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

README.md

@@ -63,15 +63,15 @@ pub fn main() void {
 This will result in the following output:
 
 ```
-debug(main):    Debug message 42
-info(main):     Info message { 1, 2, 3, 4 }
-info(main):     Info message "This is a test"
-warning(main):  Warning message main.Options = enum {
+[2024-08-28 22:22] debug(main): Debug message 42
+[2024-08-28 22:22] info(main): Info message { 1, 2, 3, 4 }
+[2024-08-28 22:22] info(main): Info message "This is a test"
+[2024-08-28 22:22] warning(main): Warning message main.Options = enum {
         a,
         b,
         c,
 } = a
-error(main):    Error message main.Struct = struct {
+[2024-08-28 22:22] error(main): Error message main.Struct = struct {
         .a = 42,
         .b = true,
         .c = []u16: { 1, 2, 3, 4, 5 },
@@ -83,3 +83,9 @@ error(main):    Error message main.Struct = struct {
         } = b,
 }
 ```
+
+## Customization
+
+For more details about the output customization see the configuration options of the `zlog` module. Following options are available:
+
+- _timestamp_ (default: `true`): Prepend the current timestamp before each log message.

build.zig

@@ -4,6 +4,14 @@ const std = @import("std");
 // declaratively construct a build graph that will be executed by an external
 // runner.
 pub fn build(b: *std.Build) void {
+    // build options to customize the log message formating
+    const include_timestamp = b.option(bool, "timestamp", "Enable inclusion of timestamps in log messages (default: true)") orelse true;
+
+    const options = b.addOptions();
+    options.addOption(bool, "timestamp", include_timestamp);
+
+    const options_module = options.createModule();
+
     // Standard target options allows the person running `zig build` to choose
     // what target to build for. Here we do not override the defaults, which
     // means any target is allowed, and the default is native. Other options
@@ -21,7 +29,9 @@ pub fn build(b: *std.Build) void {
         .root_source_file = b.path("src/zlog.zig"),
         .target = target,
         .optimize = optimize,
+        .link_libc = include_timestamp, // uses c std library <time.h>
     });
+    zlog_module.addImport("build_options", options_module);
 
     const exe = b.addExecutable(.{
         .name = "zlog",

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;
     }