From a7688c8c4b2da3223cb67924c16cca35d12335ea Mon Sep 17 00:00:00 2001
From: George Dietrich <george@dietrich.app>
Date: Fri, 10 Mar 2023 22:34:46 -0500
Subject: [PATCH 1/9] Leverage `fileapi` for opening files on windows

---
 spec/std/file_spec.cr                      |  9 +++
 src/crystal/system/file.cr                 |  2 +-
 src/crystal/system/win32/file.cr           | 72 +++++++++++++++++++++-
 src/lib_c/x86_64-windows-msvc/c/fileapi.cr | 24 +++++++-
 src/lib_c/x86_64-windows-msvc/c/io.cr      |  2 +
 src/lib_c/x86_64-windows-msvc/c/winnt.cr   |  5 +-
 6 files changed, 105 insertions(+), 9 deletions(-)

diff --git a/spec/std/file_spec.cr b/spec/std/file_spec.cr
index 104cf3e16186..8513b3bebacf 100644
--- a/spec/std/file_spec.cr
+++ b/spec/std/file_spec.cr
@@ -517,6 +517,15 @@ describe "File" do
       end
     end
 
+    it "deletes an open file" do
+      with_tempfile("delete-file.txt") do |filename|
+        file = File.open filename, "w"
+        File.exists?(file.path).should be_true
+        file.delete
+        File.exists?(file.path).should be_false
+      end
+    end
+
     it "deletes? a file" do
       with_tempfile("delete-file.txt") do |filename|
         File.open(filename, "w") { }
diff --git a/src/crystal/system/file.cr b/src/crystal/system/file.cr
index 0f645fd8a3ec..c98a013edf88 100644
--- a/src/crystal/system/file.cr
+++ b/src/crystal/system/file.cr
@@ -81,7 +81,7 @@ module Crystal::System::File
   end
 
   private def self.error_is_file_exists?(errno)
-    Errno.value.in?(Errno::EEXIST, WinError::ERROR_ALREADY_EXISTS)
+    Errno.value.in?(Errno::EEXIST, Errno::ENOENT, WinError::ERROR_ALREADY_EXISTS, WinError::ERROR_FILE_EXISTS)
   end
 
   # Closes the internal file descriptor without notifying libevent.
diff --git a/src/crystal/system/win32/file.cr b/src/crystal/system/win32/file.cr
index 225a345723cc..f3814017f8a1 100644
--- a/src/crystal/system/win32/file.cr
+++ b/src/crystal/system/win32/file.cr
@@ -26,11 +26,77 @@ module Crystal::System::File
   end
 
   def self.open(filename : String, flags : Int32, perm : ::File::Permissions) : {LibC::Int, Errno}
-    flags |= LibC::O_BINARY | LibC::O_NOINHERIT
+    access, disposition, attributes, share = self.posix_to_open_opts flags, perm
 
