An Edit x gives each of its searches the step budget, and a search that spends it says it took too much time

The budget was the compiled pattern's, spent over every search an x made: Edit ,x/x+/c/z/ over 100k lines ran out and failed, blamed on backtracking. Each search now starts with the whole budget, and one that spends it says regular expression search took too much time, gave up. (Not "too long": 9ns reads those words as ENAMETOOLONG.)

Co-Authored-By: Claude Opus 5.5 <[email protected]>

2 files changed, 18 insertions, 1 deletions

diff --git a/src/ninep/addr.zig b/src/ninep/addr.zig
index c052a665..005ad593 100644
--- a/src/ninep/addr.zig
+++ b/src/ninep/addr.zig
@@ -17,7 +17,7 @@ pub const e_col_zero = "address out of range: a column counts from 1";
 pub const e_regexp = "bad regular expression";
 /// Not "took too long": 9ns reads errors by their words, and that would be
 /// ENAMETOOLONG.
-pub const e_slow = "regular expression search gave up, backtracking past its step budget";
+pub const e_slow = "regular expression search took too much time, gave up";
 pub const e_syntax = "bad address syntax";
 pub const e_order = "addresses out of order";
 
diff --git a/src/sam_edit.zig b/src/sam_edit.zig
index 113ad14f..8f7c961f 100644
--- a/src/sam_edit.zig
+++ b/src/sam_edit.zig
@@ -456,6 +456,9 @@ const Exec = struct {
     /// reaches back into what the last one took.
     fn find(ex: *Exec, rx: *regexp.Regex, from: usize, hi: usize) Failure!?regexp.Regex.Match {
         if (from > hi) return null;
+        // The budget is each search's own: an x over 100k lines makes 100k
+        // searches, none of which is the slow one.
+        rx.steps = regexp.Regex.budget;
         const m = (rx.find(ex.text, from, hi, hi) catch return fail(ex.why, "{s}", .{addr_lang.e_slow})) orelse return null;
         var start = modal.runeStart(ex.text, m.start);
         if (start < from) start = modal.runeEnd(ex.text, m.start);
@@ -694,6 +697,20 @@ fn expectEdit(text: []const u8, command: []const u8, want: []const u8) !void {
     try std.testing.expectEqualStrings(want, got);
 }
 
+test "an x over 100k lines is 100k searches, each with its own step budget" {
+    const th = @import("ninep/testing.zig");
+    const line = "x" ** 80 ++ "\n";
+    const text = try std.testing.allocator.alloc(u8, line.len * 100_000);
+    defer std.testing.allocator.free(text);
+    for (0..100_000) |k| @memcpy(text[line.len * k ..][0..line.len], line);
+    const p = try th.withFile(std.testing.allocator, text);
+    defer p.deinit();
+    const tree = @import("ninep/tree.zig");
+    const r = th.wr(p, tree.Node.of(th.serialOf(p), .ctl), "Edit ,x/x+/c/z/\n");
+    try std.testing.expectEqual(tree.Status.ok, r.reply.status);
+    try std.testing.expect(std.mem.startsWith(u8, p.panes[0].?.file.?.content, "z\nz\n"));
+}
+
 test "sam's classic commands" {
     try expectEdit("foo x foo y foo\n", ",x/foo/c/foobar/", "foobar x foobar y foobar\n");
     try expectEdit("a b\nc d\n", ",x/ /c/_/", "a_b\nc_d\n");