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/**
Copyright (c) 2021, MariaDB Corporation.
This program is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free Software
Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with
this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA
**/
/**
@file include/fts0vlc.h
Full text variable length integer encoding/decoding.
Created 2021-10-19 Thirunarayanan Balathandayuthapani
**/
/** Return length of val if it were encoded using our VLC scheme.
@param val value to encode
@return length of value encoded, in bytes */
inline size_t fts_get_encoded_len(doc_id_t val)
{
if (val < static_cast<doc_id_t>(1) << 7)
return 1;
if (val < static_cast<doc_id_t>(1) << 14)
return 2;
if (val < static_cast<doc_id_t>(1) << 21)
return 3;
if (val < static_cast<doc_id_t>(1) << 28)
return 4;
if (val < static_cast<doc_id_t>(1) << 35)
return 5;
if (val < static_cast<doc_id_t>(1) << 42)
return 6;
if (val < static_cast<doc_id_t>(1) << 49)
return 7;
if (val < static_cast<doc_id_t>(1) << 56)
return 8;
if (val < static_cast<doc_id_t>(1) << 63)
return 9;
return 10;
}
/** Encode an integer using our VLC scheme and return the
length in bytes.
@param val value to encode
@param buf buffer, must have enough space
@return length of value encoded, in bytes */
inline byte *fts_encode_int(doc_id_t val, byte *buf)
{
if (val < static_cast<doc_id_t>(1) << 7)
goto add_1;
if (val < static_cast<doc_id_t>(1) << 14)
goto add_2;
if (val < static_cast<doc_id_t>(1) << 21)
goto add_3;
if (val < static_cast<doc_id_t>(1) << 28)
goto add_4;
if (val < static_cast<doc_id_t>(1) << 35)
goto add_5;
if (val < static_cast<doc_id_t>(1) << 42)
goto add_6;
if (val < static_cast<doc_id_t>(1) << 49)
goto add_7;
if (val < static_cast<doc_id_t>(1) << 56)
goto add_8;
if (val < static_cast<doc_id_t>(1) << 63)
goto add_9;
*buf++= static_cast<byte>(val >> 63);
add_9:
*buf++= static_cast<byte>(val >> 56) & 0x7F;
add_8:
*buf++= static_cast<byte>(val >> 49) & 0x7F;
add_7:
*buf++= static_cast<byte>(val >> 42) & 0x7F;
add_6:
*buf++= static_cast<byte>(val >> 35) & 0x7F;
add_5:
*buf++= static_cast<byte>(val >> 28) & 0x7F;
add_4:
*buf++= static_cast<byte>(val >> 21) & 0x7F;
add_3:
*buf++= static_cast<byte>(val >> 14) & 0x7F;
add_2:
*buf++= static_cast<byte>(val >> 7) & 0x7F;
add_1:
*buf++= static_cast<byte>(val) | 0x80;
return buf;
}
/** Decode and return the integer that was encoded using
our VLC scheme.
@param ptr pointer to decode from, this ptr is
incremented by the number of bytes decoded
@return value decoded */
inline doc_id_t fts_decode_vlc(const byte **ptr)
{
ut_d(const byte *const start= *ptr);
ut_ad(*start);
doc_id_t val= 0;
for (;;)
{
byte b= *(*ptr)++;
val|= (b & 0x7F);
/* High-bit on means "last byte in the encoded integer". */
if (b & 0x80)
break;
ut_ad(val < static_cast<doc_id_t>(1) << (64 - 7));
val <<= 7;
}
ut_ad(*ptr - start <= 10);
return(val);
}
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