/*
** 2011 March 24
**
** 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.
**
*************************************************************************
**
** Code for demonstartion virtual table that generates variations
** on an input word at increasing edit distances from the original.
*/
#include "sqlite3.h"
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#ifndef SQLITE_OMIT_VIRTUALTABLE
/*
** Forward declaration of objects used by this implementation
*/
typedef struct fuzzer_vtab fuzzer_vtab;
typedef struct fuzzer_cursor fuzzer_cursor;
typedef struct fuzzer_rule fuzzer_rule;
typedef struct fuzzer_seen fuzzer_seen;
typedef struct fuzzer_stem fuzzer_stem;
/*
** Each transformation rule is stored as an instance of this object.
** All rules are kept on a linked list sorted by rCost.
*/
struct fuzzer_rule {
fuzzer_rule *pNext; /* Next rule in order of increasing rCost */
float rCost; /* Cost of this transformation */
char *zFrom; /* Transform from */
char zTo[4]; /* Transform to (extra space appended) */
};
/*
** When generating fuzzed words, we have to remember all previously
** generated terms in order to suppress duplicates. Each previously
** generated term is an instance of the following structure.
*/
struct fuzzer_seen {
fuzzer_seen *pNext; /* Next with the same hash */
char zWord[4]; /* The generated term. */
};
/*
** A stem object is used to generate variants.
*/
struct fuzzer_stem {
char *zBasis; /* Word being fuzzed */
fuzzer_rule *pRule; /* Next rule to apply */
int n; /* Apply rule at this character offset */
float rBaseCost; /* Base cost of getting to zBasis */
float rCost; /* rBaseCost + cost of applying pRule at n */
fuzzer_stem *pNext; /* Next stem in rCost order */
};
/*
** A fuzzer virtual-table object
*/
struct fuzzer_vtab {
sqlite3_vtab base; /* Base class - must be first */
char *zClassName; /* Name of this class. Default: "fuzzer" */
fuzzer_rule *pRule; /* All active rules in this fuzzer */
fuzzer_rule *pNewRule; /* New rules to add when last cursor expires */
int nCursor; /* Number of active cursors */
};
/* A fuzzer cursor object */
struct fuzzer_cursor {
sqlite3_vtab_cursor base; /* Base class - must be first */
float rMax; /* Maximum cost of any term */
fuzzer_stem *pStem; /* Sorted list of stems for generating new terms */
int nSeen; /* Number of terms already generated */
int nHash; /* Number of slots in apHash */
fuzzer_seen **apHash; /* Hash table of previously generated terms */
};
/* Methods for the fuzzer module */
static int fuzzerConnect(
sqlite3 *db,
void *pAux,
int argc, const char *const*argv,
sqlite3_vtab **ppVtab,
char **pzErr
){
fuzzer_vtab *pNew;
char *zSql;
int n;
if( strcmp(argv[1],"temp")!=0 ){
*pzErr = sqlite3_mprintf("%s virtual tables must be TEMP", argv[0]);
return SQLITE_ERROR;
}
n = strlen(argv[0]) + 1;
pNew = sqlite3_malloc( sizeof(*pNew) + n );
if( pNew==0 ) return SQLITE_NOMEM;
pNew->zClassName = (char*)&pNew[1];
memcpy(pNew->zClassName, argv[0], n);
zSql = sqlite3_mprintf(
"CREATE TABLE x(word, distance, cFrom, cTo, cost, \"%w\" HIDDEN)",
argv[2]
);
sqlite3_declare_vtab(db, zSql);
sqlite3_free(zSql);
memset(pNew, 0, sizeof(*pNew));
*ppVtab = &pNew->base;
return SQLITE_OK;
}
/* Note that for this virtual table, the xCreate and xConnect
** methods are identical. */
static int fuzzerDisconnect(sqlite3_vtab *pVtab){
fuzzer_vtab *p = (fuzzer_vtab*)pVtab;
assert( p->nCursor==0 );
do{
while( p->pRule ){
fuzzer_rule *pRule = p->pRule;
p->pRule = pRule->pNext;
sqlite3_free(pRule);
}
p->pRule = p->pNewRule;
p->pNewRule = 0;
}while( p->pRule );
sqlite3_free(p);
return SQLITE_OK;
