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/*****************************************************************************
Copyright (c) 2007, 2011, Oracle and/or its affiliates. All Rights Reserved.
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.ic
Full text variable length integer encoding/decoding.
Created 2007-03-27 Sunny Bains
*******************************************************/
#ifndef INNOBASE_FTS0VLC_IC
#define INNOBASE_FTS0VLC_IC
#include "fts0types.h"
/******************************************************************//**
Return length of val if it were encoded using our VLC scheme.
FIXME: We will need to be able encode 8 bytes value
@return length of value encoded, in bytes */
UNIV_INLINE
ulint
fts_get_encoded_len(
/*================*/
ulint val) /* in: value to encode */
{
if (val <= 127) {
return(1);
} else if (val <= 16383) {
return(2);
} else if (val <= 2097151) {
return(3);
} else if (val <= 268435455) {
return(4);
} else {
/* Possibly we should care that on 64-bit machines ulint can
contain values that we can't encode in 5 bytes, but
fts_encode_int doesn't handle them either so it doesn't much
matter. */
return(5);
}
}
/******************************************************************//**
Encode an integer using our VLC scheme and return the length in bytes.
@return length of value encoded, in bytes */
UNIV_INLINE
ulint
fts_encode_int(
/*===========*/
ulint val, /* in: value to encode */
byte* buf) /* in: buffer, must have enough space */
{
ulint len;
if (val <= 127) {
*buf = (byte) val;
len = 1;
} else if (val <= 16383) {
*buf++ = (byte)(val >> 7);
*buf = (byte)(val & 0x7F);
len = 2;
} else if (val <= 2097151) {
*buf++ = (byte)(val >> 14);
*buf++ = (byte)((val >> 7) & 0x7F);
*buf = (byte)(val & 0x7F);
len = 3;
} else if (val <= 268435455) {
*buf++ = (byte)(val >> 21);
*buf++ = (byte)((val >> 14) & 0x7F);
*buf++ = (byte)((val >> 7) & 0x7F);
*buf = (byte)(val & 0x7F);
len = 4;
} else {
/* Best to keep the limitations of the 32/64 bit versions
identical, at least for the time being. */
ut_ad(val <= 4294967295u);
*buf++ = (byte)(val >> 28);
*buf++ = (byte)((val >> 21) & 0x7F);
*buf++ = (byte)((val >> 14) & 0x7F);
*buf++ = (byte)((val >> 7) & 0x7F);
*buf = (byte)(val & 0x7F);
len = 5;
}
/* High-bit on means "last byte in the encoded integer". */
*buf |= 0x80;
return(len);
}
/******************************************************************//**
Decode and return the integer that was encoded using our VLC scheme.
@return value decoded */
UNIV_INLINE
ulint
fts_decode_vlc(
/*===========*/
byte** ptr) /* in: ptr to decode from, this ptr is
incremented by the number of bytes decoded */
{
ulint val = 0;
for (;;) {
byte b = **ptr;
++*ptr;
val |= (b & 0x7F);
/* High-bit on means "last byte in the encoded integer". */
if (b & 0x80) {
break;
} else {
val <<= 7;
}
}
return(val);
}
#endif
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