From b1d3e36e2ea0d428dd333019c8346b6d4bcbc762 Mon Sep 17 00:00:00 2001
From: "Jeffrey C. Ollie" <jeff@ocjtech.us>
Date: Thu, 5 Mar 2026 10:03:58 -0600
Subject: [PATCH] windows: add GetComputerNameA so that hostname-related
 functions work

---
 src/os/hostname.zig | 37 +++++++++++++++++++++++++++++++------
 src/os/windows.zig  |  5 +++++
 2 files changed, 36 insertions(+), 6 deletions(-)

diff --git a/src/os/hostname.zig b/src/os/hostname.zig
index f728a2455..af9148fbf 100644
--- a/src/os/hostname.zig
+++ b/src/os/hostname.zig
@@ -1,4 +1,5 @@
 const std = @import("std");
+const builtin = @import("builtin");
 const posix = std.posix;
 
 pub const LocalHostnameValidationError = error{
@@ -99,9 +100,21 @@ pub fn isLocal(hostname: []const u8) LocalHostnameValidationError!bool {
     if (std.mem.eql(u8, "localhost", hostname)) return true;
 
     // If hostname is not "localhost" it must match our hostname.
-    var buf: [posix.HOST_NAME_MAX]u8 = undefined;
-    const ourHostname = try posix.gethostname(&buf);
-    return std.mem.eql(u8, hostname, ourHostname);
+    switch (builtin.os.tag) {
+        .windows => {
+            const windows = @import("windows.zig");
+            var buf: [256:0]u8 = undefined;
+            var nSize: windows.DWORD = buf.len;
+            if (windows.exp.kernel32.GetComputerNameA(&buf, &nSize) == 0) return false;
+            const ourHostname = buf[0..nSize];
+            return std.mem.eql(u8, hostname, ourHostname);
+        },
+        else => {
+            var buf: [posix.HOST_NAME_MAX]u8 = undefined;
+            const ourHostname = try posix.gethostname(&buf);
+            return std.mem.eql(u8, hostname, ourHostname);
+        },
+    }
 }
 
 test "isLocal returns true when provided hostname is localhost" {
@@ -109,9 +122,21 @@ test "isLocal returns true when provided hostname is localhost" {
 }
 
 test "isLocal returns true when hostname is local" {
-    var buf: [posix.HOST_NAME_MAX]u8 = undefined;
-    const localHostname = try posix.gethostname(&buf);
-    try std.testing.expect(try isLocal(localHostname));
+    switch (builtin.os.tag) {
+        .windows => {
+            const windows = @import("windows.zig");
+            var buf: [256:0]u8 = undefined;
+            var nSize: windows.DWORD = buf.len;
+            if (windows.exp.kernel32.GetComputerNameA(&buf, &nSize) == 0) return error.GetComputerNameFailed;
+            const localHostname = buf[0..nSize];
+            try std.testing.expect(try isLocal(localHostname));
+        },
+        else => {
+            var buf: [posix.HOST_NAME_MAX]u8 = undefined;
+            const localHostname = try posix.gethostname(&buf);
+            try std.testing.expect(try isLocal(localHostname));
+        },
+    }
 }
 
 test "isLocal returns false when hostname is not local" {
diff --git a/src/os/windows.zig b/src/os/windows.zig
index 87d1b662e..e92a54537 100644
--- a/src/os/windows.zig
+++ b/src/os/windows.zig
@@ -99,6 +99,11 @@ pub const exp = struct {
             lpStartupInfo: *windows.STARTUPINFOW,
             lpProcessInformation: *windows.PROCESS_INFORMATION,
         ) callconv(.winapi) windows.BOOL;
+        /// https://learn.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-getcomputernamea
+        pub extern "kernel32" fn GetComputerNameA(
+            lpBuffer: windows.LPSTR,
+            nSize: *windows.DWORD,
+        ) callconv(.winapi) windows.BOOL;
     };
 
     pub const PROC_THREAD_ATTRIBUTE_NUMBER = 0x0000FFFF;