[#BloombergLP-bdls-FilesystemUtil_WindowsImpUtil]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bdls.adoc[bdls]::FilesystemUtil_WindowsImpUtil
:relfileprefix: ../../
:mrdocs:

This component‐private utility `struct` provides a namespace for a suite of functions that `FilesystemUtil` uses as implementation details. These functions have a `WINDOWS_INTERFACE` template parameter, which provides access to the entities that Windows systems declare, and that the function implementations need.

== Synopsis

Declared in `<bdls_filesystemutil_windowsimputil.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<class WINDOWS_INTERFACE>
struct FilesystemUtil_WindowsImpUtil;
----

== Description

The program is ill‐formed unless the specified `WINDOWS_INTERFACE` is a class type that meets the following requirements:

* `WINDOWS_INTERFACE::BOOL` is a type alias to the `BOOL` type provided by the `windows.h` header. * `WINDOWS_INTERFACE::DWORD` is a type alias to the `DWORD` type provided by the `windows.h` header. * `WINDOWS_INTERFACE::FILETIME` is a type alias to the `FILETIME` type provided by the `windows.h` header. * `WINDOWS_INTERFACE::HANDLE` is a type alias to the `HANDLE` type provided by the `windows.h` header. * `WINDOWS_INTERFACE::INT64` is a type alias to the `IN64` type provided by the `windows.h` header. * `WINDOWS_INTERFACE::LPFILETIME` is a type alias to the `LPFILETIME` type provided by the `windows.h` header. * `WINDOWS_INTERFACE::SYSTEMTIME` is a type alias to the `LPFILETIME` type provided by the `windows.h` header. * `WINDOWS_INTERFACE::ULARGE_INTEGER` is a type alias to the `ULARGE_INTEGER` type provided by the `windows.h` header. * `WINDOWS_INTERFACE::ULONG64` is a type alias to the `ULONG64` type provided by the `windows.h` header. * `WINDOWS_INTERFACE::ULONGLONG` is a type alias to the `ULONGLONG` type provided by the `windows.h` header. * `WINDOWS_INTERFACE::WORD` is a type alias to the `WORD` type provided by the `windows.h` header. * `WINDOWS_INTERFACE::FileTimeToSystemTime` is a public, static member function that has `BOOL (const FILETIME *lpFileTime, LPSYSTEMTIME lpSystemTime)` type and whose contract is to return the result of `::FileTimeToSystemTime(lpFileTime, lpSystemTime)`, where `::FileTimeToSystemTime` is the corresponding function declared in the `windows.h` header. * `WINDOWS_INTERFACE::GetFileSize` is a public, static member function that has `DWORD (HANDLE hFile, LPDWORD lpFileSizeHigh)` type and whose contract is to return the result of `::GetFileSize(hFile, lpFileSizeHigh)`, where `::GetFileSize` is the corresponding function declared in the `windows.h` header. * `WINDOWS_INTERFACE::GetFileTime` is a public, static member function that has 'BOOL (HANDLE hFile, LPFILETIME lpCreationTime, LPFILETIME lpLastAccessTime, LPFILETIME, lpLastWriteTime)' type and whose contract is to return the result of '::GetFileTime(hFile, lpCreationTime, lpLastAccessTime, lpLastWriteTime)`, where `::GetFileTime' is the corresponding function declared in the `windows.h` header. * `WINDOWS_INTERFACE::GetLastError` is a public, static member function that has `DWORD ()` type and whose contract is to return the result of `::GetLastError()`, where `::GetLastError` is the corresponding function declared in the `windows.h` header. * `WINDOWS_INTERFACE::SystemTimeToFileTime` is a public, static member function that has `BOOL (const SYSTEMTIME *lpSystemTime, LPFILEMTIME lpFileTime)` type and whose contract is to return the result of `::SystemTimeToFileTime(lpSystemTime, lpFileTime)`, where `::SystemTimeToFileTime` is the corresponding function declared in the `windows.h` header.

== Type Aliases

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bdls/FilesystemUtil_WindowsImpUtil/FileDescriptor.adoc[`FileDescriptor`] 
| `FileDescriptor` is an alias for operating system's native file descriptor / file handle type.
| xref:BloombergLP/bdls/FilesystemUtil_WindowsImpUtil/Offset.adoc[`Offset`] 
| `Offset` is an alias for a signed integral type, and represents the offset of a location in a file.
|===


== Static Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bdls/FilesystemUtil_WindowsImpUtil/convertFileTimeToDatetime.adoc[`convertFileTimeToDatetime`] 
| Load into the specified `time` the time in the specified `lpFileTime`. Return 0 on success, and a non‐zero value otherwise. Note that the time is reported in UTC.
| xref:BloombergLP/bdls/FilesystemUtil_WindowsImpUtil/getFileSize.adoc[`getFileSize`] 
| Return the size, in bytes, of the file with the specified `descriptor`, or a negative value if an error occurs.
| xref:BloombergLP/bdls/FilesystemUtil_WindowsImpUtil/getLastModificationTime.adoc[`getLastModificationTime`] 
| Load into the specified `time` the last modification time of the file with the specified `descriptor`, as reported by the filesystem. Return 0 on success, and a non‐zero value otherwise. Note that the time is reported in UTC.
|===


== Static Data Members

[cols="1"]
|===
| Name
| xref:BloombergLP/bdls/FilesystemUtil_WindowsImpUtil/k_NANOSECONDS_PER_WINDOWS_TICK.adoc[`k_NANOSECONDS_PER_WINDOWS_TICK`] 
| xref:BloombergLP/bdls/FilesystemUtil_WindowsImpUtil/k_WINDOWS_TICKS_PER_MICROSECOND.adoc[`k_WINDOWS_TICKS_PER_MICROSECOND`] 
|===



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