1*651f58bfSDiana Picus //===-- runtime/buffer.cpp ------------------------------------------------===//
2f7be2518Speter klausler //
3f7be2518Speter klausler // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4f7be2518Speter klausler // See https://llvm.org/LICENSE.txt for license information.
5f7be2518Speter klausler // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6f7be2518Speter klausler //
7f7be2518Speter klausler //===----------------------------------------------------------------------===//
8f7be2518Speter klausler 
9f7be2518Speter klausler #include "buffer.h"
10f7be2518Speter klausler #include <algorithm>
11f7be2518Speter klausler 
12f7be2518Speter klausler namespace Fortran::runtime::io {
13f7be2518Speter klausler 
14f7be2518Speter klausler // Here's a very old trick for shifting circular buffer data cheaply
15f7be2518Speter klausler // without a need for a temporary array.
LeftShiftBufferCircularly(char * buffer,std::size_t bytes,std::size_t shift)16f7be2518Speter klausler void LeftShiftBufferCircularly(
17f7be2518Speter klausler     char *buffer, std::size_t bytes, std::size_t shift) {
18f7be2518Speter klausler   // Assume that we start with "efgabcd" and the left shift is 3.
19f7be2518Speter klausler   std::reverse(buffer, buffer + shift); // "gfeabcd"
20f7be2518Speter klausler   std::reverse(buffer, buffer + bytes); // "dcbaefg"
21f7be2518Speter klausler   std::reverse(buffer, buffer + bytes - shift); // "abcdefg"
22f7be2518Speter klausler }
231f879005STim Keith } // namespace Fortran::runtime::io
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