From 28063de488a8aa83de19cfb15b873ad943356838 Mon Sep 17 00:00:00 2001
From: sin-ack <sin-ack@users.noreply.github.com>
Date: Sat, 18 Dec 2021 11:29:51 +0000
Subject: [PATCH] AK: Add ByteBuffer::{must_,}get_bytes_for_writing()

This is useful for writing new data at the end of a ByteBuffer. For
instance, with the Stream API:

    auto pending_bytes = TRY(stream.pending_bytes());
    auto receive_buffer = TRY(buffer.get_bytes_for_writing(
        pending_bytes));
    TRY(stream.read(receive_buffer));
---
 AK/ByteBuffer.h | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/AK/ByteBuffer.h b/AK/ByteBuffer.h
index 106f650841..abf4c9d53b 100644
--- a/AK/ByteBuffer.h
+++ b/AK/ByteBuffer.h
@@ -182,6 +182,20 @@ public:
         return try_ensure_capacity_slowpath(new_capacity);
     }
 
+    /// Return a span of bytes past the end of this ByteBuffer for writing.
+    /// Ensures that the required space is available.
+    ErrorOr<Bytes> get_bytes_for_writing(size_t length)
+    {
+        TRY(try_ensure_capacity(size() + length));
+        return Bytes { data() + size(), length };
+    }
+
+    /// Like get_bytes_for_writing, but crashes if allocation fails.
+    Bytes must_get_bytes_for_writing(size_t length)
+    {
+        return MUST(get_bytes_for_writing(length));
+    }
+
     void append(char byte)
     {
         MUST(try_append(byte));