Implement File.tempfile in Crystal

spec/std/file/tempfile_spec.cr

@@ -1,4 +1,34 @@
 require "../spec_helper"
+require "../../support/tempfile"
+
+private class TestRNG(T)
+  include Random
+
+  def initialize(@data : Array(T))
+    @i = 0
+  end
+
+  def next_u : T
+    i = @i
+    @i = (i + 1) % @data.size
+    @data[i]
+  end
+
+  def reset
+    @i = 0
+  end
+end
+
+private def normalize_permissions(permissions, *, directory)
+  {% if flag?(:win32) %}
+    normalized_permissions = 0o444
+    normalized_permissions |= 0o222 if permissions.bits_set?(0o200)
+    normalized_permissions |= 0o111 if directory
+    File::Permissions.new(normalized_permissions)
+  {% else %}
+    File::Permissions.new(permissions)
+  {% end %}
+end
 
 describe File do
   describe ".tempname" do
@@ -42,6 +72,7 @@ describe File do
     it "creates and writes" do
       tempfile = File.tempfile
       tempfile.print "Hello!"
+      tempfile.info.permissions.should eq normalize_permissions(0o600, directory: false)
       tempfile.close
 
       File.exists?(tempfile.path).should be_true
@@ -53,6 +84,7 @@ describe File do
     it "accepts single suffix argument" do
       tempfile = File.tempfile ".bar"
       tempfile.print "Hello!"
+      tempfile.info.permissions.should eq normalize_permissions(0o600, directory: false)
       tempfile.close
 
       File.extname(tempfile.path).should eq(".bar")
@@ -66,6 +98,7 @@ describe File do
     it "accepts prefix and suffix arguments" do
       tempfile = File.tempfile "foo", ".bar"
       tempfile.print "Hello!"
+      tempfile.info.permissions.should eq normalize_permissions(0o600, directory: false)
       tempfile.close
 
       File.extname(tempfile.path).should eq(".bar")
@@ -156,3 +189,41 @@ describe File do
     end
   end
 end
+
+describe Crystal::System::File do
+  describe ".mktemp" do
+    it "creates random file name" do
+      with_tempfile "random-path" do |tempdir|
+        Dir.mkdir tempdir
+        fd, path = Crystal::System::File.mktemp("A", "Z", dir: tempdir, random: TestRNG.new([7, 8, 9, 10, 11, 12, 13, 14]))
+        path.should eq Path[tempdir, "A789abcdeZ"].to_s
+      ensure
+        File.from_fd(path, fd).close if fd && path
+      end
+    end
+
+    it "retries when file exists" do
+      with_tempfile "retry" do |tempdir|
+        Dir.mkdir tempdir
+        existing_path = Path[tempdir, "A789abcdeZ"]
+        File.touch existing_path
+        fd, path = Crystal::System::File.mktemp("A", "Z", dir: tempdir, random: TestRNG.new([7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22]))
+        path.should eq File.join(tempdir, "AfghijklmZ")
+      ensure
+        File.from_fd(path, fd).close if fd && path
+      end
+    end
+
+    it "raises when no valid path is found" do
+      with_tempfile "random-path" do |tempdir|
+        Dir.mkdir tempdir
+        File.touch Path[tempdir, "A789abcdeZ"]
+        expect_raises(File::AlreadyExistsError, "Error creating temporary file") do
+          fd, path = Crystal::System::File.mktemp("A", "Z", dir: tempdir, random: TestRNG.new([7, 8, 9, 10, 11, 12, 13, 14]))
+        ensure
+          File.from_fd(path, fd).close if fd && path
+        end
+      end
+    end
+  end
+end

