Implement file_lock feature

This adds lock(), lock_shared(), try_lock(), try_lock_shared(), and
unlock() to File gated behind the file_lock feature flag

8 files changed, 214 insertions, 0 deletions

diff --git a/library/std/src/sys/pal/hermit/fs.rs b/library/std/src/sys/pal/hermit/fs.rs
index 70f6981f717..17d15ed2e50 100644
--- a/library/std/src/sys/pal/hermit/fs.rs
+++ b/library/std/src/sys/pal/hermit/fs.rs
@@ -364,6 +364,26 @@ impl File {
         self.fsync()
     }
 
+    pub fn lock(&self) -> io::Result<()> {
+        unsupported()
+    }
+
+    pub fn lock_shared(&self) -> io::Result<()> {
+        unsupported()
+    }
+
+    pub fn try_lock(&self) -> io::Result<bool> {
+        unsupported()
+    }
+
+    pub fn try_lock_shared(&self) -> io::Result<bool> {
+        unsupported()
+    }
+
+    pub fn unlock(&self) -> io::Result<()> {
+        unsupported()
+    }
+
     pub fn truncate(&self, _size: u64) -> io::Result<()> {
         Err(Error::from_raw_os_error(22))
     }
diff --git a/library/std/src/sys/pal/solid/fs.rs b/library/std/src/sys/pal/solid/fs.rs
index bce9aa6d99c..776a96ff3b7 100644
--- a/library/std/src/sys/pal/solid/fs.rs
+++ b/library/std/src/sys/pal/solid/fs.rs
@@ -350,6 +350,26 @@ impl File {
         self.flush()
     }
 
+    pub fn lock(&self) -> io::Result<()> {
+        unsupported()
+    }
+
+    pub fn lock_shared(&self) -> io::Result<()> {
+        unsupported()
+    }
+
+    pub fn try_lock(&self) -> io::Result<bool> {
+        unsupported()
+    }
+
+    pub fn try_lock_shared(&self) -> io::Result<bool> {
+        unsupported()
+    }
+
+    pub fn unlock(&self) -> io::Result<()> {
+        unsupported()
+    }
+
     pub fn truncate(&self, _size: u64) -> io::Result<()> {
         unsupported()
     }
diff --git a/library/std/src/sys/pal/unix/fs.rs b/library/std/src/sys/pal/unix/fs.rs
index 39aabf0b2d6..86510542194 100644
--- a/library/std/src/sys/pal/unix/fs.rs
+++ b/library/std/src/sys/pal/unix/fs.rs
@@ -1254,6 +1254,43 @@ impl File {
         }
     }
 
+    pub fn lock(&self) -> io::Result<()> {
+        cvt(unsafe { libc::flock(self.as_raw_fd(), libc::LOCK_EX) })?;
+        return Ok(());
+    }
+
+    pub fn lock_shared(&self) -> io::Result<()> {
+        cvt(unsafe { libc::flock(self.as_raw_fd(), libc::LOCK_SH) })?;
+        return Ok(());
+    }
+
+    pub fn try_lock(&self) -> io::Result<bool> {
+        let result = cvt(unsafe { libc::flock(self.as_raw_fd(), libc::LOCK_EX | libc::LOCK_NB) });
+        if let Err(ref err) = result {
+            if err.kind() == io::ErrorKind::WouldBlock {
+                return Ok(false);
+            }
+        }
+        result?;
+        return Ok(true);
+    }
+
+    pub fn try_lock_shared(&self) -> io::Result<bool> {
+        let result = cvt(unsafe { libc::flock(self.as_raw_fd(), libc::LOCK_SH | libc::LOCK_NB) });
+        if let Err(ref err) = result {
+            if err.kind() == io::ErrorKind::WouldBlock {
+                return Ok(false);
+            }
+        }
+        result?;
+        return Ok(true);
+    }
+
+    pub fn unlock(&self) -> io::Result<()> {
+        cvt(unsafe { libc::flock(self.as_raw_fd(), libc::LOCK_UN) })?;
+        return Ok(());
+    }
+
     pub fn truncate(&self, size: u64) -> io::Result<()> {
         let size: off64_t =
             size.try_into().map_err(|e| io::Error::new(io::ErrorKind::InvalidInput, e))?;
diff --git a/library/std/src/sys/pal/unsupported/fs.rs b/library/std/src/sys/pal/unsupported/fs.rs
index 474c9fe97d1..9585ec24f68 100644
--- a/library/std/src/sys/pal/unsupported/fs.rs
+++ b/library/std/src/sys/pal/unsupported/fs.rs
@@ -198,6 +198,26 @@ impl File {
         self.0
     }
 
