fastmem: rotateOnce

src/fastmem.zig

@@ -22,5 +22,13 @@ pub inline fn copy(comptime T: type, dest: []T, source: []const T) void {
     }
 }
 
+/// Same as std.mem.rotate(T, items, 1) but more efficient by using memmove
+/// and a tmp var for the single rotated item instead of 3 calls to reverse.
+pub inline fn rotateOnce(comptime T: type, items: []T) void {
+    const tmp = items[0];
+    move(T, items[0..items.len - 1], items[1..items.len]);
+    items[items.len - 1] = tmp;
+}
+
 extern "c" fn memcpy(*anyopaque, *const anyopaque, usize) *anyopaque;
 extern "c" fn memmove(*anyopaque, *const anyopaque, usize) *anyopaque;

src/terminal/PageList.zig

@@ -6,6 +6,7 @@ const PageList = @This();
 const std = @import("std");
 const Allocator = std.mem.Allocator;
 const assert = std.debug.assert;
+const fastmem = @import("../fastmem.zig");
 const point = @import("point.zig");
 const pagepkg = @import("page.zig");
 const stylepkg = @import("style.zig");
@@ -2001,7 +2002,7 @@ pub fn eraseRow(
     // In order to move the following rows up we rotate the rows array by 1.
     // The rotate operation turns e.g. [ 0 1 2 3 ] in to [ 1 2 3 0 ], which
     // works perfectly to move all of our elements where they belong.
-    std.mem.rotate(Row, rows[pn.y..page.data.size.rows], 1);
+    fastmem.rotateOnce(Row, rows[pn.y..page.data.size.rows]);
 
     // We adjust the tracked pins in this page, moving up any that were below
     // the removed row.
@@ -2038,7 +2039,7 @@ pub fn eraseRow(
         page = next;
         rows = next_rows;
 
-        std.mem.rotate(Row, rows[0..page.data.size.rows], 1);
+        fastmem.rotateOnce(Row, rows[0..page.data.size.rows]);
 
         // Our tracked pins for this page need to be updated.
         // If the pin is in row 0 that means the corresponding row has