libc/src/__support/File/dir.h

   1 //===--- A platform independent Dir class ---------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #ifndef LLVM_LIBC_SRC_SUPPORT_FILE_DIR_H
  10 #define LLVM_LIBC_SRC_SUPPORT_FILE_DIR_H
  11
  12 #include "src/__support/CPP/span.h"
  13 #include "src/__support/error_or.h"
  14 #include "src/__support/threads/mutex.h"
  15
  16 #include <dirent.h>
  17 #include <stdlib.h>
  18
  19 namespace __llvm_libc {
  20
  21 // Platform specific function which will open the directory |name|
  22 // and return its file descriptor. Upon failure, the error value is returned.
  23 ErrorOr<int> platform_opendir(const char *name);
  24
  25 // Platform specific function which will close the directory with
  26 // file descriptor |fd|. Returns 0 on success, or the error number on failure.
  27 int platform_closedir(int fd);
  28
  29 // Platform specific function which will fetch dirents in to buffer.
  30 // Returns the number of bytes written into buffer or the error number on
  31 // failure.
  32 ErrorOr<size_t> platform_fetch_dirents(int fd, cpp::span<uint8_t> buffer);
  33
  34 // This class is designed to allow implementation of the POSIX dirent.h API.
  35 // By itself, it is platform independent but calls platform specific
  36 // functions to perform OS operations.
  37 class Dir {
  38   static constexpr size_t BUFSIZE = 1024;
  39   int fd;
  40   size_t readptr = 0;  // The current read pointer.
  41   size_t fillsize = 0; // The number of valid bytes availabe in the buffer.
  42
  43   // This is a buffer of struct dirent values which will be fetched
  44   // from the OS. Since the d_name of struct dirent can be of a variable
  45   // size, we store the data in a byte array.
  46   uint8_t buffer[BUFSIZE];
  47
  48   Mutex mutex;
  49
  50   // A directory is to be opened by the static method open and closed
  51   // by the close method. So, all constructors and destructor are declared
  52   // as private. Inappropriate constructors are declared as deleted.
  53   Dir() = delete;
  54   Dir(const Dir &) = delete;
  55
  56   explicit Dir(int fdesc)
  57       : fd(fdesc), readptr(0), fillsize(0), mutex(false, false, false) {}
  58   ~Dir() = default;
  59
  60   Dir &operator=(const Dir &) = delete;
  61
  62 public:
  63   static ErrorOr<Dir *> open(const char *path);
  64
  65   ErrorOr<struct ::dirent *> read();
  66
  67   // Returns 0 on success or the error number on failure. If an error number
  68   // was returned, then the resources associated with the directory are not
  69   // cleaned up.
  70   int close();
  71
  72   int getfd() { return fd; }
  73 };
  74
  75 } // namespace __llvm_libc
  76
  77 #endif // LLVM_LIBC_SRC_SUPPORT_FILE_DIR_H