libc/src/__support/File/linux/file.cpp

   1 //===--- Implementation of the Linux specialization of File ---------------===//
   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 #include "file.h"
  10
  11 #include "src/__support/File/file.h"
  12
  13 #include "src/__support/CPP/new.h"
  14 #include "src/__support/File/linux/lseekImpl.h"
  15 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
  16 #include "src/errno/libc_errno.h"         // For error macros
  17
  18 #include <fcntl.h> // For mode_t and other flags to the open syscall
  19 #include <stdio.h>
  20 #include <sys/syscall.h> // For syscall numbers
  21
  22 namespace LIBC_NAMESPACE {
  23
  24 FileIOResult linux_file_write(File *f, const void *data, size_t size) {
  25   auto *lf = reinterpret_cast<LinuxFile *>(f);
  26   int ret =
  27       LIBC_NAMESPACE::syscall_impl<int>(SYS_write, lf->get_fd(), data, size);
  28   if (ret < 0) {
  29     return {0, -ret};
  30   }
  31   return ret;
  32 }
  33
  34 FileIOResult linux_file_read(File *f, void *buf, size_t size) {
  35   auto *lf = reinterpret_cast<LinuxFile *>(f);
  36   int ret =
  37       LIBC_NAMESPACE::syscall_impl<int>(SYS_read, lf->get_fd(), buf, size);
  38   if (ret < 0) {
  39     return {0, -ret};
  40   }
  41   return ret;
  42 }
  43
  44 ErrorOr<long> linux_file_seek(File *f, long offset, int whence) {
  45   auto *lf = reinterpret_cast<LinuxFile *>(f);
  46   auto result = internal::lseekimpl(lf->get_fd(), offset, whence);
  47   if (!result.has_value())
  48     return result.error();
  49   return result.value();
  50 }
  51
  52 int linux_file_close(File *f) {
  53   auto *lf = reinterpret_cast<LinuxFile *>(f);
  54   int ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_close, lf->get_fd());
  55   if (ret < 0) {
  56     return -ret;
  57   }
  58   delete lf;
  59   return 0;
  60 }
  61
  62 ErrorOr<File *> openfile(const char *path, const char *mode) {
  63   using ModeFlags = File::ModeFlags;
  64   auto modeflags = File::mode_flags(mode);
  65   if (modeflags == 0) {
  66     // return {nullptr, EINVAL};
  67     return Error(EINVAL);
  68   }
  69   long open_flags = 0;
  70   if (modeflags & ModeFlags(File::OpenMode::APPEND)) {
  71     open_flags = O_CREAT | O_APPEND;
  72     if (modeflags & ModeFlags(File::OpenMode::PLUS))
  73       open_flags |= O_RDWR;
  74     else
  75       open_flags |= O_WRONLY;
  76   } else if (modeflags & ModeFlags(File::OpenMode::WRITE)) {
  77     open_flags = O_CREAT | O_TRUNC;
  78     if (modeflags & ModeFlags(File::OpenMode::PLUS))
  79       open_flags |= O_RDWR;
  80     else
  81       open_flags |= O_WRONLY;
  82   } else {
  83     if (modeflags & ModeFlags(File::OpenMode::PLUS))
  84       open_flags |= O_RDWR;
  85     else
  86       open_flags |= O_RDONLY;
  87   }
  88
  89   // File created will have 0666 permissions.
  90   constexpr long OPEN_MODE =
  91       S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH;
  92
  93 #ifdef SYS_open
  94   int fd =
  95       LIBC_NAMESPACE::syscall_impl<int>(SYS_open, path, open_flags, OPEN_MODE);
  96 #elif defined(SYS_openat)
  97   int fd = LIBC_NAMESPACE::syscall_impl<int>(SYS_openat, AT_FDCWD, path,
  98                                              open_flags, OPEN_MODE);
  99 #else
 100 #error "open and openat syscalls not available."
 101 #endif
 102
 103   if (fd < 0)
 104     return Error(-fd);
 105
 106   uint8_t *buffer;
 107   {
 108     AllocChecker ac;
 109     buffer = new (ac) uint8_t[File::DEFAULT_BUFFER_SIZE];
 110     if (!ac)
 111       return Error(ENOMEM);
 112   }
 113   AllocChecker ac;
 114   auto *file = new (ac)
 115       LinuxFile(fd, buffer, File::DEFAULT_BUFFER_SIZE, _IOFBF, true, modeflags);
 116   if (!ac)
 117     return Error(ENOMEM);
 118   return file;
 119 }
 120
 121 int get_fileno(File *f) {
 122   auto *lf = reinterpret_cast<LinuxFile *>(f);
 123   return lf->get_fd();
 124 }
 125
 126 } // namespace LIBC_NAMESPACE