/*
** 2016-06-29
**
** 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.
**
*************************************************************************
**
** This file demonstrates how to create a table-valued-function that
** returns the values in a C-language array.
** Examples:
**
** SELECT * FROM carray($ptr,5)
**
** The query above returns 5 integers contained in a C-language array
** at the address $ptr. $ptr is a pointer to the array of integers that
** has been cast to an integer.
**
** There is an optional third parameter to determine the datatype of
** the C-language array. Allowed values of the third parameter are
** 'int32', 'int64', 'double', 'char*'. Example:
**
** SELECT * FROM carray($ptr,10,'char*');
**
** HOW IT WORKS
**
** The carray "function" is really a virtual table with the
** following schema:
**
** CREATE TABLE carray(
** value,
** pointer HIDDEN,
** count HIDDEN,
** ctype TEXT HIDDEN
** );
**
** If the hidden columns "pointer" and "count" are unconstrained, then
** the virtual table has no rows. Otherwise, the virtual table interprets
** the integer value of "pointer" as a pointer to the array and "count"
** as the number of elements in the array. The virtual table steps through
** the array, element by element.
*/
#include "sqlite3ext.h"
SQLITE_EXTENSION_INIT1
#include <assert.h>
#include <string.h>
#ifndef SQLITE_OMIT_VIRTUALTABLE
/*
** Allowed datatypes
*/
#define CARRAY_INT32 0
#define CARRAY_INT64 1
#define CARRAY_DOUBLE 2
#define CARRAY_TEXT 3
/*
** Names of types
*/
static const char *azType[] = { "int32", "int64", "double", "char*" };
/* carray_cursor is a subclass of sqlite3_vtab_cursor which will
** serve as the underlying representation of a cursor that scans
** over rows of the result
*/
typedef struct carray_cursor carray_cursor;
struct carray_cursor {
sqlite3_vtab_cursor base; /* Base class - must be first */
sqlite3_int64 iRowid; /* The rowid */
sqlite3_int64 iPtr; /* Pointer to array of values */
sqlite3_int64 iCnt; /* Number of integers in the array */
unsigned char eType; /* One of the CARRAY_type values */
};
/*
** The carrayConnect() method is invoked to create a new
** carray_vtab that describes the carray virtual table.
**
** Think of this routine as the constructor for carray_vtab objects.
**
** All this routine needs to do is:
**
** (1) Allocate the carray_vtab object and initialize all fields.
**
** (2) Tell SQLite (via the sqlite3_declare_vtab() interface) what the
** result set of queries against carray will look like.
*/
static int carrayConnect(
sqlite3 *db,
void *pAux,
int argc, const char *const*argv,
sqlite3_vtab **ppVtab,
char **pzErr
){
sqlite3_vtab *pNew;
int rc;
/* Column numbers */
#define CARRAY_COLUMN_VALUE 0
#define CARRAY_COLUMN_POINTER 1
#define CARRAY_COLUMN_COUNT 2
#define CARRAY_COLUMN_CTYPE 3
rc = sqlite3_declare_vtab(db,
"CREATE TABLE x(value,pointer hidden,count hidden,ctype hidden)");
if( rc==SQLITE_OK ){
pNew = *ppVtab = sqlite3_malloc( sizeof(*pNew) );
if( pNew==0 ) return SQLITE_NOMEM;
memset(pNew, 0, sizeof(*pNew));
}
return rc;
}
/*
** This method is the destructor for carray_cursor objects.
*/
static int carrayDisconnect(sqlite3_vtab *pVtab){
sqlite3_free(pVtab);
return SQLITE_OK;
}
/*
** Constructor for a new carray_cursor object.
*/
static int carrayOpen(sqlite3_vtab *p, sqlite3_vtab_cursor **ppCursor){
carray_cursor *pCur;
pCur = sqlite3_malloc( sizeof(*pCur) );
if( pCur==0 ) return SQLITE_NOMEM;
memset(pCur, 0, sizeof(*pCur));
*ppCursor = &pCur->base;
return SQLITE_OK;
