POSIX: don't allocate memory after forking.

base/dir_reader_linux.h

+// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_DIR_READER_LINUX_H_
+#define BASE_DIR_READER_LINUX_H_
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stdint.h>
+#include <sys/syscall.h>
+#include <unistd.h>
+
+#include "base/logging.h"
+#include "base/eintr_wrapper.h"
+
+// See the comments in dir_reader_posix.h about this.
+
+namespace base {
+
+struct linux_dirent {
+  uint64_t        d_ino;
+  int64_t         d_off;
+  unsigned short  d_reclen;
+  unsigned char   d_type;
+  char            d_name[0];
+};
+
+class DirReaderLinux {
+ public:
+  explicit DirReaderLinux(const char* directory_path)
+      : fd_(open(directory_path, O_RDONLY | O_DIRECTORY)),
+        offset_(0),
+        size_(0) {
+  }
+
+  ~DirReaderLinux() {
+    if (fd_ >= 0) {
+      if (HANDLE_EINTR(close(fd_)))
+        RAW_LOG(ERROR, "Failed to close directory handle");
+    }
+  }
+
+  bool IsValid() const {
+    return fd_ >= 0;
+  }
+
+  // Move to the next entry returning false if the iteration is complete.
+  bool Next() {
+    if (size_) {
+      linux_dirent* dirent = reinterpret_cast<linux_dirent*>(&buf_[offset_]);
+      offset_ += dirent->d_reclen;
+    }
+
+    if (offset_ != size_)
+      return true;
+
+    const int r = syscall(__NR_getdents64, fd_, buf_, sizeof(buf_));
+    if (r == 0)
+      return false;
+    if (r == -1) {
+      DPLOG(FATAL) << "getdents64 returned an error: " << errno;
+      return false;
+    }
+    size_ = r;
+    offset_ = 0;
+    return true;
+  }
+
+  const char* name() const {
+    if (!size_)
+      return NULL;
+
+    const linux_dirent* dirent =
+        reinterpret_cast<const linux_dirent*>(&buf_[offset_]);
+    return dirent->d_name;
+  }
+
+  int fd() const {
+    return fd_;
+  }
+
+  static bool IsFallback() {
+    return false;
+  }
+
+ private:
+  const int fd_;
+  unsigned char buf_[512];
+  size_t offset_, size_;
+
+  DISALLOW_COPY_AND_ASSIGN(DirReaderLinux);
+};
+
+}  // namespace base
+
+#endif // BASE_DIR_READER_LINUX_H_