Rework base IO functions on Windows using HANDLE

Switch to using the Windows-specific `HANDLE` and Windows API functions instead of `FILE *` and standard library functions in all Windows IO function implementations.

Using `CreateFileW` instead of `_wfsopen` to open files is necessary, as only `CreateFileW` allows specifying all necessary sharing flags. The sharing flags `FILE_SHARE_READ` and `FILE_SHARE_WRITE` were previously already specified by using `_SH_DENYNO` with `_wfsopen`, but `FILE_SHARE_DELETE` can only be set when using `CreateFileW`. The flags are necessary so files which are in use by the game can still be opened by other processes. In particular, `FILE_SHARE_DELETE` allows deleting/renaming of open files, which was previously not possible. This was causing the smart editor saving process that renames files to fail if a map file is currently in use.

Because `CreateFileW` returns a `HANDLE` instead of a `FILE *` we have to use the `HANDLE`-based Windows IO functions everywhere.

See: https://devblogs.microsoft.com/oldnewthing/20211022-00/?p=105822

Closes ddnet#6922.

src/base/logger.h

@@ -7,7 +7,7 @@
 #include <mutex>
 #include <vector>
 
-typedef struct IOINTERNAL *IOHANDLE;
+typedef void *IOHANDLE;
 
 /**
  * @ingroup Log

src/base/system.cpp

@@ -91,10 +91,10 @@
 
 IOHANDLE io_stdin()
 {
- return (IOHANDLE)stdin;
+ return stdin;
 }
-IOHANDLE io_stdout() { return (IOHANDLE)stdout; }
-IOHANDLE io_stderr() { return (IOHANDLE)stderr; }
+IOHANDLE io_stdout() { return stdout; }
+IOHANDLE io_stderr() { return stderr; }
 
 IOHANDLE io_current_exe()
 {
@@ -258,21 +258,52 @@ IOHANDLE io_open_impl(const char *filename, int flags)
  dbg_assert(flags == (IOFLAG_READ | IOFLAG_SKIP_BOM) || flags == IOFLAG_READ || flags == IOFLAG_WRITE || flags == IOFLAG_APPEND, "flags must be read, read+skipbom, write or append");
 #if defined(CONF_FAMILY_WINDOWS)
  const std::wstring wide_filename = windows_utf8_to_wide(filename);
+ DWORD desired_access;
+ DWORD creation_disposition;
  if((flags & IOFLAG_READ) != 0)
- return (IOHANDLE)_wfsopen(wide_filename.c_str(), L"rb", _SH_DENYNO);
- if(flags == IOFLAG_WRITE)
- return (IOHANDLE)_wfsopen(wide_filename.c_str(), L"wb", _SH_DENYNO);
- if(flags == IOFLAG_APPEND)
- return (IOHANDLE)_wfsopen(wide_filename.c_str(), L"ab", _SH_DENYNO);
- return 0x0;
+ {
+ desired_access = FILE_READ_DATA;
+ creation_disposition = OPEN_EXISTING;
+ }
+ else if(flags == IOFLAG_WRITE)
+ {
+ desired_access = FILE_WRITE_DATA;
+ creation_disposition = OPEN_ALWAYS;
+ }
+ else if(flags == IOFLAG_APPEND)
+ {
+ desired_access = FILE_APPEND_DATA;
+ creation_disposition = OPEN_ALWAYS;
+ }
+ else
+ {
+ dbg_assert(false, "logic error");
+ return nullptr;
+ }
+ HANDLE handle = CreateFileW(wide_filename.c_str(), desired_access, FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE, nullptr, creation_disposition, FILE_ATTRIBUTE_NORMAL, nullptr);
+ if(handle == INVALID_HANDLE_VALUE)
+ return nullptr; // otherwise all existing checks don't work for the invalid handle
+ return handle;
 #else
+ const char *open_mode;
  if((flags & IOFLAG_READ) != 0)
- return (IOHANDLE)fopen(filename, "rb");
- if(flags == IOFLAG_WRITE)
- return (IOHANDLE)fopen(filename, "wb");
- if(flags == IOFLAG_APPEND)
- return (IOHANDLE)fopen(filename, "ab");
- return 0x0;
+ {
+ open_mode = "rb";
+ }
+ else if(flags == IOFLAG_WRITE)
+ {
+ open_mode = "wb";
+ }
+ else if(flags == IOFLAG_APPEND)
+ {
+ open_mode = "ab";
+ }
+ else
+ {
+ dbg_assert(false, "logic error");
+ return nullptr;
+ }
+ return fopen(filename, open_mode);
 #endif
 }
 
