/*
Copyright (C) 2004, 2005, 2008, 2011 Rocky Bernstein <rocky@gnu.org>
Copyright (C) 1998 Monty xiphmont@mit.edu
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/* sorted vector abstraction for paranoia */
/* Old isort got a bit complex. This re-constrains complexity to
give a go at speed through a more alpha-6-like mechanism. */
/* "Sort" is a bit of a misnomer in this implementation. It's actually
* basically a hash table of sample values (with a linked-list collision
* resolution), which lets you quickly determine where in a vector a
* particular sample value occurs.
*
* Collisions aren't due to hash collisions, as the table has one bucket
* for each possible sample value. Instead, the "collisions" represent
* multiple occurrences of a given value.
*/
#ifdef HAVE_CONFIG_H
# include "config.h"
# define __CDIO_CONFIG_H__ 1
#endif
#ifdef HAVE_STDLIB_H
#include <stdlib.h>
#endif
#ifdef HAVE_STRING_H
#include <string.h>
#endif
#include "p_block.h"
#include "isort.h"
/* ===========================================================================
* sort_alloc()
*
* Allocates and initializes a new, empty sort_info object, which can be
* used to index up to (size) samples from a vector.
*/
sort_info_t *
sort_alloc(long size)
{
sort_info_t *ret=calloc(1, sizeof(sort_info_t));
ret->vector=NULL;
ret->sortbegin=-1;
ret->size=-1;
ret->maxsize=size;
ret->head=calloc(65536,sizeof(sort_link_t *));
ret->bucketusage=calloc(1, 65536*sizeof(long));
ret->revindex=calloc(size,sizeof(sort_link_t));
ret->lastbucket=0;
return(ret);
}
/* ===========================================================================
* sort_unsortall() (internal)
*
* This function resets the index for further use with a different vector
* or range, without the overhead of an unnecessary free/alloc.
*/
void
sort_unsortall(sort_info_t *i)
{
/* If there were few enough different samples encountered (and hence few
* enough buckets used), we can just zero out those buckets. If there
* were many (2000 is picked somewhat arbitrarily), it's faster simply to
* zero out all buckets with a memset() rather than walking the data
* structure and zeroing them out one by one.
*/
if (i->lastbucket>2000) { /* a guess */
memset(i->head,0,65536*sizeof(sort_link_t *));
} else {
long b;
for (b=0; b<i->lastbucket; b++)
i->head[i->bucketusage[b]]=NULL;
}
i->lastbucket=0;
i->sortbegin=-1;
/* Curiously, this function preserves the vector association created
* by sort_setup(), but it is used only internally by sort_setup, so
* preserving this association is unnecessary.
*/
}
/* ===========================================================================
* sort_free()
*
* Releases all memory consumed by a sort_info object.
*/
void
sort_free(sort_info_t *i)
{
free(i->revindex);
free(i->head);
free(i->bucketusage);
free(i);
}
/* ===========================================================================
* sort_sort() (internal)
*
* This function builds the index to allow for fast searching for sample
* values within a portion (sortlo - sorthi) of the object's associated
* vector. It is called internally and only when needed.
*/
static void
sort_sort(sort_info_t *i,long sortlo,long sorthi)
{
long j;
/* We walk backward through the range to index because we insert new
* samples at the head of each bucket's list. At the end, they'll be
* sorted from first to last occurrence.
*/
for (j=sorthi-1; j>=sortlo; j--) {
/* i->vector[j] = the signed 16-bit sample to index.
* hv = pointer to the head of the sorted list of occurences
* of this sample
* l = the node to associate with this sample
*
* We add 32768 to convert the signed 16-bit integer to an unsigned
* range from 0 to 65535.
*
* Note that l is located within i->revindex at a position
* corresponding to the sample's position in the vector. This allows
* ipos() to determine the sample position from a returned sort_link.
