| 1 | //===-- runtime/buffer.cpp ------------------------------------------------===// |
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| 2 | // |
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| 3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
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| 4 | // See https://llvm.org/LICENSE.txt for license information. |
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| 5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
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| 6 | // |
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| 7 | //===----------------------------------------------------------------------===// |
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| 8 | |
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| 9 | #include "buffer.h" |
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| 10 | #include <algorithm> |
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| 11 | |
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| 12 | namespace Fortran::runtime::io { |
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| 13 | |
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| 14 | // Here's a very old trick for shifting circular buffer data cheaply |
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| 15 | // without a need for a temporary array. |
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| 16 | void LeftShiftBufferCircularly( |
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| 17 | char *buffer, std::size_t bytes, std::size_t shift) { |
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| 18 | // Assume that we start with "efgabcd" and the left shift is 3. |
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| 19 | std::reverse(first: buffer, last: buffer + shift); // "gfeabcd" |
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| 20 | std::reverse(first: buffer, last: buffer + bytes); // "dcbaefg" |
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| 21 | std::reverse(first: buffer, last: buffer + bytes - shift); // "abcdefg" |
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| 22 | } |
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| 23 | } // namespace Fortran::runtime::io |
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| 24 | |
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