Move most of runtime/base to libartbase/base

Enforce the layering that code in runtime/base should not depend on
runtime by separating it into libartbase.  Some of the code in
runtime/base depends on the Runtime class, so it cannot be moved yet.
Also, some of the tests depend on CommonRuntimeTest, which itself needs
to be factored (in a subsequent CL).

Bug: 22322814
Test: make -j 50 checkbuild
      make -j 50 test-art-host

Change-Id: I8b096c1e2542f829eb456b4b057c71421b77d7e2
diff --git a/libartbase/base/unix_file/README b/libartbase/base/unix_file/README
new file mode 100644
index 0000000..e9aec22
--- /dev/null
+++ b/libartbase/base/unix_file/README
@@ -0,0 +1,15 @@
+A simple C++ wrapper for Unix file I/O.
+
+This is intended to be lightweight and easy to use, similar to Java's
+RandomAccessFile and related classes. The usual C++ idioms of RAII and "you
+don't pay for what you don't use" apply.
+
+In particular, the basic RandomAccessFile interface is kept small and simple so
+it's trivial to add new implementations.
+
+This code will not log, because it can't know whether that's appropriate in
+your application.
+
+This code will, in general, return -errno on failure. If an operation consisted
+of multiple sub-operations, it will return the errno corresponding to the most
+relevant operation.
diff --git a/libartbase/base/unix_file/fd_file.cc b/libartbase/base/unix_file/fd_file.cc
new file mode 100644
index 0000000..f9da178
--- /dev/null
+++ b/libartbase/base/unix_file/fd_file.cc
@@ -0,0 +1,481 @@
+/*
+ * Copyright (C) 2009 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 "base/unix_file/fd_file.h"
+
+#include <errno.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <limits>
+
+#include <android-base/logging.h>
+
+// Includes needed for FdFile::Copy().
+#ifdef __linux__
+#include <sys/sendfile.h>
+#else
+#include <algorithm>
+#include "base/stl_util.h"
+#include "globals.h"
+#endif
+
+namespace unix_file {
+
+FdFile::FdFile()
+    : guard_state_(GuardState::kClosed), fd_(-1), auto_close_(true), read_only_mode_(false) {
+}
+
+FdFile::FdFile(int fd, bool check_usage)
+    : guard_state_(check_usage ? GuardState::kBase : GuardState::kNoCheck),
+      fd_(fd), auto_close_(true), read_only_mode_(false) {
+}
+
+FdFile::FdFile(int fd, const std::string& path, bool check_usage)
+    : FdFile(fd, path, check_usage, false) {
+}
+
+FdFile::FdFile(int fd, const std::string& path, bool check_usage, bool read_only_mode)
+    : guard_state_(check_usage ? GuardState::kBase : GuardState::kNoCheck),
+      fd_(fd), file_path_(path), auto_close_(true), read_only_mode_(read_only_mode) {
+}
+
+FdFile::FdFile(const std::string& path, int flags, mode_t mode, bool check_usage)
+    : fd_(-1), auto_close_(true) {
+  Open(path, flags, mode);
+  if (!check_usage || !IsOpened()) {
+    guard_state_ = GuardState::kNoCheck;
+  }
+}
+
+void FdFile::Destroy() {
+  if (kCheckSafeUsage && (guard_state_ < GuardState::kNoCheck)) {
+    if (guard_state_ < GuardState::kFlushed) {
+      LOG(ERROR) << "File " << file_path_ << " wasn't explicitly flushed before destruction.";
+    }
+    if (guard_state_ < GuardState::kClosed) {
+      LOG(ERROR) << "File " << file_path_ << " wasn't explicitly closed before destruction.";
+    }
+    DCHECK_GE(guard_state_, GuardState::kClosed);
+  }
+  if (auto_close_ && fd_ != -1) {
+    if (Close() != 0) {
+      PLOG(WARNING) << "Failed to close file with fd=" << fd_ << " path=" << file_path_;
+    }
+  }
+}
+
+FdFile& FdFile::operator=(FdFile&& other) {
+  if (this == &other) {
+    return *this;
+  }
+
+  if (this->fd_ != other.fd_) {
+    Destroy();  // Free old state.
+  }
+
+  guard_state_ = other.guard_state_;
+  fd_ = other.fd_;
+  file_path_ = std::move(other.file_path_);
+  auto_close_ = other.auto_close_;
+  read_only_mode_ = other.read_only_mode_;
+  other.Release();  // Release other.
+
+  return *this;
+}
+
+FdFile::~FdFile() {
+  Destroy();
+}
+
+void FdFile::moveTo(GuardState target, GuardState warn_threshold, const char* warning) {
+  if (kCheckSafeUsage) {
+    if (guard_state_ < GuardState::kNoCheck) {
+      if (warn_threshold < GuardState::kNoCheck && guard_state_ >= warn_threshold) {
+        LOG(ERROR) << warning;
+      }
+      guard_state_ = target;
+    }
+  }
+}
+
+void FdFile::moveUp(GuardState target, const char* warning) {
+  if (kCheckSafeUsage) {
+    if (guard_state_ < GuardState::kNoCheck) {
+      if (guard_state_ < target) {
+        guard_state_ = target;
+      } else if (target < guard_state_) {
+        LOG(ERROR) << warning;
+      }
+    }
+  }
+}
+
+void FdFile::DisableAutoClose() {
+  auto_close_ = false;
+}
+
+bool FdFile::Open(const std::string& path, int flags) {
+  return Open(path, flags, 0640);
+}
+
+bool FdFile::Open(const std::string& path, int flags, mode_t mode) {
+  static_assert(O_RDONLY == 0, "Readonly flag has unexpected value.");
+  DCHECK_EQ(fd_, -1) << path;
+  read_only_mode_ = ((flags & O_ACCMODE) == O_RDONLY);
+  fd_ = TEMP_FAILURE_RETRY(open(path.c_str(), flags, mode));
+  if (fd_ == -1) {
+    return false;
+  }
+  file_path_ = path;
+  if (kCheckSafeUsage && (flags & (O_RDWR | O_CREAT | O_WRONLY)) != 0) {
+    // Start in the base state (not flushed, not closed).
+    guard_state_ = GuardState::kBase;
+  } else {
+    // We are not concerned with read-only files. In that case, proper flushing and closing is
+    // not important.