src/crystal/system/file.cr

@@ -47,6 +47,43 @@ module Crystal::System::File
     m | o
   end
 
+  LOWER_ALPHANUM = "0123456789abcdefghijklmnopqrstuvwxyz".to_slice
+
+  def self.mktemp(prefix : String?, suffix : String?, dir : String, random : ::Random = ::Random::DEFAULT) : {LibC::Int, String}
+    mode = LibC::O_RDWR | LibC::O_CREAT | LibC::O_EXCL
+    perm = ::File::Permissions.new(0o600)
+
+    prefix = ::File.join(dir, prefix || "")
+    bytesize = prefix.bytesize + 8 + (suffix.try(&.bytesize) || 0)
+
+    100.times do
+      path = String.build(bytesize) do |io|
+        io << prefix
+        8.times do
+          io.write_byte LOWER_ALPHANUM.sample(random)
+        end
+        io << suffix
+      end
+
+      fd, errno = open(path, mode, perm)
+
+      if errno.none?
+        return {fd, path}
+      elsif error_is_file_exists?(errno)
+        # retry
+        next
+      else
+        raise ::File::Error.from_os_error("Error creating temporary file", errno, file: path)
+      end
+    end
+
+    raise ::File::AlreadyExistsError.new("Error creating temporary file", file: "#{prefix}********#{suffix}")
+  end
+
+  private def self.error_is_file_exists?(errno)
+    Errno.value.in?(Errno::EEXIST, WinError::ERROR_ALREADY_EXISTS)
+  end
+
   # Closes the internal file descriptor without notifying libevent.
   # This is directly used after the fork of a process to close the
   # parent's Crystal::Signal.@@pipe reference before re initializing

src/crystal/system/unix/file.cr

@@ -3,32 +3,25 @@ require "file/error"
 
 # :nodoc:
 module Crystal::System::File
-  def self.open(filename, mode, perm)
-    oflag = open_flag(mode) | LibC::O_CLOEXEC
+  def self.open(filename : String, mode : String, perm : Int32 | ::File::Permissions)
+    perm = ::File::Permissions.new(perm) if perm.is_a? Int32
 
-    fd = LibC.open(filename.check_no_null_byte, oflag, perm)
-    if fd < 0
-      raise ::File::Error.from_errno("Error opening file with mode '#{mode}'", file: filename)
+    fd, errno = open(filename, open_flag(mode), perm)
+
+    unless errno.none?
+      raise ::File::Error.from_os_error("Error opening file with mode '#{mode}'", errno, file: filename)
     end
+
     fd
   end
 
-  def self.mktemp(prefix, suffix, dir) : {LibC::Int, String}
-    prefix.try &.check_no_null_byte
-    suffix.try &.check_no_null_byte
-    dir.check_no_null_byte
-
-    dir = dir + ::File::SEPARATOR
-    path = "#{dir}#{prefix}.XXXXXX#{suffix}"
+  def self.open(filename : String, flags : Int32, perm : ::File::Permissions) : {LibC::Int, Errno}
+    filename.check_no_null_byte
+    flags |= LibC::O_CLOEXEC
 
-    if suffix
-      fd = LibC.mkstemps(path, suffix.bytesize)
-    else
-      fd = LibC.mkstemp(path)
-    end
+    fd = LibC.open(filename, flags, perm)
 
-    raise ::File::Error.from_errno("Error creating temporary file", file: path) if fd == -1
-    {fd, path}
+    {fd, fd < 0 ? Errno.value : Errno::NONE}
   end
 
   def self.info?(path : String, follow_symlinks : Bool) : ::File::Info?

src/crystal/system/wasi/file.cr

@@ -34,10 +34,6 @@ module Crystal::System::File
     raise NotImplementedError.new "Crystal::System::File#flock"
   end
 
-  def self.mktemp(prefix, suffix, dir) : {LibC::Int, String}
-    raise NotImplementedError.new "Crystal::System::File.mktemp"
-  end
-
   def self.delete(path : String, *, raise_on_missing : Bool) : Bool
     raise NotImplementedError.new "Crystal::System::File.delete"
   end

src/crystal/system/win32/file.cr

@@ -9,8 +9,6 @@ require "c/handleapi"
 module Crystal::System::File
   def self.open(filename : String, mode : String, perm : Int32 | ::File::Permissions) : LibC::Int
     perm = ::File::Permissions.new(perm) if perm.is_a? Int32
-    oflag = open_flag(mode) | LibC::O_BINARY | LibC::O_NOINHERIT
-
     # Only the owner writable bit is used, since windows only supports
     # the read only attribute.
     if perm.owner_write?
@@ -19,24 +17,20 @@ module Crystal::System::File
       perm = LibC::S_IREAD
     end
 
