| 1 | /* $Id: queue.cpp 142 2000-04-23 14:55:46Z ktk $ */
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| 2 |
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| 3 | /* SCCSID = %W% %E% */
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| 4 | /****************************************************************************
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| 5 | * *
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| 6 | * Copyright (c) IBM Corporation 1994 - 1997. *
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| 7 | * *
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| 8 | * The following IBM OS/2 source code is provided to you solely for the *
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| 9 | * the purpose of assisting you in your development of OS/2 device drivers. *
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| 10 | * You may use this code in accordance with the IBM License Agreement *
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| 11 | * provided in the IBM Device Driver Source Kit for OS/2. *
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| 12 | * *
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| 13 | ****************************************************************************/
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| 14 | /**@internal %W%
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| 15 | * @notes
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| 16 | * @version %I%
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| 17 | * @context Unless otherwise noted, all interfaces are Ring-0, 16-bit,
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| 18 | * <stack context>.
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| 19 | * @history
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| 20 | *
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| 21 | */
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| 22 | #define INCL_NOPMAPI
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| 23 | //#define INCL_DOSERRORS // for ERROR_INVALID_FUNCTION
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| 24 | #include <os2.h>
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| 25 | #include "queue.hpp"
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| 26 |
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| 27 |
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| 28 | PQUEUEELEMENT QUEUEHEAD::Head(void)
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| 29 | {
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| 30 | return(pHead);
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| 31 | }
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| 32 |
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| 33 | PQUEUEELEMENT QUEUEHEAD::Tail(void)
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| 34 | {
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| 35 | return(pTail);
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| 36 | }
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| 37 |
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| 38 | void QUEUEHEAD::PushOnHead(PQUEUEELEMENT pElement)
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| 39 | {
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| 40 | if (pHead == NULL) {
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| 41 | pElement->pNext = NULL;
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| 42 | pHead = pElement;
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| 43 | pTail = pElement;
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| 44 | }
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| 45 | else {
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| 46 | pElement->pNext = pHead;
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| 47 | pHead = pElement;
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| 48 | } /* endif */
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| 49 |
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| 50 | }
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| 51 | void QUEUEHEAD::PushOnTail(PQUEUEELEMENT pElement)
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| 52 | {
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| 53 | pElement->pNext = NULL;
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| 54 | if (pHead == NULL) {
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| 55 | pHead = pElement;
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| 56 | pTail = pElement;
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| 57 | }
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| 58 | else {
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| 59 | pTail->pNext = pElement;
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| 60 | pTail = pElement;
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| 61 | } /* endif */
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| 62 |
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| 63 | }
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| 64 | PQUEUEELEMENT QUEUEHEAD::PopHead(void)
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| 65 | {
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| 66 | PQUEUEELEMENT temp = pHead;
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| 67 |
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| 68 | if (temp) {
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| 69 | pHead = temp->pNext;
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| 70 | if (pHead == NULL)
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| 71 | pTail = NULL;
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| 72 | temp->pNext = NULL;
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| 73 | }
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| 74 | return(temp);
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| 75 | }
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| 76 | PQUEUEELEMENT QUEUEHEAD::PopTail(void)
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| 77 | {
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| 78 | PQUEUEELEMENT temp = pTail;
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| 79 | PQUEUEELEMENT temp2 = pHead;
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| 80 |
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| 81 | // only 1 element on queue or it's empty
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| 82 | // zapp the head and tail pointers
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| 83 | // zapp the next pointer in the element being returned
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| 84 | // get out of here
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| 85 | if (pHead == pTail) {
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| 86 | pHead = NULL;
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| 87 | pTail = NULL;
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| 88 | if (temp)
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| 89 | temp->pNext = NULL;
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| 90 | return(temp);
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| 91 | }
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| 92 | else {
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| 93 | if (temp) {
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| 94 | while (temp2->pNext != temp)
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| 95 | temp2 = temp2->pNext;
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| 96 | pTail = temp2;
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| 97 |
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| 98 | if (pTail == NULL)
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| 99 | pHead = NULL;
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| 100 | else
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| 101 | pTail->pNext = NULL;
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| 102 | temp->pNext = NULL;
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| 103 | }
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| 104 | }
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| 105 | return(temp);
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| 106 | }
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| 107 |
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| 108 | USHORT QUEUEHEAD::DestroyElement(PQUEUEELEMENT pElement)
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| 109 | {
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| 110 | if (PopElement(pElement)) {
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| 111 | delete(pElement);
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| 112 | return(1);
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| 113 | }
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| 114 | else
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| 115 | return(0);
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| 116 |
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| 117 |
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| 118 | }
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| 119 | PQUEUEELEMENT QUEUEHEAD::PopElement(PQUEUEELEMENT pElement)
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| 120 | {
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| 121 | PQUEUEELEMENT temp;
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| 122 |
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| 123 | // if the queue is empty return NULL
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| 124 | if (pHead == NULL)
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| 125 | return (NULL);
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| 126 |
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| 127 | // Popping the head element
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| 128 | if (pElement == pHead)
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| 129 | return(PopHead());
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| 130 |
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| 131 | // Popping the tail element
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| 132 | if (pElement == pTail)
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| 133 | return(PopTail());
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| 134 |
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| 135 | temp = pHead;
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| 136 | // walk the queue till we find the element or we hit the end
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| 137 | while ((temp->pNext != pElement) && (temp->pNext != NULL))
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| 138 | temp = temp->pNext;
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| 139 | if (temp == NULL) // element not found
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| 140 | return(NULL);
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| 141 | temp->pNext = pElement->pNext;
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| 142 | return(pElement);
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| 143 |
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| 144 | }
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| 145 | ULONG QUEUEHEAD::IsElements(void)
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| 146 | {
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| 147 | if (pHead == NULL)
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| 148 | return(0);
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| 149 | else
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| 150 | return(1);
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| 151 | }
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| 152 |
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| 153 | QUEUEHEAD::QUEUEHEAD(void)
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| 154 | {
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| 155 | pHead = NULL;
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| 156 | pTail = NULL;
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| 157 | }
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