-    fd = LibC._wopen(System.to_wstr(filename), flags, perm)
+    handle = LibC.CreateFileW(
+      System.to_wstr(filename),
+      access,
+      share, # UNIX semantics
+      nil,
+      disposition,
+      attributes,
+      LibC::HANDLE.null
+    )
+
+    if handle == LibC::INVALID_HANDLE_VALUE
+      return {-1, Errno.value}
+    end
+
+    fd = LibC._open_osfhandle handle, LibC::O_CREAT | LibC::O_TRUNC | LibC::O_RDWR | LibC::O_BINARY
+
+    if fd == -1
+      return {-1, Errno.value}
+    end
+
+    LibC._setmode fd, LibC::O_BINARY
+
+    {fd, Errno::NONE}
+  end
+
+  private def self.posix_to_open_opts(flags : Int32, perm : ::File::Permissions)
+    access = disposition = attributes = 0
+
+    case flags & (LibC::O_RDONLY | LibC::O_WRONLY | LibC::O_RDWR)
+    when LibC::O_RDONLY then access = LibC::GENERIC_READ
+    when LibC::O_WRONLY then access = LibC::GENERIC_WRITE
+    when LibC::O_RDWR   then access = LibC::GENERIC_READ | LibC::GENERIC_WRITE
+    end
+
+    if flags & LibC::O_APPEND > 0
+      access |= LibC::FILE_APPEND_DATA
+      attributes &= ~LibC::FILE_FLAG_BACKUP_SEMANTICS
+    end
+
+    share = LibC::DEFAULT_SHARE_MODE
+
+    case flags & (LibC::O_CREAT | LibC::O_EXCL | LibC::O_TRUNC)
+    when 0, LibC::O_EXCL                                                            then disposition = LibC::OPEN_EXISTING
+    when LibC::O_CREAT                                                              then disposition = LibC::OPEN_ALWAYS
+    when LibC::O_CREAT | LibC::O_EXCL, LibC::O_CREAT | LibC::O_TRUNC | LibC::O_EXCL then disposition = LibC::CREATE_NEW
+    when LibC::O_TRUNC, LibC::O_TRUNC | LibC::O_EXCL                                then disposition = LibC::TRUNCATE_EXISTING
+    when LibC::O_CREAT | LibC::O_TRUNC                                              then disposition = LibC::CREATE_ALWAYS
+    end
+
+    attributes |= LibC::FILE_ATTRIBUTE_NORMAL
+    unless perm.owner_write?
+      attributes |= LibC::FILE_ATTRIBUTE_READONLY
+    end
+
+    if flags & LibC::O_TEMPORARY > 0
+      attributes |= LibC::FILE_FLAG_DELETE_ON_CLOSE | LibC::FILE_ATTRIBUTE_TEMPORARY
+      access |= LibC::DELETE
+    end
+
+    if flags & LibC::O_SHORT_LIVED > 0
+      attributes |= LibC::FILE_ATTRIBUTE_TEMPORARY
+    end
+
+    case flags & (LibC::O_SEQUENTIAL | LibC::O_RANDOM)
+    when LibC::O_SEQUENTIAL then attributes |= LibC::FILE_FLAG_SEQUENTIAL_SCAN
+    when LibC::O_RANDOM     then attributes |= LibC::FILE_FLAG_RANDOM_ACCESS
+    end
 
-    {fd, fd == -1 ? Errno.value : Errno::NONE}
+    {access, disposition, attributes, share}
   end
 
   NOT_FOUND_ERRORS = {
diff --git a/src/lib_c/x86_64-windows-msvc/c/fileapi.cr b/src/lib_c/x86_64-windows-msvc/c/fileapi.cr
index 701a9590ca22..77c807984987 100644
--- a/src/lib_c/x86_64-windows-msvc/c/fileapi.cr
+++ b/src/lib_c/x86_64-windows-msvc/c/fileapi.cr
@@ -41,19 +41,37 @@ lib LibC
   fun SetFileAttributesW(lpFileName : LPWSTR, dwFileAttributes : DWORD) : BOOL
   fun GetFileAttributesExW(lpFileName : LPWSTR, fInfoLevelId : GET_FILEEX_INFO_LEVELS, lpFileInformation : Void*) : BOOL
 
-  OPEN_EXISTING = 3
+  CREATE_NEW        = 1
+  CREATE_ALWAYS     = 2
+  OPEN_EXISTING     = 3
+  OPEN_ALWAYS       = 4
+  TRUNCATE_EXISTING = 5
 
-  FILE_ATTRIBUTE_NORMAL      =       0x80
-  FILE_FLAG_BACKUP_SEMANTICS = 0x02000000
+  FILE_ATTRIBUTE_NORMAL    =  0x80
+  FILE_ATTRIBUTE_TEMPORARY = 0x100
+
+  FILE_FLAG_BACKUP_SEMANTICS   = 0x02000000
+  FILE_FLAG_DELETE_ON_CLOSE    = 0x04000000
+  FILE_FLAG_OPEN_REPARSE_POINT = 0x00200000
+  FILE_FLAG_RANDOM_ACCESS      = 0x10000000
+  FILE_FLAG_SEQUENTIAL_SCAN    = 0x08000000
 
