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https://github.com/scylladb/scylladb.git
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52 lines
1.1 KiB
C++
52 lines
1.1 KiB
C++
/*
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* Fast ASCII string validation.
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*
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* Copyright (c) 2018, Arm Limited.
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*/
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/*
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* SPDX-License-Identifier: LicenseRef-ScyllaDB-Source-Available-1.1
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*/
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#include "ascii.hh"
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#include <seastar/core/byteorder.hh>
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namespace utils {
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namespace ascii {
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bool validate(const uint8_t *data, size_t len) {
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// OR all bytes
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uint8_t orall = 0;
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// Fast OR by 8-bytes and two independent streams
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if (len >= 16) {
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uint64_t or1 = 0, or2 = 0;
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do {
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or1 |= seastar::read_le<uint64_t>((const char *)data);
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or2 |= seastar::read_le<uint64_t>((const char *)data+8);
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data += 16;
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len -= 16;
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} while (len >= 16);
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// Idea from Benny Halevy <bhalevy@scylladb.com>
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// - 7-th bit set ==> orall = !(non-zero) - 1 = 0 - 1 = 0xFF
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// - 7-th bit clear ==> orall = !0 - 1 = 1 - 1 = 0x00
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orall = !((or1 | or2) & 0x8080808080808080ULL) - 1;
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}
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// OR remaining bytes
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while (len--) {
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orall |= *data++;
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}
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// 7-th bit should be 0
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return orall < 0x80;
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}
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} // namespace ascii
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} // namespace utils
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