diff --git a/libs/utils/Android.mk b/libs/utils/Android.mk
index 7d4524a..2bb42ab 100644
--- a/libs/utils/Android.mk
+++ b/libs/utils/Android.mk
@@ -26,6 +26,7 @@
 	Debug.cpp \
 	FileMap.cpp \
 	Flattenable.cpp \
+	ObbFile.cpp \
 	Pool.cpp \
 	RefBase.cpp \
 	ResourceTypes.cpp \
@@ -65,6 +66,11 @@
 endif
 endif
 
+ifeq ($(HOST_OS),darwin)
+# MacOS doesn't have lseek64. However, off_t is 64-bit anyway.
+LOCAL_CFLAGS += -DOFF_T_IS_64_BIT
+endif
+
 include $(BUILD_HOST_STATIC_LIBRARY)
 
 
diff --git a/libs/utils/ObbFile.cpp b/libs/utils/ObbFile.cpp
new file mode 100644
index 0000000..3a4a03a
--- /dev/null
+++ b/libs/utils/ObbFile.cpp
@@ -0,0 +1,284 @@
+/*
+ * Copyright (C) 2010 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#define LOG_TAG "ObbFile"
+#include <utils/Log.h>
+#include <utils/ObbFile.h>
+
+//#define DEBUG 1
+
+#define kFooterTagSize 8  /* last two 32-bit integers */
+
+#define kFooterMinSize 21 /* 32-bit signature version
+                           * 32-bit package version
+                           * 32-bit package name size
+                           * 1-character package name
+                           * 32-bit footer size
+                           * 32-bit footer marker
+                           */
+
+#define kMaxBufSize    32768 /* Maximum file read buffer */
+
+#define kSignature     0x01059983U /* ObbFile signature */
+
+#define kSigVersion    1 /* We only know about signature version 1 */
+
+/* offsets in version 1 of the header */
+#define kPackageVersionOffset 4
+#define kPackageNameLenOffset 8
+#define kPackageNameOffset    12
+
+/*
+ * TEMP_FAILURE_RETRY is defined by some, but not all, versions of
+ * <unistd.h>. (Alas, it is not as standard as we'd hoped!) So, if it's
+ * not already defined, then define it here.
+ */
+#ifndef TEMP_FAILURE_RETRY
+/* Used to retry syscalls that can return EINTR. */
+#define TEMP_FAILURE_RETRY(exp) ({         \
+    typeof (exp) _rc;                      \
+    do {                                   \
+        _rc = (exp);                       \
+    } while (_rc == -1 && errno == EINTR); \
+    _rc; })
+#endif
+
+/*
+ * Work around situations where off_t is 64-bit and use off64_t in
+ * situations where it's 32-bit.
+ */
+#ifdef OFF_T_IS_64_BIT
+#define my_lseek64 lseek
+typedef off_t my_off64_t;
+#else
+#define my_lseek64 lseek64
+typedef off64_t my_off64_t;
+#endif
+
+namespace android {
+
+ObbFile::ObbFile() :
+        mVersion(-1) {
+}
+
+ObbFile::~ObbFile() {
+}
+
+bool ObbFile::readFrom(const char* filename)
+{
+    int fd;
+    bool success = false;
+
+    fd = ::open(filename, O_RDONLY);
+    if (fd < 0) {
+        goto out;
+    }
+    success = readFrom(fd);
+    close(fd);
+
+out:
+    if (!success) {
+        LOGW("failed to read from %s\n", filename);
+    }
+    return success;
+}
+
+bool ObbFile::readFrom(int fd)
+{
+    if (fd < 0) {
+        LOGW("failed to read file\n");
+        return false;
+    }
+
+    return parseObbFile(fd);
+}
+
+bool ObbFile::parseObbFile(int fd)
+{
+    my_off64_t fileLength = my_lseek64(fd, 0, SEEK_END);
+
+    if (fileLength < kFooterMinSize) {
+        if (fileLength < 0) {
+            LOGW("error seeking in ObbFile: %s\n", strerror(errno));
+        } else {
+            LOGW("file is only %lld (less than %d minimum)\n", fileLength, kFooterMinSize);
+        }
+        return false;
+    }
+
+    ssize_t actual;
+    size_t footerSize;
+
+    {
+        my_lseek64(fd, fileLength - kFooterTagSize, SEEK_SET);