   FILE_SHARE_READ   = 0x1
   FILE_SHARE_WRITE  = 0x2
   FILE_SHARE_DELETE = 0x4
 
+  DEFAULT_SHARE_MODE = FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE
+
+  GENERIC_READ  = 0x80000000
+  GENERIC_WRITE = 0x40000000
+
   fun CreateFileW(lpFileName : LPWSTR, dwDesiredAccess : DWORD, dwShareMode : DWORD,
                   lpSecurityAttributes : SECURITY_ATTRIBUTES*, dwCreationDisposition : DWORD,
                   dwFlagsAndAttributes : DWORD, hTemplateFile : HANDLE) : HANDLE
 
+  fun _open_osfhandle(osfhandle : HANDLE, flags : LibC::Int) : LibC::Int
+  fun _setmode(fd : LibC::Int, mode : LibC::Int) : LibC::Int
+
   fun ReadFile(hFile : HANDLE, lpBuffer : Void*, nNumberOfBytesToRead : DWORD, lpNumberOfBytesRead : DWORD*, lpOverlapped : OVERLAPPED*) : BOOL
 
   MAX_PATH = 260
diff --git a/src/lib_c/x86_64-windows-msvc/c/io.cr b/src/lib_c/x86_64-windows-msvc/c/io.cr
index dc3dfd345523..a76fb62a6115 100644
--- a/src/lib_c/x86_64-windows-msvc/c/io.cr
+++ b/src/lib_c/x86_64-windows-msvc/c/io.cr
@@ -16,4 +16,6 @@ lib LibC
   fun _pipe(pfds : Int*, psize : UInt, textmode : Int) : Int
   fun _dup2(fd1 : Int, fd2 : Int) : Int
   fun _commit(fd : Int) : Int
+
+  FILE_APPEND_DATA = 0x00000004
 end
diff --git a/src/lib_c/x86_64-windows-msvc/c/winnt.cr b/src/lib_c/x86_64-windows-msvc/c/winnt.cr
index edd247c2c723..5fdd69988317 100644
--- a/src/lib_c/x86_64-windows-msvc/c/winnt.cr
+++ b/src/lib_c/x86_64-windows-msvc/c/winnt.cr
@@ -19,8 +19,9 @@ lib LibC
   FILE_ATTRIBUTE_READONLY      =   0x1
   FILE_ATTRIBUTE_REPARSE_POINT = 0x400
 
-  FILE_READ_ATTRIBUTES  =   0x80
-  FILE_WRITE_ATTRIBUTES = 0x0100
+  DELETE                = 0x00010000
+  FILE_READ_ATTRIBUTES  =       0x80
+  FILE_WRITE_ATTRIBUTES =     0x0100
 
   # Memory protection constants
   PAGE_READWRITE = 0x04

From c96bc283d6897eda0fdc0ea45164a76873af1c5e Mon Sep 17 00:00:00 2001
From: George Dietrich <george@dietrich.app>
Date: Fri, 10 Mar 2023 23:41:42 -0500
Subject: [PATCH 2/9] Scope difference in file already existing conflict to
 windows

---
 src/crystal/system/file.cr       | 2 +-
 src/crystal/system/win32/file.cr | 5 +++++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/crystal/system/file.cr b/src/crystal/system/file.cr
index c98a013edf88..0f645fd8a3ec 100644
--- a/src/crystal/system/file.cr
+++ b/src/crystal/system/file.cr
@@ -81,7 +81,7 @@ module Crystal::System::File
   end
 
   private def self.error_is_file_exists?(errno)
-    Errno.value.in?(Errno::EEXIST, Errno::ENOENT, WinError::ERROR_ALREADY_EXISTS, WinError::ERROR_FILE_EXISTS)
+    Errno.value.in?(Errno::EEXIST, WinError::ERROR_ALREADY_EXISTS)
   end
 
