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index.c
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index.c
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/*
* Copyright (C) 2018 Mark Hills <mark@xwax.org>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* version 2, as published by the Free Software Foundation.
*
* 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 version 2 for more details.
*
* You should have received a copy of the GNU General Public License
* version 2 along with this program; if not, write to the Free
* Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
* MA 02110-1301, USA.
*
*/
#define _GNU_SOURCE /* strcasestr(), strdupa() */
#include <assert.h>
#include <ctype.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "index.h"
#define BLOCK 1024
#define MAX_WORDS 32
#define SEPARATOR ' '
#define ARRAY_SIZE(x) (sizeof(x) / sizeof(*x))
/*
* Initialise a record index
*/
void index_init(struct index *ls)
{
ls->record = NULL;
ls->size = 0;
ls->entries = 0;
}
/*
* Deallocate resources associated with this index
*
* The index does not allocate records itself, so it is not
* responsible for deallocating them.
*/
void index_clear(struct index *ls)
{
free(ls->record); /* may be NULL */
}
/*
* Blank the index so it contains no entries
*
* We don't de-allocate memory, but this gives us an advantage where
* index re-use is of similar size.
*/
void index_blank(struct index *ls)
{
ls->entries = 0;
}
/*
* Enlarge the storage space of the index to at least the target
* size
*
* Return: 0 on success or -1 on memory allocation failure
* Post: size of index is greater than or equal to target
*/
static int enlarge(struct index *ls, size_t target)
{
size_t p;
struct record **ln;
if (target <= ls->size)
return 0;
p = target + BLOCK - 1; /* pre-allocate additional entries */
ln = realloc(ls->record, sizeof(struct record*) * p);
if (ln == NULL) {
perror("realloc");
return -1;
}
ls->record = ln;
ls->size = p;
return 0;
}
/*
* Return: false if the caller did not call index_reserve(), otherwise
* true
*/
static bool has_space(const struct index *i)
{
return i->entries < i->size;
}
/*
* Add a record to the index
*
* Pre: at least one entry is reserved
* Post: lr is the record at the end of the index
*/
void index_add(struct index *ls, struct record *lr)
{
assert(lr != NULL);
assert(has_space(ls));
ls->record[ls->entries++] = lr;
}
/*
* Standard comparison function between two records
*/
static int record_cmp_artist(const struct record *a, const struct record *b)
{
int r;
r = strcasecmp(a->artist, b->artist);
if (r < 0)
return -1;
else if (r > 0)
return 1;
r = strcasecmp(a->title, b->title);
if (r < 0)
return -1;
else if (r > 0)
return 1;
return strcmp(a->pathname, b->pathname);
}
/*
* Compare two records principally by BPM, fastest to slowest
* followed by unknown
*/
static int record_cmp_bpm(const struct record *a, const struct record *b)
{
if (a->bpm < b->bpm)
return 1;
if (a->bpm > b->bpm)
return -1;
return record_cmp_artist(a, b);
}
/*
* Check if a record matches the given string. This function is the
* definitive code which defines what constitutes a 'match'.