}
/* The xDisconnect and xDestroy methods are also the same */
/*
** The two input rule lists are both sorted in order of increasing
** cost. Merge them together into a single list, sorted by cost, and
** return a pointer to the head of that list.
*/
static fuzzer_rule *fuzzerMergeRules(fuzzer_rule *pA, fuzzer_rule *pB){
fuzzer_rule head;
fuzzer_rule *pTail;
pTail = &head;
while( pA && pB ){
if( pA->rCost<=pB->rCost ){
pTail->pNext = pA;
pTail = pA;
pA = pA->pNext;
}else{
pTail->pNext = pB;
pTail = pB;
pB = pB->pNext;
}
}
if( pA==0 ){
pTail->pNext = pB;
}else{
pTail->pNext = pA;
}
return head.pNext;
}
/*
** Open a new fuzzer cursor.
*/
static int fuzzerOpen(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor){
fuzzer_vtab *p = (fuzzer_vtab*)pVTab;
fuzzer_cursor *pCur;
pCur = sqlite3_malloc( sizeof(*pCur) );
if( pCur==0 ) return SQLITE_NOMEM;
memset(pCur, 0, sizeof(*pCur));
*ppCursor = &pCur->base;
if( p->nCursor==0 && p->pNewRule ){
unsigned int i;
fuzzer_rule *pX;
fuzzer_rule *a[15];
for(i=0; i<sizeof(a)/sizeof(a[0]); i++) a[i] = 0;
while( (pX = p->pNewRule)!=0 ){
p->pNewRule = pX->pNext;
pX->pNext = 0;
for(i=0; a[i] && i<sizeof(a)/sizeof(a[0])-1; i++){
pX = fuzzerMergeRules(a[i], pX);
a[i] = 0;
}
a[i] = fuzzerMergeRules(a[i], pX);
}
for(pX=a[0], i=1; i<sizeof(a)/sizeof(a[0]); i++){
pX = fuzzerMergeRules(a[i], pX);
}
p->pRule = fuzzerMergeRules(p->pRule, pX);
}
return SQLITE_OK;
}
/*
** Close a fuzzer cursor.
*/
static int fuzzerClose(sqlite3_vtab_cursor *cur){
fuzzer_cursor *pCur = (fuzzer_cursor *)cur;
int i;
for(i=0; i<pCur->nHash; i++){
fuzzer_seen *pSeen = pCur->apHash[i];
while( pSeen ){
fuzzer_seen *pNext = pSeen->pNext;
sqlite3_free(pSeen);
pSeen = pNext;
}
}
sqlite3_free(pCur->apHash);
while( pCur->pStem ){
fuzzer_stem *pStem = pCur->pStem;
pCur->pStem = pStem->pNext;
sqlite3_free(pStem);
}
sqlite3_free(pCur);
return SQLITE_OK;
}
static int fuzzerNext(sqlite3_vtab_cursor *cur){
return 0;
}
static int fuzzerFilter(
sqlite3_vtab_cursor *pVtabCursor,
int idxNum, const char *idxStr,
int argc, sqlite3_value **argv
){
fuzzer_cursor *pCur = (fuzzer_cursor *)pVtabCursor;
return fuzzerNext(pVtabCursor);
}
static int fuzzerColumn(sqlite3_vtab_cursor *cur, sqlite3_context *ctx, int i){
fuzzer_cursor *pCur = (fuzzer_cursor*)cur;
return SQLITE_OK;
}
static int fuzzerRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
*pRowid = 0;
return SQLITE_OK;
}
static int fuzzerEof(sqlite3_vtab_cursor *cur){
fuzzer_cursor *pCur = (fuzzer_cursor*)cur;
return 1;
}
static int fuzzerBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo){
return SQLITE_OK;
