ext/misc/eval.c

   1 /*
   2 ** 2014-11-10
   3 **
   4 ** The author disclaims copyright to this source code.  In place of
   5 ** a legal notice, here is a blessing:
   6 **
   7 **    May you do good and not evil.
   8 **    May you find forgiveness for yourself and forgive others.
   9 **    May you share freely, never taking more than you give.
  10 **
  11 ******************************************************************************
  12 **
  13 ** This SQLite extension implements SQL function eval() which runs
  14 ** SQL statements recursively.
  15 */
  16 #include "sqlite3ext.h"
  17 SQLITE_EXTENSION_INIT1
  18 #include <string.h>
  19
  20 /*
  21 ** Structure used to accumulate the output
  22 */
  23 struct EvalResult {
  24   char *z;               /* Accumulated output */
  25   const char *zSep;      /* Separator */
  26   int szSep;             /* Size of the separator string */
  27   sqlite3_int64 nAlloc;  /* Number of bytes allocated for z[] */
  28   sqlite3_int64 nUsed;   /* Number of bytes of z[] actually used */
  29 };
  30
  31 /*
  32 ** Callback from sqlite_exec() for the eval() function.
  33 */
  34 static int callback(void *pCtx, int argc, char **argv, char **colnames){
  35   struct EvalResult *p = (struct EvalResult*)pCtx;
  36   int i;
  37   if( argv==0 ) return 0;
  38   for(i=0; i<argc; i++){
  39     const char *z = argv[i] ? argv[i] : "";
  40     size_t sz = strlen(z);
  41     if( (sqlite3_int64)sz+p->nUsed+p->szSep+1 > p->nAlloc ){
  42       char *zNew;
  43       p->nAlloc = p->nAlloc*2 + sz + p->szSep + 1;
  44       /* Using sqlite3_realloc64() would be better, but it is a recent
  45       ** addition and will cause a segfault if loaded by an older version
  46       ** of SQLite.  */
  47       zNew = p->nAlloc<=0x7fffffff ? sqlite3_realloc(p->z, (int)p->nAlloc) : 0;
  48       if( zNew==0 ){
  49         sqlite3_free(p->z);
  50         memset(p, 0, sizeof(*p));
  51         return 1;
  52       }
  53       p->z = zNew;
  54     }
  55     if( p->nUsed>0 ){
  56       memcpy(&p->z[p->nUsed], p->zSep, p->szSep);
  57       p->nUsed += p->szSep;
  58     }
  59     memcpy(&p->z[p->nUsed], z, sz);
  60     p->nUsed += sz;
  61   }
  62   return 0;
  63 }
  64
  65 /*
  66 ** Implementation of the eval(X) and eval(X,Y) SQL functions.
  67 **
  68 ** Evaluate the SQL text in X.  Return the results, using string
  69 ** Y as the separator.  If Y is omitted, use a single space character.
  70 */
  71 static void sqlEvalFunc(
  72   sqlite3_context *context,
  73   int argc,
  74   sqlite3_value **argv
  75 ){
  76   const char *zSql;
  77   sqlite3 *db;
  78   char *zErr = 0;
  79   int rc;
  80   struct EvalResult x;
  81
  82   memset(&x, 0, sizeof(x));
  83   x.zSep = " ";
  84   zSql = (const char*)sqlite3_value_text(argv[0]);
  85   if( zSql==0 ) return;
  86   if( argc>1 ){
  87     x.zSep = (const char*)sqlite3_value_text(argv[1]);
  88     if( x.zSep==0 ) return;
  89   }
  90   x.szSep = (int)strlen(x.zSep);
  91   db = sqlite3_context_db_handle(context);
  92   rc = sqlite3_exec(db, zSql, callback, &x, &zErr);
  93   if( rc!=SQLITE_OK ){
  94     sqlite3_result_error(context, zErr, -1);
  95     sqlite3_free(zErr);
  96   }else if( x.zSep==0 ){
  97     sqlite3_result_error_nomem(context);
  98     sqlite3_free(x.z);
  99   }else{
 100     sqlite3_result_text(context, x.z, (int)x.nUsed, sqlite3_free);
 101   }
 102 }
 103
 104
 105 #ifdef _WIN32
 106 __declspec(dllexport)
 107 #endif
 108 int sqlite3_eval_init(
 109   sqlite3 *db,
 110   char **pzErrMsg,
 111   const sqlite3_api_routines *pApi
 112 ){
 113   int rc = SQLITE_OK;
 114   SQLITE_EXTENSION_INIT2(pApi);
 115   (void)pzErrMsg;  /* Unused parameter */
 116   rc = sqlite3_create_function(db, "eval", 1, SQLITE_UTF8, 0,
 117                                sqlEvalFunc, 0, 0);
 118   if( rc==SQLITE_OK ){
 119     rc = sqlite3_create_function(db, "eval", 2, SQLITE_UTF8, 0,
 120                                  sqlEvalFunc, 0, 0);
 121   }
 122   return rc;
 123 }