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BLI_fileops: Harmonize 'rename' behaviors accross platforms.

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This commit aim at making the behaviors of `BLI_rename` and
`BLI_rename_overwrite` more consistent and coherent across all
supported platforms.

* `BLI_rename` now only succeeds in case the target `to` path does not
  exists (similar to Windows `rename` behavior).
* `BLI_rename_overwrite` allows to replace an existing target `to` file
  or (empty) directory (similar to Unix `rename` behavior).

NOTE: In case the target is open by some process on the system, trying
to overwrite it will still fail on Windows, while it should succeed on
Unix-like systems.

The main change for Windows is the usage of `MoveFileExW`
instead of `_wrename`, which allows for 'native support' of file
overwrite (using the `MOVEFILE_REPLACE_EXISTING` flag). Directories
still need to be explicitly removed though.

The main change for *nix systems is the use of `renamex_np` (OSX) or
`renameat2` (most Linux systems) to allow forbidding renaming to an
already existing target in an 'atomic' way.

NOTE: While this commit aims at avoiding the TOC/TOU problem as
much as possible by using available system's primitives for most
common cases, there are some situations where race conditions
(filesystem changes between checks on FS state, and actual rename
operation) remain possible.

Pull Request: https://projects.blender.org/blender/blender/pulls/115096
This commit is contained in:
Bastien Montagne
2023-11-30 22:35:00 +01:00
committed by Bastien Montagne
parent dfe1a7d039
commit 050d48edfc
5 changed files with 89 additions and 52 deletions
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7
intern/utfconv/utf_winfunc.cc
View File

@@ -72,14 +72,17 @@ int uaccess(const char *filename, int mode)
return r;
}
int urename(const char *oldname, const char *newname)
int urename(const char *oldname, const char *newname, const bool do_replace)
{
int r = -1;
UTF16_ENCODE(oldname);
UTF16_ENCODE(newname);
if (oldname_16 && newname_16) {
r = _wrename(oldname_16, newname_16);
/* Closer to UNIX `rename` behavior, as it at least allows to replace an existing file.
* Return value logic is inverted however (returns non-zero on sucess, 0 on failure).
* Note that the operation will still fail if the 'newname' existing file is opened anywhere. */
r = (MoveFileExW(oldname_16, newname_16, do_replace ? MOVEFILE_REPLACE_EXISTING : 0) == 0);
}
UTF16_UN_ENCODE(newname);

2
intern/utfconv/utf_winfunc.hh
View File

@@ -18,7 +18,7 @@
FILE *ufopen(const char *filename, const char *mode);
int uopen(const char *filename, int oflag, int pmode);
int uaccess(const char *filename, int mode);
int urename(const char *oldname, const char *newname);
int urename(const char *oldname, const char *newname, const bool do_replace);
char *u_alloc_getenv(const char *varname);
void u_free_getenv(char *val);