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// SPDX-License-Identifier: GPL-2.0
#include <linux/bitops.h>
#include <linux/math.h>
#include <linux/string.h>
#include <asm/unaligned.h>
#ifdef CONFIG_VALGRIND
#include <valgrind/memcheck.h>
#endif
#include "varint.h"
/**
* bch2_varint_encode - encode a variable length integer
* @out - destination to encode to
* @v - unsigned integer to encode
*
* Returns the size in bytes of the encoded integer - at most 9 bytes
*/
int bch2_varint_encode(u8 *out, u64 v)
{
unsigned bits = fls64(v|1);
unsigned bytes = DIV_ROUND_UP(bits, 7);
if (likely(bytes < 9)) {
v <<= bytes;
v |= ~(~0 << (bytes - 1));
v = cpu_to_le64(v);
memcpy(out, &v, bytes);
} else {
*out++ = 255;
bytes = 9;
put_unaligned_le64(v, out);
}
return bytes;
}
/**
* bch2_varint_decode - encode a variable length integer
* @in - varint to decode
* @end - end of buffer to decode from
* @out - on success, decoded integer
*
* Returns the size in bytes of the decoded integer - or -1 on failure (would
* have read past the end of the buffer)
*/
int bch2_varint_decode(const u8 *in, const u8 *end, u64 *out)
{
unsigned bytes = likely(in < end)
? ffz(*in & 255) + 1
: 1;
u64 v;
if (unlikely(in + bytes > end))
return -1;
if (likely(bytes < 9)) {
v = 0;
memcpy(&v, in, bytes);
v = le64_to_cpu(v);
v >>= bytes;
} else {
v = get_unaligned_le64(++in);
}
*out = v;
return bytes;
}
/**
* bch2_varint_encode_fast - fast version of bch2_varint_encode
*
* This version assumes it's always safe to write 8 bytes to @out, even if the
* encoded integer would be smaller.
*/
int bch2_varint_encode_fast(u8 *out, u64 v)
{
unsigned bits = fls64(v|1);
unsigned bytes = DIV_ROUND_UP(bits, 7);
if (likely(bytes < 9)) {
v <<= bytes;
v |= ~(~0 << (bytes - 1));
} else {
*out++ = 255;
bytes = 9;
}
put_unaligned_le64(v, out);
return bytes;
}
/**
* bch2_varint_decode_fast - fast version of bch2_varint_decode
*
* This version assumes that it is safe to read at most 8 bytes past the end of
* @end (we still return an error if the varint extends past @end).
*/
int bch2_varint_decode_fast(const u8 *in, const u8 *end, u64 *out)
{
#ifdef CONFIG_VALGRIND
VALGRIND_MAKE_MEM_DEFINED(in, 8);
#endif
u64 v = get_unaligned_le64(in);
unsigned bytes = ffz(*in) + 1;
if (unlikely(in + bytes > end))
return -1;
if (likely(bytes < 9)) {
v >>= bytes;
v &= ~(~0ULL << (7 * bytes));
} else {
v = get_unaligned_le64(++in);
}
*out = v;
return bytes;
}
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