From 0bd9cc0259a15a5b78bfe2889a9866800560067d Mon Sep 17 00:00:00 2001
From: Meghan Denny <hello@nektro.net>
Date: Fri, 13 Mar 2026 19:47:54 -0700
Subject: [PATCH] add CountingWriter

---
 counting_writer.zig | 27 +++++++++++++++++++++++++++
 nio.zig             |  2 ++
 2 files changed, 29 insertions(+)
 create mode 100644 counting_writer.zig

diff --git a/counting_writer.zig b/counting_writer.zig
new file mode 100644
index 0000000000000000000000000000000000000000..291ea5cb5bd75e871a3e756392350367cbcee702
--- /dev/null
+++ b/counting_writer.zig
@@ -0,0 +1,27 @@
+const std = @import("std");
+const extras = @import("extras");
+const nio = @import("./nio.zig");
+
+pub fn CountingWriter(WriterType: type) type {
+    return struct {
+        backing_writer: WriterType,
+        bytes_written: u64,
+
+        const Self = @This();
+
+        pub fn init(backing_writer: WriterType) Self {
+            return .{
+                .backing_writer = backing_writer,
+                .bytes_written = 0,
+            };
+        }
+
+        pub const WriteError = extras.Pointee(WriterType).WriteError;
+        pub usingnamespace nio.Writable(@This(), ._var);
+        pub fn write(self: *Self, bytes: []const u8) WriteError!usize {
+            const len = try self.backing_writer.write(bytes);
+            self.bytes_written += len;
+            return len;
+        }
+    };
+}
diff --git a/nio.zig b/nio.zig
index 4b563b98c3dfc9537a4a0da6a0ae95ac1e09253f..f9c07a4fe028b6d2057086a4031e6f27d0d56738 100644
--- a/nio.zig
+++ b/nio.zig
@@ -289,3 +289,5 @@ pub const FixedBufferStream = @import("./fixed_buffer_stream.zig").FixedBufferSt
 pub const BufferedReader = @import("./buffered_reader.zig").BufferedReader;
 
 pub const BufferedWriter = @import("./buffered_writer.zig").BufferedWriter;
+
+pub const CountingWriter = @import("./counting_writer.zig").CountingWriter;
-- 
2.54.0