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ee1b8dc17a
Shifting a negative value left is undefined. Signed-off-by: Tavian Barnes <tavianator@tavianator.com> Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
130 lines
2.8 KiB
C
130 lines
2.8 KiB
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 <linux/string.h>
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#include <asm/unaligned.h>
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#ifdef CONFIG_VALGRIND
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#include <valgrind/memcheck.h>
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#endif
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#include "varint.h"
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/**
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* bch2_varint_encode - encode a variable length integer
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* @out: destination to encode to
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* @v: unsigned integer to encode
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* Returns: size in bytes of the encoded integer - at most 9 bytes
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*/
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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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__le64 v_le;
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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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v_le = cpu_to_le64(v);
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memcpy(out, &v_le, bytes);
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} else {
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*out++ = 255;
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bytes = 9;
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put_unaligned_le64(v, out);
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}
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return bytes;
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}
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/**
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* bch2_varint_decode - encode a variable length integer
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* @in: varint to decode
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* @end: end of buffer to decode from
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* @out: on success, decoded integer
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* Returns: size in bytes of the decoded integer - or -1 on failure (would
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* have read past the end of the buffer)
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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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unsigned bytes = likely(in < end)
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? ffz(*in & 255) + 1
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: 1;
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u64 v;
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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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__le64 v_le = 0;
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memcpy(&v_le, in, bytes);
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v = le64_to_cpu(v_le);
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v >>= 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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/**
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* bch2_varint_encode_fast - fast version of bch2_varint_encode
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* @out: destination to encode to
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* @v: unsigned integer to encode
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* Returns: size in bytes of the encoded integer - at most 9 bytes
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*
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* This version assumes it's always safe to write 8 bytes to @out, even if the
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* encoded integer would be smaller.
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*/
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int bch2_varint_encode_fast(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 |= ~(~0U << (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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/**
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* bch2_varint_decode_fast - fast version of bch2_varint_decode
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* @in: varint to decode
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* @end: end of buffer to decode from
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* @out: on success, decoded integer
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* Returns: size in bytes of the decoded integer - or -1 on failure (would
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* have read past the end of the buffer)
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*
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* This version assumes that it is safe to read at most 8 bytes past the end of
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* @end (we still return an error if the varint extends past @end).
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*/
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int bch2_varint_decode_fast(const u8 *in, const u8 *end, u64 *out)
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{
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#ifdef CONFIG_VALGRIND
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VALGRIND_MAKE_MEM_DEFINED(in, 8);
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#endif
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u64 v = get_unaligned_le64(in);
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unsigned bytes = ffz(*in) + 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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