DCHECK(IsAligned(executable_offset, kPageSize));
+  CHECK_GT(executable_offset, sizeof(OatHeader));
+  DCHECK(IsValid());
+  DCHECK_EQ(executable_offset_, 0U);
+  executable_offset_ = executable_offset;
+  UpdateChecksum(&executable_offset_, sizeof(executable_offset));
+}
+
+}  // namespace art