1992/0612/port/malloc.c (diff list | history)

port/malloc.c on 1992/0612
1992/0612		#include <u.h> #include <libc.h>
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1992/0612		enum { MAGIC = 0xDEADBABE, MAX2SIZE = 20 };
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1992/0612		typedef struct Bucket Bucket; struct Bucket
1990/1210		{
1992/0612		int size; int magic; Bucket *next; char data[1]; };
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1992/0612		typedef struct Arena Arena; struct Arena
1990/1210		{
1992/0612		Lock; Bucket *btab[MAX2SIZE]; };
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1992/0612		static Arena arena; #define datoff ((int)&((Bucket*)0)->data)
1990/1210		void*
1992/0612		malloc(uint size)
1990/1210		{
1992/0612		int pow; Bucket *bp;
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1992/0612		for(pow = 1; pow < MAX2SIZE; pow++) { if(size <= (1<<pow)) goto good;
1990/1210		}
1992/0612		return nil; good: /* Allocate off this list */ lock(&arena); bp = arena.btab[pow]; if(bp) { arena.btab[pow] = bp->next; arena.unlock();
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1992/0612		if(bp->magic != 0) abort();
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1992/0612		bp->magic = MAGIC;
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1992/0612		memset(bp->data, 0, size); return bp->data;
1990/1210		}
1992/0612		unlock(&arena); size = sizeof(Bucket)+(1<<pow); bp = sbrk(size); if((int)bp < 0) return nil;
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1992/0612		bp->size = pow; bp->magic = MAGIC;
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1992/0612		return bp->data;
1990/1210		} void
1992/0612		free(void *ptr)
1990/1210		{
1992/0612		Bucket *bp, **l;
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1992/0612		/* Find the start of the structure */ bp = (Bucket*)((uint)ptr - datoff);
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1992/0612		if(bp->magic != MAGIC) panic("free");
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1992/0612		bp->magic = 0; lock(&arena); l = &arena.btab[bp->size]; bp->next = *l; *l = bp; unlock(&arena);
1990/1210		}