path: root/headers.c

/* 
 * Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
 * Copyright (c) 1991-1993 by Xerox Corporation.  All rights reserved.
 *
 * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
 * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
 *
 * Permission is hereby granted to copy this garbage collector for any purpose,
 * provided the above notices are retained on all copies.
 */
 
/*
 * This implements:
 * 1. allocation of heap block headers
 * 2. A map from addresses to heap block addresses to heap block headers
 *
 * Access speed is crucial.  We implement an index structure based on a 2
 * level tree.
 */
 
# include "gc_private.h"

bottom_index * GC_all_bottom_indices = 0;
 
/* Non-macro version of header location routine */
hdr * GC_find_header(h)
ptr_t h;
{
#   ifdef TL_HASH
	register hdr * result;
	GET_HDR(h, result);
	return(result);
#   else
	return(HDR(h));
#   endif
}
 
/* Routines to dynamically allocate collector data structures that will */
/* never be freed.							 */
 
static ptr_t scratch_free_ptr = 0;
 
static ptr_t scratch_end_ptr = 0;
 
ptr_t GC_scratch_alloc(bytes)
register word bytes;
{
    register ptr_t result = scratch_free_ptr;
    scratch_free_ptr += bytes;
    if (scratch_free_ptr <= scratch_end_ptr) {
        return(result);
    }
    {
        word bytes_to_get = MINHINCR * HBLKSIZE;
         
        if (bytes_to_get <= bytes) {
          /* Undo the damage, and get memory directly */
            scratch_free_ptr -= bytes;
            return((ptr_t)GET_MEM(bytes));
        }
        result = (ptr_t)GET_MEM(bytes_to_get);
        if (result == 0) {
#	    ifdef PRINTSTATS
                GC_printf0("Out of memory - trying to allocate less\n");
#	    endif
            scratch_free_ptr -= bytes;
            return((ptr_t)GET_MEM(bytes));
        }
        scratch_free_ptr = result;
        scratch_end_ptr = scratch_free_ptr + bytes_to_get;
        return(GC_scratch_alloc(bytes));
    }
}

static hdr * hdr_free_list = 0;

/* Return an uninitialized header */
static hdr * alloc_hdr()
{
    register hdr * result;
    
    if (hdr_free_list == 0) {
        result = (hdr *) GC_scratch_alloc((word)(sizeof(hdr)));
    } else {
        result = hdr_free_list;
        hdr_free_list = (hdr *) (result -> hb_next);
    }
    return(result);
}

static void free_hdr(hhdr)
hdr * hhdr;
{
    hhdr -> hb_next = (struct hblk *) hdr_free_list;
    hdr_free_list = hhdr;
}
 
GC_init_headers()
{
    register int i;
     
    for (i = 0; i < TOP_SZ; i++) {
        GC_top_index[i] = &GC_all_nils;
    }
}

/* Make sure that there is a bottom level index block for address addr  */
/* Return FALSE on failure.						*/
static bool get_index(addr)
register word addr;
{
    register word hi =
    		(word)(addr) >> (LOG_BOTTOM_SZ + LOG_HBLKSIZE);
    register bottom_index * r;
    register bottom_index * p;
    register bottom_index ** prev;
#   ifdef HASH_TL
      register i = TL_HASH(hi);
      register bottom_index * old;
      
      old = p = GC_top_index[i];
      while(p != &GC_all_nils) {
          if (p -> key == hi) return(TRUE);
          p = p -> hash_link;
      }
      r = (bottom_index*)GC_scratch_alloc((word)(sizeof (bottom_index)));
      if (r == 0) return(FALSE);
      bzero((char *)r, (int)(sizeof (bottom_index)));
      r -> hash_link = old;
      GC_top_index[i] = r;
#   else
      if (GC_top_index[hi] != &GC_all_nils) return(TRUE);
      r = (bottom_index*)GC_scratch_alloc((word)(sizeof (bottom_index)));
      if (r == 0) return(FALSE);
      GC_top_index[hi] = r;
      bzero((char *)r, (int)(sizeof (bottom_index)));
# endif
    r -> key = hi;
    /* Add it to the list of bottom indices */
      prev = &GC_all_bottom_indices;
      while ((p = *prev) != 0 && p -> key < hi) prev = &(p -> asc_link);
      r -> asc_link = p;
      *prev = r;
    return(TRUE);
}

