/*
- * Project: libFIRM
- * File name: ir/adt/pdeq.c
- * Purpose: Pdeq --- double ended queue of generic pointers.
- * Author: Christian von Roques
- * Modified by:
- * Created: 1999 by getting from fiasco
- * CVS-ID: $Id$
- * Copyright: (c) 1995, 1996 Christian von Roques
- * Licence: This file protected by GPL - GNU GENERAL PUBLIC LICENSE.
+ * Copyright (C) 1995-2008 University of Karlsruhe. All right reserved.
+ *
+ * This file is part of libFirm.
+ *
+ * This file may be distributed and/or modified under the terms of the
+ * GNU General Public License version 2 as published by the Free Software
+ * Foundation and appearing in the file LICENSE.GPL included in the
+ * packaging of this file.
+ *
+ * Licensees holding valid libFirm Professional Edition licenses may use
+ * this file in accordance with the libFirm Commercial License.
+ * Agreement provided with the Software.
+ *
+ * This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
+ * WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE.
*/
+/**
+ * @file
+ * @brief double ended queue of generic pointers.
+ * @author Christian von Roques
+ * @date 1999 by getting from fiasco
+ * @version $Id$
+ */
+#include "config.h"
-#ifdef HAVE_CONFIG_H
-# include <config.h>
-#endif
-
-#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
-#include <stdbool.h>
-# ifdef HAVE_STRING_H
-# include <string.h>
-# endif
+#include <string.h>
+#include <assert.h>
-#include "cookies.h"
-#include "debug.h"
+#include "fourcc.h"
#include "pdeq.h"
#include "xmalloc.h"
+/* Pointer Double Ended Queue */
+#define PDEQ_MAGIC1 FOURCC('P','D','E','1')
+#define PDEQ_MAGIC2 FOURCC('P','D','E','2')
-/** Size of pdeq block cache */
+/** Size of pdeq block cache. */
#define TUNE_NSAVED_PDEQS 16
-#ifndef INLINE
-#ifdef USE_GCC_INLINE
-#define INLINE inline
-#else
-#define INLINE
-#endif
-#endif
+/** A size handled efficiently by malloc(), at least 1K. */
+#define PREF_MALLOC_SIZE 2048
-/* # of data items in block */
-#define NDATA ((int)((PREF_MALLOC_SIZE - offsetof (pdeq, data)) / sizeof (void *)))
+/**
+ * Maximal number of data items in a pdeq chunk.
+ */
+#define NDATA ((PREF_MALLOC_SIZE - offsetof(pdeq, data)) / sizeof(void *))
#ifdef NDEBUG
# define VRFY(dq) ((void)0)
#else
-# define VRFY(dq) \
- (d_(df_vrfy_level,1) ? _pdeq_vrfy ((dq)) : assert ((dq) && ((dq)->cookie == PDEQ_COOKIE1)))
+# define VRFY(dq) assert((dq) && ((dq)->magic == PDEQ_MAGIC1))
#endif
-
+/**
+ * A pointer double ended queue.
+ * This structure is used as a list chunk either.
+ */
struct pdeq {
#ifndef NDEBUG
- unsigned cookie;
+ unsigned magic; /**< debug magic */
#endif
- pdeq *l_end, *r_end; /* left and right ends of the deque */
- pdeq *l, *r; /* left and right neighbour */
- int n, p;
- const void *data[1];
+ pdeq *l_end, *r_end; /**< left and right ends of the queue */
+ pdeq *l, *r; /**< left and right neighbor */
+ size_t n; /**< number of elements in the current chunk */
+ size_t p; /**< the read/write pointer */
+ const void *data[1]; /**< storage for elements */
};
-/* cache of unused, pdeq blocks to speed up new_pdeq and del_pdeq. */
-/* +1 for compilers that can't grok empty arrays */
-pdeq *pdeq_block_cache[TUNE_NSAVED_PDEQS+1];
-unsigned pdeqs_cached; /* # pdeqs in pdeq_store */
+/**
+ * cache of unused, pdeq blocks to speed up new_pdeq and del_pdeq.
+ * +1 for compilers that can't grok empty arrays
+ */
+static pdeq *pdeq_block_cache[TUNE_NSAVED_PDEQS+1];
+/**
+ * Number of pdeqs in pdeq_store.