+    pub fn lock(&self) -> io::Result<()> {
+        self.0
+    }
+
+    pub fn lock_shared(&self) -> io::Result<()> {
+        self.0
+    }
+
+    pub fn try_lock(&self) -> io::Result<bool> {
+        self.0
+    }
+
+    pub fn try_lock_shared(&self) -> io::Result<bool> {
+        self.0
+    }
+
+    pub fn unlock(&self) -> io::Result<()> {
+        self.0
+    }
+
     pub fn truncate(&self, _size: u64) -> io::Result<()> {
         self.0
     }
diff --git a/library/std/src/sys/pal/wasi/fs.rs b/library/std/src/sys/pal/wasi/fs.rs
index 59ecc45b06a..3296c762cca 100644
--- a/library/std/src/sys/pal/wasi/fs.rs
+++ b/library/std/src/sys/pal/wasi/fs.rs
@@ -420,6 +420,26 @@ impl File {
         self.fd.datasync()
     }
 
+    pub fn lock(&self) -> io::Result<()> {
+        unsupported()
+    }
+
+    pub fn lock_shared(&self) -> io::Result<()> {
+        unsupported()
+    }
+
+    pub fn try_lock(&self) -> io::Result<bool> {
+        unsupported()
+    }
+
+    pub fn try_lock_shared(&self) -> io::Result<bool> {
+        unsupported()
+    }
+
+    pub fn unlock(&self) -> io::Result<()> {
+        unsupported()
+    }
+
     pub fn truncate(&self, size: u64) -> io::Result<()> {
         self.fd.filestat_set_size(size)
     }
diff --git a/library/std/src/sys/pal/windows/c/bindings.txt b/library/std/src/sys/pal/windows/c/bindings.txt
index 9c2e4500da0..d54ec9820dc 100644
--- a/library/std/src/sys/pal/windows/c/bindings.txt
+++ b/library/std/src/sys/pal/windows/c/bindings.txt
@@ -2349,6 +2349,9 @@ Windows.Win32.Storage.FileSystem.GetFinalPathNameByHandleW
 Windows.Win32.Storage.FileSystem.GetFullPathNameW
 Windows.Win32.Storage.FileSystem.GetTempPathW
 Windows.Win32.Storage.FileSystem.INVALID_FILE_ATTRIBUTES
+Windows.Win32.Storage.FileSystem.LOCKFILE_EXCLUSIVE_LOCK
+Windows.Win32.Storage.FileSystem.LOCKFILE_FAIL_IMMEDIATELY
+Windows.Win32.Storage.FileSystem.LockFileEx
 Windows.Win32.Storage.FileSystem.LPPROGRESS_ROUTINE
 Windows.Win32.Storage.FileSystem.LPPROGRESS_ROUTINE_CALLBACK_REASON
 Windows.Win32.Storage.FileSystem.MAXIMUM_REPARSE_DATA_BUFFER_SIZE
@@ -2394,6 +2397,7 @@ Windows.Win32.Storage.FileSystem.SYMBOLIC_LINK_FLAG_DIRECTORY
 Windows.Win32.Storage.FileSystem.SYMBOLIC_LINK_FLAGS
 Windows.Win32.Storage.FileSystem.SYNCHRONIZE
 Windows.Win32.Storage.FileSystem.TRUNCATE_EXISTING
+Windows.Win32.Storage.FileSystem.UnlockFile
 Windows.Win32.Storage.FileSystem.VOLUME_NAME_DOS
 Windows.Win32.Storage.FileSystem.VOLUME_NAME_GUID
 Windows.Win32.Storage.FileSystem.VOLUME_NAME_NONE
diff --git a/library/std/src/sys/pal/windows/c/windows_sys.rs b/library/std/src/sys/pal/windows/c/windows_sys.rs
index ab5f8919d7a..f17320cfad5 100644
--- a/library/std/src/sys/pal/windows/c/windows_sys.rs
+++ b/library/std/src/sys/pal/windows/c/windows_sys.rs
@@ -65,6 +65,7 @@ windows_targets::link!("kernel32.dll" "system" fn InitOnceBeginInitialize(lpinit
 windows_targets::link!("kernel32.dll" "system" fn InitOnceComplete(lpinitonce : *mut INIT_ONCE, dwflags : u32, lpcontext : *const core::ffi::c_void) -> BOOL);