*
* Return: true if this is a match, otherwise false
*/
static bool record_match_word(struct record *re, const char *match)
{
/* Some records provide a dedicated string for matching against,
* in the same locale as "match" */
if (re->match) {
if (strcasestr(re->match, match) != NULL)
return true;
} else {
if (strcasestr(re->artist, match) != NULL)
return true;
if (strcasestr(re->title, match) != NULL)
return true;
}
return false;
}
/*
* Check for a match against the given search criteria
*
* Return: true if the given record matches, otherwise false
*/
bool record_match(struct record *re, const struct match *h)
{
char *const *matches;
matches = h->words;
while (*matches != NULL) {
if (!record_match_word(re, *matches))
return false;
matches++;
}
return true;
}
/*
* Copy the source index
*
* Return: 0 on success or -1 on memory allocation failure
* Post: on failure, dest is valid but incomplete
*/
int index_copy(const struct index *src, struct index *dest)
{
int n;
index_blank(dest);
if (index_reserve(dest, src->entries) == -1)
return -1;
for (n = 0; n < src->entries; n++)
index_add(dest, src->record[n]);
return 0;
}
/*
* Compile a search object from a given string
*
* Pre: search string is within length
*/
void match_compile(struct match *h, const char *d)
{
char *buf;
size_t n;
assert(strlen(d) < sizeof h->buf);
strcpy(h->buf, d);
buf = h->buf;
n = 0;
for (;;) {
char *s;
if (n == ARRAY_SIZE(h->words) - 1) {
fputs("Ignoring excessive words in match string.\n", stderr);
break;
}
h->words[n] = buf;
n++;
s = strchr(buf, SEPARATOR);
if (s == NULL)
break;
*s = '\0';
buf = s + 1; /* skip separator */
}
h->words[n] = NULL; /* terminate list */
}
/*
* Find entries from the source index which match
*
* Copy the subset of the source index which matches the given
* string into the destination.
*
* Return: 0 on success, or -1 on memory allocation failure
* Post: on failure, dest is valid but incomplete
*/
int index_match(struct index *src, struct index *dest,
const struct match *match)
{
int n;
struct record *re;
index_blank(dest);
for (n = 0; n < src->entries; n++) {
re = src->record[n];
if (record_match(re, match)) {
if (index_reserve(dest, 1) == -1)
return -1;
index_add(dest, re);
}
}
return 0;
}
/*
* Binary search of sorted index
*
* We implement our own binary search rather than using the bsearch()
* from stdlib.h, because we need to know the position to insert to if
* the item is not found.
*
* Pre: base is sorted
* Return: position of match >= item
* Post: on exact match, *found is true
*/
static size_t bin_search(struct record **base, size_t n,
struct record *item, int sort,
bool *found)
{
int r;
size_t mid;
struct record *x;
/* Return the first entry ordered after this one */
if (n == 0) {
*found = false;
return 0;
}
mid = n / 2;
x = base[mid];
switch (sort) {
case SORT_ARTIST:
r = record_cmp_artist(item, x);
break;
case SORT_BPM:
r = record_cmp_bpm(item, x);
break;
case SORT_PLAYLIST:
default:
abort();
}
if (r < 0)
return bin_search(base, mid, item, sort, found);
if (r > 0) {
return mid + 1
+ bin_search(base + mid + 1, n - mid - 1, item, sort, found);
}
*found = true;
return mid;
}
/*
* Insert or re-use an entry in a sorted index
*
* Pre: index is sorted
* Pre: at least one entry is reserved
* Return: pointer to item, or existing entry (ie. not NULL)
* Post: index is sorted and contains item or a matching item
*/
struct record* index_insert(struct index *ls, struct record *item,
int sort)
{
bool found;
size_t z;
z = bin_search(ls->record, ls->entries, item, sort, &found);
if (found)
return ls->record[z];
assert(has_space(ls));
memmove(ls->record + z + 1, ls->record + z,
sizeof(struct record*) * (ls->entries - z));
ls->record[z] = item;
ls->entries++;
return item;
}
/*
* Reserve space in the index for the addition of n new items
*
* This function exists separately to the insert and addition
* functions because it carries the error case.
*
* Return: -1 if not enough memory, otherwise zero
* Post: if zero is returned, index has at least n free slots
*/
int index_reserve(struct index *i, unsigned int n)
{
return enlarge(i, i->entries + n);
}
/*
* Find an identical entry, or the nearest match
*/
size_t index_find(struct index *ls, struct record *item, int sort)
{
bool found;
size_t z;
z = bin_search(ls->record, ls->entries, item, sort, &found);
return z;
}
/*
* Debug the content of a index to standard error
*/
void index_debug(struct index *ls)
{
int n;
for (n = 0; n < ls->entries; n++)
fprintf(stderr, "%d: %s\n", n, ls->record[n]->pathname);
}