106 lines
2.5 KiB
C
106 lines
2.5 KiB
C
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/*** hlback.c - help library historical back-trace routines & data
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*
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* Copyright <C> 1988, Microsoft Corporation
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*
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* Purpose:
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*
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* Revision History:
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*
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* 02-Aug-1988 ln Correct HelpNcBack
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* 19-May-1988 LN Split off from help.c
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*
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*************************************************************************/
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#include <assert.h> /* debugging assertions */
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#include <stdio.h>
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#if defined (OS2)
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#else
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#include <windows.h>
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#endif
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#include "help.h" /* global (help & user) decl */
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#include "helpfile.h" /* help file format definition */
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#include "helpsys.h" /* internal (help sys only) decl*/
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/*************************************************************************
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**
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** cBack, iBackLast, rgncBack
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** System context back-trace list.
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**
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** cBack - Number of entries in back-trace list
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** iBackLast - Index to last back trace entry
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** rgncBack - Array of back-trace entries
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*/
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extern ushort cBack; /* Number of Back-List entries */
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static ushort iBackLast; /* Back-List Last entry index */
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static nc rgncBack[MAXBACK+1]; /* Back-List */
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/************************************************************************
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**
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** HelpNcRecord - Remember context for back-trace
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**
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** Purpose:
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** records a context number for back-trace.
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**
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** Entry:
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** ncCur = context number to record.
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**
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** Exit:
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** none
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**
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** Exceptions:
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** none
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*/
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void far pascal LOADDS HelpNcRecord(ncCur)
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nc ncCur;
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{
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ushort *pcBack = &cBack;
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if ((ncCur.mh || ncCur.cn) &&
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((ncCur.mh != rgncBack[iBackLast].mh) ||
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(ncCur.cn != rgncBack[iBackLast].cn))) {
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iBackLast = (ushort)(((int)iBackLast + 1) % MAXBACK);
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rgncBack[iBackLast] = ncCur;
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if (*pcBack < MAXBACK)
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(*pcBack)++;
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}
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/* end HelpNcRecord */}
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/******************************************************************************
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**
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** HelpNcBack - Return previously viewed context
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**
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** Purpose:
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** Returns the context number corresponding to the historically previously
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** viewed topic.
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**
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** Entry:
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** None
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**
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** Exit:
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** Returns context number
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**
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** Exceptions:
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** Returns NULL on backup list exhuasted
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**
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** Algorithm:
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**
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** If backlist not empty
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** context is last entry in back list
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** remove last entry
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** else
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** return NULL
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*/
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nc far pascal LOADDS HelpNcBack(void) {
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nc ncLast = {0,0}; /* return value */
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ushort *pcBack = &cBack;
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if (*pcBack) {
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ncLast = rgncBack[iBackLast];
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iBackLast = iBackLast == 0 ? (ushort)MAXBACK-1 : (ushort)iBackLast-1;
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(*pcBack)--;
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}
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return ncLast;
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/* end HelpNcBack */}
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