 windows_targets::link!("kernel32.dll" "system" fn InitializeProcThreadAttributeList(lpattributelist : LPPROC_THREAD_ATTRIBUTE_LIST, dwattributecount : u32, dwflags : u32, lpsize : *mut usize) -> BOOL);
 windows_targets::link!("kernel32.dll" "system" fn LocalFree(hmem : HLOCAL) -> HLOCAL);
+windows_targets::link!("kernel32.dll" "system" fn LockFileEx(hfile : HANDLE, dwflags : LOCK_FILE_FLAGS, dwreserved : u32, nnumberofbytestolocklow : u32, nnumberofbytestolockhigh : u32, lpoverlapped : *mut OVERLAPPED) -> BOOL);
 windows_targets::link!("kernel32.dll" "system" fn MoveFileExW(lpexistingfilename : PCWSTR, lpnewfilename : PCWSTR, dwflags : MOVE_FILE_FLAGS) -> BOOL);
 windows_targets::link!("kernel32.dll" "system" fn MultiByteToWideChar(codepage : u32, dwflags : MULTI_BYTE_TO_WIDE_CHAR_FLAGS, lpmultibytestr : PCSTR, cbmultibyte : i32, lpwidecharstr : PWSTR, cchwidechar : i32) -> i32);
 windows_targets::link!("kernel32.dll" "system" fn QueryPerformanceCounter(lpperformancecount : *mut i64) -> BOOL);
@@ -96,6 +97,7 @@ windows_targets::link!("kernel32.dll" "system" fn TlsGetValue(dwtlsindex : u32)
 windows_targets::link!("kernel32.dll" "system" fn TlsSetValue(dwtlsindex : u32, lptlsvalue : *const core::ffi::c_void) -> BOOL);
 windows_targets::link!("kernel32.dll" "system" fn TryAcquireSRWLockExclusive(srwlock : *mut SRWLOCK) -> BOOLEAN);
 windows_targets::link!("kernel32.dll" "system" fn TryAcquireSRWLockShared(srwlock : *mut SRWLOCK) -> BOOLEAN);
+windows_targets::link!("kernel32.dll" "system" fn UnlockFile(hfile : HANDLE, dwfileoffsetlow : u32, dwfileoffsethigh : u32, nnumberofbytestounlocklow : u32, nnumberofbytestounlockhigh : u32) -> BOOL);
 windows_targets::link!("kernel32.dll" "system" fn UpdateProcThreadAttribute(lpattributelist : LPPROC_THREAD_ATTRIBUTE_LIST, dwflags : u32, attribute : usize, lpvalue : *const core::ffi::c_void, cbsize : usize, lppreviousvalue : *mut core::ffi::c_void, lpreturnsize : *const usize) -> BOOL);
 windows_targets::link!("kernel32.dll" "system" fn WaitForMultipleObjects(ncount : u32, lphandles : *const HANDLE, bwaitall : BOOL, dwmilliseconds : u32) -> WAIT_EVENT);
 windows_targets::link!("kernel32.dll" "system" fn WaitForSingleObject(hhandle : HANDLE, dwmilliseconds : u32) -> WAIT_EVENT);
@@ -2725,6 +2727,9 @@ pub struct LINGER {
     pub l_onoff: u16,
     pub l_linger: u16,
 }
+pub const LOCKFILE_EXCLUSIVE_LOCK: LOCK_FILE_FLAGS = 2u32;
+pub const LOCKFILE_FAIL_IMMEDIATELY: LOCK_FILE_FLAGS = 1u32;
+pub type LOCK_FILE_FLAGS = u32;
 pub type LPOVERLAPPED_COMPLETION_ROUTINE = Option<
     unsafe extern "system" fn(
         dwerrorcode: u32,
diff --git a/library/std/src/sys/pal/windows/fs.rs b/library/std/src/sys/pal/windows/fs.rs
index aab471e28ea..bc728d498c3 100644
--- a/library/std/src/sys/pal/windows/fs.rs
+++ b/library/std/src/sys/pal/windows/fs.rs
@@ -346,6 +346,94 @@ impl File {
         self.fsync()
     }
 
