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#include <stdlib.h> |
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#include "bakery.h" |
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/* Hilfsfunktion, um höchsten Wert (integer) in einem Array zu bestimmen */ |
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int maxValueInList(int list[], int list_length) { |
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int i; |
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int max_value = 0; |
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for (i = 0; i < list_length; i++) { |
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if (list[i] > max_value) |
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max_value = list[i]; |
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} |
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return max_value; |
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} |
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/* Initialisiert Struktur zur Verwaltung kritischer Abschnitte */ |
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void My_InitializeCriticalSection( MY_LPCRITICAL_SECTION * sec ) { |
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int i; |
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/* Datenstruktur "erzeugen" */ |
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*sec = malloc(sizeof(struct _crit_sec)); |
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/* Felder der Datenstruktur mit "0" initialisieren */ |
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for (i = 0; i < MAX_THREADS; i++) { |
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(*sec)->choosing[i] = 0; |
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(*sec)->number[i] = 0; |
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} |
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} |
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/* Gibt Speicher zur Verwaltung kritischer Abschnitte wieder frei */ |
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void My_DeleteCriticalSection( MY_LPCRITICAL_SECTION sec ) { |
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/* Datenstruktur freigeben */ |
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free(sec); |
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} |
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/* Eintritt in kritischen Abschnitt */ |
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void My_EnterCriticalSection( int ThId, MY_LPCRITICAL_SECTION sec ) { |
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int j; |
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/* Beginn der Ticket-ID Berechnung */ |
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sec->choosing[ThId] = 1; |
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/* Neue Ticket-ID berechnen und zuweisen */ |
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sec->number[ThId] = maxValueInList(sec->number, MAX_THREADS) + 1; |
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/* Ende der Ticket-ID Berechnung */ |
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sec->choosing[ThId] = 0; |
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/* Alle Threads durchlaufen */ |
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for (j = 0; j < MAX_THREADS; j++) { |
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/* Warten, falls ein anderer Thread momentan eine Ticket-ID berechnet (busy wait) */ |
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while (sec->choosing[j] == 1); |
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/* Bakery Algorithmus: Warten, bis man an der Reihe ist (busy wait) */ |
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while ( (sec->number[j] != 0) && |
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( |
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(sec->number[j] < sec->number[ThId]) || |
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((sec->number[j] == sec->number[ThId]) && j < ThId) |
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) |
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); |
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} |
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} |
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/* Austritt aus kritischem Abschnitt */ |
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void My_LeaveCriticalSection( int ThId, MY_LPCRITICAL_SECTION sec ) { |
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/* Ticket löschen */ |
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sec->number[ThId] = 0; |
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} |
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