/* Install a header for block h.  */
/* The header is uninitialized.	  */
/* Returns FALSE on failure.	  */
bool GC_install_header(h)
register struct hblk * h;
{
    hdr * result;
    
    if (!get_index((word) h)) return(FALSE);
    result = alloc_hdr();
    SET_HDR(h, result);
    return(result != 0);
}

/* Set up forwarding counts for block h of size sz */
bool GC_install_counts(h, sz)
register struct hblk * h;
register word sz; /* bytes */
{
    register struct hblk * hbp;
    register int i;
    
    for (hbp = h; (char *)hbp < (char *)h + sz; hbp += BOTTOM_SZ) {
        if (!get_index((word) hbp)) return(FALSE);
    }
    if (!get_index((word)h + sz - 1)) return(FALSE);
    for (hbp = h + 1; (char *)hbp < (char *)h + sz; hbp += 1) {
        i = HBLK_PTR_DIFF(hbp, h);
        SET_HDR(hbp, (hdr *)(i > MAX_JUMP? MAX_JUMP : i));
    }
    return(TRUE);
}

/* Remove the header for block h */
void GC_remove_header(h)
register struct hblk * h;
{
    hdr ** ha;
    
    GET_HDR_ADDR(h, ha);
    free_hdr(*ha);
    *ha = 0;
}

/* Remove forwarding counts for h */
void GC_remove_counts(h, sz)
register struct hblk * h;
register word sz; /* bytes */
{
    register struct hblk * hbp;
    
    for (hbp = h+1; (char *)hbp < (char *)h + sz; hbp += 1) {
        SET_HDR(hbp, 0);
    }
}

/* Apply fn to all allocated blocks */
/*VARARGS1*/
void GC_apply_to_all_blocks(fn, client_data)
void (*fn)(/* struct hblk *h, word client_data */);
word client_data;
{
    register int j;
    register bottom_index * index_p;
    
    for (index_p = GC_all_bottom_indices; index_p != 0;
         index_p = index_p -> asc_link) {
        for (j = BOTTOM_SZ-1; j >= 0;) {
            if (!IS_FORWARDING_ADDR_OR_NIL(index_p->index[j])) {
                if (index_p->index[j]->hb_map != GC_invalid_map) {
                    (*fn)(((struct hblk *)
                  	      (((index_p->key << LOG_BOTTOM_SZ) + (word)j)
                  	       << LOG_HBLKSIZE)),
                          client_data);
                }
                j--;
             } else if (index_p->index[j] == 0) {
                j--;
             } else {
                j -= (int)(index_p->index[j]);
             }
         }
     }
}

/* Get the next valid block whose address is at least h	*/
/* Return 0 if there is none.				*/
struct hblk * GC_next_block(h)
struct hblk * h;
{
    register bottom_index * bi;
    register word j = ((word)h >> LOG_HBLKSIZE) & (BOTTOM_SZ-1);
    
    GET_BI(h, bi);
    if (bi == &GC_all_nils) {
        register int hi = (word)h >> (LOG_BOTTOM_SZ + LOG_HBLKSIZE);
        bi = GC_all_bottom_indices;
        while (bi != 0 && bi -> key < hi) bi = bi -> asc_link;
        j = 0;
    }
    while(bi != 0) {
        while (j < BOTTOM_SZ) {
            if (IS_FORWARDING_ADDR_OR_NIL(bi -> index[j])) {
                j++;
            } else {
                if (bi->index[j]->hb_map != GC_invalid_map) {
                    return((struct hblk *)
                  	      (((bi -> key << LOG_BOTTOM_SZ) + j)
                  	       << LOG_HBLKSIZE));
                } else {
                    j += divHBLKSZ(bi->index[j] -> hb_sz);
                }
            }
        }
        j = 0;
        bi = bi -> asc_link;
    }
    return(0);
}