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/*-
* Public Domain 2014-2016 MongoDB, Inc.
* Public Domain 2008-2014 WiredTiger, Inc.
*
* This is free and unencumbered software released into the public domain.
*
* Anyone is free to copy, modify, publish, use, compile, sell, or
* distribute this software, either in source code form or as a compiled
* binary, for any purpose, commercial or non-commercial, and by any
* means.
*
* In jurisdictions that recognize copyright laws, the author or authors
* of this software dedicate any and all copyright interest in the
* software to the public domain. We make this dedication for the benefit
* of the public at large and to the detriment of our heirs and
* successors. We intend this dedication to be an overt act of
* relinquishment in perpetuity of all present and future rights to this
* software under copyright law.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
* IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
* OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*/
#include <stdlib.h>
#include <errno.h>
#include <stdint.h>
#include <wiredtiger_ext.h>
/*
* A simple WiredTiger collator for indices having a single integer key,
* where the ordering is descending (reversed). This collator also
* requires that primary key be an integer.
*/
/* Local collator structure. */
typedef struct {
WT_COLLATOR collator; /* Must come first */
WT_EXTENSION_API *wt_api; /* Extension API */
} REVINT_COLLATOR;
/*
* revint_compare --
* WiredTiger reverse integer collation, used for tests.
*/
static int
revint_compare(WT_COLLATOR *collator,
WT_SESSION *session, const WT_ITEM *k1, const WT_ITEM *k2, int *cmp)
{
const REVINT_COLLATOR *revint_collator;
WT_EXTENSION_API *wtapi;
WT_PACK_STREAM *pstream;
int ret;
int64_t i1, i2, p1, p2;
i1 = i2 = p1 = p2 = 0;
revint_collator = (const REVINT_COLLATOR *)collator;
wtapi = revint_collator->wt_api;
/*
* All indices using this collator have an integer key, and the
* primary key is also an integer. A collator is usually passed the
* concatenation of index key and primary key (when available),
* hence we initially unpack using "ii".
*
* A collator may also be called with an item that includes a index
* key and no primary key. Among items having the same index key,
* an item with no primary key should sort before an item with a
* primary key. The reason is that if the application calls
* WT_CURSOR::search on a index key for which there are more than
* one value, the search key will not yet have a primary key. We
* want to position the cursor at the 'first' matching index key so
* that repeated calls to WT_CURSOR::next will see them all.
*
* To keep this code simple, we do not reverse the ordering
* when comparing primary keys.
*/
if ((ret = wtapi->unpack_start(
wtapi, session, "ii", k1->data, k1->size, &pstream)) != 0 ||
(ret = wtapi->unpack_int(wtapi, pstream, &i1)) != 0)
goto err;
if ((ret = wtapi->unpack_int(wtapi, pstream, &p1)) != 0)
/* A missing primary key is OK and sorts first. */
p1 = INT64_MIN;
if ((ret = wtapi->pack_close(wtapi, pstream, NULL)) != 0)
goto err;
/* Unpack the second pair of numbers. */
if ((ret = wtapi->unpack_start(
wtapi, session, "ii", k2->data, k2->size, &pstream)) != 0 ||
(ret = wtapi->unpack_int(wtapi, pstream, &i2)) != 0)
goto err;
if ((ret = wtapi->unpack_int(wtapi, pstream, &p2)) != 0)
/* A missing primary key is OK and sorts first. */
p2 = INT64_MIN;
if ((ret = wtapi->pack_close(wtapi, pstream, NULL)) != 0)
goto err;
/* sorting is reversed */
if (i1 < i2)
*cmp = 1;
else if (i1 > i2)
*cmp = -1;
/* compare primary keys next, not reversed */
else if (p1 < p2)
*cmp = -1;
else if (p1 > p2)
*cmp = 1;
else
*cmp = 0; /* index key and primary key are same */
err: return (ret);
}
/*
* revint_terminate --
* Terminate is called to free the collator and any associated memory.
*/
static int
revint_terminate(WT_COLLATOR *collator, WT_SESSION *session)
{
(void)session; /* Unused parameters */
/* Free the allocated memory. */
free(collator);
return (0);
}
/*
* wiredtiger_extension_init --
* WiredTiger revint collation extension.
*/
int
wiredtiger_extension_init(WT_CONNECTION *connection, WT_CONFIG_ARG *config)
{
REVINT_COLLATOR *revint_collator;
(void)config; /* Unused parameters */
if ((revint_collator = calloc(1, sizeof(REVINT_COLLATOR))) == NULL)
return (errno);
revint_collator->collator.compare = revint_compare;
revint_collator->collator.terminate = revint_terminate;
revint_collator->wt_api = connection->get_extension_api(connection);
return (connection->add_collator(
connection, "revint", &revint_collator->collator, NULL));
}
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