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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  Filename: /audio/gsm_amr/c/src/add.c
32 
33 ------------------------------------------------------------------------------
34  REVISION HISTORY
35 
36  Description: Created separate file for add function. Sync'ed up with the
37           current template and fixed tabs.
38 
39  Description: Changed all occurrences of L_sum with sum.
40 
41  Description: Changed function protype to pass in pointer to Overflow flag
42                 as a parameter.
43 
44  Description: Removed code that updates MOPS counter
45 
46  Who:                       Date:
47  Description:
48 
49 ------------------------------------------------------------------------------
50  MODULE DESCRIPTION
51 
52  Summation function with overflow control
53 
54 ------------------------------------------------------------------------------
55 */
56 
57 
58 /*----------------------------------------------------------------------------
59 ; INCLUDES
60 ----------------------------------------------------------------------------*/
61 #include    "basic_op.h"
62 
63 /*----------------------------------------------------------------------------
64 ; MACROS
65 ; [Define module specific macros here]
66 ----------------------------------------------------------------------------*/
67 
68 /*----------------------------------------------------------------------------
69 ; DEFINES
70 ; [Include all pre-processor statements here. Include conditional
71 ; compile variables also.]
72 ----------------------------------------------------------------------------*/
73 
74 /*----------------------------------------------------------------------------
75 ; LOCAL FUNCTION DEFINITIONS
76 ; [List function prototypes here]
77 ----------------------------------------------------------------------------*/
78 
79 /*----------------------------------------------------------------------------
80 ; LOCAL VARIABLE DEFINITIONS
81 ; [Variable declaration - defined here and used outside this module]
82 ----------------------------------------------------------------------------*/
83 
84 
85 /*
86 ------------------------------------------------------------------------------
87  FUNCTION NAME: add
88 ------------------------------------------------------------------------------
89  INPUT AND OUTPUT DEFINITIONS
90 
91  Inputs:
92     var1 = 16 bit short signed integer (Word16) whose value falls in
93            the range : 0xffff 8000 <= var1 <= 0x0000 7fff.
94 
95     var2 = 16 bit short signed integer (Word16) whose value falls in
96            the range : 0xffff 8000 <= var2 <= 0x0000 7fff.
97 
98     pOverflow = pointer to overflow (Flag)
99 
100  Outputs:
101     pOverflow -> 1 if the add operation resulted in overflow
102 
103  Returns:
104     sum = 16-bit limited sum of var1 and var2 (Word16)
105 
106  Global Variables Used:
107     None
108 
109  Local Variables Needed:
110     None
111 
112 ------------------------------------------------------------------------------
113  FUNCTION DESCRIPTION
114 
115  This function performs the addition (var1+var2) with overflow control and
116  saturation; the 16 bit result is set at +32767 when overflow occurs or at
117  -32768 when underflow occurs.
118 
119 ------------------------------------------------------------------------------
120  REQUIREMENTS
121 
122  None
123 
124 ------------------------------------------------------------------------------
125  REFERENCES
126 
127  [1] add.c, UMTS GSM AMR speech codec, R99 - Version 3.2.0, March 2, 2001
128 
129 ------------------------------------------------------------------------------
130  PSEUDO-CODE
131 
132  Word16 add (Word16 var1, Word16 var2)
133 {
134     Word16 var_out;
135     Word32 sum;
136 
137     sum = (Word32) var1 + var2;
138 
139 * The reference ETSI code uses a global flag for Overflow inside the function
140 * saturate(). In the actual implementation a pointer to Overflow flag is passed in
141 * as a parameter to the function
142 
143     var_out = saturate (sum);
144 #if (WMOPS)
145     multiCounter[currCounter].add++;
146 #endif
147     return (var_out);
148 }
149 
150 ------------------------------------------------------------------------------
151  RESOURCES USED [optional]
152 
153  When the code is written for a specific target processor the
154  the resources used should be documented below.
155 
156  HEAP MEMORY USED: x bytes
157 
158  STACK MEMORY USED: x bytes
159 
160  CLOCK CYCLES: (cycle count equation for this function) + (variable
161                 used to represent cycle count for each subroutine
162                 called)
163      where: (cycle count variable) = cycle count for [subroutine
164                                      name]
165 
166 ------------------------------------------------------------------------------
167  CAUTION [optional]
168  [State any special notes, constraints or cautions for users of this function]
169 
170 ------------------------------------------------------------------------------
171 */
172 
173 /*----------------------------------------------------------------------------
174 ; FUNCTION CODE
175 ----------------------------------------------------------------------------*/
add(Word16 var1,Word16 var2,Flag * pOverflow)176 Word16 add(Word16 var1, Word16 var2, Flag *pOverflow)
177 {
178     /*----------------------------------------------------------------------------
179     ; Define all local variables
180     ----------------------------------------------------------------------------*/
181     Word32 sum;
182     sum = (Word32) var1 + var2;
183 
184     /* Saturate result (if necessary). */
185     /* Replaced function call with in-line code             */
186     /* to conserve MIPS, i.e., var_out = saturate (sum)  */
187 
188     if (sum > 0X00007fffL)
189     {
190         *pOverflow = 1;
191         sum = MAX_16;
192     }
193     else if (sum < (Word32) 0xffff8000L)
194     {
195         *pOverflow = 1;
196         sum = MIN_16;
197     }
198 
199     /* Return the sum as a 16 bit value by type casting Word32 to Word16 */
200 
201     return ((Word16) sum);
202 }
203 
204