From 7ee7530f2f4068c2642136a484e945ffa4b89cee Mon Sep 17 00:00:00 2001
From: Ben Sinclair <ben@typius.com>
Date: Tue, 12 Mar 2024 12:35:51 +1100
Subject: [PATCH] Fix formatting for fractions with leading zeroes

---
 util/format.zig      | 18 ++++++++----------
 util/format_test.zig | 25 ++++++++++++++++++++-----
 2 files changed, 28 insertions(+), 15 deletions(-)

diff --git a/util/format.zig b/util/format.zig
index 1d1f3fc..c0c3899 100644
--- a/util/format.zig
+++ b/util/format.zig
@@ -2,23 +2,21 @@ const std = @import("std");
 const Color = @import("./color.zig").Color;
 const log = std.log.scoped(.zbench_format);
 
-pub fn duration(buffer: []u8, d: u64) ![]u8 {
+pub fn duration(buffer: []u8, nanoseconds: u64) ![]u8 {
     const units = [_][]const u8{ "ns", "µs", "ms", "s" };
 
-    var scaledDuration: u64 = d;
+    var scaled: f64 = @floatFromInt(nanoseconds);
     var unitIndex: usize = 0;
 
-    var fractionalPart: u64 = 0;
-
-    while (scaledDuration >= 1_000 and unitIndex < units.len - 1) {
-        fractionalPart = scaledDuration % 1_000;
-        scaledDuration /= 1_000;
+    while (scaled >= 1000.0 and unitIndex < units.len - 1) {
+        scaled /= 1000.0;
         unitIndex += 1;
     }
 
-    const formatted = try std.fmt.bufPrint(buffer, "{d}.{d}{s}", .{ scaledDuration, fractionalPart, units[unitIndex] });
-
-    return formatted;
+    return if (0 < unitIndex) try std.fmt.bufPrint(buffer, "{d:.3}{s}", .{
+        scaled,
+        units[unitIndex],
+    }) else try std.fmt.bufPrint(buffer, "{d}ns", .{nanoseconds});
 }
 
 pub fn memorySize(bytes: u64, allocator: std.mem.Allocator) ![]const u8 {
diff --git a/util/format_test.zig b/util/format_test.zig
index 1fe2257..c39a61c 100644
--- a/util/format_test.zig
+++ b/util/format_test.zig
@@ -8,27 +8,42 @@ test "duration" {
 
     {
         const result = try format.duration(buffer[0..], 1);
-        try std.testing.expectEqualSlices(u8, "1.0ns", result);
+        try std.testing.expectEqualSlices(u8, "1ns", result);
     }
 
     {
         const result = try format.duration(buffer[0..], 999);
-        try std.testing.expectEqualSlices(u8, "999.0ns", result);
+        try std.testing.expectEqualSlices(u8, "999ns", result);
     }
 
     {
         const result = try format.duration(buffer[0..], 1000);
-        try std.testing.expectEqualSlices(u8, "1.0µs", result);
+        try std.testing.expectEqualSlices(u8, "1.000µs", result);
     }
 
     {
         const result = try format.duration(buffer[0..], 1000000);
-        try std.testing.expectEqualSlices(u8, "1.0ms", result);
+        try std.testing.expectEqualSlices(u8, "1.000ms", result);
     }
 
     {
         const result = try format.duration(buffer[0..], 1000000000);
-        try std.testing.expectEqualSlices(u8, "1.0s", result);
+        try std.testing.expectEqualSlices(u8, "1.000s", result);
+    }
+
+    {
+        const result = try format.duration(buffer[0..], 1234567890);
+        try std.testing.expectEqualSlices(u8, "1.235s", result);
+    }
+
+    {
+        const result = try format.duration(buffer[0..], 1023456789);
+        try std.testing.expectEqualSlices(u8, "1.023s", result);
+    }
+
+    {
+        const result = try format.duration(buffer[0..], 1999999999);
+        try std.testing.expectEqualSlices(u8, "2.000s", result);
     }
 
     {