+    guard_state_ = GuardState::kNoCheck;
+  }
+  return true;
+}
+
+int FdFile::Close() {
+  int result = close(fd_);
+
+  // Test here, so the file is closed and not leaked.
+  if (kCheckSafeUsage) {
+    DCHECK_GE(guard_state_, GuardState::kFlushed) << "File " << file_path_
+        << " has not been flushed before closing.";
+    moveUp(GuardState::kClosed, nullptr);
+  }
+
+#if defined(__linux__)
+  // close always succeeds on linux, even if failure is reported.
+  UNUSED(result);
+#else
+  if (result == -1) {
+    return -errno;
+  }
+#endif
+
+  fd_ = -1;
+  file_path_ = "";
+  return 0;
+}
+
+int FdFile::Flush() {
+  DCHECK(!read_only_mode_);
+
+#ifdef __linux__
+  int rc = TEMP_FAILURE_RETRY(fdatasync(fd_));
+#else
+  int rc = TEMP_FAILURE_RETRY(fsync(fd_));
+#endif
+
+  moveUp(GuardState::kFlushed, "Flushing closed file.");
+  if (rc == 0) {
+    return 0;
+  }
+
+  // Don't report failure if we just tried to flush a pipe or socket.
+  return errno == EINVAL ? 0 : -errno;
+}
+
+int64_t FdFile::Read(char* buf, int64_t byte_count, int64_t offset) const {
+#ifdef __linux__
+  int rc = TEMP_FAILURE_RETRY(pread64(fd_, buf, byte_count, offset));
+#else
+  int rc = TEMP_FAILURE_RETRY(pread(fd_, buf, byte_count, offset));
+#endif
+  return (rc == -1) ? -errno : rc;
+}
+
+int FdFile::SetLength(int64_t new_length) {
+  DCHECK(!read_only_mode_);
+#ifdef __linux__
+  int rc = TEMP_FAILURE_RETRY(ftruncate64(fd_, new_length));
+#else
+  int rc = TEMP_FAILURE_RETRY(ftruncate(fd_, new_length));
+#endif
+  moveTo(GuardState::kBase, GuardState::kClosed, "Truncating closed file.");
+  return (rc == -1) ? -errno : rc;
+}
+
+int64_t FdFile::GetLength() const {
+  struct stat s;
+  int rc = TEMP_FAILURE_RETRY(fstat(fd_, &s));
+  return (rc == -1) ? -errno : s.st_size;
+}
+
+int64_t FdFile::Write(const char* buf, int64_t byte_count, int64_t offset) {
+  DCHECK(!read_only_mode_);
+#ifdef __linux__
+  int rc = TEMP_FAILURE_RETRY(pwrite64(fd_, buf, byte_count, offset));
+#else
+  int rc = TEMP_FAILURE_RETRY(pwrite(fd_, buf, byte_count, offset));
+#endif
+  moveTo(GuardState::kBase, GuardState::kClosed, "Writing into closed file.");
+  return (rc == -1) ? -errno : rc;
+}
+
+int FdFile::Fd() const {
+  return fd_;
+}
+
+bool FdFile::ReadOnlyMode() const {
+  return read_only_mode_;
+}
+
+bool FdFile::CheckUsage() const {
+  return guard_state_ != GuardState::kNoCheck;
+}
+
+bool FdFile::IsOpened() const {
+  return fd_ >= 0;
+}
+
+static ssize_t ReadIgnoreOffset(int fd, void *buf, size_t count, off_t offset) {
+  DCHECK_EQ(offset, 0);
+  return read(fd, buf, count);
+}
+
+template <ssize_t (*read_func)(int, void*, size_t, off_t)>
+static bool ReadFullyGeneric(int fd, void* buffer, size_t byte_count, size_t offset) {
+  char* ptr = static_cast<char*>(buffer);
+  while (byte_count > 0) {
+    ssize_t bytes_read = TEMP_FAILURE_RETRY(read_func(fd, ptr, byte_count, offset));
+    if (bytes_read <= 0) {
+      // 0: end of file
+      // -1: error
+      return false;
+    }
+    byte_count -= bytes_read;  // Reduce the number of remaining bytes.
+    ptr += bytes_read;  // Move the buffer forward.
+    offset += static_cast<size_t>(bytes_read);  // Move the offset forward.
+  }
+  return true;
+}
+
+bool FdFile::ReadFully(void* buffer, size_t byte_count) {
+  return ReadFullyGeneric<ReadIgnoreOffset>(fd_, buffer, byte_count, 0);
+}
+
+bool FdFile::PreadFully(void* buffer, size_t byte_count, size_t offset) {
+  return ReadFullyGeneric<pread>(fd_, buffer, byte_count, offset);
+}
+
+template <bool kUseOffset>
+bool FdFile::WriteFullyGeneric(const void* buffer, size_t byte_count, size_t offset) {
+  DCHECK(!read_only_mode_);
+  moveTo(GuardState::kBase, GuardState::kClosed, "Writing into closed file.");
+  DCHECK(kUseOffset || offset == 0u);
+  const char* ptr = static_cast<const char*>(buffer);
+  while (byte_count > 0) {
+    ssize_t bytes_written = kUseOffset
+        ? TEMP_FAILURE_RETRY(pwrite(fd_, ptr, byte_count, offset))
+        : TEMP_FAILURE_RETRY(write(fd_, ptr, byte_count));
+    if (bytes_written == -1) {
+      return false;
+    }
+    byte_count -= bytes_written;  // Reduce the number of remaining bytes.
+    ptr += bytes_written;  // Move the buffer forward.
+    offset += static_cast<size_t>(bytes_written);
+  }
+  return true;
+}
+
+bool FdFile::PwriteFully(const void* buffer, size_t byte_count, size_t offset) {
+  return WriteFullyGeneric<true>(buffer, byte_count, offset);
+}
+
+bool FdFile::WriteFully(const void* buffer, size_t byte_count) {
+  return WriteFullyGeneric<false>(buffer, byte_count, 0u);
+}
+
+bool FdFile::Copy(FdFile* input_file, int64_t offset, int64_t size) {
+  DCHECK(!read_only_mode_);
+  off_t off = static_cast<off_t>(offset);
+  off_t sz = static_cast<off_t>(size);
+  if (offset < 0 || static_cast<int64_t>(off) != offset ||
+      size < 0 || static_cast<int64_t>(sz) != size ||
+      sz > std::numeric_limits<off_t>::max() - off) {
+    errno = EINVAL;
+    return false;
+  }
+  if (size == 0) {
+    return true;
+  }
+#ifdef __linux__
+  // Use sendfile(), available for files since linux kernel 2.6.33.
