root/third_party/sqlite/src/ext/fts3/fts3_expr.c

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DEFINITIONS

This source file includes following definitions.
  1. fts3isspace
  2. fts3MallocZero
  3. getNextToken
  4. fts3ReallocOrFree
  5. getNextString
  6. getNextNode
  7. opPrecedence
  8. insertBinaryOperator
  9. fts3ExprParse
  10. sqlite3Fts3ExprParse
  11. sqlite3Fts3ExprFree
  12. queryTestTokenizer
  13. exprToString
  14. fts3ExprTest
  15. sqlite3Fts3ExprInitTestInterface

/*
** 2008 Nov 28
**
** 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 module contains code that implements a parser for fts3 query strings
** (the right-hand argument to the MATCH operator). Because the supported 
** syntax is relatively simple, the whole tokenizer/parser system is
** hand-coded. 
*/
#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3)

/*
** By default, this module parses the legacy syntax that has been 
** traditionally used by fts3. Or, if SQLITE_ENABLE_FTS3_PARENTHESIS
** is defined, then it uses the new syntax. The differences between
** the new and the old syntaxes are:
**
**  a) The new syntax supports parenthesis. The old does not.
**
**  b) The new syntax supports the AND and NOT operators. The old does not.
**
**  c) The old syntax supports the "-" token qualifier. This is not 
**     supported by the new syntax (it is replaced by the NOT operator).
**
**  d) When using the old syntax, the OR operator has a greater precedence
**     than an implicit AND. When using the new, both implicity and explicit
**     AND operators have a higher precedence than OR.
**
** If compiled with SQLITE_TEST defined, then this module exports the
** symbol "int sqlite3_fts3_enable_parentheses". Setting this variable
** to zero causes the module to use the old syntax. If it is set to 
** non-zero the new syntax is activated. This is so both syntaxes can
** be tested using a single build of testfixture.
**
** The following describes the syntax supported by the fts3 MATCH
** operator in a similar format to that used by the lemon parser
** generator. This module does not use actually lemon, it uses a
** custom parser.
**
**   query ::= andexpr (OR andexpr)*.
**
**   andexpr ::= notexpr (AND? notexpr)*.
**
**   notexpr ::= nearexpr (NOT nearexpr|-TOKEN)*.
**   notexpr ::= LP query RP.
**
**   nearexpr ::= phrase (NEAR distance_opt nearexpr)*.
**
**   distance_opt ::= .
**   distance_opt ::= / INTEGER.
**
**   phrase ::= TOKEN.
**   phrase ::= COLUMN:TOKEN.
**   phrase ::= "TOKEN TOKEN TOKEN...".
*/

#ifdef SQLITE_TEST
int sqlite3_fts3_enable_parentheses = 0;
#else
# ifdef SQLITE_ENABLE_FTS3_PARENTHESIS 
#  define sqlite3_fts3_enable_parentheses 1
# else
#  define sqlite3_fts3_enable_parentheses 0
# endif
#endif

/*
** Default span for NEAR operators.
*/
#define SQLITE_FTS3_DEFAULT_NEAR_PARAM 10

#include "fts3Int.h"
#include <string.h>
#include <assert.h>

typedef struct ParseContext ParseContext;
struct ParseContext {
  sqlite3_tokenizer *pTokenizer;      /* Tokenizer module */
  const char **azCol;                 /* Array of column names for fts3 table */
  int nCol;                           /* Number of entries in azCol[] */
  int iDefaultCol;                    /* Default column to query */
  sqlite3_context *pCtx;              /* Write error message here */
  int nNest;                          /* Number of nested brackets */
};

/*
** This function is equivalent to the standard isspace() function. 
**
** The standard isspace() can be awkward to use safely, because although it
** is defined to accept an argument of type int, its behaviour when passed
** an integer that falls outside of the range of the unsigned char type
** is undefined (and sometimes, "undefined" means segfault). This wrapper
** is defined to accept an argument of type char, and always returns 0 for
** any values that fall outside of the range of the unsigned char type (i.e.
** negative values).
*/
static int fts3isspace(char c){
  return c==' ' || c=='\t' || c=='\n' || c=='\r' || c=='\v' || c=='\f';
}

