feat(rtl): add cmdline parser

src/rtl/cmdline.zig

@@ -0,0 +1,58 @@
+//! Command-line arguments parser.
+//! This is used to parse the kernel cmdline.
+const std = @import("std");
+
+/// Get the string value of `key` in `cmdline`.
+pub fn get_string(cmdline: []const u8, key: []const u8) ?[]const u8 {
+    var parts = std.mem.splitAny(u8, cmdline, " ");
+    while (parts.next()) |part| {
+        if (part.len > key.len + 1 and
+            std.mem.startsWith(u8, part, key) and
+            part[key.len] == '=')
+        {
+            return part[key.len + 1 ..];
+        }
+    }
+    return null;
+}
+
+/// Get the integer value of `key` in `cmdline`.
+pub fn get_number(cmdline: []const u8, key: []const u8) ?i64 {
+    const str = get_string(cmdline, key);
+    if (str) |s| {
+        const res = std.fmt.parseInt(i64, s, 10) catch return null;
+        return res;
+    }
+    return null;
+}
+
+test "get_string() should return the value of a key" {
+    const cmdline = "foo=bar baz=qux";
+    const value = get_string(cmdline, "foo");
+    try std.testing.expectEqualStrings("bar", value.?);
+    try std.testing.expectEqualStrings("qux", get_string(cmdline, "baz").?);
+}
+
+test "get_string() should return null if the key is not found" {
+    const cmdline = "foo=bar baz=qux";
+    try std.testing.expect(get_string(cmdline, "quux") == null);
+}
+
+test "malformed key-value pairs should be ignored" {
+    const cmdline = "foo=bar baz qux=quux";
+    try std.testing.expectEqualStrings("bar", get_string(cmdline, "foo").?);
+    try std.testing.expect(get_string(cmdline, "baz") == null);
+    try std.testing.expectEqualStrings("quux", get_string(cmdline, "qux").?);
+}
+
+test "get_number() should return the integer value of a key" {
+    const cmdline = "foo=42 baz=100";
+    try std.testing.expectEqual(42, get_number(cmdline, "foo").?);
+    try std.testing.expectEqual(100, get_number(cmdline, "baz").?);
+}
+
+test "get_number() should return null if the key is not found or value is not an integer" {
+    const cmdline = "foo=42 baz=qux";
+    try std.testing.expect(get_number(cmdline, "quux") == null);
+    try std.testing.expect(get_number(cmdline, "baz") == null);
+}

src/rtl/root.zig

@@ -3,6 +3,7 @@ const std = @import("std");
 pub const List = @import("list.zig").List;
 pub const SeqLock = @import("seqlock.zig").SeqLock;
 pub const barrier = @import("barrier.zig");
+pub const cmdline = @import("cmdline.zig");
 pub const pairing_heap = @import("pairing_heap.zig");
 pub const PairingHeap = pairing_heap.PairingHeap;