*/
sort_link_t **hv = i->head+i->vector[j]+32768;
sort_link_t *l = i->revindex+j;
/* If this is the first time we've encountered this sample, add its
* bucket to the list of buckets used. This list is used only for
* resetting the index quickly.
*/
if(*hv==NULL){
i->bucketusage[i->lastbucket] = i->vector[j]+32768;
i->lastbucket++;
}
/* Point the new node at the old head, then assign the new node as
* the new head.
*/
l->next=*hv;
*hv=l;
}
/* Mark the index as initialized.
*/
i->sortbegin=0;
}
/* ===========================================================================
* sort_setup()
*
* This function initializes a previously allocated sort_info_t. The
* sort_info_t is associated with a vector of samples of length
* (size), whose position begins at (*abspos) within the CD's stream
* of samples. Only the range of samples between (sortlo, sorthi)
* will eventually be indexed for fast searching. (sortlo, sorthi)
* are absolute sample positions.
*
* ???: Why is abspos a pointer? Why not just store a copy?
*
* Note: size *must* be <= the size given to the preceding sort_alloc(),
* but no error checking is done here.
*/
void
sort_setup(sort_info_t *i, int16_t *vector, long int *abspos,
long int size, long int sortlo, long int sorthi)
{
/* Reset the index if it has already been built.
*/
if (i->sortbegin!=-1)
sort_unsortall(i);
i->vector=vector;
i->size=size;
i->abspos=abspos;
/* Convert the absolute (sortlo, sorthi) to offsets within the vector.
* Note that the index will not be built until sort_getmatch() is called.
* Here we're simply hanging on to the range to index until then.
*/
i->lo = min(size, max(sortlo - *abspos, 0));
i->hi = max(0, min(sorthi - *abspos, size));
}
/* ===========================================================================
* sort_getmatch()
*
* This function returns a sort_link_t pointer which refers to the
* first sample equal to (value) in the vector. It only searches for
* hits within (overlap) samples of (post), where (post) is an offset
* within the vector. The caller can determine the position of the
* matched sample using ipos(sort_info *, sort_link *).
*
* This function returns NULL if no matches were found.
*/
sort_link_t *
sort_getmatch(sort_info_t *i, long post, long overlap, int value)
{
sort_link_t *ret;
/* If the vector hasn't been indexed yet, index it now.
*/
if (i->sortbegin==-1)
sort_sort(i,i->lo,i->hi);
/* Now we reuse lo and hi */
/* We'll only return samples within (overlap) samples of (post).
* Clamp the boundaries to search to the boundaries of the array,
* convert the signed sample to an unsigned offset, and store the
* state so that future calls to sort_nextmatch do the right thing.
*
* Reusing lo and hi this way is awful.
*/
post=max(0,min(i->size,post));
i->val=value+32768;
i->lo=max(0,post-overlap); /* absolute position */
i->hi=min(i->size,post+overlap); /* absolute position */
/* Walk through the linked list of samples with this value, until
* we find the first one within the bounds specified. If there
* aren't any, return NULL.
*/
ret=i->head[i->val];
while (ret) {
/* ipos() calculates the offset (in terms of the original vector)
* of this hit.
*/
if (ipos(i,ret)<i->lo) {
ret=ret->next;
} else {
if (ipos(i,ret)>=i->hi)
ret=NULL;
break;
}
}
/*i->head[i->val]=ret;*/
return(ret);
}
/* ===========================================================================
* sort_nextmatch()
*
* This function returns a sort_link_t pointer which refers to the next sample
* matching the criteria previously passed to sort_getmatch(). See
* sort_getmatch() for details.
*
* This function returns NULL if no further matches were found.
*/
sort_link_t *
sort_nextmatch(sort_info_t *i, sort_link_t *prev)
{
sort_link_t *ret=prev->next;
/* If there aren't any more hits, or we've passed the boundary requested
* of sort_getmatch(), we're done.
*/
if (!ret || ipos(i,ret)>=i->hi)
return(NULL);
return(ret);
}