/*
** Allocate nByte bytes of memory using sqlite3_malloc(). If successful,
** zero the memory before returning a pointer to it. If unsuccessful, 
** return NULL.
*/
static void *fts3MallocZero(int nByte){
  void *pRet = sqlite3_malloc(nByte);
  if( pRet ) memset(pRet, 0, nByte);
  return pRet;
}


/*
** Extract the next token from buffer z (length n) using the tokenizer
** and other information (column names etc.) in pParse. Create an Fts3Expr
** structure of type FTSQUERY_PHRASE containing a phrase consisting of this
** single token and set *ppExpr to point to it. If the end of the buffer is
** reached before a token is found, set *ppExpr to zero. It is the
** responsibility of the caller to eventually deallocate the allocated 
** Fts3Expr structure (if any) by passing it to sqlite3_free().
**
** Return SQLITE_OK if successful, or SQLITE_NOMEM if a memory allocation
** fails.
*/
static int getNextToken(
  ParseContext *pParse,                   /* fts3 query parse context */
  int iCol,                               /* Value for Fts3Phrase.iColumn */
  const char *z, int n,                   /* Input string */
  Fts3Expr **ppExpr,                      /* OUT: expression */
  int *pnConsumed                         /* OUT: Number of bytes consumed */
){
  sqlite3_tokenizer *pTokenizer = pParse->pTokenizer;
  sqlite3_tokenizer_module const *pModule = pTokenizer->pModule;
  int rc;
  sqlite3_tokenizer_cursor *pCursor;
  Fts3Expr *pRet = 0;
  int nConsumed = 0;

  rc = pModule->xOpen(pTokenizer, z, n, &pCursor);
  if( rc==SQLITE_OK ){
    const char *zToken;
    int nToken, iStart, iEnd, iPosition;
    int nByte;                               /* total space to allocate */

    pCursor->pTokenizer = pTokenizer;
    rc = pModule->xNext(pCursor, &zToken, &nToken, &iStart, &iEnd, &iPosition);

    if( rc==SQLITE_OK ){
      nByte = sizeof(Fts3Expr) + sizeof(Fts3Phrase) + nToken;
      pRet = (Fts3Expr *)fts3MallocZero(nByte);
      if( !pRet ){
        rc = SQLITE_NOMEM;
      }else{
        pRet->eType = FTSQUERY_PHRASE;
        pRet->pPhrase = (Fts3Phrase *)&pRet[1];
        pRet->pPhrase->nToken = 1;
        pRet->pPhrase->iColumn = iCol;
        pRet->pPhrase->aToken[0].n = nToken;
        pRet->pPhrase->aToken[0].z = (char *)&pRet->pPhrase[1];
        memcpy(pRet->pPhrase->aToken[0].z, zToken, nToken);

        if( iEnd<n && z[iEnd]=='*' ){
          pRet->pPhrase->aToken[0].isPrefix = 1;
          iEnd++;
        }
        if( !sqlite3_fts3_enable_parentheses && iStart>0 && z[iStart-1]=='-' ){
          pRet->pPhrase->isNot = 1;
        }
      }
      nConsumed = iEnd;
    }

    pModule->xClose(pCursor);
  }
  
  *pnConsumed = nConsumed;
  *ppExpr = pRet;
  return rc;
}


/*
** Enlarge a memory allocation.  If an out-of-memory allocation occurs,
** then free the old allocation.
*/
static void *fts3ReallocOrFree(void *pOrig, int nNew){
  void *pRet = sqlite3_realloc(pOrig, nNew);
  if( !pRet ){
    sqlite3_free(pOrig);
  }
  return pRet;
}