+  off_t end = off + sz;
+  while (off != end) {
+    int result = TEMP_FAILURE_RETRY(
+        sendfile(Fd(), input_file->Fd(), &off, end - off));
+    if (result == -1) {
+      return false;
+    }
+    // Ignore the number of bytes in `result`, sendfile() already updated `off`.
+  }
+#else
+  if (lseek(input_file->Fd(), off, SEEK_SET) != off) {
+    return false;
+  }
+  constexpr size_t kMaxBufferSize = 4 * ::art::kPageSize;
+  const size_t buffer_size = std::min<uint64_t>(size, kMaxBufferSize);
+  art::UniqueCPtr<void> buffer(malloc(buffer_size));
+  if (buffer == nullptr) {
+    errno = ENOMEM;
+    return false;
+  }
+  while (size != 0) {
+    size_t chunk_size = std::min<uint64_t>(buffer_size, size);
+    if (!input_file->ReadFully(buffer.get(), chunk_size) ||
+        !WriteFully(buffer.get(), chunk_size)) {
+      return false;
+    }
+    size -= chunk_size;
+  }
+#endif
+  return true;
+}
+
+bool FdFile::Unlink() {
+  if (file_path_.empty()) {
+    return false;
+  }
+
+  // Try to figure out whether this file is still referring to the one on disk.
+  bool is_current = false;
+  {
+    struct stat this_stat, current_stat;
+    int cur_fd = TEMP_FAILURE_RETRY(open(file_path_.c_str(), O_RDONLY));
+    if (cur_fd > 0) {
+      // File still exists.
+      if (fstat(fd_, &this_stat) == 0 && fstat(cur_fd, &current_stat) == 0) {
+        is_current = (this_stat.st_dev == current_stat.st_dev) &&
+                     (this_stat.st_ino == current_stat.st_ino);
+      }
+      close(cur_fd);
+    }
+  }
+
+  if (is_current) {
+    unlink(file_path_.c_str());
+  }
+
+  return is_current;
+}
+
+bool FdFile::Erase(bool unlink) {
+  DCHECK(!read_only_mode_);
+
+  bool ret_result = true;
+  if (unlink) {
+    ret_result = Unlink();
+  }
+
+  int result;
+  result = SetLength(0);
+  result = Flush();
+  result = Close();
+  // Ignore the errors.
+
+  return ret_result;
+}
+
+int FdFile::FlushCloseOrErase() {
+  DCHECK(!read_only_mode_);
+  int flush_result = Flush();
+  if (flush_result != 0) {
+    LOG(ERROR) << "CloseOrErase failed while flushing a file.";
+    Erase();
+    return flush_result;
+  }
+  int close_result = Close();
+  if (close_result != 0) {
+    LOG(ERROR) << "CloseOrErase failed while closing a file.";
+    Erase();
+    return close_result;
+  }
+  return 0;
+}
+
+int FdFile::FlushClose() {
+  DCHECK(!read_only_mode_);
+  int flush_result = Flush();
+  if (flush_result != 0) {
+    LOG(ERROR) << "FlushClose failed while flushing a file.";
+  }
+  int close_result = Close();
+  if (close_result != 0) {
+    LOG(ERROR) << "FlushClose failed while closing a file.";
+  }
+  return (flush_result != 0) ? flush_result : close_result;
+}
+
+void FdFile::MarkUnchecked() {
+  guard_state_ = GuardState::kNoCheck;
+}
+
+bool FdFile::ClearContent() {
+  DCHECK(!read_only_mode_);
+  if (SetLength(0) < 0) {
+    PLOG(ERROR) << "Failed to reset the length";
+    return false;
+  }
+  return ResetOffset();
+}
+
+bool FdFile::ResetOffset() {
+  DCHECK(!read_only_mode_);
+  off_t rc =  TEMP_FAILURE_RETRY(lseek(fd_, 0, SEEK_SET));
+  if (rc == static_cast<off_t>(-1)) {
+    PLOG(ERROR) << "Failed to reset the offset";
+    return false;
+  }
+  return true;
+}
+
+int FdFile::Compare(FdFile* other) {
+  int64_t length = GetLength();
+  int64_t length2 = other->GetLength();
+  if (length != length2) {
+    return length < length2 ? -1 : 1;
+  }
+  static const size_t kBufferSize = 4096;
+  std::unique_ptr<uint8_t[]> buffer1(new uint8_t[kBufferSize]);
+  std::unique_ptr<uint8_t[]> buffer2(new uint8_t[kBufferSize]);
+  size_t offset = 0;
+  while (length > 0) {
+    size_t len = std::min(kBufferSize, static_cast<size_t>(length));
+    if (!PreadFully(&buffer1[0], len, offset)) {
+      return -1;
+    }
+    if (!other->PreadFully(&buffer2[0], len, offset)) {
+      return 1;
+    }
+    int result = memcmp(&buffer1[0], &buffer2[0], len);
+    if (result != 0) {
+      return result;
+    }
+    length -= len;
+    offset += len;
+  }
+  return 0;
+}
+
+}  // namespace unix_file
diff --git a/libartbase/base/unix_file/fd_file.h b/libartbase/base/unix_file/fd_file.h
new file mode 100644
index 0000000..fe3317f
--- /dev/null
+++ b/libartbase/base/unix_file/fd_file.h
@@ -0,0 +1,195 @@
+/*
+ * Copyright (C) 2009 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.
+ */
+
+#ifndef ART_LIBARTBASE_BASE_UNIX_FILE_FD_FILE_H_
+#define ART_LIBARTBASE_BASE_UNIX_FILE_FD_FILE_H_
+
+#include <fcntl.h>
+
+#include <string>
+
+#include "base/macros.h"
+#include "base/unix_file/random_access_file.h"
+
+namespace unix_file {
+
+// If true, check whether Flush and Close are called before destruction.