+ */
+static unsigned pdeqs_cached;
-static INLINE void
-free_pdeq_block (pdeq *p)
+/**
+ * Free a pdeq chunk, put in into the cache if possible.
+ *
+ * @param p The pdeq chunk.
+ */
+static inline void free_pdeq_block (pdeq *p)
{
#ifndef NDEBUG
- p->cookie = 0xbadf00d1;
+ p->magic = 0xbadf00d1;
#endif
- if (pdeqs_cached < TUNE_NSAVED_PDEQS) {
- if (d_ (df_pdeq, 2)) printf ("[%p ==> pdeq_block_cache] ", p);
- pdeq_block_cache[pdeqs_cached++] = p;
- } else {
- if (d_ (df_pdeq, 2)) printf ("[%p ==> free] ", p);
- xfree (p);
- }
+ if (pdeqs_cached < TUNE_NSAVED_PDEQS) {
+ pdeq_block_cache[pdeqs_cached++] = p;
+ } else {
+ xfree (p);
+ }
}
-
-static INLINE pdeq *
-alloc_pdeq_block (void)
+/**
+ * Allocate a new pdeq chunk, get it from the cache if possible.
+ *
+ * @return A new pdeq chunk.
+ */
+static inline pdeq *alloc_pdeq_block (void)
{
- pdeq *p;
- if (TUNE_NSAVED_PDEQS && pdeqs_cached) {
- p = pdeq_block_cache[--pdeqs_cached];
- if (d_ (df_pdeq, 2)) printf ("[pdeq_block_cache ==> %p] ", p);
- } else {
- p = xmalloc (PREF_MALLOC_SIZE);
- if (d_ (df_pdeq, 2)) printf ("[malloc ==> %p] ", p);
- }
- return p;
+ pdeq *p;
+ if (TUNE_NSAVED_PDEQS && pdeqs_cached) {
+ p = pdeq_block_cache[--pdeqs_cached];
+ } else {
+ p = (pdeq*) xmalloc(PREF_MALLOC_SIZE);
+ }
+ return p;
}
#ifndef NDEBUG
-void
-_pdeq_vrfy (pdeq *dq)
+/**
+ * Verify a double ended list, assert if failure.
+ *
+ * @param dq The list to verify.
+ */
+void _pdeq_vrfy(pdeq *dq)
{
- pdeq *q;
-
- if (d_ (df_pdeq, 5)) printf ("[pdeq_vrfy %p] ", dq);
-
- assert ( dq
- && (dq->cookie == PDEQ_COOKIE1)
- && (dq->l_end && dq->r_end));
- q = dq->l_end;
- while (q) {
- assert ( ((q == dq) || (q->cookie == PDEQ_COOKIE2))
- && ((q == dq->l_end) ^ (q->l!=0))
- && ((q == dq->r_end) ^ (q->r!=0))
- && (!q->l || (q == q->l->r))
- && ((q->n>=0) && (q->n<=NDATA))
- && ((q == dq->l_end) || (q == dq->r_end) || (q->n == NDATA))
- && ((q->p>=0) && (q->p<NDATA)));
- q = q->r;
- }
+ pdeq *q;
+
+ assert ( dq
+ && (dq->magic == PDEQ_MAGIC1)
+ && (dq->l_end && dq->r_end));
+ q = dq->l_end;
+ while (q) {
+ assert ( ((q == dq) || (q->magic == PDEQ_MAGIC2))
+ && ((q == dq->l_end) ^ (q->l != NULL))
+ && ((q == dq->r_end) ^ (q->r != NULL))
+ && (!q->l || (q == q->l->r))
+ && (q->n <= NDATA)
+ && ((q == dq->l_end) || (q == dq->r_end) || (q->n == NDATA))
+ && (q->p < NDATA));
+ q = q->r;
+ }
}
#endif
-
-pdeq *
-new_pdeq (void)
+/* Creates a new double ended pointer list. */
+pdeq *new_pdeq(void)
{
- pdeq *dq;
+ pdeq *dq;
- dq = alloc_pdeq_block();
+ dq = alloc_pdeq_block();
#ifndef NDEBUG
- dq->cookie = PDEQ_COOKIE1;
+ dq->magic = PDEQ_MAGIC1;
#endif
- dq->l_end = dq->r_end = dq;
- dq->l = dq->r = NULL;
- dq->n = dq->p = 0;