   # Closes the internal file descriptor without notifying libevent.
diff --git a/src/crystal/system/win32/file.cr b/src/crystal/system/win32/file.cr
index f3814017f8a1..88035ecff44b 100644
--- a/src/crystal/system/win32/file.cr
+++ b/src/crystal/system/win32/file.cr
@@ -39,6 +39,11 @@ module Crystal::System::File
     )
 
     if handle == LibC::INVALID_HANDLE_VALUE
+      # Map ERROR_FILE_EXISTS to Errno::EEXIST to avoid changing semantics of other systems
+      if WinError.value.error_file_exists?
+        Errno.value = Errno::EEXIST
+      end
+
       return {-1, Errno.value}
     end
 

From 8cedeb69c074e6c455db2135be5e2d50a072ef95 Mon Sep 17 00:00:00 2001
From: George Dietrich <george@dietrich.app>
Date: Sat, 11 Mar 2023 00:32:39 -0500
Subject: [PATCH 3/9] Pass correct flags to `_open_osfhandle`

---
 src/crystal/system/win32/file.cr         | 8 ++++++--
 src/lib_c/x86_64-windows-msvc/c/io.cr    | 2 --
 src/lib_c/x86_64-windows-msvc/c/winnt.cr | 2 ++
 3 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/src/crystal/system/win32/file.cr b/src/crystal/system/win32/file.cr
index 88035ecff44b..5b7cb03a6fe0 100644
--- a/src/crystal/system/win32/file.cr
+++ b/src/crystal/system/win32/file.cr
@@ -47,13 +47,17 @@ module Crystal::System::File
       return {-1, Errno.value}
     end
 
-    fd = LibC._open_osfhandle handle, LibC::O_CREAT | LibC::O_TRUNC | LibC::O_RDWR | LibC::O_BINARY
+    fd = LibC._open_osfhandle handle, flags
 
     if fd == -1
       return {-1, Errno.value}
     end
 
-    LibC._setmode fd, LibC::O_BINARY
+    if flags & LibC::O_BINARY > 0
+      LibC._setmode fd, LibC::O_BINARY
+    elsif flags & LibC::O_TEXT > 0
+      LibC._setmode fd, LibC::O_TEXT
+    end
 
     {fd, Errno::NONE}
   end
diff --git a/src/lib_c/x86_64-windows-msvc/c/io.cr b/src/lib_c/x86_64-windows-msvc/c/io.cr
index a76fb62a6115..dc3dfd345523 100644
--- a/src/lib_c/x86_64-windows-msvc/c/io.cr
+++ b/src/lib_c/x86_64-windows-msvc/c/io.cr
@@ -16,6 +16,4 @@ lib LibC
   fun _pipe(pfds : Int*, psize : UInt, textmode : Int) : Int
   fun _dup2(fd1 : Int, fd2 : Int) : Int
   fun _commit(fd : Int) : Int
-
-  FILE_APPEND_DATA = 0x00000004
 end
diff --git a/src/lib_c/x86_64-windows-msvc/c/winnt.cr b/src/lib_c/x86_64-windows-msvc/c/winnt.cr
index 5fdd69988317..36c887f78ba7 100644
--- a/src/lib_c/x86_64-windows-msvc/c/winnt.cr
+++ b/src/lib_c/x86_64-windows-msvc/c/winnt.cr
@@ -19,6 +19,8 @@ lib LibC
   FILE_ATTRIBUTE_READONLY      =   0x1
   FILE_ATTRIBUTE_REPARSE_POINT = 0x400
 
+  FILE_APPEND_DATA = 0x00000004
+
   DELETE                = 0x00010000
   FILE_READ_ATTRIBUTES  =       0x80
   FILE_WRITE_ATTRIBUTES =     0x0100

From dfc0148a3d415f7b8857f729ec6864e5cc5c7c66 Mon Sep 17 00:00:00 2001
From: George Dietrich <george@dietrich.app>
Date: Sat, 11 Mar 2023 10:14:51 -0500
Subject: [PATCH 4/9] Simplify `posix_to_open_opts` logic

