134 lines
3.1 KiB
C++
134 lines
3.1 KiB
C++
/**
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* =========================================================================
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* File : bucket.cpp
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* Project : 0 A.D.
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* Description : bucket allocator
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* =========================================================================
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*/
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// license: GPL; see lib/license.txt
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#include "precompiled.h"
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#include "bucket.h"
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#include "lib/bits.h"
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#include "mem_util.h"
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// power-of-2 isn't required; value is arbitrary.
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const size_t bucketSize = 4000;
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LibError bucket_create(Bucket* b, size_t el_size)
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{
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b->freelist = 0;
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b->el_size = mem_RoundUpToAlignment(el_size);
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// note: allocating here avoids the is-this-the-first-time check
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// in bucket_alloc, which speeds things up.
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b->bucket = (u8*)malloc(bucketSize);
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if(!b->bucket)
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{
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// cause next bucket_alloc to retry the allocation
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b->pos = bucketSize;
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b->num_buckets = 0;
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WARN_RETURN(ERR::NO_MEM);
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}
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*(u8**)b->bucket = 0; // terminate list
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b->pos = mem_RoundUpToAlignment(sizeof(u8*));
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b->num_buckets = 1;
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return INFO::OK;
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}
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void bucket_destroy(Bucket* b)
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{
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while(b->bucket)
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{
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u8* prev_bucket = *(u8**)b->bucket;
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free(b->bucket);
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b->bucket = prev_bucket;
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b->num_buckets--;
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}
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debug_assert(b->num_buckets == 0);
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// poison pill: cause subsequent alloc and free to fail
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b->freelist = 0;
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b->el_size = bucketSize;
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}
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void* bucket_alloc(Bucket* b, size_t size)
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{
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size_t el_size = b->el_size? b->el_size : mem_RoundUpToAlignment(size);
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// must fit in a bucket
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debug_assert(el_size <= bucketSize-sizeof(u8*));
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// try to satisfy alloc from freelist
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void* el = mem_freelist_Detach(b->freelist);
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if(el)
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return el;
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// if there's not enough space left, close current bucket and
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// allocate another.
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if(b->pos+el_size > bucketSize)
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{
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u8* bucket = (u8*)malloc(bucketSize);
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if(!bucket)
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return 0;
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*(u8**)bucket = b->bucket;
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b->bucket = bucket;
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// skip bucket list field and align (note: malloc already
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// aligns to at least 8 bytes, so don't take b->bucket into account)
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b->pos = mem_RoundUpToAlignment(sizeof(u8*));;
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b->num_buckets++;
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}
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void* ret = b->bucket+b->pos;
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b->pos += el_size;
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return ret;
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}
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void* bucket_fast_alloc(Bucket* b)
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{
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// try to satisfy alloc from freelist
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void* el = mem_freelist_Detach(b->freelist);
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if(el)
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return el;
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// if there's not enough space left, close current bucket and
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// allocate another.
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if(b->pos+b->el_size > bucketSize)
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{
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u8* bucket = (u8*)malloc(bucketSize);
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*(u8**)bucket = b->bucket;
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b->bucket = bucket;
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// skip bucket list field (alignment is only pointer-size)
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b->pos = sizeof(u8*);
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b->num_buckets++;
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}
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void* ret = b->bucket+b->pos;
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b->pos += b->el_size;
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return ret;
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}
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void bucket_free(Bucket* b, void* el)
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{
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if(b->el_size == 0)
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{
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DEBUG_WARN_ERR(ERR::LOGIC); // cannot free variable-size items
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return;
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}
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mem_freelist_AddToFront(b->freelist, el);
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// note: checking if <el> was actually allocated from <b> is difficult:
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// it may not be in the currently open bucket, so we'd have to
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// iterate over the list - too much work.
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}
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