From 90714a38311ec79500c0257670985bfe5d6c9a1b Mon Sep 17 00:00:00 2001
From: Jimmi Holst Christensen <rainbowhejsil@gmail.com>
Date: Fri, 19 Jan 2018 21:30:57 +0100
Subject: [PATCH] Implemented windows versions of seekTo and getPos

---
 std/io.zig               | 30 ++++++++++++++++++++++++++++++
 std/os/windows/index.zig |  8 ++++++++
 2 files changed, 38 insertions(+)

diff --git a/std/io.zig b/std/io.zig
index 605553b0ea..5121fd0c21 100644
--- a/std/io.zig
+++ b/std/io.zig
@@ -204,6 +204,15 @@ pub const File = struct {
                     };
                 }
             },
+            Os.windows => {
+                if (system.SetFilePointerEx(self.handle, amount, null, system.FILE_CURRENT) == 0) {
+                    const err = system.GetLastError();
+                    return switch (err) {
+                        system.ERROR.INVALID_PARAMETER => error.BadFd,
+                        else => os.unexpectedErrorPosix(err),
+                    };
+                }
+            },
             else => @compileError("unsupported OS"),
         }
     }
@@ -224,6 +233,15 @@ pub const File = struct {
                     };
                 }
             },
+            Os.windows => {
+                if (system.SetFilePointerEx(self.handle, @bitCast(isize, pos), null, system.FILE_BEGIN) == 0) {
+                    const err = system.GetLastError();
+                    return switch (err) {
+                        system.ERROR.INVALID_PARAMETER => error.BadFd,
+                        else => os.unexpectedErrorWindows(err),
+                    };
+                }
+            },
             else => @compileError("unsupported OS: " ++ @tagName(builtin.os)),
         }
     }
@@ -245,6 +263,18 @@ pub const File = struct {
                 }
                 return result;
             },
+            Os.windows => {
+                var pos : usize = undefined;
+                if (system.SetFilePointerEx(self.handle, 0, @ptrCast(system.PLARGE_INTEGER, &pos), system.FILE_CURRENT) == 0) {
+                    const err = system.GetLastError();
+                    return switch (err) {
+                        system.ERROR.INVALID_PARAMETER => error.BadFd,
+                        else => os.unexpectedErrorWindows(err),
+                    };
+                }
+
+                return pos;
+            },
             else => @compileError("unsupported OS"),
         }
     }
diff --git a/std/os/windows/index.zig b/std/os/windows/index.zig
index d460e94f64..b10d373d78 100644
--- a/std/os/windows/index.zig
+++ b/std/os/windows/index.zig
@@ -74,6 +74,9 @@ pub extern "kernel32" stdcallcc fn ReadFile(in_hFile: HANDLE, out_lpBuffer: LPVO
     in_nNumberOfBytesToRead: DWORD, out_lpNumberOfBytesRead: &DWORD,
     in_out_lpOverlapped: ?&OVERLAPPED) -> BOOL;
 
+pub extern "kernel32" stdcallcc fn SetFilePointerEx(in_fFile: HANDLE, in_liDistanceToMove: LARGE_INTEGER, 
+    out_opt_ldNewFilePointer: ?PLARGE_INTEGER, in_dwMoveMethod: DWORD) -> BOOL;
+
 pub extern "kernel32" stdcallcc fn SetHandleInformation(hObject: HANDLE, dwMask: DWORD, dwFlags: DWORD) -> BOOL;
 
 pub extern "kernel32" stdcallcc fn Sleep(dwMilliseconds: DWORD);
@@ -126,6 +129,7 @@ pub const UNICODE = false;
 pub const WCHAR = u16;
 pub const WORD = u16;
 pub const LARGE_INTEGER = i64;
+pub const PLARGE_INTEGER = &LARGE_INTEGER;
 
 pub const TRUE = 1;
 pub const FALSE = 0;
@@ -289,3 +293,7 @@ pub const MOVEFILE_DELAY_UNTIL_REBOOT = 4;
 pub const MOVEFILE_FAIL_IF_NOT_TRACKABLE = 32;
 pub const MOVEFILE_REPLACE_EXISTING = 1;
 pub const MOVEFILE_WRITE_THROUGH = 8;
+
+pub const FILE_BEGIN = 0;
+pub const FILE_CURRENT = 1;
+pub const FILE_END = 2;
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