pw_kvs: Check that AlignedWrite buffer is at least write alignment

Check that the internal buffer for AlignedWrite<> is at least the size
of the write alignment that was given as an argument.

Change-Id: Ia438bfcac2540ca6c2b06ea9383a7682d158e7d9

pw_kvs/public/pw_kvs/alignment.h

diff --git a/pw_kvs/public/pw_kvs/alignment.h b/pw_kvs/public/pw_kvs/alignment.h
index b2dcbc3..2663846 100644
--- a/pw_kvs/public/pw_kvs/alignment.h
+++ b/pw_kvs/public/pw_kvs/alignment.h
@@ -97,6 +97,12 @@
 StatusWithSize AlignedWrite(Output& output,
                             size_t alignment_bytes,
                             span<const span<const std::byte>> data) {
+  // TODO: This should convert to PW_CHECK once that is available for use in
+  // host tests.
+  if (alignment_bytes > kBufferSize) {
+    return StatusWithSize(Status::INTERNAL);
+  }
+
   AlignedWriterBuffer<kBufferSize> buffer(alignment_bytes, output);
 
   for (const span<const std::byte>& chunk : data) {