}
/*
** Destructor for a carray_cursor.
*/
static int carrayClose(sqlite3_vtab_cursor *cur){
sqlite3_free(cur);
return SQLITE_OK;
}
/*
** Advance a carray_cursor to its next row of output.
*/
static int carrayNext(sqlite3_vtab_cursor *cur){
carray_cursor *pCur = (carray_cursor*)cur;
pCur->iRowid++;
return SQLITE_OK;
}
/*
** Return values of columns for the row at which the carray_cursor
** is currently pointing.
*/
static int carrayColumn(
sqlite3_vtab_cursor *cur, /* The cursor */
sqlite3_context *ctx, /* First argument to sqlite3_result_...() */
int i /* Which column to return */
){
carray_cursor *pCur = (carray_cursor*)cur;
sqlite3_int64 x = 0;
switch( i ){
case CARRAY_COLUMN_POINTER: x = pCur->iPtr; break;
case CARRAY_COLUMN_COUNT: x = pCur->iCnt; break;
case CARRAY_COLUMN_CTYPE: {
sqlite3_result_text(ctx, azType[pCur->eType], -1, SQLITE_STATIC);
return SQLITE_OK;
}
default: {
switch( pCur->eType ){
case CARRAY_INT32: {
int *p = (int*)pCur->iPtr;
sqlite3_result_int(ctx, p[pCur->iRowid-1]);
return SQLITE_OK;
}
case CARRAY_INT64: {
sqlite3_int64 *p = (sqlite3_int64*)pCur->iPtr;
sqlite3_result_int64(ctx, p[pCur->iRowid-1]);
return SQLITE_OK;
}
case CARRAY_DOUBLE: {
double *p = (double*)pCur->iPtr;
sqlite3_result_double(ctx, p[pCur->iRowid-1]);
return SQLITE_OK;
}
case CARRAY_TEXT: {
const char **p = (const char**)pCur->iPtr;
sqlite3_result_text(ctx, p[pCur->iRowid-1], -1, SQLITE_TRANSIENT);
return SQLITE_OK;
}
}
}
}
sqlite3_result_int64(ctx, x);
return SQLITE_OK;
}
/*
** Return the rowid for the current row. In this implementation, the
** rowid is the same as the output value.
*/
static int carrayRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
carray_cursor *pCur = (carray_cursor*)cur;
*pRowid = pCur->iRowid;
return SQLITE_OK;
}
/*
** Return TRUE if the cursor has been moved off of the last
** row of output.
*/
static int carrayEof(sqlite3_vtab_cursor *cur){
carray_cursor *pCur = (carray_cursor*)cur;
return pCur->iRowid>pCur->iCnt;
}
/*
** This method is called to "rewind" the carray_cursor object back
** to the first row of output.
*/
static int carrayFilter(
sqlite3_vtab_cursor *pVtabCursor,
int idxNum, const char *idxStr,
int argc, sqlite3_value **argv
){
carray_cursor *pCur = (carray_cursor *)pVtabCursor;
if( idxNum ){
pCur->iPtr = sqlite3_value_int64(argv[0]);
pCur->iCnt = sqlite3_value_int64(argv[1]);
if( idxNum<3 ){
pCur->eType = CARRAY_INT32;
}else{
unsigned char i;
const char *zType = (const char*)sqlite3_value_text(argv[2]);
for(i=0; i<sizeof(azType)/sizeof(azType[0]); i++){
if( sqlite3_stricmp(zType, azType[i])==0 ) break;
}
if( i>=sizeof(azType)/sizeof(azType[0]) ){
pVtabCursor->pVtab->zErrMsg = sqlite3_mprintf(
"unknown datatype: %Q", zType);
return SQLITE_ERROR;
}else{
pCur->eType = i;
}
}
}else{
pCur->iPtr = 0;
pCur->iCnt = 0;
}
pCur->iRowid = 1;
return SQLITE_OK;