---
 src/crystal/system/win32/file.cr | 21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/src/crystal/system/win32/file.cr b/src/crystal/system/win32/file.cr
index 5b7cb03a6fe0..88184715ece9 100644
--- a/src/crystal/system/win32/file.cr
+++ b/src/crystal/system/win32/file.cr
@@ -63,21 +63,20 @@ module Crystal::System::File
   end
 
   private def self.posix_to_open_opts(flags : Int32, perm : ::File::Permissions)
-    access = disposition = attributes = 0
+    disposition = 0
 
-    case flags & (LibC::O_RDONLY | LibC::O_WRONLY | LibC::O_RDWR)
-    when LibC::O_RDONLY then access = LibC::GENERIC_READ
-    when LibC::O_WRONLY then access = LibC::GENERIC_WRITE
-    when LibC::O_RDWR   then access = LibC::GENERIC_READ | LibC::GENERIC_WRITE
-    end
+    access = if flags & LibC::O_WRONLY > 0
+               LibC::GENERIC_WRITE
+             elsif flags & LibC::O_RDWR > 0
+               LibC::GENERIC_READ | LibC::GENERIC_WRITE
+             else
+               LibC::GENERIC_READ
+             end
 
     if flags & LibC::O_APPEND > 0
       access |= LibC::FILE_APPEND_DATA
-      attributes &= ~LibC::FILE_FLAG_BACKUP_SEMANTICS
     end
 
-    share = LibC::DEFAULT_SHARE_MODE
-
     case flags & (LibC::O_CREAT | LibC::O_EXCL | LibC::O_TRUNC)
     when 0, LibC::O_EXCL                                                            then disposition = LibC::OPEN_EXISTING
     when LibC::O_CREAT                                                              then disposition = LibC::OPEN_ALWAYS
@@ -86,7 +85,7 @@ module Crystal::System::File
     when LibC::O_CREAT | LibC::O_TRUNC                                              then disposition = LibC::CREATE_ALWAYS
     end
 
-    attributes |= LibC::FILE_ATTRIBUTE_NORMAL
+    attributes = LibC::FILE_ATTRIBUTE_NORMAL
     unless perm.owner_write?
       attributes |= LibC::FILE_ATTRIBUTE_READONLY
     end
@@ -105,7 +104,7 @@ module Crystal::System::File
     when LibC::O_RANDOM     then attributes |= LibC::FILE_FLAG_RANDOM_ACCESS
     end
 
-    {access, disposition, attributes, share}
+    {access, disposition, attributes, LibC::DEFAULT_SHARE_MODE}
   end
 
   NOT_FOUND_ERRORS = {

From 3886053339942eedaa9b39de323e4455342f0990 Mon Sep 17 00:00:00 2001
From: George Dietrich <george@dietrich.app>
Date: Mon, 13 Mar 2023 12:34:37 -0400
Subject: [PATCH 5/9] Address PR feedback

---
 src/crystal/system/file.cr       |  2 +-
 src/crystal/system/win32/file.cr | 44 +++++++++++++++-----------------
 2 files changed, 22 insertions(+), 24 deletions(-)

diff --git a/src/crystal/system/file.cr b/src/crystal/system/file.cr
index 0f645fd8a3ec..89d29512c28e 100644
--- a/src/crystal/system/file.cr
+++ b/src/crystal/system/file.cr
@@ -81,7 +81,7 @@ module Crystal::System::File
   end
 
   private def self.error_is_file_exists?(errno)
-    Errno.value.in?(Errno::EEXIST, WinError::ERROR_ALREADY_EXISTS)
+    errno.in?(Errno::EEXIST, WinError::ERROR_ALREADY_EXISTS)
   end
 
