Reland of Initial version of file wrapper

webrtc/base/file_posix.cc

+/*
+ *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "webrtc/base/file.h"
+
+#include <errno.h>
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <limits>
+
+#include "webrtc/base/checks.h"
+
+namespace rtc {
+
+File File::Open(const std::string& path) {
+  return File(::open(path.c_str(), O_RDWR));
+}
+
+size_t File::Write(const uint8_t* data, size_t length) {
+  size_t total_written = 0;
+  do {
+    ssize_t written;
+    do {
+      written = ::write(file_, data + total_written, length - total_written);
+    } while (written == -1 && errno == EINTR);
+    if (written == -1)
+      break;
+    total_written += written;
+  } while (total_written < length);
+  return total_written;
+}
+
+size_t File::Read(uint8_t* buffer, size_t length) {
+  size_t total_read = 0;
+  do {
+    ssize_t read;
+    do {
+      read = ::read(file_, buffer + total_read, length - total_read);
+    } while (read == -1 && errno == EINTR);
+    if (read == -1)
+      break;
+    total_read += read;
+  } while (total_read < length);
+  return total_read;
+}
+
+size_t File::WriteAt(const uint8_t* data, size_t length, size_t offset) {
+  size_t total_written = 0;
+  do {
+    ssize_t written;
+    do {
+      written = ::pwrite(file_, data + total_written, length - total_written,
+                         offset + total_written);
+    } while (written == -1 && errno == EINTR);
+    if (written == -1)
+      break;
+    total_written += written;
+  } while (total_written < length);
+  return total_written;
+}
+
+size_t File::ReadAt(uint8_t* buffer, size_t length, size_t offset) {
+  size_t total_read = 0;
+  do {
+    ssize_t read;
+    do {
+      read = ::pread(file_, buffer + total_read, length - total_read,
+                     offset + total_read);
+    } while (read == -1 && errno == EINTR);
+    if (read == -1)
+      break;
+    total_read += read;
+  } while (total_read < length);
+  return total_read;
+}
+
+bool File::Seek(size_t offset) {
+  RTC_DCHECK_LE(offset, static_cast<size_t>(std::numeric_limits<off_t>::max()));
+  return lseek(file_, static_cast<off_t>(offset), SEEK_SET) != -1;
+}
+
+bool File::Close() {
+  if (file_ == rtc::kInvalidPlatformFileValue)
+    return false;
+  bool ret = close(file_) == 0;
+  file_ = rtc::kInvalidPlatformFileValue;
+  return ret;
+}
+
+}  // namespace rtc