+static constexpr bool kCheckSafeUsage = true;
+
+// A RandomAccessFile implementation backed by a file descriptor.
+//
+// Not thread safe.
+class FdFile : public RandomAccessFile {
+ public:
+  FdFile();
+  // Creates an FdFile using the given file descriptor. Takes ownership of the
+  // file descriptor. (Use DisableAutoClose to retain ownership.)
+  FdFile(int fd, bool checkUsage);
+  FdFile(int fd, const std::string& path, bool checkUsage);
+  FdFile(int fd, const std::string& path, bool checkUsage, bool read_only_mode);
+
+  FdFile(const std::string& path, int flags, bool checkUsage)
+      : FdFile(path, flags, 0640, checkUsage) {}
+  FdFile(const std::string& path, int flags, mode_t mode, bool checkUsage);
+
+  // Move constructor.
+  FdFile(FdFile&& other)
+      : guard_state_(other.guard_state_),
+        fd_(other.fd_),
+        file_path_(std::move(other.file_path_)),
+        auto_close_(other.auto_close_),
+        read_only_mode_(other.read_only_mode_) {
+    other.Release();  // Release the src.
+  }
+
+  // Move assignment operator.
+  FdFile& operator=(FdFile&& other);
+
+  // Release the file descriptor. This will make further accesses to this FdFile invalid. Disables
+  // all further state checking.
+  int Release() {
+    int tmp_fd = fd_;
+    fd_ = -1;
+    guard_state_ = GuardState::kNoCheck;
+    auto_close_ = false;
+    return tmp_fd;
+  }
+
+  void Reset(int fd, bool check_usage) {
+    if (fd_ != -1 && fd_ != fd) {
+      Destroy();
+    }
+    fd_ = fd;
+    if (check_usage) {
+      guard_state_ = fd == -1 ? GuardState::kNoCheck : GuardState::kBase;
+    } else {
+      guard_state_ = GuardState::kNoCheck;
+    }
+    // Keep the auto_close_ state.
+  }
+
+  // Destroys an FdFile, closing the file descriptor if Close hasn't already
+  // been called. (If you care about the return value of Close, call it
+  // yourself; this is meant to handle failure cases and read-only accesses.
+  // Note though that calling Close and checking its return value is still no
+  // guarantee that data actually made it to stable storage.)
+  virtual ~FdFile();
+
+  // RandomAccessFile API.
+  int Close() OVERRIDE WARN_UNUSED;
+  int64_t Read(char* buf, int64_t byte_count, int64_t offset) const OVERRIDE WARN_UNUSED;
+  int SetLength(int64_t new_length) OVERRIDE WARN_UNUSED;
+  int64_t GetLength() const OVERRIDE;
+  int64_t Write(const char* buf, int64_t byte_count, int64_t offset) OVERRIDE WARN_UNUSED;
+
+  int Flush() OVERRIDE WARN_UNUSED;
+
+  // Short for SetLength(0); Flush(); Close();
+  // If the file was opened with a path name and unlink = true, also calls Unlink() on the path.
+  // Note that it is the the caller's responsibility to avoid races.
+  bool Erase(bool unlink = false);
+
+  // Call unlink() if the file was opened with a path, and if open() with the name shows that
+  // the file descriptor of this file is still up-to-date. This is still racy, though, and it
+  // is up to the caller to ensure correctness in a multi-process setup.
+  bool Unlink();
+
+  // Try to Flush(), then try to Close(); If either fails, call Erase().
+  int FlushCloseOrErase() WARN_UNUSED;
+
+  // Try to Flush and Close(). Attempts both, but returns the first error.
+  int FlushClose() WARN_UNUSED;
+
+  // Bonus API.
+  int Fd() const;
+  bool ReadOnlyMode() const;
+  bool CheckUsage() const;
+  bool IsOpened() const;
+  const std::string& GetPath() const {
+    return file_path_;
+  }
+  void DisableAutoClose();
+  bool ReadFully(void* buffer, size_t byte_count) WARN_UNUSED;
+  bool PreadFully(void* buffer, size_t byte_count, size_t offset) WARN_UNUSED;
+  bool WriteFully(const void* buffer, size_t byte_count) WARN_UNUSED;
+  bool PwriteFully(const void* buffer, size_t byte_count, size_t offset) WARN_UNUSED;
+
+  // Copy data from another file.
+  bool Copy(FdFile* input_file, int64_t offset, int64_t size);
+  // Clears the file content and resets the file offset to 0.
+  // Returns true upon success, false otherwise.
+  bool ClearContent();
+  // Resets the file offset to the beginning of the file.
+  bool ResetOffset();
+
+  // This enum is public so that we can define the << operator over it.
+  enum class GuardState {
+    kBase,           // Base, file has not been flushed or closed.
+    kFlushed,        // File has been flushed, but not closed.
+    kClosed,         // File has been flushed and closed.
+    kNoCheck         // Do not check for the current file instance.
+  };
+
+  // WARNING: Only use this when you know what you're doing!
+  void MarkUnchecked();
+
+  // Compare against another file. Returns 0 if the files are equivalent, otherwise returns -1 or 1
+  // depending on if the lenghts are different. If the lengths are the same, the function returns
+  // the difference of the first byte that differs.
+  int Compare(FdFile* other);
+
+ protected:
+  // If the guard state indicates checking (!=kNoCheck), go to the target state "target". Print the
+  // given warning if the current state is or exceeds warn_threshold.
+  void moveTo(GuardState target, GuardState warn_threshold, const char* warning);
+
+  // If the guard state indicates checking (<kNoCheck), and is below the target state "target", go
+  // to "target." If the current state is higher (excluding kNoCheck) than the trg state, print the
+  // warning.
+  void moveUp(GuardState target, const char* warning);
+
+  // Forcefully sets the state to the given one. This can overwrite kNoCheck.
+  void resetGuard(GuardState new_state) {
+    if (kCheckSafeUsage) {
+      guard_state_ = new_state;
+    }
+  }
+
+  GuardState guard_state_;
+
+  // Opens file 'file_path' using 'flags' and 'mode'.