   # Closes the internal file descriptor without notifying libevent.
diff --git a/src/crystal/system/win32/file.cr b/src/crystal/system/win32/file.cr
index 88184715ece9..c0f80fb5e694 100644
--- a/src/crystal/system/win32/file.cr
+++ b/src/crystal/system/win32/file.cr
@@ -26,12 +26,12 @@ module Crystal::System::File
   end
 
   def self.open(filename : String, flags : Int32, perm : ::File::Permissions) : {LibC::Int, Errno}
-    access, disposition, attributes, share = self.posix_to_open_opts flags, perm
+    access, disposition, attributes = self.posix_to_open_opts flags, perm
 
     handle = LibC.CreateFileW(
       System.to_wstr(filename),
       access,
-      share, # UNIX semantics
+      LibC::DEFAULT_SHARE_MODE, # UNIX semantics
       nil,
       disposition,
       attributes,
@@ -40,11 +40,7 @@ module Crystal::System::File
 
     if handle == LibC::INVALID_HANDLE_VALUE
       # Map ERROR_FILE_EXISTS to Errno::EEXIST to avoid changing semantics of other systems
-      if WinError.value.error_file_exists?
-        Errno.value = Errno::EEXIST
-      end
-
-      return {-1, Errno.value}
+      return {-1, WinError.value.error_file_exists? ? Errno::EEXIST : Errno.value}
     end
 
     fd = LibC._open_osfhandle handle, flags
@@ -63,26 +59,28 @@ module Crystal::System::File
   end
 
   private def self.posix_to_open_opts(flags : Int32, perm : ::File::Permissions)
-    disposition = 0
-
-    access = if flags & LibC::O_WRONLY > 0
-               LibC::GENERIC_WRITE
-             elsif flags & LibC::O_RDWR > 0
-               LibC::GENERIC_READ | LibC::GENERIC_WRITE
-             else
-               LibC::GENERIC_READ
-             end
+    access = 0
+    access |= LibC::GENERIC_WRITE unless flags == LibC::O_RDONLY
+    access |= LibC::GENERIC_READ unless flags & LibC::O_WRONLY > 0
 
     if flags & LibC::O_APPEND > 0
       access |= LibC::FILE_APPEND_DATA
     end
 
-    case flags & (LibC::O_CREAT | LibC::O_EXCL | LibC::O_TRUNC)
-    when 0, LibC::O_EXCL                                                            then disposition = LibC::OPEN_EXISTING
-    when LibC::O_CREAT                                                              then disposition = LibC::OPEN_ALWAYS
-    when LibC::O_CREAT | LibC::O_EXCL, LibC::O_CREAT | LibC::O_TRUNC | LibC::O_EXCL then disposition = LibC::CREATE_NEW
-    when LibC::O_TRUNC, LibC::O_TRUNC | LibC::O_EXCL                                then disposition = LibC::TRUNCATE_EXISTING
-    when LibC::O_CREAT | LibC::O_TRUNC                                              then disposition = LibC::CREATE_ALWAYS
+    if flags & LibC::O_TRUNC > 0
+      if flags & LibC::O_CREAT > 0
+        disposition = LibC::CREATE_ALWAYS
+      else
+        disposition = LibC::TRUNCATE_EXISTING
+      end
+    elsif flags & LibC::O_CREAT > 0
+      if flags & LibC::O_EXCL > 0
+        disposition = LibC::CREATE_NEW
+      else
+        disposition = LibC::OPEN_ALWAYS
+      end
+    else
+      disposition = LibC::OPEN_EXISTING
     end
 
     attributes = LibC::FILE_ATTRIBUTE_NORMAL
@@ -104,7 +102,7 @@ module Crystal::System::File
     when LibC::O_RANDOM     then attributes |= LibC::FILE_FLAG_RANDOM_ACCESS
     end
 
-    {access, disposition, attributes, LibC::DEFAULT_SHARE_MODE}
+    {access, disposition, attributes}
   end
 
   NOT_FOUND_ERRORS = {

From 3da1fdf0122551e9c03650e91fd30e074dfddf01 Mon Sep 17 00:00:00 2001
From: George Dietrich <george@dietrich.app>
Date: Mon, 13 Mar 2023 17:36:21 -0400
Subject: [PATCH 6/9] Leverage `Int#bits_set?`

---
 src/crystal/system/win32/file.cr | 27 ++++++++++++++-------------
 1 file changed, 14 insertions(+), 13 deletions(-)

diff --git a/src/crystal/system/win32/file.cr b/src/crystal/system/win32/file.cr
index c0f80fb5e694..fea4d0a9ca0e 100644
--- a/src/crystal/system/win32/file.cr
+++ b/src/crystal/system/win32/file.cr
@@ -49,9 +49,9 @@ module Crystal::System::File
       return {-1, Errno.value}
     end
 
