From cf266ec2a73e48dcd67961a0e0cff87bf12d78f2 Mon Sep 17 00:00:00 2001
From: Jarred Sumner <jarred@jarredsumner.com>
Date: Thu, 20 Feb 2025 13:14:56 -0800
Subject: [PATCH] fix

---
 src/fs.zig        |  2 +-
 src/sys.zig       |  8 ++++++++
 src/windows_c.zig | 26 ++++++++++++++++++++++++++
 3 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/src/fs.zig b/src/fs.zig
index aeb824680a..37f0002b10 100644
--- a/src/fs.zig
+++ b/src/fs.zig
@@ -1246,7 +1246,7 @@ pub const FileSystem = struct {
 
                 const read_buf = try file.preadAll(buf, 0).unwrap();
                 const prev_file_pos = if (comptime Environment.isWindows) try file.getPos().unwrap() else 0;
-                if (comptime Environment.isWindows) try file.seekTo(prev_file_pos);
+                if (comptime Environment.isWindows) try file.seekTo(@intCast(prev_file_pos));
                 file_contents = buf[0..read_buf];
 
                 if (strings.BOM.detect(file_contents)) |bom| {
diff --git a/src/sys.zig b/src/sys.zig
index 684e5ad3bf..23512974ce 100644
--- a/src/sys.zig
+++ b/src/sys.zig
@@ -2101,6 +2101,14 @@ pub fn pread(fd: bun.FileDescriptor, buf: []u8, offset: i64) Maybe(usize) {
         }
     }
 
+    if (comptime Environment.isWindows) {
+        if (bun.FDImpl.decode(fd).kind == .uv) {
+            return sys_uv.pread(fd, buf, offset);
+        }
+
+        return bun.C.readFile(fd, buf, @as(u64, @intCast(offset)));
+    }
+
     const ioffset = @as(i64, @bitCast(offset)); // the OS treats this as unsigned
     while (true) {
         const rc = pread_sym(fd.cast(), buf.ptr, adjusted_len, ioffset);
diff --git a/src/windows_c.zig b/src/windows_c.zig
index 21a91e741f..520c76804b 100644
--- a/src/windows_c.zig
+++ b/src/windows_c.zig
@@ -1330,6 +1330,32 @@ pub fn moveOpenedFileAt(
         Maybe(void).errno(rc, .NtSetInformationFile);
 }
 
+/// If buffer's length exceeds what a Windows DWORD integer can hold, it will be broken into
+/// multiple non-atomic reads.
+pub fn readFile(in_hFile: bun.FileDescriptor, buffer: []u8, offset: ?u64) Maybe(usize) {
+    const want_read_count: w.DWORD = @min(@as(w.DWORD, std.math.maxInt(w.DWORD)), buffer.len);
+    var amt_read: w.DWORD = undefined;
+    var overlapped_data: w.OVERLAPPED = undefined;
+    const overlapped: ?*w.OVERLAPPED = if (offset) |off| blk: {
+        overlapped_data = .{
+            .Internal = 0,
+            .InternalHigh = 0,
+            .DUMMYUNIONNAME = .{
+                .DUMMYSTRUCTNAME = .{
+                    .Offset = @as(u32, @truncate(off)),
+                    .OffsetHigh = @as(u32, @truncate(off >> 32)),
+                },
+            },
+            .hEvent = null,
+        };
+        break :blk &overlapped_data;
+    } else null;
+    if (w.kernel32.ReadFile(in_hFile.cast(), buffer.ptr, want_read_count, &amt_read, overlapped) == 0) {
+        return .{ .err = bun.sys.Error.fromCode(bun.windows.getLastErrno(), .read) };
+    }
+    return .{ .result = amt_read };
+}
+
 /// Same as moveOpenedFileAt but allows new_path to be a path relative to new_dir_fd.
 ///
 /// Aka: moveOpenedFileAtLoose(fd, dir, ".\\a\\relative\\not-normalized-path.txt", false);