+ dq->l_end = dq->r_end = dq;
+ dq->l = dq->r = NULL;
+ dq->n = dq->p = 0;
- VRFY (dq);
- if (d_ (df_pdeq, 1)) printf ("(new_pdeq ==> %p)\n", dq);
- return dq;
+ VRFY(dq);
+ return dq;
}
-
-pdeq *
-new_pdeq1 (const void *x)
+/* Creates a new double ended pointer list and puts an initial pointer element in. */
+pdeq *new_pdeq1(const void *x)
{
- return pdeq_putr (new_pdeq(), x);
+ return pdeq_putr(new_pdeq(), x);
}
-
-void
-del_pdeq (pdeq *dq)
+/* Delete a double ended pointer list. */
+void del_pdeq(pdeq *dq)
{
- pdeq *q, *qq;
+ pdeq *q, *qq;
- VRFY (dq);
+ VRFY(dq);
- q = dq->l_end; /* left end of chain */
- /* pdeq trunk empty, but !pdeq_empty() ==> trunk not in chain */
- if (dq->n == 0 && dq->l_end != dq ) {
- free_pdeq_block (dq);
- }
+ q = dq->l_end; /* left end of chain */
+ /* pdeq trunk empty, but !pdeq_empty() ==> trunk not in chain */
+ if (dq->n == 0 && dq->l_end != dq ) {
+ free_pdeq_block(dq);
+ }
- /* Free all blocks in the pdeq chain */
- do {
- qq = q->r;
- free_pdeq_block (q);
- } while ((q = qq));
+ /* Free all blocks in the pdeq chain */
+ do {
+ qq = q->r;
+ free_pdeq_block(q);
+ } while ((q = qq));
- if (d_ (df_pdeq, 1)) printf ("(del_pdeq %p)\n", dq);
}
-
-bool
-pdeq_empty (pdeq *dq)
+/* Checks if a list is empty. */
+int pdeq_empty(pdeq *dq)
{
- VRFY (dq);
- if (d_ (df_pdeq, 4)) printf ("(pdeq_empty %p ==> %d)\n", dq, dq->l_end->n == 0);
- return dq->l_end->n == 0;
+ VRFY(dq);
+ return dq->l_end->n == 0;
}
-
-int
-pdeq_len (pdeq *dq)
+/* Returns the length of a double ended pointer list. */
+size_t pdeq_len(pdeq *dq)
{
- int n;
- pdeq *q;
+ size_t n;
+ pdeq *q;
- VRFY (dq);
+ VRFY(dq);
- n = 0;
- q = dq->l_end;
- do {
- n += q->n;
- q = q->r;
- } while (q);
+ n = 0;
+ q = dq->l_end;
+ do {
+ n += q->n;
+ q = q->r;
+ } while (q);
- if (d_ (df_pdeq, 4)) printf ("(pdeq_len %p ==> %d)\n", dq, n);
- return n;
+ return n;
}
-
-pdeq *
-pdeq_putr (pdeq *dq, const void *x)
+/* Add a pointer to the right site of a double ended pointer list. */
+pdeq *pdeq_putr(pdeq *dq, const void *x)
{
- pdeq *rdq;
- int n;
- bool pr = 0;
+ pdeq *rdq;
+ size_t n;
- VRFY (dq);
+ VRFY(dq);
- rdq = dq->r_end;
- if (rdq->n >= NDATA) { /* tailblock full */
- pdeq *ndq;
+ rdq = dq->r_end;
+ if (rdq->n >= NDATA) { /* tailblock full */
+ pdeq *ndq;
- ndq = dq; /* try to reuse trunk, but ... */
- if (dq->n) { /* ... if trunk used */
- /* allocate and init new block */
- ndq = alloc_pdeq_block ();
- pr = d_ (df_pdeq, 2);
+ ndq = dq; /* try to reuse trunk, but ... */
+ if (dq->n) { /* ... if trunk used */
+ /* allocate and init new block */
+ ndq = alloc_pdeq_block();
#ifndef NDEBUG
- ndq->cookie = PDEQ_COOKIE2;
+ ndq->magic = PDEQ_MAGIC2;
#endif