/*
** Buffer zInput, length nInput, contains the contents of a quoted string
** that appeared as part of an fts3 query expression. Neither quote character
** is included in the buffer. This function attempts to tokenize the entire
** input buffer and create an Fts3Expr structure of type FTSQUERY_PHRASE 
** containing the results.
**
** If successful, SQLITE_OK is returned and *ppExpr set to point at the
** allocated Fts3Expr structure. Otherwise, either SQLITE_NOMEM (out of memory
** error) or SQLITE_ERROR (tokenization error) is returned and *ppExpr set
** to 0.
*/
static int getNextString(
  ParseContext *pParse,                   /* fts3 query parse context */
  const char *zInput, int nInput,         /* Input string */
  Fts3Expr **ppExpr                       /* OUT: expression */
){
  sqlite3_tokenizer *pTokenizer = pParse->pTokenizer;
  sqlite3_tokenizer_module const *pModule = pTokenizer->pModule;
  int rc;
  Fts3Expr *p = 0;
  sqlite3_tokenizer_cursor *pCursor = 0;
  char *zTemp = 0;
  int nTemp = 0;

  rc = pModule->xOpen(pTokenizer, zInput, nInput, &pCursor);
  if( rc==SQLITE_OK ){
    int ii;
    pCursor->pTokenizer = pTokenizer;
    for(ii=0; rc==SQLITE_OK; ii++){
      const char *zToken;
      int nToken, iBegin, iEnd, iPos;
      rc = pModule->xNext(pCursor, &zToken, &nToken, &iBegin, &iEnd, &iPos);
      if( rc==SQLITE_OK ){
        int nByte = sizeof(Fts3Expr) + sizeof(Fts3Phrase);
        p = fts3ReallocOrFree(p, nByte+ii*sizeof(Fts3PhraseToken));
        zTemp = fts3ReallocOrFree(zTemp, nTemp + nToken);
        if( !p || !zTemp ){
          goto no_mem;
        }
        if( ii==0 ){
          memset(p, 0, nByte);
          p->pPhrase = (Fts3Phrase *)&p[1];
        }
        p->pPhrase = (Fts3Phrase *)&p[1];
        memset(&p->pPhrase->aToken[ii], 0, sizeof(Fts3PhraseToken));
        p->pPhrase->nToken = ii+1;
        p->pPhrase->aToken[ii].n = nToken;
        memcpy(&zTemp[nTemp], zToken, nToken);
        nTemp += nToken;
        if( iEnd<nInput && zInput[iEnd]=='*' ){
          p->pPhrase->aToken[ii].isPrefix = 1;
        }else{
          p->pPhrase->aToken[ii].isPrefix = 0;
        }
      }
    }

    pModule->xClose(pCursor);
    pCursor = 0;
  }

  if( rc==SQLITE_DONE ){
    int jj;
    char *zNew = NULL;
    int nNew = 0;
    int nByte = sizeof(Fts3Expr) + sizeof(Fts3Phrase);
    nByte += (p?(p->pPhrase->nToken-1):0) * sizeof(Fts3PhraseToken);
    p = fts3ReallocOrFree(p, nByte + nTemp);
    if( !p ){
      goto no_mem;
    }
    if( zTemp ){
      zNew = &(((char *)p)[nByte]);
      memcpy(zNew, zTemp, nTemp);
    }else{
      memset(p, 0, nByte+nTemp);
    }
    p->pPhrase = (Fts3Phrase *)&p[1];
    for(jj=0; jj<p->pPhrase->nToken; jj++){
      p->pPhrase->aToken[jj].z = &zNew[nNew];
      nNew += p->pPhrase->aToken[jj].n;
    }
    sqlite3_free(zTemp);
    p->eType = FTSQUERY_PHRASE;
    p->pPhrase->iColumn = pParse->iDefaultCol;
    rc = SQLITE_OK;
  }

  *ppExpr = p;
  return rc;
no_mem:

  if( pCursor ){
    pModule->xClose(pCursor);
  }
  sqlite3_free(zTemp);
  sqlite3_free(p);
  *ppExpr = 0;
  return SQLITE_NOMEM;
}

