Appendable

The body buffer type used in messages. Manages a growable byte buffer.

---

What It Is

Appendable is a dynamically growable byte buffer. Messages use it for the body field:

pub const Message = struct {
    bhdr: BinaryHeader = .{},
    thdrs: TextHeaders = .{},
    body: Appendable = .{},   // <-- This
    // ...
};

You don't create Appendable directly. tofu creates and manages it. You just use it.

---

Reading Data

Get the current content:

const data = msg.?.body.body();  // Returns ?[]const u8

Returns null if:

• Buffer not allocated
• Buffer is empty (length = 0)

Safe pattern:

if (msg.?.body.body()) |data| {
    // data is []const u8
    processData(data);
} else {
    // No body data
}

---

Writing Data

Add bytes to the buffer:

try msg.?.body.append(my_data);  // Grows automatically if needed

Replace all content:

try msg.?.body.copy(new_data);   // Resets then appends

Clear the buffer:

msg.?.body.reset();  // Sets length to 0, keeps memory allocated

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Methods Summary

Method	Returns	Description
body()	?[]const u8	Current data slice, or null if empty
append(data)	!void	Add bytes, auto-grows buffer
copy(data)	!void	Replace content (reset + append)
reset()	void	Clear length to 0, keep memory

---

Size Limit

64 KiB - 1 maximum

Body content is limited to 65535 bytes (64 KiB - 1). For larger data, use streaming with the more flag.

---

Memory Management

tofu handles all memory:

• Buffer is pre-allocated when message is created
• append() grows buffer automatically if needed
• reset() clears without freeing (efficient for reuse)

[//]: # (- Buffer is freed when message returns to pool) - consider add this functionality to pool

You never need to call init() or deinit().

---

Common Patterns

Check before read

var msg: ?*Message = try chnls.waitReceive(timeout);
defer ampe.put(&msg);

if (msg.?.body.body()) |data| {
    // Process data
} else {
    // Empty body - handle accordingly
}

Build response in place

// Reuse received message for response
msg.?.bhdr.proto.opCode = .Response;
msg.?.body.reset();                    // Clear old content
try msg.?.body.append("result: ");     // Add new content
try msg.?.body.append(result_data);
_ = try chnls.post(&msg);

Accumulate streamed data

var buffer = std.ArrayList(u8).init(allocator);
defer buffer.deinit();

while (true) {
    var msg: ?*Message = try chnls.waitReceive(timeout);
    defer ampe.put(&msg);

    if (msg.?.body.body()) |chunk| {
        try buffer.appendSlice(chunk);
    }

    if (!msg.?.hasMore()) break;
}
// buffer.items contains all accumulated data