+  bool Open(const std::string& file_path, int flags);
+  bool Open(const std::string& file_path, int flags, mode_t mode);
+
+ private:
+  template <bool kUseOffset>
+  bool WriteFullyGeneric(const void* buffer, size_t byte_count, size_t offset);
+
+  void Destroy();  // For ~FdFile and operator=(&&).
+
+  int fd_;
+  std::string file_path_;
+  bool auto_close_;
+  bool read_only_mode_;
+
+  DISALLOW_COPY_AND_ASSIGN(FdFile);
+};
+
+std::ostream& operator<<(std::ostream& os, const FdFile::GuardState& kind);
+
+}  // namespace unix_file
+
+#endif  // ART_LIBARTBASE_BASE_UNIX_FILE_FD_FILE_H_
diff --git a/libartbase/base/unix_file/fd_file_test.cc b/libartbase/base/unix_file/fd_file_test.cc
new file mode 100644
index 0000000..042fbc9
--- /dev/null
+++ b/libartbase/base/unix_file/fd_file_test.cc
@@ -0,0 +1,288 @@
+/*
+ * Copyright (C) 2009 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 "base/unix_file/fd_file.h"
+#include "base/unix_file/random_access_file_test.h"
+#include "common_runtime_test.h"  // For ScratchFile
+#include "gtest/gtest.h"
+
+namespace unix_file {
+
+class FdFileTest : public RandomAccessFileTest {
+ protected:
+  virtual RandomAccessFile* MakeTestFile() {
+    return new FdFile(fileno(tmpfile()), false);
+  }
+};
+
+TEST_F(FdFileTest, Read) {
+  TestRead();
+}
+
+TEST_F(FdFileTest, SetLength) {
+  TestSetLength();
+}
+
+TEST_F(FdFileTest, Write) {
+  TestWrite();
+}
+
+TEST_F(FdFileTest, UnopenedFile) {
+  FdFile file;
+  EXPECT_EQ(-1, file.Fd());
+  EXPECT_FALSE(file.IsOpened());
+  EXPECT_TRUE(file.GetPath().empty());
+}
+
+TEST_F(FdFileTest, OpenClose) {
+  std::string good_path(GetTmpPath("some-file.txt"));
+  FdFile file(good_path, O_CREAT | O_WRONLY, true);
+  ASSERT_TRUE(file.IsOpened());
+  EXPECT_GE(file.Fd(), 0);
+  EXPECT_TRUE(file.IsOpened());
+  EXPECT_FALSE(file.ReadOnlyMode());
+  EXPECT_EQ(0, file.Flush());
+  EXPECT_EQ(0, file.Close());
+  EXPECT_EQ(-1, file.Fd());
+  EXPECT_FALSE(file.IsOpened());
+  FdFile file2(good_path, O_RDONLY, true);
+  EXPECT_TRUE(file2.IsOpened());
+  EXPECT_TRUE(file2.ReadOnlyMode());
+  EXPECT_GE(file2.Fd(), 0);
+
+  ASSERT_EQ(file2.Close(), 0);
+  ASSERT_EQ(unlink(good_path.c_str()), 0);
+}
+
+TEST_F(FdFileTest, ReadFullyEmptyFile) {
+  // New scratch file, zero-length.
+  art::ScratchFile tmp;
+  FdFile file(tmp.GetFilename(), O_RDONLY, false);
+  ASSERT_TRUE(file.IsOpened());
+  EXPECT_TRUE(file.ReadOnlyMode());
+  EXPECT_GE(file.Fd(), 0);
+  uint8_t buffer[16];
+  EXPECT_FALSE(file.ReadFully(&buffer, 4));
+}
+
+template <size_t Size>
+static void NullTerminateCharArray(char (&array)[Size]) {
+  array[Size - 1] = '\0';
+}
+
+TEST_F(FdFileTest, ReadFullyWithOffset) {
+  // New scratch file, zero-length.
+  art::ScratchFile tmp;
+  FdFile file(tmp.GetFilename(), O_RDWR, false);
+  ASSERT_TRUE(file.IsOpened());
+  EXPECT_GE(file.Fd(), 0);
+  EXPECT_FALSE(file.ReadOnlyMode());
+
+  char ignore_prefix[20] = {'a', };
+  NullTerminateCharArray(ignore_prefix);
+  char read_suffix[10] = {'b', };
+  NullTerminateCharArray(read_suffix);
+
+  off_t offset = 0;
+  // Write scratch data to file that we can read back into.
+  EXPECT_TRUE(file.Write(ignore_prefix, sizeof(ignore_prefix), offset));
+  offset += sizeof(ignore_prefix);
+  EXPECT_TRUE(file.Write(read_suffix, sizeof(read_suffix), offset));
+
+  ASSERT_EQ(file.Flush(), 0);
+
+  // Reading at an offset should only produce 'bbbb...', since we ignore the 'aaa...' prefix.
+  char buffer[sizeof(read_suffix)];
+  EXPECT_TRUE(file.PreadFully(buffer, sizeof(read_suffix), offset));
+  EXPECT_STREQ(&read_suffix[0], &buffer[0]);
+
+  ASSERT_EQ(file.Close(), 0);
+}
+
+TEST_F(FdFileTest, ReadWriteFullyWithOffset) {
+  // New scratch file, zero-length.
+  art::ScratchFile tmp;
+  FdFile file(tmp.GetFilename(), O_RDWR, false);
+  ASSERT_GE(file.Fd(), 0);
+  EXPECT_TRUE(file.IsOpened());
+  EXPECT_FALSE(file.ReadOnlyMode());
+
+  const char* test_string = "This is a test string";
+  size_t length = strlen(test_string) + 1;
+  const size_t offset = 12;
+  std::unique_ptr<char[]> offset_read_string(new char[length]);
+  std::unique_ptr<char[]> read_string(new char[length]);
+
+  // Write scratch data to file that we can read back into.
+  EXPECT_TRUE(file.PwriteFully(test_string, length, offset));
+  ASSERT_EQ(file.Flush(), 0);
+
+  // Test reading both the offsets.