@@ -293,7 +324,13 @@ IOHANDLE io_open(const char *filename, int flags)
 
 unsigned io_read(IOHANDLE io, void *buffer, unsigned size)
 {
+#if defined(CONF_FAMILY_WINDOWS)
+ DWORD actual_size;
+ ReadFile((HANDLE)io, buffer, size, &actual_size, nullptr);
+ return actual_size;
+#else
  return fread(buffer, 1, size, (FILE *)io);
+#endif
 }
 
 void io_read_all(IOHANDLE io, void **result, unsigned *result_len)
@@ -343,14 +380,31 @@ char *io_read_all_str(IOHANDLE io)
 
 unsigned io_skip(IOHANDLE io, int size)
 {
- fseek((FILE *)io, size, SEEK_CUR);
- return size;
+ return io_seek(io, size, IOSEEK_CUR);
 }
 
 int io_seek(IOHANDLE io, int offset, int origin)
 {
+#if defined(CONF_FAMILY_WINDOWS)
+ DWORD move_method;
+ switch(origin)
+ {
+ case IOSEEK_START:
+ move_method = FILE_BEGIN;
+ break;
+ case IOSEEK_CUR:
+ move_method = FILE_CURRENT;
+ break;
+ case IOSEEK_END:
+ move_method = FILE_END;
+ break;
+ default:
+ dbg_assert(false, "origin invalid");
+ return -1;
+ }
+ return SetFilePointer((HANDLE)io, offset, nullptr, move_method);
+#else
  int real_origin;
-
  switch(origin)
  {
  case IOSEEK_START:
@@ -363,15 +417,20 @@ int io_seek(IOHANDLE io, int offset, int origin)
  real_origin = SEEK_END;
  break;
  default:
+ dbg_assert(false, "origin invalid");
  return -1;
  }
-
  return fseek((FILE *)io, offset, real_origin);
+#endif
 }
 
 long int io_tell(IOHANDLE io)
 {
+#if defined(CONF_FAMILY_WINDOWS)
+ return SetFilePointer((HANDLE)io, 0, nullptr, FILE_CURRENT);
+#else
  return ftell((FILE *)io);
+#endif
 }
 
 long int io_length(IOHANDLE io)
@@ -385,12 +444,23 @@ long int io_length(IOHANDLE io)
 
 int io_error(IOHANDLE io)
 {
+#if defined(CONF_FAMILY_WINDOWS)
+ // Only works when called directly after the operation that failed
+ return GetLastError();
+#else
  return ferror((FILE *)io);
+#endif
 }
 
 unsigned io_write(IOHANDLE io, const void *buffer, unsigned size)
 {
+#if defined(CONF_FAMILY_WINDOWS)
+ DWORD actual_size;
+ WriteFile((HANDLE)io, buffer, size, &actual_size, nullptr);
+ return actual_size;
+#else
  return fwrite(buffer, 1, size, (FILE *)io);
+#endif
 }
 
 bool io_write_newline(IOHANDLE io)
@@ -404,12 +474,20 @@ bool io_write_newline(IOHANDLE io)
 
 int io_close(IOHANDLE io)
 {
+#if defined(CONF_FAMILY_WINDOWS)
+ return CloseHandle((HANDLE)io) == 0;
+#else
  return fclose((FILE *)io) != 0;
+#endif
 }
 
 int io_flush(IOHANDLE io)
 {
+#if defined(CONF_FAMILY_WINDOWS)
+ return FlushFileBuffers((HANDLE)io) == FALSE;
+#else
  return fflush((FILE *)io);
+#endif
 }
 
 int io_sync(IOHANDLE io)
@@ -419,7 +497,7 @@ int io_sync(IOHANDLE io)
  return 1;
  }
 #if defined(CONF_FAMILY_WINDOWS)
- return FlushFileBuffers((HANDLE)_get_osfhandle(_fileno((FILE *)io))) == 0;
+ return FlushFileBuffers((HANDLE)io) == 0;
 #else
  return fsync(fileno((FILE *)io)) != 0;
 #endif

src/base/system.h

@@ -223,7 +223,7 @@ enum
  IO_MAX_PATH_LENGTH = 512,
 };
 
-typedef struct IOINTERNAL *IOHANDLE;
+typedef void *IOHANDLE;
 
 /**
  * Opens a file.