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#include <u.h>
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#include <libc.h>
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#include <bin.h>
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enum
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{
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	StructAlign = sizeof(union {vlong vl; double d; ulong p; void *v;
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				struct{vlong v;}vs; struct{double d;}ds; struct{ulong p;}ss; struct{void *v;}xs;})
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};
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enum
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{
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	BinSize	= 8*1024
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};
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struct Bin
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{
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	Bin	*next;
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	ulong	total;			/* total bytes allocated in can->next */
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	uintptr	pos;
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	uintptr	end;
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	uintptr	v;			/* last value allocated */
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	uchar	body[BinSize];
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};
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/*
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 * allocator which allows an entire set to be freed at one time
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 */
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static Bin*
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mkbin(Bin *bin, ulong size)
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{
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	Bin *b;
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	size = ((size << 1) + (BinSize - 1)) & ~(BinSize - 1);
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	b = malloc(sizeof(Bin) + size - BinSize);
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	if(b == nil)
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		return nil;
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	b->next = bin;
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	b->total = 0;
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	if(bin != nil)
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		b->total = bin->total + bin->pos - (uintptr)bin->body;
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	b->pos = (uintptr)b->body;
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	b->end = b->pos + size;
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	return b;
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}
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void*
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binalloc(Bin **bin, ulong size, int zero)
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{
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	Bin *b;
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	uintptr p;
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	if(size == 0)
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		size = 1;
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	b = *bin;
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	if(b == nil){
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		b = mkbin(nil, size);
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		if(b == nil)
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			return nil;
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		*bin = b;
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	}
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	p = b->pos;
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	p = (p + (StructAlign - 1)) & ~(StructAlign - 1);
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	if(p + size > b->end){
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		b = mkbin(b, size);
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		if(b == nil)
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			return nil;
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		*bin = b;
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		p = b->pos;
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	}
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	b->pos = p + size;
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	b->v = p;
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	if(zero)
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		memset((void*)p, 0, size);
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	return (void*)p;
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}
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void*
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bingrow(Bin **bin, void *op, ulong osize, ulong size, int zero)
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{
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	Bin *b;
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	void *np;
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	uintptr p;
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	p = (uintptr)op;
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	b = *bin;
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	if(b != nil && p == b->v && p + size <= b->end){
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		b->pos = p + size;
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		if(zero)
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			memset((char*)p + osize, 0, size - osize);
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		return op;
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	}
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	np = binalloc(bin, size, zero);
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	if(np == nil)
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		return nil;
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	memmove(np, op, osize);
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	return np;
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}
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void
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binfree(Bin **bin)
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{
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	Bin *last;
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	while(*bin != nil){
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		last = *bin;
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		*bin = (*bin)->next;
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		last->pos = (uintptr)last->body;
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		free(last);
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	}
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}