}
/*
** SQLite will invoke this method one or more times while planning a query
** that uses the carray virtual table. This routine needs to create
** a query plan for each invocation and compute an estimated cost for that
** plan.
**
** In this implementation idxNum is used to represent the
** query plan. idxStr is unused.
**
** idxNum is 2 if the pointer= and count= constraints exist,
** 3 if the ctype= constraint also exists, and is 0 otherwise.
** If idxNum is 0, then carray becomes an empty table.
*/
static int carrayBestIndex(
sqlite3_vtab *tab,
sqlite3_index_info *pIdxInfo
){
int i; /* Loop over constraints */
int ptrIdx = -1; /* Index of the pointer= constraint, or -1 if none */
int cntIdx = -1; /* Index of the count= constraint, or -1 if none */
int ctypeIdx = -1; /* Index of the ctype= constraint, or -1 if none */
const struct sqlite3_index_constraint *pConstraint;
pConstraint = pIdxInfo->aConstraint;
for(i=0; i<pIdxInfo->nConstraint; i++, pConstraint++){
if( pConstraint->usable==0 ) continue;
if( pConstraint->op!=SQLITE_INDEX_CONSTRAINT_EQ ) continue;
switch( pConstraint->iColumn ){
case CARRAY_COLUMN_POINTER:
ptrIdx = i;
break;
case CARRAY_COLUMN_COUNT:
cntIdx = i;
break;
case CARRAY_COLUMN_CTYPE:
ctypeIdx = i;
break;
}
}
if( ptrIdx>=0 && cntIdx>=0 ){
pIdxInfo->aConstraintUsage[ptrIdx].argvIndex = 1;
pIdxInfo->aConstraintUsage[ptrIdx].omit = 1;
pIdxInfo->aConstraintUsage[cntIdx].argvIndex = 2;
pIdxInfo->aConstraintUsage[cntIdx].omit = 1;
pIdxInfo->estimatedCost = (double)1;
pIdxInfo->estimatedRows = 100;
pIdxInfo->idxNum = 2;
if( ctypeIdx>=0 ){
pIdxInfo->aConstraintUsage[ctypeIdx].argvIndex = 3;
pIdxInfo->aConstraintUsage[ctypeIdx].omit = 1;
pIdxInfo->idxNum = 3;
}
}else{
pIdxInfo->estimatedCost = (double)2147483647;
pIdxInfo->estimatedRows = 2147483647;
pIdxInfo->idxNum = 0;
}
return SQLITE_OK;
}
/*
** This following structure defines all the methods for the
** carray virtual table.
*/
static sqlite3_module carrayModule = {
0, /* iVersion */
0, /* xCreate */
carrayConnect, /* xConnect */
carrayBestIndex, /* xBestIndex */
carrayDisconnect, /* xDisconnect */
0, /* xDestroy */
carrayOpen, /* xOpen - open a cursor */
carrayClose, /* xClose - close a cursor */
carrayFilter, /* xFilter - configure scan constraints */
carrayNext, /* xNext - advance a cursor */
carrayEof, /* xEof - check for end of scan */
carrayColumn, /* xColumn - read data */
carrayRowid, /* xRowid - read data */
0, /* xUpdate */
0, /* xBegin */
0, /* xSync */
0, /* xCommit */
0, /* xRollback */
0, /* xFindMethod */
0, /* xRename */
};
#endif /* SQLITE_OMIT_VIRTUALTABLE */
#ifdef _WIN32
__declspec(dllexport)
#endif
int sqlite3_carray_init(
sqlite3 *db,
char **pzErrMsg,
const sqlite3_api_routines *pApi
){
int rc = SQLITE_OK;
SQLITE_EXTENSION_INIT2(pApi);
#ifndef SQLITE_OMIT_VIRTUALTABLE
rc = sqlite3_create_module(db, "carray", &carrayModule, 0);
#endif
return rc;
}