/* ALMLIB.C for CC8, by Mark Miller 5/27/91. */››#include "STDIO.H"››#define MEMSTART 1536›#define MEMSIZE 256›/* num of bytes for alloc info. */›#define INFOLEN 2›#define FREE_SPC 1›#define USED_SPC 2››/*›  Does housekeeping on memory space.  If there are consecutive memory›  spaces that are freed, it will consolidate these spaces into one free space.›*/››update()›$(›  /* ptr to alloc info.; ptr to first free space found */›  char *loc, *tempaddr;›  /* size of a space; accum for size of consecutive spaces */›  int size, templen;›  /* flag for first non-free space found (after free space(s) found) */›  int done;››  loc = MEMSTART;›  templen = 0;›  /* search through memory space until end, for free space to consolidate */›  while(loc < MEMSTART+MEMSIZE)›  $(›    if(*loc == FREE_SPC)›    $(›      /* if space is free, search for consecutive free spaces */›      size = *(loc+1);›      /* hold first free-space pos */›      tempaddr = loc;›      /* get size of this space */›      templen = size;›      /* get to next info. bytes */›      loc += size+INFOLEN;›      done = 0;›      while((loc < MEMSTART+MEMSIZE) && !done)›      $(›        /* if next space is free, add its free space to accum */›        if(*loc == FREE_SPC)›        $(›          size = *(loc+1);›          templen += size+INFOLEN;›        $) /* if */›        else›          /* otherwise, done with present search */›          done = 1;›        /* go to next info. bytes */›        loc += size+INFOLEN;›      $) /* while */›      /* if more than one free space was found, record this free space */›      /* at first free-space pos */›      if(templen != size)›        *(tempaddr+1) = templen;›      templen = 0;›    $) /* if */›    else›      /* if space is not free, go to next info. bytes (next space) */›      loc += size+INFOLEN;›  $) /* while */›$) /* update */››/*›  Finds a free space for something of specified size (data type does not›  matter).  If no free space can be found with specified size, malloc›  will return NULL.›  Currently malloc only works in the 256 byte space of Page 6 (location›  1536 decimal).›*/››char *malloc(size)›  int size;›$(›  /* ptr to info. bytes; ptr to allocated space */›  char *loc, *bloc;›  /* amt of space free/used */›  int space;›  /* flag for when free space found and allocated; flag for when update() */›  /* is called */›  int done, updated;››  loc = MEMSTART;›  /* if memory area is completely unused, put in info. bytes, set to */›  /* free space */›  if(*loc == 0)›  $(›    *loc = FREE_SPC;›    *(loc+1) = MEMSIZE-2;›  $) /* if */››  bloc = NULL;›  updated = 0;›  done = 0;›  while(!done)›  $(›    /* search for free space of specified size (or more) */›    while((loc < MEMSTART+MEMSIZE) && !done)›    $(›      space = *(loc+1);›      /* if space is free, allocate it and return ptr to it.  Also put */›      /* modified info. bytes after allocated space */›      if((*loc == FREE_SPC) && ((space == size) || (space >= size+INFOLEN)))›      $(›        *loc = USED_SPC;›        *(loc+1) = size;›        if(space >= size+INFOLEN)›        $(›          *(loc+INFOLEN+size) = FREE_SPC;›          *(loc+INFOLEN+1+size) = space-size-INFOLEN;›        $) /* if */›        bloc = loc+INFOLEN;›        done = 1;›      $) /* if */›      else›        /* otherwise, go to next info. bytes */›        loc += space+INFOLEN;›    $) /* while */›    if(!updated && !done)›    $(›      update();›      updated = 1;›      loc = MEMSTART;›    $)›    else›      done = 1;›  $) /* while */›  return bloc;›$) /* malloc */››/*›  Deallocates space pointed to by addr.›*/››free(addr)›  char *addr;›$(›  int size;››  if((addr >= MEMSTART) && (addr < MEMSTART+MEMSIZE))›    *(addr-2) = FREE_SPC;›$) /* free */››/*›  Allocation Memory Reset:›  Sets all bytes in memory space to 0, just in case any data is there.›*/››almreset()›$(›  clear(MEMSTART-1, MEMSIZE+1);›$)››/*›  Allocation Memory Dump:›  This function is provided for program debugging purposes.  It displays, in›  decimal form, what is in the memory area used for dynamic memory›  allocation by malloc().›*/››almdump()›$(›  char *addr;››  printf("Allocation memory dump from location\n");›  printf("%d to %d, in bytes:\n", MEMSTART, MEMSTART + MEMSIZE);›  for(addr = MEMSTART; addr <= MEMSTART+MEMSIZE; addr++)›    printf("%d ", *addr);›  printf("\nPress RETURN to continue");›  getchar();›$) /* almdump */›