diff options
Diffstat (limited to 'third_party/rust/same-file/src/win.rs')
| -rw-r--r-- | third_party/rust/same-file/src/win.rs | 172 |
1 files changed, 172 insertions, 0 deletions
diff --git a/third_party/rust/same-file/src/win.rs b/third_party/rust/same-file/src/win.rs new file mode 100644 index 0000000000..6924739977 --- /dev/null +++ b/third_party/rust/same-file/src/win.rs @@ -0,0 +1,172 @@ +use std::fs::File; +use std::hash::{Hash, Hasher}; +use std::io; +use std::os::windows::io::{AsRawHandle, IntoRawHandle, RawHandle}; +use std::path::Path; + +use winapi_util as winutil; + +// For correctness, it is critical that both file handles remain open while +// their attributes are checked for equality. In particular, the file index +// numbers on a Windows stat object are not guaranteed to remain stable over +// time. +// +// See the docs and remarks on MSDN: +// https://msdn.microsoft.com/en-us/library/windows/desktop/aa363788(v=vs.85).aspx +// +// It gets worse. It appears that the index numbers are not always +// guaranteed to be unique. Namely, ReFS uses 128 bit numbers for unique +// identifiers. This requires a distinct syscall to get `FILE_ID_INFO` +// documented here: +// https://msdn.microsoft.com/en-us/library/windows/desktop/hh802691(v=vs.85).aspx +// +// It seems straight-forward enough to modify this code to use +// `FILE_ID_INFO` when available (minimum Windows Server 2012), but I don't +// have access to such Windows machines. +// +// Two notes. +// +// 1. Java's NIO uses the approach implemented here and appears to ignore +// `FILE_ID_INFO` altogether. So Java's NIO and this code are +// susceptible to bugs when running on a file system where +// `nFileIndex{Low,High}` are not unique. +// +// 2. LLVM has a bug where they fetch the id of a file and continue to use +// it even after the handle has been closed, so that uniqueness is no +// longer guaranteed (when `nFileIndex{Low,High}` are unique). +// bug report: http://lists.llvm.org/pipermail/llvm-bugs/2014-December/037218.html +// +// All said and done, checking whether two files are the same on Windows +// seems quite tricky. Moreover, even if the code is technically incorrect, +// it seems like the chances of actually observing incorrect behavior are +// extremely small. Nevertheless, we mitigate this by checking size too. +// +// In the case where this code is erroneous, two files will be reported +// as equivalent when they are in fact distinct. This will cause the loop +// detection code to report a false positive, which will prevent descending +// into the offending directory. As far as failure modes goes, this isn't +// that bad. + +#[derive(Debug)] +pub struct Handle { + kind: HandleKind, + key: Option<Key>, +} + +#[derive(Debug)] +enum HandleKind { + /// Used when opening a file or acquiring ownership of a file. + Owned(winutil::Handle), + /// Used for stdio. + Borrowed(winutil::HandleRef), +} + +#[derive(Debug, Eq, PartialEq, Hash)] +struct Key { + volume: u64, + index: u64, +} + +impl Eq for Handle {} + +impl PartialEq for Handle { + fn eq(&self, other: &Handle) -> bool { + // Need this branch to satisfy `Eq` since `Handle`s with + // `key.is_none()` wouldn't otherwise. + if self as *const Handle == other as *const Handle { + return true; + } else if self.key.is_none() || other.key.is_none() { + return false; + } + self.key == other.key + } +} + +impl AsRawHandle for crate::Handle { + fn as_raw_handle(&self) -> RawHandle { + match self.0.kind { + HandleKind::Owned(ref h) => h.as_raw_handle(), + HandleKind::Borrowed(ref h) => h.as_raw_handle(), + } + } +} + +impl IntoRawHandle for crate::Handle { + fn into_raw_handle(self) -> RawHandle { + match self.0.kind { + HandleKind::Owned(h) => h.into_raw_handle(), + HandleKind::Borrowed(h) => h.as_raw_handle(), + } + } +} + +impl Hash for Handle { + fn hash<H: Hasher>(&self, state: &mut H) { + self.key.hash(state); + } +} + +impl Handle { + pub fn from_path<P: AsRef<Path>>(p: P) -> io::Result<Handle> { + let h = winutil::Handle::from_path_any(p)?; + let info = winutil::file::information(&h)?; + Ok(Handle::from_info(HandleKind::Owned(h), info)) + } + + pub fn from_file(file: File) -> io::Result<Handle> { + let h = winutil::Handle::from_file(file); + let info = winutil::file::information(&h)?; + Ok(Handle::from_info(HandleKind::Owned(h), info)) + } + + fn from_std_handle(h: winutil::HandleRef) -> io::Result<Handle> { + match winutil::file::information(&h) { + Ok(info) => Ok(Handle::from_info(HandleKind::Borrowed(h), info)), + // In a Windows console, if there is no pipe attached to a STD + // handle, then GetFileInformationByHandle will return an error. + // We don't really care. The only thing we care about is that + // this handle is never equivalent to any other handle, which is + // accomplished by setting key to None. + Err(_) => Ok(Handle { kind: HandleKind::Borrowed(h), key: None }), + } + } + + fn from_info( + kind: HandleKind, + info: winutil::file::Information, + ) -> Handle { + Handle { + kind: kind, + key: Some(Key { + volume: info.volume_serial_number(), + index: info.file_index(), + }), + } + } + + pub fn stdin() -> io::Result<Handle> { + Handle::from_std_handle(winutil::HandleRef::stdin()) + } + + pub fn stdout() -> io::Result<Handle> { + Handle::from_std_handle(winutil::HandleRef::stdout()) + } + + pub fn stderr() -> io::Result<Handle> { + Handle::from_std_handle(winutil::HandleRef::stderr()) + } + + pub fn as_file(&self) -> &File { + match self.kind { + HandleKind::Owned(ref h) => h.as_file(), + HandleKind::Borrowed(ref h) => h.as_file(), + } + } + + pub fn as_file_mut(&mut self) -> &mut File { + match self.kind { + HandleKind::Owned(ref mut h) => h.as_file_mut(), + HandleKind::Borrowed(ref mut h) => h.as_file_mut(), + } + } +} |