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142 lines
3.6 KiB
Text
142 lines
3.6 KiB
Text
/*****************************************************************************
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Copyright (c) 2007, 2011, Oracle and/or its affiliates. All Rights Reserved.
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This program is free software; you can redistribute it and/or modify it under
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the terms of the GNU General Public License as published by the Free Software
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Foundation; version 2 of the License.
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This program is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
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You should have received a copy of the GNU General Public License along with
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this program; if not, write to the Free Software Foundation, Inc.,
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51 Franklin Street, Suite 500, Boston, MA 02110-1335 USA
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*****************************************************************************/
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/******************************************************************//**
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@file include/fts0vlc.ic
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Full text variable length integer encoding/decoding.
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Created 2007-03-27 Sunny Bains
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*******************************************************/
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#ifndef INNOBASE_FTS0VLC_IC
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#define INNOBASE_FTS0VLC_IC
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#include "fts0types.h"
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/******************************************************************//**
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Return length of val if it were encoded using our VLC scheme.
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FIXME: We will need to be able encode 8 bytes value
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@return length of value encoded, in bytes */
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UNIV_INLINE
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ulint
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fts_get_encoded_len(
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/*================*/
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ulint val) /* in: value to encode */
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{
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if (val <= 127) {
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return(1);
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} else if (val <= 16383) {
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return(2);
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} else if (val <= 2097151) {
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return(3);
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} else if (val <= 268435455) {
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return(4);
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} else {
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/* Possibly we should care that on 64-bit machines ulint can
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contain values that we can't encode in 5 bytes, but
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fts_encode_int doesn't handle them either so it doesn't much
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matter. */
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return(5);
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}
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}
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/******************************************************************//**
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Encode an integer using our VLC scheme and return the length in bytes.
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@return length of value encoded, in bytes */
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UNIV_INLINE
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ulint
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fts_encode_int(
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/*===========*/
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ulint val, /* in: value to encode */
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byte* buf) /* in: buffer, must have enough space */
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{
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ulint len;
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if (val <= 127) {
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*buf = (byte) val;
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len = 1;
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} else if (val <= 16383) {
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*buf++ = (byte)(val >> 7);
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*buf = (byte)(val & 0x7F);
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len = 2;
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} else if (val <= 2097151) {
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*buf++ = (byte)(val >> 14);
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*buf++ = (byte)((val >> 7) & 0x7F);
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*buf = (byte)(val & 0x7F);
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len = 3;
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} else if (val <= 268435455) {
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*buf++ = (byte)(val >> 21);
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*buf++ = (byte)((val >> 14) & 0x7F);
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*buf++ = (byte)((val >> 7) & 0x7F);
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*buf = (byte)(val & 0x7F);
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len = 4;
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} else {
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/* Best to keep the limitations of the 32/64 bit versions
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identical, at least for the time being. */
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ut_ad(val <= 4294967295u);
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*buf++ = (byte)(val >> 28);
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*buf++ = (byte)((val >> 21) & 0x7F);
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*buf++ = (byte)((val >> 14) & 0x7F);
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*buf++ = (byte)((val >> 7) & 0x7F);
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*buf = (byte)(val & 0x7F);
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len = 5;
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}
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/* High-bit on means "last byte in the encoded integer". */
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*buf |= 0x80;
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return(len);
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}
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/******************************************************************//**
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Decode and return the integer that was encoded using our VLC scheme.
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@return value decoded */
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UNIV_INLINE
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ulint
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fts_decode_vlc(
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/*===========*/
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byte** ptr) /* in: ptr to decode from, this ptr is
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incremented by the number of bytes decoded */
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{
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ulint val = 0;
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for (;;) {
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byte b = **ptr;
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++*ptr;
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val |= (b & 0x7F);
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/* High-bit on means "last byte in the encoded integer". */
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if (b & 0x80) {
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break;
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} else {
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val <<= 7;
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}
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}
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return(val);
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}
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#endif
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