mirror of /home/gitosis/repositories/libowfat.git
60 lines
2.1 KiB
C
60 lines
2.1 KiB
C
/* this header file comes from libowfat, http://www.fefe.de/libowfat/ */
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#ifndef IARRAY_H
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#define IARRAY_H
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/* This header defines an indirect array for use with the io_* routines.
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* Assumptions:
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* - the elements are small (many fit on one page),
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* - the platform has an atomic compare-and-swap instruction
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* - the compiler supports it via __sync_val_compare_and_swap
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*
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* Implementation parameters:
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* - once an element is allocated, it stays allocated and at the same place
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* - there is no deleting elements or moving elements around
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* - we are not coordinating access to elements, only providing pointers to them
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* - new elements are allocated upwards, not arbitrarily (like file descriptors on Unix)
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* - meant for long-running processes, destruction is provided only as an afterthought for completeness
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*/
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#include <libowfat/uint64.h>
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#include <stddef.h>
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#ifdef _WIN32
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#include <windows.h>
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#else
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#include <pthread.h>
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#endif
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/* The basic data structure is a static array of pointers to pages.
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* Each page also contains a next pointer to form a linked list.
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* To get to element n, you take n % the number of elements in the
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* static array (iarray->pages) to get to the list of pages that
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* contains it. Then keep going to the next page until you are on the
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* right page.
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* Note: The elements on each page are not contiguous. If the fanout is
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* 16, the indices on page 0 are 0, 16, 32, ...
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* To get to element 0, you'd go to iarray->pages[0].data,
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* to get to element 1, you'd go to iarray->pages[1].data,
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* to get to element 16, you'd go to iarray->pages[0].data+iarray->elemsize.
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*/
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typedef struct _iarray_page {
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struct _iarray_page* next;
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char data[];
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} iarray_page;
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typedef struct {
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iarray_page* pages[16];
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size_t elemsize,elemperpage,bytesperpage,len;
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} iarray;
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void iarray_init(iarray* ia,size_t elemsize);
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void* iarray_get(iarray* ia,size_t pos);
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void* iarray_allocate(iarray* ia,size_t pos);
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size_t iarray_length(iarray* ia);
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/* WARNING: do not use the array during or after iarray_free, make sure
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* no threads are potentially doing anything with the iarray while it is
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* being freed! */
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void iarray_free(iarray* ia);
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#endif
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