-    if flags & LibC::O_BINARY > 0
+    if flags.bits_set? LibC::O_BINARY
       LibC._setmode fd, LibC::O_BINARY
-    elsif flags & LibC::O_TEXT > 0
+    elsif flags.bits_set? LibC::O_TEXT
       LibC._setmode fd, LibC::O_TEXT
     end
 
@@ -61,20 +61,20 @@ module Crystal::System::File
   private def self.posix_to_open_opts(flags : Int32, perm : ::File::Permissions)
     access = 0
     access |= LibC::GENERIC_WRITE unless flags == LibC::O_RDONLY
-    access |= LibC::GENERIC_READ unless flags & LibC::O_WRONLY > 0
+    access |= LibC::GENERIC_READ unless flags.bits_set? LibC::O_WRONLY
 
-    if flags & LibC::O_APPEND > 0
+    if flags.bits_set? LibC::O_APPEND
       access |= LibC::FILE_APPEND_DATA
     end
 
-    if flags & LibC::O_TRUNC > 0
-      if flags & LibC::O_CREAT > 0
+    if flags.bits_set? LibC::O_TRUNC
+      if flags.bits_set? LibC::O_CREAT
         disposition = LibC::CREATE_ALWAYS
       else
         disposition = LibC::TRUNCATE_EXISTING
       end
-    elsif flags & LibC::O_CREAT > 0
-      if flags & LibC::O_EXCL > 0
+    elsif flags.bits_set? LibC::O_CREAT
+      if flags.bits_set? LibC::O_EXCL
         disposition = LibC::CREATE_NEW
       else
         disposition = LibC::OPEN_ALWAYS
@@ -88,18 +88,19 @@ module Crystal::System::File
       attributes |= LibC::FILE_ATTRIBUTE_READONLY
     end
 
-    if flags & LibC::O_TEMPORARY > 0
+    if flags.bits_set? LibC::O_TEMPORARY
       attributes |= LibC::FILE_FLAG_DELETE_ON_CLOSE | LibC::FILE_ATTRIBUTE_TEMPORARY
       access |= LibC::DELETE
     end
 
-    if flags & LibC::O_SHORT_LIVED > 0
+    if flags.bits_set? LibC::O_SHORT_LIVED
       attributes |= LibC::FILE_ATTRIBUTE_TEMPORARY
     end
 
-    case flags & (LibC::O_SEQUENTIAL | LibC::O_RANDOM)
-    when LibC::O_SEQUENTIAL then attributes |= LibC::FILE_FLAG_SEQUENTIAL_SCAN
-    when LibC::O_RANDOM     then attributes |= LibC::FILE_FLAG_RANDOM_ACCESS
+    if flags.bits_set? LibC::O_SEQUENTIAL
+      attributes |= LibC::FILE_FLAG_SEQUENTIAL_SCAN
+    elsif flags.bits_set? LibC::O_RANDOM
+      attributes |= LibC::FILE_FLAG_RANDOM_ACCESS
     end
 
     {access, disposition, attributes}

From 3be60879212c6260b16e68ee32579b72ec47e66d Mon Sep 17 00:00:00 2001
From: George Dietrich <george@dietrich.app>
Date: Tue, 14 Mar 2023 09:08:54 -0400
Subject: [PATCH 7/9] Move some bindings to proper file

---
 src/lib_c/x86_64-windows-msvc/c/fileapi.cr | 3 ---
 src/lib_c/x86_64-windows-msvc/c/io.cr      | 2 ++
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/src/lib_c/x86_64-windows-msvc/c/fileapi.cr b/src/lib_c/x86_64-windows-msvc/c/fileapi.cr
index 77c807984987..9b88b5341c09 100644
--- a/src/lib_c/x86_64-windows-msvc/c/fileapi.cr
+++ b/src/lib_c/x86_64-windows-msvc/c/fileapi.cr
@@ -69,9 +69,6 @@ lib LibC
                   lpSecurityAttributes : SECURITY_ATTRIBUTES*, dwCreationDisposition : DWORD,
                   dwFlagsAndAttributes : DWORD, hTemplateFile : HANDLE) : HANDLE
 
