1 /*---------------------------------------------------------------------------* 2 * log_tabl.h * 3 * * 4 * Copyright 2007, 2008 Nuance Communciations, Inc. * 5 * * 6 * Licensed under the Apache License, Version 2.0 (the 'License'); * 7 * you may not use this file except in compliance with the License. * 8 * * 9 * You may obtain a copy of the License at * 10 * http://www.apache.org/licenses/LICENSE-2.0 * 11 * * 12 * Unless required by applicable law or agreed to in writing, software * 13 * distributed under the License is distributed on an 'AS IS' BASIS, * 14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * 15 * See the License for the specific language governing permissions and * 16 * limitations under the License. * 17 * * 18 *---------------------------------------------------------------------------*/ 19 20 #ifndef _h_log_tabl_ 21 #define _h_log_tabl_ 22 23 #define LOG_SCALE 1024 /* smallest scale is about 0.1 dB */ 24 #define LOG_SCALE_SHIFT 10 25 26 /** 27 * @todo document 28 */ 29 typedef struct 30 { 31 int size; 32 int shift; 33 int scale; 34 unsigned long mask; 35 const int *table; 36 } 37 log_table_info; 38 39 void create_lookup_log(log_table_info *logtab, int num_bits); 40 int log_lookup(log_table_info *logtab, int operand, int shift); 41 int inv_log_lookup(log_table_info *logtab, int operand); 42 void destroy_lookup_log(log_table_info *logtab); 43 int integer_square_root(int operand); 44 45 46 47 #endif 48