/*
** Function getNextNode(), which is called by fts3ExprParse(), may itself
** call fts3ExprParse(). So this forward declaration is required.
*/
static int fts3ExprParse(ParseContext *, const char *, int, Fts3Expr **, int *);

/*
** The output variable *ppExpr is populated with an allocated Fts3Expr 
** structure, or set to 0 if the end of the input buffer is reached.
**
** Returns an SQLite error code. SQLITE_OK if everything works, SQLITE_NOMEM
** if a malloc failure occurs, or SQLITE_ERROR if a parse error is encountered.
** If SQLITE_ERROR is returned, pContext is populated with an error message.
*/
static int getNextNode(
  ParseContext *pParse,                   /* fts3 query parse context */
  const char *z, int n,                   /* Input string */
  Fts3Expr **ppExpr,                      /* OUT: expression */
  int *pnConsumed                         /* OUT: Number of bytes consumed */
){
  static const struct Fts3Keyword {
    char *z;                              /* Keyword text */
    unsigned char n;                      /* Length of the keyword */
    unsigned char parenOnly;              /* Only valid in paren mode */
    unsigned char eType;                  /* Keyword code */
  } aKeyword[] = {
    { "OR" ,  2, 0, FTSQUERY_OR   },
    { "AND",  3, 1, FTSQUERY_AND  },
    { "NOT",  3, 1, FTSQUERY_NOT  },
    { "NEAR", 4, 0, FTSQUERY_NEAR }
  };
  int ii;
  int iCol;
  int iColLen;
  int rc;
  Fts3Expr *pRet = 0;

  const char *zInput = z;
  int nInput = n;

  /* Skip over any whitespace before checking for a keyword, an open or
  ** close bracket, or a quoted string. 
  */
  while( nInput>0 && fts3isspace(*zInput) ){
    nInput--;
    zInput++;
  }
  if( nInput==0 ){
    return SQLITE_DONE;
  }

  /* See if we are dealing with a keyword. */
  for(ii=0; ii<(int)(sizeof(aKeyword)/sizeof(struct Fts3Keyword)); ii++){
    const struct Fts3Keyword *pKey = &aKeyword[ii];

    if( (pKey->parenOnly & ~sqlite3_fts3_enable_parentheses)!=0 ){
      continue;
    }

    if( nInput>=pKey->n && 0==memcmp(zInput, pKey->z, pKey->n) ){
      int nNear = SQLITE_FTS3_DEFAULT_NEAR_PARAM;
      int nKey = pKey->n;
      char cNext;

      /* If this is a "NEAR" keyword, check for an explicit nearness. */
      if( pKey->eType==FTSQUERY_NEAR ){
        assert( nKey==4 );
        if( zInput[4]=='/' && zInput[5]>='0' && zInput[5]<='9' ){
          nNear = 0;
          for(nKey=5; zInput[nKey]>='0' && zInput[nKey]<='9'; nKey++){
            nNear = nNear * 10 + (zInput[nKey] - '0');
          }
        }
      }

      /* At this point this is probably a keyword. But for that to be true,
      ** the next byte must contain either whitespace, an open or close
      ** parenthesis, a quote character, or EOF. 
      */
      cNext = zInput[nKey];
      if( fts3isspace(cNext) 
       || cNext=='"' || cNext=='(' || cNext==')' || cNext==0
      ){
        pRet = (Fts3Expr *)fts3MallocZero(sizeof(Fts3Expr));
        if( !pRet ){
          return SQLITE_NOMEM;
        }
        pRet->eType = pKey->eType;
        pRet->nNear = nNear;
        *ppExpr = pRet;
        *pnConsumed = (int)((zInput - z) + nKey);
        return SQLITE_OK;
      }

      /* Turns out that wasn't a keyword after all. This happens if the
      ** user has supplied a token such as "ORacle". Continue.
      */
    }
  }

