os: use handle based APIs to read directories on windows

This CL updates File.readdir() on windows so it uses
GetFileInformationByHandleEx with FILE_ID_BOTH_DIR_INFO
instead of Find* APIs. The former is more performant because
it allows us to buffer IO calls and reduces the number of system calls,
passing from 1 per file to 1 every ~100 files
(depending on the size of the file name and the size of the buffer).

This change improve performance of File.ReadDir by 20-30%.

name        old time/op    new time/op    delta
ReadDir-12     562µs ±14%     385µs ± 9%  -31.60%  (p=0.000 n=9+9)

name        old alloc/op   new alloc/op   delta
ReadDir-12    29.7kB ± 0%    29.5kB ± 0%   -0.88%  (p=0.000 n=8+10)

name        old allocs/op  new allocs/op  delta
ReadDir-12       399 ± 0%       397 ± 0%   -0.50%  (p=0.000 n=10+10)

This change also speeds up calls to os.SameFile when using FileStats
returned from File.readdir(), as their file ID can be inferred while
reading the directory.

Change-Id: Id56a338ee66c39656b564105cac131099218fb5d
Reviewed-on: https://go-review.googlesource.com/c/go/+/452995
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Damien Neil <dneil@google.com>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
Run-TryBot: Quim Muntal <quimmuntal@gmail.com>
Reviewed-by: Bryan Mills <bcmills@google.com>

2 files changed, 61 insertions, 32 deletions

diff --git a/src/internal/syscall/windows/syscall_windows.go b/src/internal/syscall/windows/syscall_windows.go
index 8ace2a27e7..311d083f45 100644
--- a/src/internal/syscall/windows/syscall_windows.go
+++ b/src/internal/syscall/windows/syscall_windows.go
@@ -367,3 +367,23 @@ func LoadGetFinalPathNameByHandle() error {
 //sys	DestroyEnvironmentBlock(block *uint16) (err error) = userenv.DestroyEnvironmentBlock
 
 //sys	RtlGenRandom(buf []byte) (err error) = advapi32.SystemFunction036
+
+type FILE_ID_BOTH_DIR_INFO struct {
+	NextEntryOffset uint32
+	FileIndex       uint32
+	CreationTime    syscall.Filetime
+	LastAccessTime  syscall.Filetime
+	LastWriteTime   syscall.Filetime
+	ChangeTime      syscall.Filetime
+	EndOfFile       uint64
+	AllocationSize  uint64
+	FileAttributes  uint32
+	FileNameLength  uint32
+	EaSize          uint32
+	ShortNameLength uint32
+	ShortName       [12]uint16
+	FileID          uint64
+	FileName        [1]uint16
+}
+
+//sys	GetVolumeInformationByHandle(file syscall.Handle, volumeNameBuffer *uint16, volumeNameSize uint32, volumeNameSerialNumber *uint32, maximumComponentLength *uint32, fileSystemFlags *uint32, fileSystemNameBuffer *uint16, fileSystemNameSize uint32) (err error) = GetVolumeInformationByHandleW
diff --git a/src/internal/syscall/windows/zsyscall_windows.go b/src/internal/syscall/windows/zsyscall_windows.go
index afd64e318e..fd2f255b9b 100644
--- a/src/internal/syscall/windows/zsyscall_windows.go
+++ b/src/internal/syscall/windows/zsyscall_windows.go
@@ -45,38 +45,39 @@ var (
 	moduserenv  = syscall.NewLazyDLL(sysdll.Add("userenv.dll"))
 	modws2_32   = syscall.NewLazyDLL(sysdll.Add("ws2_32.dll"))
 