+    pub fn lock(&self) -> io::Result<()> {
+        cvt(unsafe {
+            let mut overlapped = mem::zeroed();
+            c::LockFileEx(
+                self.handle.as_raw_handle(),
+                c::LOCKFILE_EXCLUSIVE_LOCK,
+                0,
+                u32::MAX,
+                u32::MAX,
+                &mut overlapped,
+            )
+        })?;
+        Ok(())
+    }
+
+    pub fn lock_shared(&self) -> io::Result<()> {
+        cvt(unsafe {
+            let mut overlapped = mem::zeroed();
+            c::LockFileEx(self.handle.as_raw_handle(), 0, 0, u32::MAX, u32::MAX, &mut overlapped)
+        })?;
+        Ok(())
+    }
+
+    pub fn try_lock(&self) -> io::Result<bool> {
+        let result = cvt(unsafe {
+            let mut overlapped = mem::zeroed();
+            c::LockFileEx(
+                self.handle.as_raw_handle(),
+                c::LOCKFILE_EXCLUSIVE_LOCK | c::LOCKFILE_FAIL_IMMEDIATELY,
+                0,
+                u32::MAX,
+                u32::MAX,
+                &mut overlapped,
+            )
+        });
+
+        if let Err(ref err) = result {
+            if err.raw_os_error() == Some(c::ERROR_IO_PENDING as i32)
+                || err.raw_os_error() == Some(c::ERROR_LOCK_VIOLATION as i32)
+            {
+                return Ok(false);
+            }
+        }
+        result?;
+        Ok(true)
+    }
+
+    pub fn try_lock_shared(&self) -> io::Result<bool> {
+        let result = cvt(unsafe {
+            let mut overlapped = mem::zeroed();
+            c::LockFileEx(
+                self.handle.as_raw_handle(),
+                c::LOCKFILE_FAIL_IMMEDIATELY,
+                0,
+                u32::MAX,
+                u32::MAX,
+                &mut overlapped,
+            )
+        });
+
+        if let Err(ref err) = result {
+            if err.raw_os_error() == Some(c::ERROR_IO_PENDING as i32)
+                || err.raw_os_error() == Some(c::ERROR_LOCK_VIOLATION as i32)
+            {
+                return Ok(false);
+            }
+        }
+        result?;
+        Ok(true)
+    }
+
+    pub fn unlock(&self) -> io::Result<()> {
+        // Unlock the handle twice because LockFileEx() allows a file handle to acquire
+        // both an exclusive and shared lock, in which case the documentation states that:
+        // "...two unlock operations are necessary to unlock the region; the first unlock operation
+        // unlocks the exclusive lock, the second unlock operation unlocks the shared lock"
+        cvt(unsafe { c::UnlockFile(self.handle.as_raw_handle(), 0, 0, u32::MAX, u32::MAX) })?;
+        let result =
+            cvt(unsafe { c::UnlockFile(self.handle.as_raw_handle(), 0, 0, u32::MAX, u32::MAX) });
+        if let Err(ref err) = result {
+            if err.raw_os_error() == Some(c::ERROR_NOT_LOCKED as i32) {
+                return Ok(());
+            }
+        }
+        result?;
+        Ok(())
+    }
+
     pub fn truncate(&self, size: u64) -> io::Result<()> {
         let info = c::FILE_END_OF_FILE_INFO { EndOfFile: size as i64 };
         api::set_file_information_by_handle(self.handle.as_raw_handle(), &info).io_result()