Add the eval() SQL function extension in ext/misc/eval.c.

FossilOrigin-Name: 27cf665b957f2c0ced403e3032099e80c295598f

ext/misc/eval.c

@@ -0,0 +1,119 @@
+/*
+** 2014-11-10
+**
+** 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 SQLite extension implements SQL function eval() which runs
+** SQL statements recursively.
+*/
+#include "sqlite3ext.h"
+SQLITE_EXTENSION_INIT1
+#include <string.h>
+
+/*
+** Structure used to accumulate the output
+*/
+struct EvalResult {
+  char *z;            /* Accumulated output */
+  const char *zSep;   /* Separator */
+  int szSep;          /* Size of the separator string */
+  int nAlloc;         /* Number of bytes allocated for z[] */
+  int nUsed;          /* Number of bytes of z[] actually used */
+};
+
+/*
+** Callback from sqlite_exec() for the eval() function.
+*/
+static int callback(void *pCtx, int argc, char **argv, char **colnames){
+  struct EvalResult *p = (struct EvalResult*)pCtx;
+  int i; 
+  for(i=0; i<argc; i++){
+    const char *z = argv[i] ? argv[i] : "";
+    size_t sz = strlen(z);
+    if( sz+p->nUsed+p->szSep+1 > p->nAlloc ){
+      char *zNew;
+      p->nAlloc = p->nAlloc*2 + sz + p->szSep + 1;
+      zNew = sqlite3_realloc(p->z, p->nAlloc);
+      if( zNew==0 ){
+        sqlite3_free(p->z);
+        memset(p, 0, sizeof(*p));
+        return 1;
+      }
+      p->z = zNew;
+    }
+    if( p->nUsed>0 ){
+      memcpy(&p->z[p->nUsed], p->zSep, p->szSep);
+      p->nUsed += p->szSep;
+    }
+    memcpy(&p->z[p->nUsed], z, sz);
+    p->nUsed += sz;
+  }
+  return 0;
+}
+
+/*
+** Implementation of the eval(X) and eval(X,Y) SQL functions.
+**
+** Evaluate the SQL text in X.  Return the results, using string
+** Y as the separator.  If Y is omitted, use a single space character.
+*/
+static void sqlEvalFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  const char *zSql;
+  sqlite3 *db;
+  char *zErr = 0;
+  int rc;
+  struct EvalResult x;
+
+  memset(&x, 0, sizeof(x));
+  x.zSep = " ";
+  zSql = (const char*)sqlite3_value_text(argv[0]);
+  if( zSql==0 ) return;
+  if( argc>1 ){
+    x.zSep = (const char*)sqlite3_value_text(argv[1]);
+    if( x.zSep==0 ) return;
+  }
+  x.szSep = (int)strlen(x.zSep);
+  db = sqlite3_context_db_handle(context);
+  rc = sqlite3_exec(db, zSql, callback, &x, &zErr);
+  if( rc!=SQLITE_OK ){
+    sqlite3_result_error(context, zErr, -1);
+    sqlite3_free(zErr);
+  }else if( x.zSep==0 ){
+    sqlite3_result_error_nomem(context);
+    sqlite3_free(x.z);
+  }else{
+    sqlite3_result_text(context, x.z, x.nUsed, sqlite3_free);
+  }
+}
+
+
+#ifdef _WIN32
+__declspec(dllexport)
+#endif
+int sqlite3_eval_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, "eval", 1, SQLITE_UTF8, 0,
+                               sqlEvalFunc, 0, 0);
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_create_function(db, "eval", 2, SQLITE_UTF8, 0,
+                                 sqlEvalFunc, 0, 0);
+  }
+  return rc;
+}