-    fd = LibC._wopen(System.to_wstr(filename), oflag, perm)
-    if fd == -1
-      raise ::File::Error.from_errno("Error opening file with mode '#{mode}'", file: filename)
+    fd, errno = open(filename, open_flag(mode), ::File::Permissions.new(perm))
+    unless errno.none?
+      raise ::File::Error.from_os_error("Error opening file with mode '#{mode}'", errno, file: filename)
     end
 
     fd
   end
 
-  def self.mktemp(prefix : String?, suffix : String?, dir : String) : {LibC::Int, String}
-    path = "#{dir}#{::File::SEPARATOR}#{prefix}.#{::Random::Secure.hex}#{suffix}"
+  def self.open(filename : String, flags : Int32, perm : ::File::Permissions) : {LibC::Int, Errno}
+    flags |= LibC::O_BINARY | LibC::O_NOINHERIT
 
-    mode = LibC::O_RDWR | LibC::O_CREAT | LibC::O_EXCL | LibC::O_BINARY | LibC::O_NOINHERIT
-    fd = LibC._wopen(System.to_wstr(path), mode, ::File::DEFAULT_CREATE_PERMISSIONS)
-    if fd == -1
-      raise ::File::Error.from_errno("Error creating temporary file", file: path)
-    end
+    fd = LibC._wopen(System.to_wstr(filename), flags, perm)
 
-    {fd, path}
+    {fd, fd == -1 ? Errno.value : Errno::NONE}
   end
 
   NOT_FOUND_ERRORS = {

src/file.cr

@@ -94,6 +94,11 @@ class File < IO::FileDescriptor
     super(fd, blocking)
   end
 
+  # :nodoc:
+  def self.from_fd(path : String, fd : Int, *, blocking = false, encoding = nil, invalid = nil)
+    new(path, fd, blocking: blocking, encoding: encoding, invalid: invalid)
+  end
+
   # Opens the file named by *filename*.
   #
   # *mode* must be one of the following file open modes:

src/lib_c/aarch64-darwin/c/fcntl.cr

@@ -12,6 +12,7 @@ lib LibC
   O_CREAT    =    0x0200
   O_NOFOLLOW =    0x0100
   O_TRUNC    =    0x0400
+  O_EXCL     =    0x0800
   O_APPEND   =    0x0008
   O_NONBLOCK =    0x0004
   O_SYNC     =    0x0080

src/lib_c/aarch64-linux-gnu/c/fcntl.cr

@@ -10,6 +10,7 @@ lib LibC
   FD_CLOEXEC =         1
   O_CLOEXEC  = 0o2000000
   O_CREAT    =     0o100
+  O_EXCL     =     0o200
   O_NOFOLLOW =  0o100000
   O_TRUNC    =    0o1000
   O_APPEND   =    0o2000

src/lib_c/aarch64-linux-musl/c/fcntl.cr

@@ -10,6 +10,7 @@ lib LibC
   FD_CLOEXEC =         1
   O_CLOEXEC  = 0o2000000
   O_CREAT    =     0o100
+  O_EXCL     =     0o200
   O_NOFOLLOW =  0o100000
   O_TRUNC    =    0o1000
   O_APPEND   =    0o2000

src/lib_c/arm-linux-gnueabihf/c/fcntl.cr

@@ -10,6 +10,7 @@ lib LibC
   FD_CLOEXEC =         1
   O_CLOEXEC  = 0o2000000
   O_CREAT    =     0o100
+  O_EXCL     =     0o200
   O_NOFOLLOW =  0o100000
   O_TRUNC    =    0o1000
   O_APPEND   =    0o2000