- ndq->l_end = ndq->r_end = NULL;
- }
+ ndq->l_end = ndq->r_end = NULL;
+ }
- ndq->r = NULL;
- ndq->l = rdq; rdq->r = ndq;
- ndq->n = 0; ndq->p = 0;
- dq->r_end = ndq;
- rdq = ndq;
- }
+ ndq->r = NULL;
+ ndq->l = rdq; rdq->r = ndq;
+ ndq->n = 0; ndq->p = 0;
+ dq->r_end = ndq;
+ rdq = ndq;
+ }
- n = rdq->n++ + rdq->p;
- if (n >= NDATA) n -= NDATA;
+ n = rdq->n++ + rdq->p;
+ if (n >= NDATA) n -= NDATA;
- rdq->data[n] = x;
+ rdq->data[n] = x;
- VRFY (dq);
- if (d_ (df_pdeq, 3) || pr) printf ("(pdeq_putr %p %p)\n", dq, x);
- return dq;
+ VRFY(dq);
+ return dq;
}
-
-pdeq *
-pdeq_putl (pdeq *dq, const void *x)
+/* Add a pointer to the left site of a double ended pointer list. */
+pdeq *pdeq_putl(pdeq *dq, const void *x)
{
- pdeq *ldq;
- int p;
- bool pr = 0;
+ pdeq *ldq;
+ size_t p;
- VRFY (dq);
+ VRFY(dq);
- ldq = dq->l_end;
- if (ldq->n >= NDATA) { /* headblock full */
- pdeq *ndq;
+ ldq = dq->l_end;
+ if (ldq->n >= NDATA) { /* headblock full */
+ pdeq *ndq;
- ndq = dq; /* try to reuse trunk, but ... */
- if (dq->n) { /* ... if trunk used */
- /* allocate and init new block */
- ndq = alloc_pdeq_block ();
- pr = d_ (df_pdeq, 2);
+ ndq = dq; /* try to reuse trunk, but ... */
+ if (dq->n) { /* ... if trunk used */
+ /* allocate and init new block */
+ ndq = alloc_pdeq_block();
#ifndef NDEBUG
- ndq->cookie = PDEQ_COOKIE2;
+ ndq->magic = PDEQ_MAGIC2;
#endif
- ndq->l_end = ndq->r_end = NULL;
- }
-
- ndq->l = NULL;
- ndq->r = ldq; ldq->l = ndq;
- ndq->n = 0; ndq->p = 0;
- dq->l_end = ndq;
- ldq = ndq;
- }
-
- ldq->n++;
- p = ldq->p - 1;
- if (p < 0) p += NDATA;
- ldq->p = p;
-
- ldq->data[p] = x;
-
- VRFY (dq);
- if (d_ (df_pdeq, 3) || pr) printf ("(pdeq_putl %p %p)\n", dq, x);
- return dq;
+ ndq->l_end = ndq->r_end = NULL;
+ }
+
+ ndq->l = NULL;
+ ndq->r = ldq; ldq->l = ndq;
+ ndq->n = 0; ndq->p = 0;
+ dq->l_end = ndq;
+ ldq = ndq;
+ }
+
+ ldq->n++;
+ if (ldq->p == 0)
+ p = NDATA;
+ else
+ p = ldq->p - 1;
+ ldq->p = p;
+
+ ldq->data[p] = x;
+
+ VRFY(dq);
+ return dq;
}
-
-void *
-pdeq_getr (pdeq *dq)
+/* Retrieve a pointer from the right site of a double ended pointer list. */
+void *pdeq_getr(pdeq *dq)
{
- pdeq *rdq;
- const void *x;
- int n;
- bool pr = 0;
-
- VRFY (dq);
- assert (dq->l_end->n);
-
- rdq = dq->r_end;
- n = rdq->p + --rdq->n;
- if (n>=NDATA) n -= NDATA;
- x = rdq->data[n];
-
- if (rdq->n == 0) {
- if (rdq->l) {
- dq->r_end = rdq->l;
- rdq->l->r = NULL;
- rdq->l = NULL;
- } else {
- dq->r_end = dq->l_end = dq;
- }
- if (dq != rdq) {
- free_pdeq_block (rdq);
- pr = d_ (df_pdeq, 2);
- }
- }
-
- VRFY (dq);
- if (d_ (df_pdeq, 3) || pr) printf ("(pdeq_getr %p ==> %p)\n", dq, x);
- return (void *)x;
+ pdeq *rdq;
+ const void *x;
+ size_t n;
+
+ VRFY(dq);
