/*
** 2018-02-09
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
******************************************************************************
**
** SQL functions for z-order (Morton code) transformations.
**
** zorder(X0,X0,..,xN) Generate an N+1 dimension Morton code
**
** unzorder(Z,N,I) Extract the I-th dimension from N-dimensional
** Morton code Z.
*/
#include "sqlite3ext.h"
SQLITE_EXTENSION_INIT1
#include <assert.h>
#include <string.h>
/*
** Functions: zorder(X0,X1,....)
**
** Convert integers X0, X1, ... into morton code.
**
** The output is a signed 64-bit integer. If any argument is too large,
** an error is thrown.
*/
static void zorderFunc(
sqlite3_context *context,
int argc,
sqlite3_value **argv
){
sqlite3_int64 z, x[63];
int i, j;
z = 0;
for(i=0; i<argc; i++){
x[i] = sqlite3_value_int64(argv[i]);
}
if( argc>0 ){
for(i=0; i<63; i++){
j = i%argc;
z |= (x[j]&1)<<i;
x[j] >>= 1;
}
}
sqlite3_result_int64(context, z);
for(i=0; i<argc; i++){
if( x[i] ){
sqlite3_result_error(context, "parameter too large", -1);
}
}
}
/*
** Functions: unzorder(Z,N,I)
**
** Assuming that Z is an N-dimensional Morton code, extract the I-th
** dimension.
*/
static void unzorderFunc(
sqlite3_context *context,
int argc,
sqlite3_value **argv
){
sqlite3_int64 z, n, i, x;
int j, k;
z = sqlite3_value_int64(argv[0]);
n = sqlite3_value_int64(argv[1]);
i = sqlite3_value_int64(argv[2]);
x = 0;
for(k=0, j=i; j<63; j+=n, k++){
x |= ((z>>j)&1)<<k;
}
sqlite3_result_int64(context, x);
}
#ifdef _WIN32
__declspec(dllexport)
#endif
int sqlite3_zorder_init(
sqlite3 *db,
char **pzErrMsg,
const sqlite3_api_routines *pApi
){
int rc = SQLITE_OK;
SQLITE_EXTENSION_INIT2(pApi);
(void)pzErrMsg; /* Unused parameter */
rc = sqlite3_create_function(db, "zorder", -1, SQLITE_UTF8, 0,
zorderFunc, 0, 0);
if( rc==SQLITE_OK ){
rc = sqlite3_create_function(db, "unzorder", 3, SQLITE_UTF8, 0,
unzorderFunc, 0, 0);
}
return rc;
}