Make all file access 64-bit (uint64_t)

This changes the types of a big number of variables.

General rules:
- Using `uint64_t` in general. We also considered `int64_t` but eventually
  settled on keeping it unsigned, which is also closer to what one would expect
  with `size_t`/`off_t`.
- We only keep `int64_t` for `seek_end` (takes a negative offset from the end)
  and for the `Variant` bindings, since `Variant::INT` is `int64_t`. This means
  we only need to guard against passing negative values in `core_bind.cpp`.
- Using `uint32_t` integers for concepts not needing such a huge range, like
  pages, blocks, etc.

In addition:
- Improve usage of integer types in some related places; namely, `DirAccess`,
  core binds.

Note:
- On Windows, `_ftelli64` reports invalid values when using 32-bit MinGW with
  version < 8.0. This was an upstream bug fixed in 8.0. It breaks support for
  big files on 32-bit Windows builds made with that toolchain. We might add a
  workaround.

Fixes #44363.
Fixes godotengine/godot-proposals#400.

Co-authored-by: Rémi Verschelde <rverschelde@gmail.com>

drivers/windows/dir_access_windows.cpp

@@ -325,13 +325,14 @@ FileType DirAccessWindows::get_file_type(const String& p_file) const {
 	return (attr&FILE_ATTRIBUTE_DIRECTORY)?FILE_TYPE_
 }
 */
-size_t DirAccessWindows::get_space_left() {
+
+uint64_t DirAccessWindows::get_space_left() {
 	uint64_t bytes = 0;
 	if (!GetDiskFreeSpaceEx(NULL, (PULARGE_INTEGER)&bytes, NULL, NULL))
 		return 0;
 
 	//this is either 0 or a value in bytes.
-	return (size_t)bytes;
+	return bytes;
 }
 
 String DirAccessWindows::get_filesystem_type() const {

drivers/windows/dir_access_windows.h

@@ -79,8 +79,7 @@ public:
 	virtual Error rename(String p_path, String p_new_path);
 	virtual Error remove(String p_path);
 
-	//virtual FileType get_file_type() const;
-	size_t get_space_left();
+	uint64_t get_space_left();
 
 	virtual String get_filesystem_type() const;
 

drivers/windows/file_access_windows.cpp

@@ -188,34 +188,38 @@ String FileAccessWindows::get_path_absolute() const {
 bool FileAccessWindows::is_open() const {
 	return (f != NULL);
 }
-void FileAccessWindows::seek(size_t p_position) {
+
+void FileAccessWindows::seek(uint64_t p_position) {
 	ERR_FAIL_COND(!f);
+
 	last_error = OK;
-	if (fseek(f, p_position, SEEK_SET))
+	if (_fseeki64(f, p_position, SEEK_SET))
 		check_errors();
 	prev_op = 0;
 }
+
 void FileAccessWindows::seek_end(int64_t p_position) {
 	ERR_FAIL_COND(!f);
-	if (fseek(f, p_position, SEEK_END))
+	if (_fseeki64(f, p_position, SEEK_END))
 		check_errors();
 	prev_op = 0;
 }
-size_t FileAccessWindows::get_position() const {
-	size_t aux_position = 0;
-	aux_position = ftell(f);
-	if (!aux_position) {
+
+uint64_t FileAccessWindows::get_position() const {
+	int64_t aux_position = _ftelli64(f);
+	if (aux_position < 0) {
 		check_errors();
-	};
+	}
 	return aux_position;
 }
-size_t FileAccessWindows::get_len() const {
+
+uint64_t FileAccessWindows::get_len() const {
 	ERR_FAIL_COND_V(!f, 0);
 
-	size_t pos = get_position();
-	fseek(f, 0, SEEK_END);
-	int size = get_position();
-	fseek(f, pos, SEEK_SET);
+	uint64_t pos = get_position();
+	_fseeki64(f, 0, SEEK_END);
+	uint64_t size = get_position();
+	_fseeki64(f, pos, SEEK_SET);
 
 	return size;
 }
@@ -242,17 +246,17 @@ uint8_t FileAccessWindows::get_8() const {
 	return b;
 }
 
-int FileAccessWindows::get_buffer(uint8_t *p_dst, int p_length) const {
+uint64_t FileAccessWindows::get_buffer(uint8_t *p_dst, uint64_t p_length) const {
 	ERR_FAIL_COND_V(!p_dst && p_length > 0, -1);
-	ERR_FAIL_COND_V(p_length < 0, -1);
 	ERR_FAIL_COND_V(!f, -1);
+
 	if (flags == READ_WRITE || flags == WRITE_READ) {
 		if (prev_op == WRITE) {
 			fflush(f);
 		}
 		prev_op = READ;
 	}
-	int read = fread(p_dst, 1, p_length, f);
+	uint64_t read = fread(p_dst, 1, p_length, f);
 	check_errors();
 	return read;
 };
@@ -281,7 +285,7 @@ void FileAccessWindows::store_8(uint8_t p_dest) {
 	fwrite(&p_dest, 1, 1, f);
 }
 
-void FileAccessWindows::store_buffer(const uint8_t *p_src, int p_length) {
+void FileAccessWindows::store_buffer(const uint8_t *p_src, uint64_t p_length) {
 	ERR_FAIL_COND(!f);
 	if (flags == READ_WRITE || flags == WRITE_READ) {
 		if (prev_op == READ) {

drivers/windows/file_access_windows.h

@@ -56,21 +56,21 @@ public:
 	virtual String get_path() const; /// returns the path for the current open file
 	virtual String get_path_absolute() const; /// returns the absolute path for the current open file
 
-	virtual void seek(size_t p_position); ///< seek to a given position
+	virtual void seek(uint64_t p_position); ///< seek to a given position
 	virtual void seek_end(int64_t p_position = 0); ///< seek from the end of file
-	virtual size_t get_position() const; ///< get position in the file
-	virtual size_t get_len() const; ///< get size of the file
+	virtual uint64_t get_position() const; ///< get position in the file
+	virtual uint64_t get_len() const; ///< get size of the file
 
 	virtual bool eof_reached() const; ///< reading passed EOF
 
 	virtual uint8_t get_8() const; ///< get a byte
-	virtual int get_buffer(uint8_t *p_dst, int p_length) const;
+	virtual uint64_t get_buffer(uint8_t *p_dst, uint64_t p_length) const;
 
 	virtual Error get_error() const; ///< get last error
 
 	virtual void flush();
 	virtual void store_8(uint8_t p_dest); ///< store a byte
-	virtual void store_buffer(const uint8_t *p_src, int p_length); ///< store an array of bytes
+	virtual void store_buffer(const uint8_t *p_src, uint64_t p_length); ///< store an array of bytes
 
 	virtual bool file_exists(const String &p_name); ///< return true if a file exists