flang/runtime/buffer.cpp

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