  /* Check for an open bracket. */
  if( sqlite3_fts3_enable_parentheses ){
    if( *zInput=='(' ){
      int nConsumed;
      pParse->nNest++;
      rc = fts3ExprParse(pParse, &zInput[1], nInput-1, ppExpr, &nConsumed);
      if( rc==SQLITE_OK && !*ppExpr ){
        rc = SQLITE_DONE;
      }
      *pnConsumed = (int)((zInput - z) + 1 + nConsumed);
      return rc;
    }
  
    /* Check for a close bracket. */
    if( *zInput==')' ){
      pParse->nNest--;
      *pnConsumed = (int)((zInput - z) + 1);
      return SQLITE_DONE;
    }
  }

  /* See if we are dealing with a quoted phrase. If this is the case, then
  ** search for the closing quote and pass the whole string to getNextString()
  ** for processing. This is easy to do, as fts3 has no syntax for escaping
  ** a quote character embedded in a string.
  */
  if( *zInput=='"' ){
    for(ii=1; ii<nInput && zInput[ii]!='"'; ii++);
    *pnConsumed = (int)((zInput - z) + ii + 1);
    if( ii==nInput ){
      return SQLITE_ERROR;
    }
    return getNextString(pParse, &zInput[1], ii-1, ppExpr);
  }


  /* If control flows to this point, this must be a regular token, or 
  ** the end of the input. Read a regular token using the sqlite3_tokenizer
  ** interface. Before doing so, figure out if there is an explicit
  ** column specifier for the token. 
  **
  ** TODO: Strangely, it is not possible to associate a column specifier
  ** with a quoted phrase, only with a single token. Not sure if this was
  ** an implementation artifact or an intentional decision when fts3 was
  ** first implemented. Whichever it was, this module duplicates the 
  ** limitation.
  */
  iCol = pParse->iDefaultCol;
  iColLen = 0;
  for(ii=0; ii<pParse->nCol; ii++){
    const char *zStr = pParse->azCol[ii];
    int nStr = (int)strlen(zStr);
    if( nInput>nStr && zInput[nStr]==':' 
     && sqlite3_strnicmp(zStr, zInput, nStr)==0 
    ){
      iCol = ii;
      iColLen = (int)((zInput - z) + nStr + 1);
      break;
    }
  }
  rc = getNextToken(pParse, iCol, &z[iColLen], n-iColLen, ppExpr, pnConsumed);
  *pnConsumed += iColLen;
  return rc;
}

/*
** The argument is an Fts3Expr structure for a binary operator (any type
** except an FTSQUERY_PHRASE). Return an integer value representing the
** precedence of the operator. Lower values have a higher precedence (i.e.
** group more tightly). For example, in the C language, the == operator
** groups more tightly than ||, and would therefore have a higher precedence.
**
** When using the new fts3 query syntax (when SQLITE_ENABLE_FTS3_PARENTHESIS
** is defined), the order of the operators in precedence from highest to
** lowest is:
**
**   NEAR
**   NOT
**   AND (including implicit ANDs)
**   OR
**
** Note that when using the old query syntax, the OR operator has a higher
** precedence than the AND operator.
*/
static int opPrecedence(Fts3Expr *p){
  assert( p->eType!=FTSQUERY_PHRASE );
  if( sqlite3_fts3_enable_parentheses ){
    return p->eType;
  }else if( p->eType==FTSQUERY_NEAR ){
    return 1;
  }else if( p->eType==FTSQUERY_OR ){
    return 2;
  }
  assert( p->eType==FTSQUERY_AND );
  return 3;
}

/*
** Argument ppHead contains a pointer to the current head of a query 
** expression tree being parsed. pPrev is the expression node most recently
** inserted into the tree. This function adds pNew, which is always a binary
** operator node, into the expression tree based on the relative precedence
** of pNew and the existing nodes of the tree. This may result in the head
** of the tree changing, in which case *ppHead is set to the new root node.
*/
static void insertBinaryOperator(
  Fts3Expr **ppHead,       /* Pointer to the root node of a tree */
  Fts3Expr *pPrev,         /* Node most recently inserted into the tree */
  Fts3Expr *pNew           /* New binary node to insert into expression tree */
){
  Fts3Expr *pSplit = pPrev;
  while( pSplit->pParent && opPrecedence(pSplit->pParent)<=opPrecedence(pNew) ){
    pSplit = pSplit->pParent;
  }

  if( pSplit->pParent ){
    assert( pSplit->pParent->pRight==pSplit );
    pSplit->pParent->pRight = pNew;
    pNew->pParent = pSplit->pParent;
  }else{
    *ppHead = pNew;
  }
  pNew->pLeft = pSplit;
  pSplit->pParent = pNew;
}