+  EXPECT_TRUE(file.PreadFully(&offset_read_string[0], length, offset));
+  EXPECT_STREQ(test_string, &offset_read_string[0]);
+
+  EXPECT_TRUE(file.PreadFully(&read_string[0], length, 0u));
+  EXPECT_NE(memcmp(&read_string[0], test_string, length), 0);
+
+  ASSERT_EQ(file.Close(), 0);
+}
+
+TEST_F(FdFileTest, Copy) {
+  art::ScratchFile src_tmp;
+  FdFile src(src_tmp.GetFilename(), O_RDWR, false);
+  ASSERT_GE(src.Fd(), 0);
+  ASSERT_TRUE(src.IsOpened());
+
+  char src_data[] = "Some test data.";
+  ASSERT_TRUE(src.WriteFully(src_data, sizeof(src_data)));  // Including the zero terminator.
+  ASSERT_EQ(0, src.Flush());
+  ASSERT_EQ(static_cast<int64_t>(sizeof(src_data)), src.GetLength());
+
+  art::ScratchFile dest_tmp;
+  FdFile dest(src_tmp.GetFilename(), O_RDWR, false);
+  ASSERT_GE(dest.Fd(), 0);
+  ASSERT_TRUE(dest.IsOpened());
+
+  ASSERT_TRUE(dest.Copy(&src, 0, sizeof(src_data)));
+  ASSERT_EQ(0, dest.Flush());
+  ASSERT_EQ(static_cast<int64_t>(sizeof(src_data)), dest.GetLength());
+
+  char check_data[sizeof(src_data)];
+  ASSERT_TRUE(dest.PreadFully(check_data, sizeof(src_data), 0u));
+  CHECK_EQ(0, memcmp(check_data, src_data, sizeof(src_data)));
+
+  ASSERT_EQ(0, dest.Close());
+  ASSERT_EQ(0, src.Close());
+}
+
+TEST_F(FdFileTest, MoveConstructor) {
+  // New scratch file, zero-length.
+  art::ScratchFile tmp;
+  FdFile file(tmp.GetFilename(), O_RDWR, false);
+  ASSERT_TRUE(file.IsOpened());
+  EXPECT_GE(file.Fd(), 0);
+
+  int old_fd = file.Fd();
+
+  FdFile file2(std::move(file));
+  EXPECT_FALSE(file.IsOpened());
+  EXPECT_TRUE(file2.IsOpened());
+  EXPECT_EQ(old_fd, file2.Fd());
+
+  ASSERT_EQ(file2.Flush(), 0);
+  ASSERT_EQ(file2.Close(), 0);
+}
+
+TEST_F(FdFileTest, OperatorMoveEquals) {
+  // Make sure the read_only_ flag is correctly copied
+  // over.
+  art::ScratchFile tmp;
+  FdFile file(tmp.GetFilename(), O_RDONLY, false);
+  ASSERT_TRUE(file.ReadOnlyMode());
+
+  FdFile file2(tmp.GetFilename(), O_RDWR, false);
+  ASSERT_FALSE(file2.ReadOnlyMode());
+
+  file2 = std::move(file);
+  ASSERT_TRUE(file2.ReadOnlyMode());
+}
+
+TEST_F(FdFileTest, EraseWithPathUnlinks) {
+  // New scratch file, zero-length.
+  art::ScratchFile tmp;
+  std::string filename = tmp.GetFilename();
+  tmp.Close();  // This is required because of the unlink race between the scratch file and the
+                // FdFile, which leads to close-guard breakage.
+  FdFile file(filename, O_RDWR, false);
+  ASSERT_TRUE(file.IsOpened());
+  EXPECT_GE(file.Fd(), 0);
+  uint8_t buffer[16] = { 0 };
+  EXPECT_TRUE(file.WriteFully(&buffer, sizeof(buffer)));
+  EXPECT_EQ(file.Flush(), 0);
+
+  EXPECT_TRUE(file.Erase(true));
+
+  EXPECT_FALSE(file.IsOpened());
+
+  EXPECT_FALSE(art::OS::FileExists(filename.c_str())) << filename;
+}
+
+TEST_F(FdFileTest, Compare) {
+  std::vector<uint8_t> buffer;
+  constexpr int64_t length = 17 * art::KB;
+  for (size_t i = 0; i < length; ++i) {
+    buffer.push_back(static_cast<uint8_t>(i));
+  }
+
+  auto reset_compare = [&](art::ScratchFile& a, art::ScratchFile& b) {
+    a.GetFile()->ResetOffset();
+    b.GetFile()->ResetOffset();
+    return a.GetFile()->Compare(b.GetFile());
+  };
+
+  art::ScratchFile tmp;
+  EXPECT_TRUE(tmp.GetFile()->WriteFully(&buffer[0], length));
+  EXPECT_EQ(tmp.GetFile()->GetLength(), length);
+
+  art::ScratchFile tmp2;
+  EXPECT_TRUE(tmp2.GetFile()->WriteFully(&buffer[0], length));
+  EXPECT_EQ(tmp2.GetFile()->GetLength(), length);
+
+  // Basic equality check.
+  tmp.GetFile()->ResetOffset();
+  tmp2.GetFile()->ResetOffset();
+  // Files should be the same.
+  EXPECT_EQ(reset_compare(tmp, tmp2), 0);
+
+  // Change a byte near the start.
+  ++buffer[2];
+  art::ScratchFile tmp3;
+  EXPECT_TRUE(tmp3.GetFile()->WriteFully(&buffer[0], length));
+  --buffer[2];
+  EXPECT_NE(reset_compare(tmp, tmp3), 0);
+
+  // Change a byte near the middle.
+  ++buffer[length / 2];
+  art::ScratchFile tmp4;
+  EXPECT_TRUE(tmp4.GetFile()->WriteFully(&buffer[0], length));
+  --buffer[length / 2];
+  EXPECT_NE(reset_compare(tmp, tmp4), 0);
+
+  // Change a byte near the end.