-	procAdjustTokenPrivileges        = modadvapi32.NewProc("AdjustTokenPrivileges")
-	procDuplicateTokenEx             = modadvapi32.NewProc("DuplicateTokenEx")
-	procImpersonateSelf              = modadvapi32.NewProc("ImpersonateSelf")
-	procLookupPrivilegeValueW        = modadvapi32.NewProc("LookupPrivilegeValueW")
-	procOpenThreadToken              = modadvapi32.NewProc("OpenThreadToken")
-	procRevertToSelf                 = modadvapi32.NewProc("RevertToSelf")
-	procSetTokenInformation          = modadvapi32.NewProc("SetTokenInformation")
-	procSystemFunction036            = modadvapi32.NewProc("SystemFunction036")
-	procGetAdaptersAddresses         = modiphlpapi.NewProc("GetAdaptersAddresses")
-	procGetACP                       = modkernel32.NewProc("GetACP")
-	procGetComputerNameExW           = modkernel32.NewProc("GetComputerNameExW")
-	procGetConsoleCP                 = modkernel32.NewProc("GetConsoleCP")
-	procGetCurrentThread             = modkernel32.NewProc("GetCurrentThread")
-	procGetFileInformationByHandleEx = modkernel32.NewProc("GetFileInformationByHandleEx")
-	procGetFinalPathNameByHandleW    = modkernel32.NewProc("GetFinalPathNameByHandleW")
-	procGetModuleFileNameW           = modkernel32.NewProc("GetModuleFileNameW")
-	procLockFileEx                   = modkernel32.NewProc("LockFileEx")
-	procModule32FirstW               = modkernel32.NewProc("Module32FirstW")
-	procModule32NextW                = modkernel32.NewProc("Module32NextW")
-	procMoveFileExW                  = modkernel32.NewProc("MoveFileExW")
-	procMultiByteToWideChar          = modkernel32.NewProc("MultiByteToWideChar")
-	procSetFileInformationByHandle   = modkernel32.NewProc("SetFileInformationByHandle")
-	procUnlockFileEx                 = modkernel32.NewProc("UnlockFileEx")
-	procVirtualQuery                 = modkernel32.NewProc("VirtualQuery")
-	procNetShareAdd                  = modnetapi32.NewProc("NetShareAdd")
-	procNetShareDel                  = modnetapi32.NewProc("NetShareDel")
-	procNetUserGetLocalGroups        = modnetapi32.NewProc("NetUserGetLocalGroups")
-	procGetProcessMemoryInfo         = modpsapi.NewProc("GetProcessMemoryInfo")
-	procCreateEnvironmentBlock       = moduserenv.NewProc("CreateEnvironmentBlock")
-	procDestroyEnvironmentBlock      = moduserenv.NewProc("DestroyEnvironmentBlock")
-	procGetProfilesDirectoryW        = moduserenv.NewProc("GetProfilesDirectoryW")
-	procWSASocketW                   = modws2_32.NewProc("WSASocketW")
+	procAdjustTokenPrivileges         = modadvapi32.NewProc("AdjustTokenPrivileges")
+	procDuplicateTokenEx              = modadvapi32.NewProc("DuplicateTokenEx")
+	procImpersonateSelf               = modadvapi32.NewProc("ImpersonateSelf")
+	procLookupPrivilegeValueW         = modadvapi32.NewProc("LookupPrivilegeValueW")
+	procOpenThreadToken               = modadvapi32.NewProc("OpenThreadToken")
+	procRevertToSelf                  = modadvapi32.NewProc("RevertToSelf")
+	procSetTokenInformation           = modadvapi32.NewProc("SetTokenInformation")
+	procSystemFunction036             = modadvapi32.NewProc("SystemFunction036")
+	procGetAdaptersAddresses          = modiphlpapi.NewProc("GetAdaptersAddresses")
+	procGetACP                        = modkernel32.NewProc("GetACP")
+	procGetComputerNameExW            = modkernel32.NewProc("GetComputerNameExW")
+	procGetConsoleCP                  = modkernel32.NewProc("GetConsoleCP")
+	procGetCurrentThread              = modkernel32.NewProc("GetCurrentThread")
+	procGetFileInformationByHandleEx  = modkernel32.NewProc("GetFileInformationByHandleEx")
+	procGetFinalPathNameByHandleW     = modkernel32.NewProc("GetFinalPathNameByHandleW")
+	procGetModuleFileNameW            = modkernel32.NewProc("GetModuleFileNameW")
+	procGetVolumeInformationByHandleW = modkernel32.NewProc("GetVolumeInformationByHandleW")
+	procLockFileEx                    = modkernel32.NewProc("LockFileEx")
+	procModule32FirstW                = modkernel32.NewProc("Module32FirstW")
+	procModule32NextW                 = modkernel32.NewProc("Module32NextW")
+	procMoveFileExW                   = modkernel32.NewProc("MoveFileExW")
+	procMultiByteToWideChar           = modkernel32.NewProc("MultiByteToWideChar")
+	procSetFileInformationByHandle    = modkernel32.NewProc("SetFileInformationByHandle")
+	procUnlockFileEx                  = modkernel32.NewProc("UnlockFileEx")
+	procVirtualQuery                  = modkernel32.NewProc("VirtualQuery")
+	procNetShareAdd                   = modnetapi32.NewProc("NetShareAdd")
+	procNetShareDel                   = modnetapi32.NewProc("NetShareDel")
+	procNetUserGetLocalGroups         = modnetapi32.NewProc("NetUserGetLocalGroups")
+	procGetProcessMemoryInfo          = modpsapi.NewProc("GetProcessMemoryInfo")
+	procCreateEnvironmentBlock        = moduserenv.NewProc("CreateEnvironmentBlock")
+	procDestroyEnvironmentBlock       = moduserenv.NewProc("DestroyEnvironmentBlock")
+	procGetProfilesDirectoryW         = moduserenv.NewProc("GetProfilesDirectoryW")
+	procWSASocketW                    = modws2_32.NewProc("WSASocketW")
 )
 
 func adjustTokenPrivileges(token syscall.Token, disableAllPrivileges bool, newstate *TOKEN_PRIVILEGES, buflen uint32, prevstate *TOKEN_PRIVILEGES, returnlen *uint32) (ret uint32, err error) {
@@ -219,6 +220,14 @@ func GetModuleFileName(module syscall.Handle, fn *uint16, len uint32) (n uint32,
 	return
 }
 
+func GetVolumeInformationByHandle(file syscall.Handle, volumeNameBuffer *uint16, volumeNameSize uint32, volumeNameSerialNumber *uint32, maximumComponentLength *uint32, fileSystemFlags *uint32, fileSystemNameBuffer *uint16, fileSystemNameSize uint32) (err error) {
+	r1, _, e1 := syscall.Syscall9(procGetVolumeInformationByHandleW.Addr(), 8, uintptr(file), uintptr(unsafe.Pointer(volumeNameBuffer)), uintptr(volumeNameSize), uintptr(unsafe.Pointer(volumeNameSerialNumber)), uintptr(unsafe.Pointer(maximumComponentLength)), uintptr(unsafe.Pointer(fileSystemFlags)), uintptr(unsafe.Pointer(fileSystemNameBuffer)), uintptr(fileSystemNameSize), 0)
+	if r1 == 0 {
+		err = errnoErr(e1)
+	}
+	return
+}
+
 func LockFileEx(file syscall.Handle, flags uint32, reserved uint32, bytesLow uint32, bytesHigh uint32, overlapped *syscall.Overlapped) (err error) {
 	r1, _, e1 := syscall.Syscall6(procLockFileEx.Addr(), 6, uintptr(file), uintptr(flags), uintptr(reserved), uintptr(bytesLow), uintptr(bytesHigh), uintptr(unsafe.Pointer(overlapped)))
 	if r1 == 0 {