zig perf print

2024/02/p1/main.zig

@@ -1,37 +1,41 @@
 const std = @import("std");
+const time = std.time;
+const Timer = time.Timer;
 
 pub fn main() !void {
     var file = try std.fs.cwd()
         .openFile("../input.txt", .{});
     defer file.close();
+    var buf: [32 * 1024]u8 = undefined;
+    buf[try file.read(&buf) - 1] = ' ';
+    // _ = try file.read(&buf);
 
-    var buf_reader = std.io.bufferedReader(file.reader());
-    var in_stream = buf_reader.reader();
+    var timer = try Timer.start();
 
-    var buf: [64]u8 = undefined;
     var t: u32 = 0;
-    while (try in_stream.readUntilDelimiterOrEof(&buf, '\n')) |line| {
+    var split = std.mem.splitScalar(u8, &buf, '\n');
+    out: while (split.next()) |line| {
+        // if (line[0] == 0) continue;
         var split_iter = std.mem.split(u8, line, " ");
 
         var dir: i8 = 0;
-        var prev = try std.fmt.parseInt(i8, split_iter.next() orelse unreachable, 10);
-        t += while (split_iter.next()) |strnum| {
+        var prev = try std.fmt.parseInt(i8, split_iter.next().?, 10);
+        while (split_iter.next()) |strnum| {
             const n = try std.fmt.parseInt(i8, strnum, 10);
             const d = prev - n;
-            prev = n;
             if (d == 0 or @abs(d) > 3)
-                break 0;
+                continue :out;
 
             if (dir == 0) {
                 dir = d;
-            } else if (!sameSign(dir, d)) {
-                break 0;
-            }
-        } else 1;
-    }
-    std.debug.print("Total {d}\n", .{t});
-}
+            } else if (d ^ dir < 0)
+                continue :out;
+            prev = n;
+        }
 
-pub fn sameSign(n1: i8, n2: i8) bool {
-    return (n1 < 0) == (n2 < 0);
+        t += 1;
+    }
+
+    const elapsed: f64 = @floatFromInt(timer.read());
+    std.debug.print("Total {d} in {d:.6}µs\n", .{ t, elapsed / time.ns_per_us });
 }