+  ++buffer[length - 5];
+  art::ScratchFile tmp5;
+  EXPECT_TRUE(tmp5.GetFile()->WriteFully(&buffer[0], length));
+  --buffer[length - 5];
+  EXPECT_NE(reset_compare(tmp, tmp5), 0);
+
+  // Reference check
+  art::ScratchFile tmp6;
+  EXPECT_TRUE(tmp6.GetFile()->WriteFully(&buffer[0], length));
+  EXPECT_EQ(reset_compare(tmp, tmp6), 0);
+}
+
+TEST_F(FdFileTest, PipeFlush) {
+  int pipefd[2];
+  ASSERT_EQ(0, pipe2(pipefd, O_CLOEXEC));
+
+  FdFile file(pipefd[1], true);
+  ASSERT_TRUE(file.WriteFully("foo", 3));
+  ASSERT_EQ(0, file.Flush());
+  ASSERT_EQ(0, file.FlushCloseOrErase());
+  close(pipefd[0]);
+}
+
+}  // namespace unix_file
diff --git a/libartbase/base/unix_file/random_access_file.h b/libartbase/base/unix_file/random_access_file.h
new file mode 100644
index 0000000..d2124cc
--- /dev/null
+++ b/libartbase/base/unix_file/random_access_file.h
@@ -0,0 +1,68 @@
+/*
+ * Copyright (C) 2009 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.
+ */
+
+#ifndef ART_LIBARTBASE_BASE_UNIX_FILE_RANDOM_ACCESS_FILE_H_
+#define ART_LIBARTBASE_BASE_UNIX_FILE_RANDOM_ACCESS_FILE_H_
+
+#include <stdint.h>
+
+namespace unix_file {
+
+// A file interface supporting random-access reading and writing of content,
+// along with the ability to set the length of a file (smaller or greater than
+// its current extent).
+//
+// This interface does not support a stream position (i.e. every read or write
+// must specify an offset). This interface does not imply any buffering policy.
+//
+// All operations return >= 0 on success or -errno on failure.
+//
+// Implementations never return EINTR; callers are spared the need to manually
+// retry interrupted operations.
+//
+// Any concurrent access to files should be externally synchronized.
+class RandomAccessFile {
+ public:
+  virtual ~RandomAccessFile() { }
+
+  virtual int Close() = 0;
+
+  // Reads 'byte_count' bytes into 'buf' starting at offset 'offset' in the
+  // file. Returns the number of bytes actually read.
+  virtual int64_t Read(char* buf, int64_t byte_count, int64_t offset) const = 0;
+
+  // Sets the length of the file to 'new_length'. If this is smaller than the
+  // file's current extent, data is discarded. If this is greater than the
+  // file's current extent, it is as if a write of the relevant number of zero
+  // bytes occurred. Returns 0 on success.
+  virtual int SetLength(int64_t new_length) = 0;
+
+  // Returns the current size of this file.
+  virtual int64_t GetLength() const = 0;
+
+  // Writes 'byte_count' bytes from 'buf' starting at offset 'offset' in the
+  // file. Zero-byte writes are acceptable, and writes past the end are as if
+  // a write of the relevant number of zero bytes also occurred. Returns the
+  // number of bytes actually written.
+  virtual int64_t Write(const char* buf, int64_t byte_count, int64_t offset) = 0;
+
+  // Flushes file data.
+  virtual int Flush() = 0;
+};
+
+}  // namespace unix_file
+
+#endif  // ART_LIBARTBASE_BASE_UNIX_FILE_RANDOM_ACCESS_FILE_H_
diff --git a/libartbase/base/unix_file/random_access_file_test.h b/libartbase/base/unix_file/random_access_file_test.h
new file mode 100644
index 0000000..1de5f7b
--- /dev/null
+++ b/libartbase/base/unix_file/random_access_file_test.h
@@ -0,0 +1,183 @@
+/*
+ * Copyright (C) 2009 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.
+ */
+
+#ifndef ART_LIBARTBASE_BASE_UNIX_FILE_RANDOM_ACCESS_FILE_TEST_H_
+#define ART_LIBARTBASE_BASE_UNIX_FILE_RANDOM_ACCESS_FILE_TEST_H_
+
+#include <errno.h>
+#include <memory>
+#include <string>
+
+#include "common_runtime_test.h"
+
+namespace unix_file {
+
+class RandomAccessFileTest : public testing::Test {
+ protected:
+  virtual ~RandomAccessFileTest() {
+  }
+
+  // Override this to return an instance of the subclass under test that's
+  // backed by a temporary file.
+  virtual RandomAccessFile* MakeTestFile() = 0;
+
+  virtual void SetUp() {
+    art::CommonRuntimeTest::SetUpAndroidData(android_data_);
+  }
+
+  virtual void TearDown() {
+    art::CommonRuntimeTest::TearDownAndroidData(android_data_, true);
+  }
+
+  std::string GetTmpPath(const std::string& name) {
+    std::string path;
+    path = android_data_;
+    path += "/";
+    path += name;
+    return path;
+  }
+
+  // TODO(enh): ReadString (and WriteString) might be generally useful.
+  static bool ReadString(RandomAccessFile* f, std::string* s) {
+    s->clear();
+    char buf[256];
+    int64_t n = 0;
+    int64_t offset = 0;
+    while ((n = f->Read(buf, sizeof(buf), offset)) > 0) {
+      s->append(buf, n);
+      offset += n;
+    }
+    return n != -1;
+  }
+
+  void TestRead() {
+    char buf[256];
+    std::unique_ptr<RandomAccessFile> file(MakeTestFile());
+
+    // Reading from the start of an empty file gets you zero bytes, however many
+    // you ask for.
+    ASSERT_EQ(0, file->Read(buf, 0, 0));
+    ASSERT_EQ(0, file->Read(buf, 123, 0));
+
+    const std::string content("hello");
+    ASSERT_EQ(content.size(), static_cast<uint64_t>(file->Write(content.data(), content.size(), 0)));
+
+    TestReadContent(content, file.get());
+
+    CleanUp(file.get());
+  }
+
+  void TestReadContent(const std::string& content, RandomAccessFile* file) {
+    const int buf_size = content.size() + 10;
+    std::unique_ptr<char[]> buf(new char[buf_size]);
+    // Can't read from a negative offset.
+    ASSERT_EQ(-EINVAL, file->Read(buf.get(), 0, -123));
+
+    // Reading too much gets us just what's in the file.
+    ASSERT_EQ(content.size(), static_cast<uint64_t>(file->Read(buf.get(), buf_size, 0)));
+    ASSERT_EQ(std::string(buf.get(), content.size()), content);
+
+    // We only get as much as we ask for.
