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a3e7226268
Previous varint implementation used by the inode code was not nearly as fast as it could have been; partly because it was attempting to encode integers up to 96 bits (for timestamps) but this meant that encoding and decoding the length required a table lookup. Instead, we'll just encode timestamps greater than 64 bits as two separate varints; this will make decoding/encoding of inodes significantly faster overall. Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com> Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
44 lines
736 B
C
44 lines
736 B
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/bitops.h>
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#include <linux/math.h>
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#include <asm/unaligned.h>
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#include "varint.h"
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int bch2_varint_encode(u8 *out, u64 v)
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{
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unsigned bits = fls64(v|1);
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unsigned bytes = DIV_ROUND_UP(bits, 7);
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if (likely(bytes < 9)) {
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v <<= bytes;
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v |= ~(~0 << (bytes - 1));
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} else {
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*out++ = 255;
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bytes = 9;
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}
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put_unaligned_le64(v, out);
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return bytes;
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}
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int bch2_varint_decode(const u8 *in, const u8 *end, u64 *out)
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{
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u64 v = get_unaligned_le64(in);
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unsigned bytes = ffz(v & 255) + 1;
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if (unlikely(in + bytes > end))
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return -1;
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if (likely(bytes < 9)) {
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v >>= bytes;
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v &= ~(~0ULL << (7 * bytes));
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} else {
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v = get_unaligned_le64(++in);
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}
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*out = v;
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return bytes;
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}
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