-  fun _open_osfhandle(osfhandle : HANDLE, flags : LibC::Int) : LibC::Int
-  fun _setmode(fd : LibC::Int, mode : LibC::Int) : LibC::Int
-
   fun ReadFile(hFile : HANDLE, lpBuffer : Void*, nNumberOfBytesToRead : DWORD, lpNumberOfBytesRead : DWORD*, lpOverlapped : OVERLAPPED*) : BOOL
 
   MAX_PATH = 260
diff --git a/src/lib_c/x86_64-windows-msvc/c/io.cr b/src/lib_c/x86_64-windows-msvc/c/io.cr
index dc3dfd345523..94a5b7b582a3 100644
--- a/src/lib_c/x86_64-windows-msvc/c/io.cr
+++ b/src/lib_c/x86_64-windows-msvc/c/io.cr
@@ -16,4 +16,6 @@ lib LibC
   fun _pipe(pfds : Int*, psize : UInt, textmode : Int) : Int
   fun _dup2(fd1 : Int, fd2 : Int) : Int
   fun _commit(fd : Int) : Int
+  fun _open_osfhandle(osfhandle : HANDLE, flags : LibC::Int) : LibC::Int
+  fun _setmode(fd : LibC::Int, mode : LibC::Int) : LibC::Int
 end

From dd120016a7b762bcdea5266ba50ee1426a5250c0 Mon Sep 17 00:00:00 2001
From: George Dietrich <george@dietrich.app>
Date: Tue, 14 Mar 2023 11:30:09 -0400
Subject: [PATCH 8/9] Always open in binary mode

---
 src/crystal/system/win32/file.cr | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/src/crystal/system/win32/file.cr b/src/crystal/system/win32/file.cr
index fea4d0a9ca0e..52073b8ebf1f 100644
--- a/src/crystal/system/win32/file.cr
+++ b/src/crystal/system/win32/file.cr
@@ -49,11 +49,8 @@ module Crystal::System::File
       return {-1, Errno.value}
     end
 
-    if flags.bits_set? LibC::O_BINARY
-      LibC._setmode fd, LibC::O_BINARY
-    elsif flags.bits_set? LibC::O_TEXT
-      LibC._setmode fd, LibC::O_TEXT
-    end
+    # Only binary mode is supported
+    LibC._setmode fd, LibC::O_BINARY
 
     {fd, Errno::NONE}
   end

From e3bf5a0c5f1dcd4fdcd1eccdfe001c5c67e72bee Mon Sep 17 00:00:00 2001
From: George Dietrich <george@dietrich.app>
Date: Tue, 14 Mar 2023 11:54:03 -0400
Subject: [PATCH 9/9] Revert to previous `access` handling logic

---
 src/crystal/system/win32/file.cr | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/src/crystal/system/win32/file.cr b/src/crystal/system/win32/file.cr
index 52073b8ebf1f..49ebf92702ae 100644
--- a/src/crystal/system/win32/file.cr
+++ b/src/crystal/system/win32/file.cr
@@ -56,9 +56,13 @@ module Crystal::System::File
   end
 
   private def self.posix_to_open_opts(flags : Int32, perm : ::File::Permissions)
-    access = 0
-    access |= LibC::GENERIC_WRITE unless flags == LibC::O_RDONLY
-    access |= LibC::GENERIC_READ unless flags.bits_set? LibC::O_WRONLY
+    access = if flags.bits_set? LibC::O_WRONLY
+               LibC::GENERIC_WRITE
+             elsif flags.bits_set? LibC::O_RDWR
+               LibC::GENERIC_READ | LibC::GENERIC_WRITE
+             else
+               LibC::GENERIC_READ
+             end
 
     if flags.bits_set? LibC::O_APPEND
       access |= LibC::FILE_APPEND_DATA