141 lines
4.3 KiB
C
141 lines
4.3 KiB
C
/* =====> SBIGMXP.C */
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/* TIPC Scheme '84 Runtime Support - Memory Allocation Routines
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(C) Copyright 1984, 1985 by Texas Instruments Incorporated.
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All rights reserved.
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Author: Terry Caudill
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Installation: Texas Instruments Incorporated, Austin, Texas
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Division: Data Systems Group
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Project: PC Scheme
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Comments: This code was lifted from SBIGMEM.C, which was used to
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allocate objects greater than on page in size. It was
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modified to understand expanded memory and is tied closely
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to EXPSMMU.ASM
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Date Written: 4 June 86
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*/
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#include "scheme.h"
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/* Turn off assertions in SBIGMXP.C for performance reasons */
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#define ASSERT(arg) /* do nothing */
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#define ENTER(xyz) /* do nothing */
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extern unsigned first_page; /* paragraph address of first physical page */
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/************************************************************************/
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/* Allocate a Large BLock in Scheme's Memory */
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/************************************************************************/
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alloc_big_block(reg, type, size)
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int reg[2]; /* register to receive pointer to allocated block */
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int type; /* type code of block to be allocated */
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unsigned size; /* size of block in bytes (including block header) */
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{
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int number_of_pages; /* number of pages required to satisy request */
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int page; /* page number where large block can be allocated */
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number_of_pages = ((size + (PAGESIZE - 1)) / PAGESIZE);
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if ((page = find_big_block(number_of_pages)) == -1)
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{
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garbage(); /* Invoke Garbage Collector to reclaim memory */
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if ((page = find_big_block(number_of_pages)) == -1)
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{
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gcsquish(); /* Try compacting memory */
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if ((page = find_big_block(number_of_pages)) == -1)
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{
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out_of_memory(); /* attempt to execute SCHEME-RESET */
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/* Note: The above procedure returns control elsewhere */
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}
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}
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}
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zero_page(page);
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put_ptr(page, 0, type, size);
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nextcell[page] = END_LIST;
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if (size <= psize[page] - BLK_OVHD)
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{
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put_ptr(page, size, FREETYPE, psize[page] - size);
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nextcell[page] = size;
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}
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ptype[page] = type + type;
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w_attrib[page] = pageattr[type];
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pagelink[page] = pagelist[type];
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pagelist[type] = page;
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reg[C_PAGE] = ADJPAGE(page);
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reg[C_DISP] = 0;
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} /* end of function: alloc_big_block(reg, type, size) */
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find_big_block(number_of_pages)
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int number_of_pages; /* number of contiguous pages required */
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{
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int free_pages[NUMPAGES+1]; /* free page table */
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int i,j; /* our old favorite index variables */
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int page; /* working page number */
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int page_found = -1; /* page number of first page in big block */
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int FirstEmmPage; /* First expanded memory page */
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ENTER(find_big_block);
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FirstEmmPage = exppage();
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/* Initialize free_pages table */
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for (i = 0; i <= NUMPAGES; i++)
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free_pages[i] = -1;
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/* Record the number of all free pages */
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page = freepage;
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while (page != END_LIST)
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{
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ASSERT(page >= 0 && page < NUMPAGES /* subchk? */);
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ASSERT(free_pages[page] == -1 /* infinite loop? */);
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free_pages[page] = page;
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page = pagelink[page];
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}
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/* Search for a contiguous group of pages to satisfy request */
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for (i = 0; i < NUMPAGES - DEDPAGES - number_of_pages; i++)
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{
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if (free_pages[i] != -1)
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{
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j = 1;
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while (free_pages[i+j] != -1 &&
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(((free_pages[i] < FirstEmmPage) && (free_pages[i+j] < FirstEmmPage)) ||
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((free_pages[i] >= FirstEmmPage) && (free_pages[i+j] >= FirstEmmPage))
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)
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)
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{
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j++;
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if (j >= number_of_pages)
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{
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/* required number of pages found-- adjust page table */
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page_found = free_pages[i];
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psize[page_found] = PAGESIZE * number_of_pages;
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free_pages[i] = -1;
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for (j = 1; j < number_of_pages; j++)
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{
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page = free_pages[i+j];
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psize[page] = 0;
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attrib[page].nomemory = 1;
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free_pages[i+j] = -1;
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}
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/* update list of free pages */
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freepage = END_LIST;
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for (i = NUMPAGES; i > DEDPAGES; i--)
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{
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if (free_pages[i] != -1)
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{
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pagelink[(j = free_pages[i])] = freepage;
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freepage = j;
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}
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}
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return(page_found);
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}
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}
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i += j;
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}
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}
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return(-1); /* no pages found */
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} /* end of function: find_big_block(number_of_pages) */
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