| /* ------------------------------------------------------------------ |
| * Copyright (C) 1998-2009 PacketVideo |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either |
| * express or implied. |
| * See the License for the specific language governing permissions |
| * and limitations under the License. |
| * ------------------------------------------------------------------- |
| */ |
| /**************************************************************************************** |
| Portions of this file are derived from the following 3GPP standard: |
| |
| 3GPP TS 26.073 |
| ANSI-C code for the Adaptive Multi-Rate (AMR) speech codec |
| Available from http://www.3gpp.org |
| |
| (C) 2004, 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TTA, TTC) |
| Permission to distribute, modify and use this file under the standard license |
| terms listed above has been obtained from the copyright holder. |
| ****************************************************************************************/ |
| /* |
| |
| Filename: /audio/gsm_amr/c/src/sub.c |
| |
| ------------------------------------------------------------------------------ |
| REVISION HISTORY |
| |
| Description: Created separate file for the sub function. Sync'ed up with the |
| current template and fixed tabs. |
| |
| Description: Changed all occurrences of L_diff to diff, deleted "short" in |
| the definition of var1 and var2, and fixed the range values. |
| |
| Description: Changed function prototype passing in a pointer to overflow flag |
| instead of using global data. |
| |
| Description: Changes made per formal review comments. |
| 1. Changed the parameter name fron "overflow" to "pOverflow" |
| 2. Updated template |
| 3. Updated reference section |
| |
| Description: Removed conditional code that updates WMOPS counter |
| |
| Description: |
| 1. Modified if-else structure to save cycles by processing |
| the most common case faster. |
| |
| Who: Date: |
| Description: |
| |
| ------------------------------------------------------------------------------ |
| MODULE DESCRIPTION |
| |
| Subtraction function with overflow control |
| |
| ------------------------------------------------------------------------------ |
| */ |
| |
| /*---------------------------------------------------------------------------- |
| ; INCLUDES |
| ----------------------------------------------------------------------------*/ |
| #include "basic_op.h" |
| |
| /*---------------------------------------------------------------------------- |
| ; MACROS |
| ; [Define module specific macros here] |
| ----------------------------------------------------------------------------*/ |
| |
| /*---------------------------------------------------------------------------- |
| ; DEFINES |
| ; [Include all pre-processor statements here. Include conditional |
| ; compile variables also.] |
| ----------------------------------------------------------------------------*/ |
| |
| /*---------------------------------------------------------------------------- |
| ; LOCAL FUNCTION DEFINITIONS |
| ; [List function prototypes here] |
| ----------------------------------------------------------------------------*/ |
| |
| /*---------------------------------------------------------------------------- |
| ; LOCAL VARIABLE DEFINITIONS |
| ; [Variable declaration - defined here and used outside this module] |
| ----------------------------------------------------------------------------*/ |
| |
| |
| /* |
| ------------------------------------------------------------------------------ |
| FUNCTION NAME: sub |
| ------------------------------------------------------------------------------ |
| INPUT AND OUTPUT DEFINITIONS |
| |
| Inputs: |
| var1 = 16 bit short signed integer (Word16) whose value falls in |
| the range : 0xffff 8000 <= var1 <= 0x0000 7fff. |
| |
| var2 = 16 bit short signed integer (Word16) whose value falls in |
| the range : 0xffff 8000 <= var2 <= 0x0000 7fff. |
| |
| pOverflow = pointer to overflow (Flag) |
| |
| Outputs: |
| pOverflow -> 1 if the subtract operation resulted in overflow |
| |
| Returns: |
| diff = 16-bit limited difference between var1 and var2 (Word16) |
| |
| Global Variables Used: |
| None |
| |
| Local Variables Needed: |
| None |
| |
| ------------------------------------------------------------------------------ |
| FUNCTION DESCRIPTION |
| |
| This function performs the subtraction (var1-var2) with overflow control and |
| saturation; the 16 bit result is set at +32767 when overflow occurs or at |
| -32768 when underflow occurs. |
| |
| ------------------------------------------------------------------------------ |
| REQUIREMENTS |
| |
| None |
| |
| ------------------------------------------------------------------------------ |
| REFERENCES |
| |
| [1] sub() function in basicop2.c, UMTS GSM AMR speech codec, R99 - |
| Version 3.2.0, March 2, 2001 |
| |
| ------------------------------------------------------------------------------ |
| |
| PSEUDO-CODE |
| |
| Word16 sub (Word16 var1, Word16 var2) |
| { |
| Word16 var_out; |
| Word32 diff; |
| |
| diff = (Word32) var1 - var2; |
| |
| * The reference ETSI code uses a global flag for Overflow inside the function |
| * saturate(). In the actual implementation a pointer to Overflow flag is passed |
| * in as a parameter to the function |
| |
| var_out = saturate (diff); |
| |
| #if (WMOPS) |
| multiCounter[currCounter].sub++; |
| #endif |
| |
| return (var_out); |
| } |
| |
| ------------------------------------------------------------------------------ |
| RESOURCES USED [optional] |
| |
| When the code is written for a specific target processor the |
| the resources used should be documented below. |
| |
| HEAP MEMORY USED: x bytes |
| |
| STACK MEMORY USED: x bytes |
| |
| CLOCK CYCLES: (cycle count equation for this function) + (variable |
| used to represent cycle count for each subroutine |
| called) |
| where: (cycle count variable) = cycle count for [subroutine |
| name] |
| |
| ------------------------------------------------------------------------------ |
| CAUTION [optional] |
| [State any special notes, constraints or cautions for users of this function] |
| |
| ------------------------------------------------------------------------------ |
| */ |
| |
| /*---------------------------------------------------------------------------- |
| ; FUNCTION CODE |
| ----------------------------------------------------------------------------*/ |
| |
| #ifdef __clang__ |
| __attribute__((no_sanitize("integer"))) |
| #endif |
| Word16 sub(Word16 var1, Word16 var2, Flag *pOverflow) |
| { |
| |
| Word32 diff; |
| |
| diff = (Word32) var1 - var2; |
| |
| /* Saturate result (if necessary). */ |
| /* Replaced function call with in-line code */ |
| /* to conserve MIPS, i.e., var_out = saturate (diff) */ |
| |
| |
| if ((UWord32)(diff - 0xFFFF8000L) > 0x000FFFF) |
| { |
| if (diff > (Word32) 0x0007FFFL) |
| { |
| diff = MAX_16; |
| } |
| else |
| { |
| diff = MIN_16; |
| } |
| |
| *pOverflow = 1; |
| } |
| |
| |
| return ((Word16) diff); |
| } |