1 /* ------------------------------------------------------------------
2 * Copyright (C) 1998-2009 PacketVideo
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
13 * express or implied.
14 * See the License for the specific language governing permissions
15 * and limitations under the License.
16 * -------------------------------------------------------------------
17 */
18 /****************************************************************************************
19 Portions of this file are derived from the following 3GPP standard:
20
21 3GPP TS 26.073
22 ANSI-C code for the Adaptive Multi-Rate (AMR) speech codec
23 Available from http://www.3gpp.org
24
25 (C) 2004, 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TTA, TTC)
26 Permission to distribute, modify and use this file under the standard license
27 terms listed above has been obtained from the copyright holder.
28 ****************************************************************************************/
29 /*
30
31 Pathname: ./gsm-amr/c/src/shr_r.c
32
33 ------------------------------------------------------------------------------
34 REVISION HISTORY
35
36 Description: Created separate file for the shr_r function. Sync'ed up
37 with the current template and fixed tabs.
38
39 Description: Passing around pOverflow as per EPOC changes.
40
41 Who: Date:
42 Description:
43
44 ------------------------------------------------------------------------------
45 INPUT AND OUTPUT DEFINITIONS
46
47 Inputs:
48 var1 = 16 bit short signed integer (Word16) whose value falls in
49 the range : 0xffff 8000 <= var1 <= 0x0000 7fff.
50 var2 = 16 bit short signed integer (Word16) whose value falls in
51 the range : 0xffff 8000 <= var2 <= 0x0000 7fff.
52
53 Local Stores/Buffers/Pointers Needed:
54 None
55
56 Global Stores/Buffers/Pointers Needed:
57 None
58
59 Outputs:
60 var_out = shifted input w/ rounding (Word16)
61
62 Pointers and Buffers Modified:
63 None
64
65 Local Stores Modified:
66 None
67
68 Global Stores Modified:
69 None
70
71 ------------------------------------------------------------------------------
72 FUNCTION DESCRIPTION
73
74 This function arithmetically shifts the 16 bit input var1 right var2 positions
75 with rounding. If var2 is negative, arithmetically shift var1 left by
76 -var2 with rounding. Saturate the result in case of underflows or
77 overflows.
78
79 - If var2 is greater than zero :
80 if (sub(shl(shr(var1,var2),1),shr(var1,sub(var2,1))))
81 is equal to zero
82 then
83 shr_r(var1,var2) = shr(var1,var2)
84 else
85 shr_r(var1,var2) = add(shr(var1,var2),1)
86 - If var2 is less than or equal to zero :
87 shr_r(var1,var2) = shr(var1,var2).
88
89 ------------------------------------------------------------------------------
90 REQUIREMENTS
91
92 None
93
94 ------------------------------------------------------------------------------
95 REFERENCES
96
97 [1] basicop2.c, ETS Version 2.0.0, February 8, 1999
98
99 ------------------------------------------------------------------------------
100 PSEUDO-CODE
101
102 Word16 shr_r (Word16 var1, Word16 var2)
103 {
104 Word16 var_out;
105
106 if (var2 > 15)
107 {
108 var_out = 0;
109 }
110 else
111 {
112 var_out = shr (var1, var2);
113 #if (WMOPS)
114 multiCounter[currCounter].shr--;
115 #endif
116
117 if (var2 > 0)
118 {
119 if ((var1 & ((Word16) 1 << (var2 - 1))) != 0)
120 {
121 var_out++;
122 }
123 }
124 }
125 #if (WMOPS)
126 multiCounter[currCounter].shr_r++;
127 #endif
128 return (var_out);
129 }
130
131 ------------------------------------------------------------------------------
132 RESOURCES USED
133 When the code is written for a specific target processor the
134 the resources used should be documented below.
135
136 STACK USAGE: [stack count for this module] + [variable to represent
137 stack usage for each subroutine called]
138
139 where: [stack usage variable] = stack usage for [subroutine
140 name] (see [filename].ext)
141
142 DATA MEMORY USED: x words
143
144 PROGRAM MEMORY USED: x words
145
146 CLOCK CYCLES: [cycle count equation for this module] + [variable
147 used to represent cycle count for each subroutine
148 called]
149
150 where: [cycle count variable] = cycle count for [subroutine
151 name] (see [filename].ext)
152
153 ------------------------------------------------------------------------------
154 */
155
156
157 /*----------------------------------------------------------------------------
158 ; INCLUDES
159 ----------------------------------------------------------------------------*/
160 #include "basic_op.h"
161
162 /*----------------------------------------------------------------------------
163 ; MACROS
164 ; Define module specific macros here
165 ----------------------------------------------------------------------------*/
166
167 /*----------------------------------------------------------------------------
168 ; DEFINES
169 ; Include all pre-processor statements here. Include conditional
170 ; compile variables also.
171 ----------------------------------------------------------------------------*/
172
173 /*----------------------------------------------------------------------------
174 ; LOCAL FUNCTION DEFINITIONS
175 ; Function Prototype declaration
176 ----------------------------------------------------------------------------*/
177
178 /*----------------------------------------------------------------------------
179 ; LOCAL STORE/BUFFER/POINTER DEFINITIONS
180 ; Variable declaration - defined here and used outside this module
181 ----------------------------------------------------------------------------*/
182
183 /*----------------------------------------------------------------------------
184 ; EXTERNAL FUNCTION REFERENCES
185 ; Declare functions defined elsewhere and referenced in this module
186 ----------------------------------------------------------------------------*/
187
188 /*----------------------------------------------------------------------------
189 ; EXTERNAL GLOBAL STORE/BUFFER/POINTER REFERENCES
190 ; Declare variables used in this module but defined elsewhere
191 ----------------------------------------------------------------------------*/
192
193 /*----------------------------------------------------------------------------
194 ; FUNCTION CODE
195 ----------------------------------------------------------------------------*/
shr_r(Word16 var1,Word16 var2,Flag * pOverflow)196 Word16 shr_r(Word16 var1, Word16 var2, Flag *pOverflow)
197 {
198 /*----------------------------------------------------------------------------
199 ; Define all local variables
200 ----------------------------------------------------------------------------*/
201 Word16 var_out;
202
203 /*----------------------------------------------------------------------------
204 ; Function body here
205 ----------------------------------------------------------------------------*/
206 if (var2 > 15)
207 {
208 var_out = 0;
209 }
210 else
211 {
212 var_out = shr(var1, var2, pOverflow);
213 if (var2 > 0)
214 {
215 if ((var1 & ((Word16) 1 << (var2 - 1))) != 0)
216 {
217 var_out++;
218 }
219 }
220 }
221
222 /*----------------------------------------------------------------------------
223 ; Return nothing or data or data pointer
224 ----------------------------------------------------------------------------*/
225 return (var_out);
226 }
227