From d48251d0f0d2de2f618afe65db3ba425b332d5c4 Mon Sep 17 00:00:00 2001
From: Ryan Liptak <squeek502@hotmail.com>
Date: Sat, 13 Jul 2024 17:29:18 -0700
Subject: [PATCH] ArgIteratorWindows.init: Take `[]const u16` slice instead of
 multi-item pointer
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Now that we use the PEB to get the precise length of the command line string, there's no need for a multi-item pointer/sliceTo call. This provides a minor speedup:

    Benchmark 1 (153 runs): benchargv-before.exe
      measurement          mean ± σ            min … max           outliers         delta
      wall_time          32.7ms ±  429us    32.1ms … 36.9ms          1 ( 1%)        0%
      peak_rss           6.49MB ± 5.62KB    6.46MB … 6.49MB         14 ( 9%)        0%
    Benchmark 2 (157 runs): benchargv-after.exe
      measurement          mean ± σ            min … max           outliers         delta
      wall_time          31.9ms ±  236us    31.4ms … 32.7ms          4 ( 3%)        ⚡-  2.4% ±  0.2%
      peak_rss           6.49MB ± 4.77KB    6.46MB … 6.49MB         14 ( 9%)          +  0.0% ±  0.0%
---
 lib/std/process.zig | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/lib/std/process.zig b/lib/std/process.zig
index 434e0fbbcc..f4b24a8013 100644
--- a/lib/std/process.zig
+++ b/lib/std/process.zig
@@ -664,7 +664,7 @@ pub const ArgIteratorWasi = struct {
 pub const ArgIteratorWindows = struct {
     allocator: Allocator,
     /// Encoded as WTF-16 LE.
-    cmd_line: [:0]const u16,
+    cmd_line: []const u16,
     index: usize = 0,
     /// Owned by the iterator. Long enough to hold contiguous NUL-terminated slices
     /// of each argument encoded as WTF-8.
@@ -678,9 +678,8 @@ pub const ArgIteratorWindows = struct {
     ///
     /// The iterator stores and uses `cmd_line_w`, so its memory must be valid for
     /// at least as long as the returned ArgIteratorWindows.
-    pub fn init(allocator: Allocator, cmd_line_w: [*:0]const u16) InitError!ArgIteratorWindows {
-        const cmd_line = mem.sliceTo(cmd_line_w, 0);
-        const wtf8_len = unicode.calcWtf8Len(cmd_line);
+    pub fn init(allocator: Allocator, cmd_line_w: []const u16) InitError!ArgIteratorWindows {
+        const wtf8_len = unicode.calcWtf8Len(cmd_line_w);
 
         // This buffer must be large enough to contain contiguous NUL-terminated slices
         // of each argument.
@@ -694,7 +693,7 @@ pub const ArgIteratorWindows = struct {
 
         return .{
             .allocator = allocator,
-            .cmd_line = cmd_line,
+            .cmd_line = cmd_line_w,
             .buffer = buffer,
         };
     }
@@ -1151,8 +1150,8 @@ pub const ArgIterator = struct {
         }
         if (native_os == .windows) {
             const cmd_line = std.os.windows.peb().ProcessParameters.CommandLine;
-            const cmd_line_w = cmd_line.Buffer.?[0 .. cmd_line.Length / 2 :0];
-            return ArgIterator{ .inner = try InnerType.init(allocator, cmd_line_w.ptr) };
+            const cmd_line_w = cmd_line.Buffer.?[0 .. cmd_line.Length / 2];
+            return ArgIterator{ .inner = try InnerType.init(allocator, cmd_line_w) };
         }
 
         return ArgIterator{ .inner = InnerType.init() };