summary refs log tree commit diff stats
path: root/lib/std/tempfiles.nim
blob: 1e1bbd403facde018b950af37ea94520650b46c7 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
#
#
#            Nim's Runtime Library
#        (c) Copyright 2021 Nim contributors
#
#    See the file "copying.txt", included in this
#    distribution, for details about the copyright.
#

## This module creates temporary files and directories.

import os, random


const
  maxRetry = 10000
  letters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
  nimTempPathLength {.intdefine.} = 8


when defined(windows):
  import winlean

  var O_RDWR {.importc: "_O_RDWR", header: "<fcntl.h>".}: cint

  proc c_fdopen(
    filehandle: cint,
    mode: cstring
  ): File {.importc: "_fdopen",header: "<stdio.h>".}

  proc open_osfhandle(osh: Handle, mode: cint): cint {.
    importc: "_open_osfhandle", header: "<io.h>".}

  proc close_osfandle(fd: cint): cint {.
    importc: "_close", header: "<io.h>".}
else:
  import posix

  proc c_fdopen(
    filehandle: cint,
    mode: cstring
  ): File {.importc: "fdopen",header: "<stdio.h>".}


proc safeOpen(filename: string): File =
  ## Open files exclusively.
  when defined(windows):
    let dwShareMode = FILE_SHARE_DELETE or FILE_SHARE_READ or FILE_SHARE_WRITE
    let dwCreation = CREATE_NEW
    let dwFlags = FILE_FLAG_BACKUP_SEMANTICS or FILE_ATTRIBUTE_NORMAL
    let handle = createFileW(newWideCString(filename), GENERIC_READ or GENERIC_WRITE, dwShareMode,
                              nil, dwCreation, dwFlags, Handle(0))

    if handle == INVALID_HANDLE_VALUE:
      raiseOSError(osLastError(), filename)

    let fileHandle = open_osfhandle(handle, O_RDWR)
    if fileHandle == -1:
      discard closeHandle(handle)
      raiseOSError(osLastError(), filename)

    result = c_fdopen(fileHandle, "w+")
    if result == nil:
      discard close_osfandle(fileHandle)
      raiseOSError(osLastError(), filename)
  else:
    let flags = posix.O_RDWR or posix.O_CREAT or posix.O_EXCL

    let fileHandle = posix.open(filename, flags)
    if fileHandle == -1:
      raiseOSError(osLastError(), filename)

    result = c_fdopen(fileHandle, "w+")
    if result == nil:
      discard posix.close(fileHandle) # TODO handles failure when closing file
      raiseOSError(osLastError(), filename)

template randomPathName(length: Natural): string =
  var res = newString(length)
  var state = initRand()
  for i in 0 ..< length:
    res[i] = state.sample(letters)
  res

proc createTempFile*(prefix, suffix: string, dir = ""): tuple[fd: File, path: string] =
  ## `createTempFile` creates a new temporary file in the directory `dir`.
  ## 
  ## If `dir` is the empty string, the default directory for temporary files
  ## (`getTempDir <os.html#getTempDir>`_) will be used.
  ## The temporary file name begins with `prefix` and ends with `suffix`.
  ## `createTempFile` returns a file handle to an open file and the path of that file.
  ## 
  ## If failing to create a temporary file, `IOError` will be raised.
  ##
  ## .. note:: It is the caller's responsibility to remove the file when no longer needed.
  ##
  var dir = dir
  if dir.len == 0:
    dir = getTempDir()

  createDir(dir)

  for i in 0 ..< maxRetry:
    result.path = dir / (prefix & randomPathName(nimTempPathLength) & suffix)
    try:
      result.fd = safeOpen(result.path)
    except OSError:
      continue
    return

  raise newException(IOError, "Failed to create a temporary file under directory " & dir)

proc createTempDir*(prefix, suffix: string, dir = ""): string =
  ## `createTempDir` creates a new temporary directory in the directory `dir`.
  ##
  ## If `dir` is the empty string, the default directory for temporary files
  ## (`getTempDir <os.html#getTempDir>`_) will be used.
  ## The temporary directory name begins with `prefix` and ends with `suffix`.
  ## `createTempDir` returns the path of that temporary firectory.
  ##
  ## If failing to create a temporary directory, `IOError` will be raised.
  ##
  ## .. note:: It is the caller's responsibility to remove the directory when no longer needed.
  ##
  var dir = dir
  if dir.len == 0:
    dir = getTempDir()

  createDir(dir)

  for i in 0 ..< maxRetry:
    result = dir / (prefix & randomPathName(nimTempPathLength) & suffix)
    try:
      if not existsOrCreateDir(result):
        return
    except OSError:
      continue

  raise newException(IOError, "Failed to create a temporary directory under directory " & dir)