+ assert(dq->l_end->n);
+
+ rdq = dq->r_end;
+ n = rdq->p + --rdq->n;
+ if (n >= NDATA) n -= NDATA;
+ x = rdq->data[n];
+
+ if (rdq->n == 0) {
+ if (rdq->l) {
+ dq->r_end = rdq->l;
+ rdq->l->r = NULL;
+ rdq->l = NULL;
+ } else {
+ dq->r_end = dq->l_end = dq;
+ }
+ if (dq != rdq) {
+ free_pdeq_block(rdq);
+ }
+ }
+
+ VRFY(dq);
+ return (void *)x;
}
-
-void *
-pdeq_getl (pdeq *dq)
+/* Retrieve a pointer from the left site of a double ended pointer list. */
+void *pdeq_getl(pdeq *dq)
{
- pdeq *ldq;
- const void *x;
- int p;
- bool pr = 0;
-
- VRFY (dq);
- assert (dq->l_end->n);
-
- ldq = dq->l_end;
- p = ldq->p;
- x = ldq->data[p];
- if (++p >= NDATA) p = 0;
- ldq->p = p;
-
- if (--ldq->n == 0) {
- if (ldq->r) {
- dq->l_end = ldq->r;
- ldq->r->l = NULL;
- ldq->r = NULL;
- } else {
- dq->l_end = dq->r_end = dq;
- }
- if (dq != ldq) {
- free_pdeq_block (ldq);
- pr = d_ (df_pdeq, 2);
- }
- }
-
- VRFY (dq);
- if (d_ (df_pdeq, 3) || pr) printf ("(pdeq_getl %p ==> %p)\n", dq, x);
- return (void *)x;
+ pdeq *ldq;
+ const void *x;
+ size_t p;
+
+ VRFY(dq);
+ assert(dq->l_end->n);
+
+ ldq = dq->l_end;
+ p = ldq->p;
+ x = ldq->data[p];
+ if (++p >= NDATA) p = 0;
+ ldq->p = p;
+
+ if (--ldq->n == 0) {
+ if (ldq->r) {
+ dq->l_end = ldq->r;
+ ldq->r->l = NULL;
+ ldq->r = NULL;
+ } else {
+ dq->l_end = dq->r_end = dq;
+ }
+ if (dq != ldq) {
+ free_pdeq_block(ldq);
+ }
+ }
+
+ VRFY(dq);
+ return (void *)x;
}
-
-bool
-pdeq_contains (pdeq *dq, const void *x)
+/*
+ * Returns non-zero if a double ended pointer list
+ * contains a pointer x.
+ */
+int pdeq_contains(pdeq *dq, const void *x)
{
- pdeq *q;
+ pdeq *q;
- VRFY (dq);
+ VRFY(dq);
- q = dq->l_end;
- do {
- int p, ep;
+ q = dq->l_end;
+ do {
+ size_t p, ep;
- p = q->p; ep = p + q->n;
+ p = q->p; ep = p + q->n;
- if (ep > NDATA) {
- do if (q->data[p] == x) goto found; while (++p < NDATA);
- p = 0;
- ep -= NDATA;
- }
+ if (ep > NDATA) {
+ do {
+ if (q->data[p] == x) return 1;
+ } while (++p < NDATA);
+ p = 0;
+ ep -= NDATA;
+ }
- while (p < ep) if (q->data[p++] == x) goto found;
+ while (p < ep) {
+ if (q->data[p++] == x) return 1;
+ }
- q = q->r;
- } while (q);
+ q = q->r;
+ } while (q);
- if (d_ (df_pdeq, 3)) printf ("(pdeq_contains %p %p ==> 0)\n", dq, x);
- return 0;
-
-found: /* The two gotos can be optimized away, if !DEBUG */
- if (d_ (df_pdeq, 3)) printf ("(pdeq_contains %p %p ==> 1)\n", dq, x);
- return 1;
+ return 0;
}
-
-void *
-pdeq_search (pdeq *dq, cmp_fun cmp, const void *key)
+/*
+ * Search a key in a double ended pointer list, the search
+ * is controlled by a compare function.
+ * An element is found, if the compare function returns 0.
+ * The search is started from the left site of the list.