src/lib_c/i386-linux-gnu/c/fcntl.cr

@@ -10,6 +10,7 @@ lib LibC
   FD_CLOEXEC =         1
   O_CLOEXEC  = 0o2000000
   O_CREAT    =     0o100
+  O_EXCL     =     0o200
   O_NOFOLLOW =  0o400000
   O_TRUNC    =    0o1000
   O_APPEND   =    0o2000

src/lib_c/i386-linux-musl/c/fcntl.cr

@@ -10,6 +10,7 @@ lib LibC
   FD_CLOEXEC =         1
   O_CLOEXEC  = 0o2000000
   O_CREAT    =     0o100
+  O_EXCL     =     0o200
   O_NOFOLLOW =  0o400000
   O_TRUNC    =    0o1000
   O_APPEND   =    0o2000

src/lib_c/wasm32-wasi/c/fcntl.cr

@@ -10,6 +10,7 @@ lib LibC
   FD_CLOEXEC = 1
   O_CLOEXEC  = 0
   O_CREAT    = 1_u16 << 12
+  O_EXCL     = 4_u16 << 12
   O_NOFOLLOW = 0x01000000
   O_TRUNC    = 8_u16 << 12
   O_APPEND   =      1_u16

src/lib_c/x86_64-darwin/c/fcntl.cr

@@ -12,6 +12,7 @@ lib LibC
   O_CREAT    =    0x0200
   O_NOFOLLOW =    0x0100
   O_TRUNC    =    0x0400
+  O_EXCL     =    0x0800
   O_APPEND   =    0x0008
   O_NONBLOCK =    0x0004
   O_SYNC     =    0x0080

src/lib_c/x86_64-dragonfly/c/fcntl.cr

@@ -9,6 +9,7 @@ lib LibC
   F_SETFL    =       4
   FD_CLOEXEC =       1
   O_CLOEXEC  = 0x20000
+  O_EXCL     =  0x0800
   O_TRUNC    =  0x0400
   O_CREAT    =  0x0200
   O_NOFOLLOW =  0x0100

src/lib_c/x86_64-freebsd/c/fcntl.cr

@@ -12,6 +12,7 @@ lib LibC
   O_CREAT    =     0x0200
   O_NOFOLLOW =     0x0100
   O_TRUNC    =     0x0400
+  O_EXCL     =     0x0800
   O_APPEND   =     0x0008
   O_NONBLOCK =     0x0004
   O_SYNC     =     0x0080

src/lib_c/x86_64-linux-gnu/c/fcntl.cr

@@ -10,6 +10,7 @@ lib LibC
   FD_CLOEXEC =         1
   O_CLOEXEC  = 0o2000000
   O_CREAT    =     0o100
+  O_EXCL     =     0o200
   O_NOFOLLOW =  0o400000
   O_TRUNC    =    0o1000
   O_APPEND   =    0o2000

src/lib_c/x86_64-linux-musl/c/fcntl.cr

@@ -10,6 +10,7 @@ lib LibC
   FD_CLOEXEC =         1
   O_CLOEXEC  = 0o2000000
   O_CREAT    =     0o100
+  O_EXCL     =     0o200
   O_NOFOLLOW =  0o400000
   O_TRUNC    =    0o1000
   O_APPEND   =    0o2000

src/lib_c/x86_64-netbsd/c/fcntl.cr

@@ -12,6 +12,7 @@ lib LibC
   O_CREAT    =   0x0200
   O_NOFOLLOW =   0x0100
   O_TRUNC    =   0x0400
+  O_EXCL     =   0x0800
   O_APPEND   =   0x0008
   O_NONBLOCK =   0x0004
   O_SYNC     =   0x0080

src/lib_c/x86_64-openbsd/c/fcntl.cr

@@ -12,6 +12,7 @@ lib LibC
   O_CREAT    =  0x0200
   O_NOFOLLOW =  0x0100
   O_TRUNC    =  0x0400
+  O_EXCL     =  0x0800
   O_APPEND   =  0x0008
   O_NONBLOCK =  0x0004
   O_SYNC     =  0x0080