diff --git a/media/libdatasource/ClearFileSource.cpp b/media/libdatasource/ClearFileSource.cpp
new file mode 100644
index 0000000..afafa23
--- /dev/null
+++ b/media/libdatasource/ClearFileSource.cpp
@@ -0,0 +1,143 @@
+/*
+ * Copyright (C) 2018 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_NDEBUG 0
+#define LOG_TAG "ClearFileSource"
+#include <utils/Log.h>
+
+#include <datasource/ClearFileSource.h>
+#include <media/stagefright/foundation/ADebug.h>
+#include <media/stagefright/FoundationUtils.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+
+namespace android {
+
+ClearFileSource::ClearFileSource(const char *filename)
+    : mFd(-1),
+      mOffset(0),
+      mLength(-1),
+      mName("<null>") {
+
+    if (filename) {
+        mName = String8::format("FileSource(%s)", filename);
+    }
+    ALOGV("%s", filename);
+    mFd = open(filename, O_LARGEFILE | O_RDONLY);
+
+    if (mFd >= 0) {
+        mLength = lseek64(mFd, 0, SEEK_END);
+    } else {
+        ALOGE("Failed to open file '%s'. (%s)", filename, strerror(errno));
+    }
+}
+
+ClearFileSource::ClearFileSource(int fd, int64_t offset, int64_t length)
+    : mFd(fd),
+      mOffset(offset),
+      mLength(length),
+      mName("<null>") {
+    ALOGV("fd=%d (%s), offset=%lld, length=%lld",
+            fd, nameForFd(fd).c_str(), (long long) offset, (long long) length);
+
+    if (mOffset < 0) {
+        mOffset = 0;
+    }
+    if (mLength < 0) {
+        mLength = 0;
+    }
+    if (mLength > INT64_MAX - mOffset) {
+        mLength = INT64_MAX - mOffset;
+    }
+    struct stat s;
+    if (fstat(fd, &s) == 0) {
+        if (mOffset > s.st_size) {
+            mOffset = s.st_size;
+            mLength = 0;
+        }
+        if (mOffset + mLength > s.st_size) {
+            mLength = s.st_size - mOffset;
+        }
+    }
+    if (mOffset != offset || mLength != length) {
+        ALOGW("offset/length adjusted from %lld/%lld to %lld/%lld",
+                (long long) offset, (long long) length,
+                (long long) mOffset, (long long) mLength);
+    }
+
+    mName = String8::format(
+            "FileSource(fd(%s), %lld, %lld)",
+            nameForFd(fd).c_str(),
+            (long long) mOffset,
+            (long long) mLength);
+
+}
+
+ClearFileSource::~ClearFileSource() {
+    if (mFd >= 0) {
+        ::close(mFd);
+        mFd = -1;
+    }
+}
+
+status_t ClearFileSource::initCheck() const {
+    return mFd >= 0 ? OK : NO_INIT;
+}
+
+ssize_t ClearFileSource::readAt(off64_t offset, void *data, size_t size) {
+    if (mFd < 0) {
+        return NO_INIT;
+    }
+
+    Mutex::Autolock autoLock(mLock);
+    if (mLength >= 0) {
+        if (offset >= mLength) {
+            return 0;  // read beyond EOF.
+        }
+        uint64_t numAvailable = mLength - offset;
+        if ((uint64_t)size > numAvailable) {
+            size = numAvailable;
+        }
+    }
+    return readAt_l(offset, data, size);
+}
+
+ssize_t ClearFileSource::readAt_l(off64_t offset, void *data, size_t size) {
+    off64_t result = lseek64(mFd, offset + mOffset, SEEK_SET);
+    if (result == -1) {
+        ALOGE("seek to %lld failed", (long long)(offset + mOffset));
+        return UNKNOWN_ERROR;
+    }
+
+    return ::read(mFd, data, size);
+}
+
+status_t ClearFileSource::getSize(off64_t *size) {
+    Mutex::Autolock autoLock(mLock);
+
+    if (mFd < 0) {
+        return NO_INIT;
+    }
+
+    *size = mLength;
+
+    return OK;
+}
+
+}  // namespace android