}
/*
** Disallow all attempts to DELETE or UPDATE. Only INSERTs are allowed.
**
** On an insert, the cFrom, cTo, and cost columns are used to construct
** a new rule. All other columns are ignored. The rule is ignored
** if cFrom and cTo are identical. A NULL value for cFrom or cTo is
** interpreted as an empty string. The cost must be positive.
*/
static int fuzzerUpdate(
sqlite3_vtab *pVTab,
int argc,
sqlite3_value **argv,
sqlite_int64 *pRowid
){
fuzzer_vtab *p = (fuzzer_vtab*)pVTab;
fuzzer_rule *pRule;
const char *zFrom;
int nFrom;
const char *zTo;
int nTo;
float rCost;
if( argc!=8 ){
sqlite3_free(pVTab->zErrMsg);
pVTab->zErrMsg = sqlite3_mprintf("cannot delete from a %s virtual table",
p->zClassName);
return SQLITE_CONSTRAINT;
}
if( sqlite3_value_type(argv[0])!=SQLITE_NULL ){
sqlite3_free(pVTab->zErrMsg);
pVTab->zErrMsg = sqlite3_mprintf("cannot update a %s virtual table",
p->zClassName);
return SQLITE_CONSTRAINT;
}
zFrom = (char*)sqlite3_value_text(argv[4]);
if( zFrom==0 ) zFrom = "";
zTo = (char*)sqlite3_value_text(argv[5]);
if( zTo==0 ) zTo = "";
if( strcmp(zFrom,zTo)==0 ){
/* Silently ignore null transformations */
return SQLITE_OK;
}
rCost = (float)sqlite3_value_double(argv[6]);
if( rCost<=0 ){
sqlite3_free(pVTab->zErrMsg);
pVTab->zErrMsg = sqlite3_mprintf("cost must be positive");
return SQLITE_CONSTRAINT;
}
nFrom = strlen(zFrom)+1;
nTo = strlen(zTo)+1;
if( nTo<4 ) nTo = 4;
pRule = sqlite3_malloc( sizeof(*pRule) + nFrom + nTo - 4 );
if( pRule==0 ){
return SQLITE_NOMEM;
}
pRule->zFrom = &pRule->zTo[nTo];
memcpy(pRule->zFrom, zFrom, nFrom);
memcpy(pRule->zTo, zTo, nTo);
pRule->rCost = rCost;
pRule->pNext = p->pNewRule;
p->pNewRule = pRule;
return SQLITE_OK;
}
/*
** A virtual table module that provides read-only access to a
** Tcl global variable namespace.
*/
static sqlite3_module fuzzerModule = {
0, /* iVersion */
fuzzerConnect,
fuzzerConnect,
fuzzerBestIndex,
fuzzerDisconnect,
fuzzerDisconnect,
fuzzerOpen, /* xOpen - open a cursor */
fuzzerClose, /* xClose - close a cursor */
fuzzerFilter, /* xFilter - configure scan constraints */
fuzzerNext, /* xNext - advance a cursor */
fuzzerEof, /* xEof - check for end of scan */
fuzzerColumn, /* xColumn - read data */
fuzzerRowid, /* xRowid - read data */
fuzzerUpdate, /* xUpdate - INSERT */
0, /* xBegin */
0, /* xSync */
0, /* xCommit */
0, /* xRollback */
0, /* xFindMethod */
0, /* xRename */
};
#endif /* SQLITE_OMIT_VIRTUALTABLE */
/*
** Register the fuzzer virtual table
*/
int fuzzer_register(sqlite3 *db){
int rc = SQLITE_OK;
#ifndef SQLITE_OMIT_VIRTUALTABLE
rc = sqlite3_create_module(db, "fuzzer", &fuzzerModule, 0);
#endif
return rc;
}
#ifdef SQLITE_TEST
#include <tcl.h>
/*
** Decode a pointer to an sqlite3 object.
*/
extern int getDbPointer(Tcl_Interp *interp, const char *zA, sqlite3 **ppDb);
/*
** Register the echo virtual table module.
*/
static int register_fuzzer_module(
ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
Tcl_Interp *interp, /* The TCL interpreter that invoked this command */
int objc, /* Number of arguments */
Tcl_Obj *CONST objv[] /* Command arguments */
){
sqlite3 *db;
if( objc!=2 ){
Tcl_WrongNumArgs(interp, 1, objv, "DB");
return TCL_ERROR;
}
if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
fuzzer_register(db);
return TCL_OK;
}
/*
** Register commands with the TCL interpreter.
*/
int Sqlitetestfuzzer_Init(Tcl_Interp *interp){
static struct {
char *zName;
Tcl_ObjCmdProc *xProc;
void *clientData;
} aObjCmd[] = {
{ "register_fuzzer_module", register_fuzzer_module, 0 },
};
int i;
for(i=0; i<sizeof(aObjCmd)/sizeof(aObjCmd[0]); i++){
Tcl_CreateObjCommand(interp, aObjCmd[i].zName,
aObjCmd[i].xProc, aObjCmd[i].clientData, 0);
}
return TCL_OK;
}
#endif /* SQLITE_TEST */