+
+        char *footer = new char[kFooterTagSize];
+        actual = TEMP_FAILURE_RETRY(read(fd, footer, kFooterTagSize));
+        if (actual != kFooterTagSize) {
+            LOGW("couldn't read footer signature: %s\n", strerror(errno));
+            return false;
+        }
+
+        unsigned int fileSig = get4LE((unsigned char*)footer + sizeof(int32_t));
+        if (fileSig != kSignature) {
+            LOGW("footer didn't match magic string (expected 0x%08x; got 0x%08x)\n",
+                    kSignature, fileSig);
+            return false;
+        }
+
+        footerSize = get4LE((unsigned char*)footer);
+        if (footerSize > (size_t)fileLength - kFooterTagSize
+                || footerSize > kMaxBufSize) {
+            LOGW("claimed footer size is too large (0x%08lx; file size is 0x%08llx)\n",
+                    footerSize, fileLength);
+            return false;
+        }
+    }
+
+    my_off64_t fileOffset = fileLength - footerSize - kFooterTagSize;
+    if (my_lseek64(fd, fileOffset, SEEK_SET) != fileOffset) {
+        LOGW("seek %lld failed: %s\n", fileOffset, strerror(errno));
+        return false;
+    }
+
+    size_t readAmount = kMaxBufSize;
+    if (readAmount > footerSize)
+        readAmount = footerSize;
+
+    char* scanBuf = (char*)malloc(readAmount);
+    if (scanBuf == NULL) {
+        LOGW("couldn't allocate scanBuf: %s\n", strerror(errno));
+        return false;
+    }
+
+    actual = TEMP_FAILURE_RETRY(read(fd, scanBuf, readAmount));
+    // readAmount is guaranteed to be less than kMaxBufSize
+    if (actual != (ssize_t)readAmount) {
+        LOGI("couldn't read ObbFile footer: %s\n", strerror(errno));
+        free(scanBuf);
+        return false;
+    }
+
+#ifdef DEBUG
+    for (int i = 0; i < readAmount; ++i) {
+        LOGI("char: 0x%02x", scanBuf[i]);
+    }
+#endif
+
+    uint32_t sigVersion = get4LE((unsigned char*)scanBuf);
+    if (sigVersion != kSigVersion) {
+        LOGW("Unsupported ObbFile version %d\n", sigVersion);
+        free(scanBuf);
+        return false;
+    }
+
+    mVersion = (int32_t) get4LE((unsigned char*)scanBuf + kPackageVersionOffset);
+
+    uint32_t packageNameLen = get4LE((unsigned char*)scanBuf + kPackageNameLenOffset);
+    if (packageNameLen <= 0
+            || packageNameLen > (footerSize - kPackageNameOffset)) {
+        LOGW("bad ObbFile package name length (0x%08x)\n", packageNameLen);
+        free(scanBuf);
+        return false;
+    }
+
+    char* packageName = reinterpret_cast<char*>(scanBuf + kPackageNameOffset);
+    mPackageName = String8(const_cast<char*>(packageName), packageNameLen);
+
+    free(scanBuf);
+    return true;
+}
+
+bool ObbFile::writeTo(const char* filename)
+{
+    int fd;
+    bool success = false;
+
+    fd = ::open(filename, O_WRONLY);
+    if (fd < 0) {
+        goto out;
+    }
+    success = writeTo(fd);
+    close(fd);
+
+out:
+    if (!success) {
+        LOGW("failed to write to %s: %s\n", filename, strerror(errno));
+    }
+    return success;
+}
+
+bool ObbFile::writeTo(int fd)
+{
+    if (fd < 0) {
+        return false;
+    }
+
+    if (mPackageName.size() == 0 || mVersion == -1) {
+        LOGW("tried to write uninitialized ObbFile data");
+        return false;
+    }
+
+    unsigned char intBuf[sizeof(uint32_t)+1];
+    memset(&intBuf, 0, sizeof(intBuf));
+
+    put4LE(intBuf, kSigVersion);
+    if (write(fd, &intBuf, sizeof(uint32_t)) != (ssize_t)sizeof(uint32_t)) {