+    const size_t short_request = 2;
+    ASSERT_LT(short_request, content.size());
+    ASSERT_EQ(short_request, static_cast<uint64_t>(file->Read(buf.get(), short_request, 0)));
+    ASSERT_EQ(std::string(buf.get(), short_request),
+              content.substr(0, short_request));
+
+    // We don't have to start at the beginning.
+    const int non_zero_offset = 2;
+    ASSERT_GT(non_zero_offset, 0);
+    ASSERT_EQ(short_request, static_cast<uint64_t>(file->Read(buf.get(), short_request,
+                                                              non_zero_offset)));
+    ASSERT_EQ(std::string(buf.get(), short_request),
+              content.substr(non_zero_offset, short_request));
+
+    // Reading past the end gets us nothing.
+    ASSERT_EQ(0, file->Read(buf.get(), buf_size, file->GetLength()));
+    ASSERT_EQ(0, file->Read(buf.get(), buf_size, file->GetLength() + 1));
+  }
+
+  void TestSetLength() {
+    const std::string content("hello");
+    std::unique_ptr<RandomAccessFile> file(MakeTestFile());
+    ASSERT_EQ(content.size(), static_cast<uint64_t>(file->Write(content.data(), content.size(), 0)));
+    ASSERT_EQ(content.size(), static_cast<uint64_t>(file->GetLength()));
+
+    // Can't give a file a negative length.
+    ASSERT_EQ(-EINVAL, file->SetLength(-123));
+
+    // Can truncate the file.
+    int64_t new_length = 2;
+    ASSERT_EQ(0, file->SetLength(new_length));
+    ASSERT_EQ(new_length, file->GetLength());
+    std::string new_content;
+    ASSERT_TRUE(ReadString(file.get(), &new_content));
+    ASSERT_EQ(content.substr(0, 2), new_content);
+
+    // Expanding the file appends zero bytes.
+    new_length = file->GetLength() + 1;
+    ASSERT_EQ(0, file->SetLength(new_length));
+    ASSERT_EQ(new_length, file->GetLength());
+    ASSERT_TRUE(ReadString(file.get(), &new_content));
+    ASSERT_EQ('\0', new_content[new_length - 1]);
+
+    CleanUp(file.get());
+  }
+
+  void TestWrite() {
+    const std::string content("hello");
+    std::unique_ptr<RandomAccessFile> file(MakeTestFile());
+
+    // Can't write to a negative offset.
+    ASSERT_EQ(-EINVAL, file->Write(content.data(), 0, -123));
+
+    // Writing zero bytes of data is a no-op.
+    ASSERT_EQ(0, file->Write(content.data(), 0, 0));
+    ASSERT_EQ(0, file->GetLength());
+
+    // We can write data.
+    ASSERT_EQ(content.size(), static_cast<uint64_t>(file->Write(content.data(), content.size(), 0)));
+    ASSERT_EQ(content.size(), static_cast<uint64_t>(file->GetLength()));
+    std::string new_content;
+    ASSERT_TRUE(ReadString(file.get(), &new_content));
+    ASSERT_EQ(new_content, content);
+
+    // We can read it back.
+    char buf[256];
+    ASSERT_EQ(content.size(), static_cast<uint64_t>(file->Read(buf, sizeof(buf), 0)));
+    ASSERT_EQ(std::string(buf, content.size()), content);
+
+    // We can append data past the end.
+    ASSERT_EQ(content.size(), static_cast<uint64_t>(file->Write(content.data(), content.size(),
+                                                                file->GetLength() + 1)));
+    int64_t new_length = 2*content.size() + 1;
+    ASSERT_EQ(file->GetLength(), new_length);
+    ASSERT_TRUE(ReadString(file.get(), &new_content));
+    ASSERT_EQ(std::string("hello\0hello", new_length), new_content);
+
+    CleanUp(file.get());
+  }
+
+  virtual void CleanUp(RandomAccessFile* file ATTRIBUTE_UNUSED) {
+  }
+
+ protected:
+  std::string android_data_;
+};
+
+}  // namespace unix_file
+
+#endif  // ART_LIBARTBASE_BASE_UNIX_FILE_RANDOM_ACCESS_FILE_TEST_H_
diff --git a/libartbase/base/unix_file/random_access_file_utils.cc b/libartbase/base/unix_file/random_access_file_utils.cc
new file mode 100644
index 0000000..aae65c1
--- /dev/null
+++ b/libartbase/base/unix_file/random_access_file_utils.cc
@@ -0,0 +1,40 @@
+/*
+ * Copyright (C) 2009 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 "base/unix_file/random_access_file_utils.h"
+
+#include <vector>
+
+#include "base/unix_file/random_access_file.h"
+
+namespace unix_file {
+
+bool CopyFile(const RandomAccessFile& src, RandomAccessFile* dst) {
+  // We don't call src->GetLength because some files (those in /proc, say)
+  // don't know how long they are. We just read until there's nothing left.
+  std::vector<char> buf(4096);
+  int64_t offset = 0;
+  int64_t n;
+  while ((n = src.Read(&buf[0], buf.size(), offset)) > 0) {
+    if (dst->Write(&buf[0], n, offset) != n) {
+      return false;
+    }
+    offset += n;
+  }
+  return n >= 0;
+}
+
+}  // namespace unix_file
diff --git a/libartbase/base/unix_file/random_access_file_utils.h b/libartbase/base/unix_file/random_access_file_utils.h
new file mode 100644
index 0000000..47c4c2a
--- /dev/null
+++ b/libartbase/base/unix_file/random_access_file_utils.h
@@ -0,0 +1,30 @@
+/*
+ * Copyright (C) 2009 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.
+ */
+
+#ifndef ART_LIBARTBASE_BASE_UNIX_FILE_RANDOM_ACCESS_FILE_UTILS_H_
+#define ART_LIBARTBASE_BASE_UNIX_FILE_RANDOM_ACCESS_FILE_UTILS_H_
+
+namespace unix_file {
+
+class RandomAccessFile;
+
+// Copies from 'src' to 'dst'. Reads all the data from 'src', and writes it
+// to 'dst'. Not thread-safe. Neither file will be closed.
+bool CopyFile(const RandomAccessFile& src, RandomAccessFile* dst);
+
+}  // namespace unix_file
+
+#endif  // ART_LIBARTBASE_BASE_UNIX_FILE_RANDOM_ACCESS_FILE_UTILS_H_