+ */
+void *pdeq_search(pdeq *dq, cmp_fun cmp, const void *key)
{
- pdeq *q;
- int p;
-
- VRFY (dq);
+ pdeq *q;
+ size_t p;
- q = dq->l_end;
- do {
- int ep;
+ VRFY(dq);
- p = q->p; ep = p + q->n;
+ q = dq->l_end;
+ do {
+ size_t ep;
- if (ep > NDATA) {
- do if (!cmp (q->data[p], key)) goto found; while (++p < NDATA);
- p = 0;
- ep -= NDATA;
- }
+ p = q->p; ep = p + q->n;
- while (p < ep) if (!cmp (q->data[p++], key)) goto found;
+ if (ep > NDATA) {
+ do {
+ if (!cmp(q->data[p], key)) return (void *)q->data[p-1];
+ } while (++p < NDATA);
+ p = 0;
+ ep -= NDATA;
+ }
- q = q->r;
- } while (q);
+ while (p < ep) {
+ if (!cmp(q->data[p++], key)) return (void *)q->data[p-1];
+ }
- if (d_ (df_pdeq, 3)) printf ("(pdeq_search %p %p %p ==> 0)\n", dq, cmp, key);
- return NULL;
+ q = q->r;
+ } while (q);
-found: /* The two gotos can be optimized away, if !DEBUG */
- if (d_ (df_pdeq, 3)) printf ("(pdeq_contains %p %p %p ==> %p)\n",
- dq, cmp, key, q->data[p]);
- return (void *)q->data[p-1];
+ return NULL;
}
-
-void **
-pdeq_copyl (pdeq *dq, const void **dst)
+/*
+ * Convert the double ended pointer list into a linear array beginning from
+ * left, the first element in the linear array will be the left one.
+ */
+void **pdeq_copyl(pdeq *dq, const void **dst)
{
- pdeq *q;
- const void **d = dst;
+ pdeq *q;
+ const void **d = dst;
- VRFY (dq);
+ VRFY(dq);
- q = dq->l_end;
- while (q) {
- int p, n;
+ q = dq->l_end;
+ while (q) {
+ size_t p, n;
- p = q->p; n = q->n;
+ p = q->p; n = q->n;
- if (n + p > NDATA) {
- int nn = NDATA - p;
- memcpy (d, &q->data[p], nn * sizeof (void *)); d += nn;
- p = 0; n -= nn;
- }
+ if (n + p > NDATA) {
+ /* p is always < NDATA */
+ size_t nn = NDATA - p;
+ memcpy((void *) d, &q->data[p], nn * sizeof(void *)); d += nn;
+ p = 0; n -= nn;
+ }
- memcpy (d, &q->data[p], n * sizeof (void *)); d += n;
+ memcpy((void *) d, &q->data[p], n * sizeof(void *)); d += n;
- q = q->r;
- }
+ q = q->r;
+ }
- if (d_ (df_pdeq, 3)) printf ("(pdeq_copyl %p %p ==> %p)\n", dq, dst, d);
- return (void **)dst;
+ return (void **)dst;
}
-
-void **
-pdeq_copyr (pdeq *dq, const void **dst)
+/*
+ * Convert the double ended pointer list into a linear array beginning from
+ * right, the first element in the linear array will be the right one.
+ */
+void **pdeq_copyr(pdeq *dq, const void **dst)
{
- pdeq *q;
- const void **d = dst;
-
- VRFY (dq);
-
- q = dq->r_end;
- while (q) {
- int p, i;
-
- p = q->p; i = q->n + p - 1;
- if (i >= NDATA) {
- i -= NDATA;
- do *d++ = q->data[i]; while (--i >= 0);
- i = NDATA - 1;
- }
-
- do *d++ = q->data[i]; while (--i >= p);
-
- q = q->l;
- }
-
- if (d_ (df_pdeq, 3)) printf ("(pdeq_copyr %p %p ==> %p)\n", dq, dst, d);
- return (void **)dst;
+ pdeq *q;
+ const void **d = dst;
+
+ VRFY(dq);
+
+ q = dq->r_end;
+ while (q) {
+ size_t p, i;
+
+ p = q->p; i = q->n + p - 1;
+ if (i >= NDATA) {
+ i -= NDATA;
+ for (;; --i) {
+ *d++ = q->data[i];
+ if (i == 0)
+ break;
+ }
+ i = NDATA - 1;
+ }
+
+ for (;; --i) {
+ *d++ = q->data[i];
+ if (i <= p)
+ break;
+ }
+
+ q = q->l;
+ }
+
+ return (void **)dst;
}