c281867f46
Relocated some syslib functions to utils library; Changed location of 'Multiuser startup ..." echo in /etc/rc
178 lines
4 KiB
C
Executable file
178 lines
4 KiB
C
Executable file
/* malloc(), realloc(), free() - simple memory allocation routines
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*
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* This is a very small and simple minded malloc Author: Kees J. Bot
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* implementation. Ideal for things like a 29 Jan 1994
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* bootstrap program, or for debugging. Six times
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* slower than any good malloc.
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*/
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#define nil 0
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#define sbrk _sbrk
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#include <stddef.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <string.h>
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#include <limits.h>
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#if !DEBUG
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#define NDEBUG 1
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#define debug(expr) ((void) 0)
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#else
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#define debug(expr) expr
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#endif
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#include <assert.h>
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typedef struct cell {
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size_t size; /* Size of a malloc()'ed object. */
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#if DEBUG
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unsigned magic; /* To recognize a cell. */
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#endif
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struct cell *next; /* Next cell on the free list. */
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#if DEBUG
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unsigned sacred; /* Don't touch while unallocated. */
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#endif
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} cell_t;
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#if UINT_MAX <= 0xFFFF
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#define MAGIC 0x537B
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#else
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#define MAGIC 0x537BC0D8
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#endif
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/* Size of the header of an object. */
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#define HDR_SIZE offsetof(cell_t, next)
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/* An offset from a cell pointer to a next cell. */
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#define offset(cp, size) ((cell_t *) ((char *) (cp) + (size)))
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/* Address of the object in a cell and back. */
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#define cell2obj(cp) ((void *) ((char *) (cp) + HDR_SIZE))
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#define obj2cell(op) ((cell_t *) ((char *) (op) - HDR_SIZE))
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/* The free list. */
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static cell_t *freelist;
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void *malloc(size_t size)
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/* Allocate an object of at least the given size. */
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{
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cell_t **pcp, *cp;
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size += HDR_SIZE;
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if (size < sizeof(cell_t)) size= sizeof(cell_t);
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/* Align to a word. Use a real malloc if you need better alignment. */
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size= (size + sizeof(int) - 1) & ~(sizeof(int) - 1);
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/* Space for a magic number at the end of the chunk. */
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debug(size += sizeof(unsigned));
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for (;;) {
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/* Do a first fit search. */
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pcp= &freelist;
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while ((cp= *pcp) != nil) {
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cell_t *next= cp->next;
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assert(cp->magic == MAGIC);
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assert(cp->sacred == MAGIC);
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if (offset(cp, cp->size) == next) {
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/* Join adjacent free cells. */
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assert(next->magic == MAGIC);
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assert(next->sacred == MAGIC);
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cp->size+= next->size;
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cp->next= next->next;
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continue; /* Try again. */
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}
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if (size <= cp->size) break; /* Big enough. */
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/* Next cell. */
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pcp= &cp->next;
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}
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if (cp != nil) break; /* Found a big enough chunk. */
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/* Allocate a new chunk at the break. */
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if ((cp= (cell_t *) sbrk(size)) == (cell_t *) -1) {
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return nil;
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}
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cp->size= size;
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cp->next= nil;
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debug(cp->magic= MAGIC);
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debug(cp->sacred= MAGIC);
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*pcp= cp;
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}
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/* We've got a cell that is big enough. Can we break it up? */
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if (cp->size >= size + sizeof(cell_t)) {
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cell_t *next= offset(cp, size);
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next->size= cp->size - size;
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next->next= cp->next;
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debug(next->magic= MAGIC);
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debug(next->sacred= MAGIC);
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cp->size= size;
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cp->next= next;
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}
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/* Unchain the cell we've found and return an address in it. */
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*pcp= cp->next;
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debug(memset(cell2obj(cp), 0xAA, cp->size - HDR_SIZE));
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debug(((unsigned *) offset(cp, cp->size))[-1]= MAGIC);
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return cell2obj(cp);
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}
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void free(void *op)
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/* Deallocate an object. */
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{
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cell_t **prev, *next, *cp;
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if (op == nil) return; /* Aaargh. */
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cp= obj2cell(op);
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assert(cp->magic == MAGIC);
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assert(((unsigned *) offset(cp, cp->size))[-1] == MAGIC);
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debug(cp->sacred= MAGIC);
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/* Find the spot where the object belongs. */
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prev= &freelist;
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while ((next= *prev) != nil && next < cp) {
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assert(next->magic == MAGIC);
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assert(next->sacred == MAGIC);
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prev= &next->next;
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}
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/* Put the new free cell in the list. */
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*prev= cp;
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cp->next= next;
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#if DEBUG
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/* Check the rest of the list. */
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while (next != nil) {
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assert(next->magic == MAGIC);
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assert(next->sacred == MAGIC);
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next= next->next;
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}
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#endif
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}
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void *realloc(void *op, size_t size)
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/* Change the size of an object. Don't bother being smart, just copy it. */
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{
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size_t oldsize;
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void *new;
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oldsize= op == nil ? 0 : obj2cell(op)->size - HDR_SIZE;
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new= malloc(size);
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memcpy(new, op, oldsize > size ? size : oldsize);
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free(op);
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return new;
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}
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/*
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* $PchId: malloc.c,v 1.4 1996/02/22 09:15:56 philip Exp $
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*/
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