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/****************************************************************************************
19Portions 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)
26Permission to distribute, modify and use this file under the standard license
27terms 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----------------------------------------------------------------------------*/
176Word16 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