+        LOGW("couldn't write signature version: %s", strerror(errno));
+        return false;
+    }
+
+    put4LE(intBuf, mVersion);
+    if (write(fd, &intBuf, sizeof(uint32_t)) != (ssize_t)sizeof(uint32_t)) {
+        LOGW("couldn't write package version");
+        return false;
+    }
+
+    size_t packageNameLen = mPackageName.size();
+    put4LE(intBuf, packageNameLen);
+    if (write(fd, &intBuf, sizeof(uint32_t)) != (ssize_t)sizeof(uint32_t)) {
+        LOGW("couldn't write package name length: %s", strerror(errno));
+        return false;
+    }
+
+    if (write(fd, mPackageName.string(), packageNameLen) != (ssize_t)packageNameLen) {
+        LOGW("couldn't write package name: %s", strerror(errno));
+        return false;
+    }
+
+    put4LE(intBuf, 3*sizeof(uint32_t) + packageNameLen);
+    if (write(fd, &intBuf, sizeof(uint32_t)) != (ssize_t)sizeof(uint32_t)) {
+        LOGW("couldn't write footer size: %s", strerror(errno));
+        return false;
+    }
+
+    put4LE(intBuf, kSignature);
+    if (write(fd, &intBuf, sizeof(uint32_t)) != (ssize_t)sizeof(uint32_t)) {
+        LOGW("couldn't write footer magic signature: %s", strerror(errno));
+        return false;
+    }
+
+    return true;
+}
+
+}
diff --git a/libs/utils/tests/Android.mk b/libs/utils/tests/Android.mk
index 92ebfd7..f1b8cd5 100644
--- a/libs/utils/tests/Android.mk
+++ b/libs/utils/tests/Android.mk
@@ -3,6 +3,7 @@
 include $(CLEAR_VARS)
 
 test_src_files := \
+	ObbFile_test.cpp \
 	PollLoop_test.cpp
 
 shared_libraries := \
diff --git a/libs/utils/tests/ObbFile_test.cpp b/libs/utils/tests/ObbFile_test.cpp
new file mode 100644
index 0000000..05aaf08
--- /dev/null
+++ b/libs/utils/tests/ObbFile_test.cpp
@@ -0,0 +1,75 @@
+/*
+ * Copyright (C) 2010 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#define LOG_TAG "ObbFile_test"
+#include <utils/Log.h>
+#include <utils/ObbFile.h>
+#include <utils/RefBase.h>
+#include <utils/String8.h>
+
+#include <gtest/gtest.h>
+
+namespace android {
+
+#define TEST_FILENAME "/test.obb"
+
+class ObbFileTest : public testing::Test {
+protected:
+    sp<ObbFile> mObbFile;
+    char* mExternalStorage;
+    char* mFileName;
+
+    virtual void SetUp() {
+        mObbFile = new ObbFile();
+        mExternalStorage = getenv("EXTERNAL_STORAGE");
+
+        const int totalLen = strlen(mExternalStorage) + strlen(TEST_FILENAME) + 1;
+        mFileName = new char[totalLen];
+        snprintf(mFileName, totalLen, "%s%s", mExternalStorage, TEST_FILENAME);
+    }
+
+    virtual void TearDown() {
+    }
+};
+
+TEST_F(ObbFileTest, ReadFailure) {
+	EXPECT_FALSE(mObbFile->readFrom(-1))
+			<< "No failure on invalid file descriptor";
+}
+
+TEST_F(ObbFileTest, WriteThenRead) {
+    const char* packageName = "com.example.obbfile";
+    const int32_t versionNum = 1;
+
+    mObbFile->setPackageName(String8(packageName));
+    mObbFile->setVersion(versionNum);
+
+    EXPECT_TRUE(mObbFile->writeTo(mFileName))
+            << "couldn't write to fake .obb file";
+
+    mObbFile = new ObbFile();
+
+    EXPECT_TRUE(mObbFile->readFrom(mFileName))
+            << "couldn't read from fake .obb file";
+
+    EXPECT_EQ(versionNum, mObbFile->getVersion())
+			<< "version didn't come out the same as it went in";
+    const char* currentPackageName = mObbFile->getPackageName().string();
+    EXPECT_STREQ(packageName, currentPackageName)
+			<< "package name didn't come out the same as it went in";
+}
+
+}