兩個函數取自UNIX?版本6?malloc.c文件，一個為malloc函數，一個為mfree函數??

2515:/*map數組是一個空閑資源列表，其中每個存儲區由其長度和相對地址定義*/??

??????struct?map???

2516:?{??

2517:?????????char?*m_size;??

2518:?????????char?*m_addr;??

2519:?};??

2520:?/*?---------------------------???????*/??

2521:???

2522:?/*?

2523:??*?Allocate?size?units?from?the?given?

2524:??*?map.?Return?the?base?of?the?allocated?

2525:??*?space.?

2526:??*?Algorithm?is?first?fit.?

2527:??*/??

2528:?malloc(mp,?size)??

2529:?struct?map?*mp;??

2530:?{??

2531:?????????register?int?a;??

2532:?????????register?struct?map?*bp;??

2533:???

2534:?????????for?(bp?=?mp;?bp->m_size;?bp++)?{?/*搜索map數組，直到到達map列表尾部，或者搜索到一個長度滿足請求的空閑空間*/??

2535:?????????????????if?(bp->m_size?>=?size)?{?/*該空閑塊滿足請求*/??

2536:?????????????????????????a?=?bp->m_addr;???/*記錄該區首地址*/??

2537:?????????????????????????bp->m_addr?=+?size;?/*空閑塊地址首端大小為size塊被分配，因此首地址前移size*/??

2538:?????????????????????????if?((bp->m_size?=-?size)?==?0)?/*分配的空閑塊大小剛好等于請求空間的大小*/??

2539:?????????????????????????????????do?{????/*將該空間塊在map中的后繼記錄前移*/??

2540:?????????????????????????????????????????bp++;??

2541:?????????????????????????????????????????(bp-1)->m_addr?=?bp->m_addr;??

2542:?????????????????????????????????}?while?((bp-1)->m_size?=?bp->m_size);??

2543:?????????????????????????return(a);??

2544:?????????????????}??

2545:?????????}??

2546:?????????return(0);??

2547:?}??

2548:?/*?---------------------------???????*/??

2549:???

2550:?/*?

2551:??*?Free?the?previously?allocated?space?aa?

2552:??*?of?size?units?into?the?specified?map.?

2553:??*?Sort?aa?into?map?and?combine?on?

2554:??*?one?or?both?ends?if?possible.?

2555:??*/??

??/*將一個大小為size，起始地址為aa的存儲區還給map*/??

2556:?mfree(mp,?size,?aa)??

2557:?struct?map?*mp;??

2558:?{??

2559:?????????register?struct?map?*bp;??

2560:?????????register?int?t;??

2561:?????????register?int?a;??

2562:???

2563:?????????a?=?aa;??

2564:?????????for?(bp?=?mp;?bp->m_addr<=a?&&?bp->m_size!=0;?bp++);?/*搜索map，直到找到map中起始地址小于釋放空間地址的記錄*/??

2565:?????????if?(bp>mp?&&?(bp-1)->m_addr+(bp-1)->m_size?==?a)?{?/*釋放空間和前一空間連續*/??

2566:?????????????????(bp-1)->m_size?=+?size;?/*map中前一元素的大小增加被釋放空間的大小*/??

2567:?????????????????if?(a+size?==?bp->m_addr)?{?/*釋放的存儲區是否與map中下一個區塊相鄰*/??

2568:?????????????????????????(bp-1)->m_size?=+?bp->m_size;?/*合并被釋放塊和后一塊存儲區*/??

2569:?????????????????????????while?(bp->m_size)?{?/*前移余下的存儲區*/??

2570:?????????????????????????????????bp++;??

2571:?????????????????????????????????(bp-1)->m_addr?=?bp->m_addr;??

2572:?????????????????????????????????(bp-1)->m_size?=?bp->m_size;??

2573:?????????????????????????}??

2574:?????????????????}??

2575:?????????}?else?{?/*不與前一空間連續*/??

2576:?????????????????if?(a+size?==?bp->m_addr?&&?bp->m_size)?{?/*是否與后一空間連續*/??

2577:?????????????????????????bp->m_addr?=-?size;??

2578:?????????????????????????bp->m_size?=+?size;??

2579:?????????????????}?else?if?(size)?do?{?/*釋放空間大小不為0，在map中加入新記錄，后移map中余下的空間記錄*/??

2580:?????????????????????????t?=?bp->m_addr;??

2581:?????????????????????????bp->m_addr?=?a;??

2582:?????????????????????????a?=?t;??

2583:?????????????????????????t?=?bp->m_size;??

2584:?????????????????????????bp->m_size?=?size;??

2585:?????????????????????????bp++;??

2586:?????????????????}?while?(size?=?t);??

2587:?????????}??

2588:?}??

2589:?/*?---------------------------???????*/?

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