[libc-commits] [libc] [libc] Support dynamically-grown lines in FlatFileDatabase (PR #223811)

[Alexey Samsonov via libc-commits]

================
@@ -0,0 +1,104 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Growable byte buffer with explicit lifetime management.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC___SUPPORT_PWD_DYNAMIC_BUFFER_H
+#define LLVM_LIBC_SRC___SUPPORT_PWD_DYNAMIC_BUFFER_H
+
+#include "hdr/func/free.h"
+#include "hdr/func/realloc.h"
+#include "hdr/types/size_t.h"
+#include "src/__support/CPP/limits.h"
+#include "src/__support/CPP/span.h"
+#include "src/__support/CPP/type_traits/is_trivially_destructible.h"
+#include "src/__support/macros/attributes.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace pwd {
+
+// A heap-backed, growable byte buffer for the flat-file database engine.
+//
+// This type is trivially destructible by design, so an instance can be a
+// constant-initialised process global. The owner releases the storage
+// explicitly when done.
+class DynamicBuffer {
+  static constexpr size_t INITIAL_CAPACITY = 256;
----------------
vonosmas wrote:

Out-of-curiosity - what if we make it 1024, so that if the lines fit into the "regular" default size (_SC_GETGR_R_SIZE_MAX) there will be no reallocations.

I don't care too much it about it though.

https://github.com/llvm/llvm-project/pull/223811