add(timestamp): timestamp build configuration option to add timestamps before log messages

src/zlog.zig

@@ -1,13 +1,7 @@
+const build_options = @import("build_options");
+const c_time = if (build_options.timestamp) @cImport(@cInclude("time.h")) else null;
 const std = @import("std");
 
-// pub fn format(value: ?, comptime fmt: []const u8, options: std.fmt.FormatOptions, writer: anytype) !void
-// TODO: provide comptime helper function to add format function for user types:
-// - pretty printing
-// - compact printing
-// - show types of struct members
-// Maybe the corresponding configurations for the `format` function could also
-// be effected by build time configurations
-
 pub const std_options: std.Options = .{
     .logFn = logFn,
 };
@@ -20,15 +14,9 @@ fn logFn(
     args: anytype,
 ) void {
     // TODO: provide build time configuration to allow tweaking corresponding output
-    // - add timestamp to all log messages
     // - change output file for writing messages to (default `stderr`)
-
-    // TODO: improve formatting output, such that the resulting log has a good feel
-    // - should there be indenting?
-    // - should there be spacing?
-    // - should the messages be aligned (left, center, right)?
     const level_txt = comptime message_level.asText();
-    const prefix = if (scope == .default) ":\t" else "(" ++ @tagName(scope) ++ "):\t";
+    const prefix = if (scope == .default) ": " else "(" ++ @tagName(scope) ++ "): ";
     const stderr = std.io.getStdErr().writer();
     var bw = std.io.bufferedWriter(stderr);
     const writer = bw.writer();
@@ -36,6 +24,14 @@ fn logFn(
     std.debug.lockStdErr();
     defer std.debug.unlockStdErr();
     nosuspend {
+        if (build_options.timestamp) {
+            const curtime = c_time.time(null);
+            const tm = c_time.localtime(&curtime);
+
+            var buf: [32]u8 = undefined;
+            _ = c_time.strftime(@ptrCast(&buf), 32, "%F %R", tm);
+            writer.print("[{s}] ", .{buf}) catch return;
+        }
         writer.print(level_txt ++ prefix ++ format ++ "\n", args) catch return;
         bw.flush() catch return;
     }