/*
** Parse the fts3 query expression found in buffer z, length n. This function
** returns either when the end of the buffer is reached or an unmatched 
** closing bracket - ')' - is encountered.
**
** If successful, SQLITE_OK is returned, *ppExpr is set to point to the
** parsed form of the expression and *pnConsumed is set to the number of
** bytes read from buffer z. Otherwise, *ppExpr is set to 0 and SQLITE_NOMEM
** (out of memory error) or SQLITE_ERROR (parse error) is returned.
*/
static int fts3ExprParse(
  ParseContext *pParse,                   /* fts3 query parse context */
  const char *z, int n,                   /* Text of MATCH query */
  Fts3Expr **ppExpr,                      /* OUT: Parsed query structure */
  int *pnConsumed                         /* OUT: Number of bytes consumed */
){
  Fts3Expr *pRet = 0;
  Fts3Expr *pPrev = 0;
  Fts3Expr *pNotBranch = 0;               /* Only used in legacy parse mode */
  int nIn = n;
  const char *zIn = z;
  int rc = SQLITE_OK;
  int isRequirePhrase = 1;

  while( rc==SQLITE_OK ){
    Fts3Expr *p = 0;
    int nByte = 0;
    rc = getNextNode(pParse, zIn, nIn, &p, &nByte);
    if( rc==SQLITE_OK ){
      int isPhrase;

      if( !sqlite3_fts3_enable_parentheses 
       && p->eType==FTSQUERY_PHRASE && p->pPhrase->isNot 
      ){
        /* Create an implicit NOT operator. */
        Fts3Expr *pNot = fts3MallocZero(sizeof(Fts3Expr));
        if( !pNot ){
          sqlite3Fts3ExprFree(p);
          rc = SQLITE_NOMEM;
          goto exprparse_out;
        }
        pNot->eType = FTSQUERY_NOT;
        pNot->pRight = p;
        if( pNotBranch ){
          pNot->pLeft = pNotBranch;
        }
        pNotBranch = pNot;
        p = pPrev;
      }else{
        int eType = p->eType;
        assert( eType!=FTSQUERY_PHRASE || !p->pPhrase->isNot );
        isPhrase = (eType==FTSQUERY_PHRASE || p->pLeft);

        /* The isRequirePhrase variable is set to true if a phrase or
        ** an expression contained in parenthesis is required. If a
        ** binary operator (AND, OR, NOT or NEAR) is encounted when
        ** isRequirePhrase is set, this is a syntax error.
        */
        if( !isPhrase && isRequirePhrase ){
          sqlite3Fts3ExprFree(p);
          rc = SQLITE_ERROR;
          goto exprparse_out;
        }
  
        if( isPhrase && !isRequirePhrase ){
          /* Insert an implicit AND operator. */
          Fts3Expr *pAnd;
          assert( pRet && pPrev );
          pAnd = fts3MallocZero(sizeof(Fts3Expr));
          if( !pAnd ){
            sqlite3Fts3ExprFree(p);
            rc = SQLITE_NOMEM;
            goto exprparse_out;
          }
          pAnd->eType = FTSQUERY_AND;
          insertBinaryOperator(&pRet, pPrev, pAnd);
          pPrev = pAnd;
        }

        /* This test catches attempts to make either operand of a NEAR
        ** operator something other than a phrase. For example, either of
        ** the following:
        **
        **    (bracketed expression) NEAR phrase
        **    phrase NEAR (bracketed expression)
        **
        ** Return an error in either case.
        */
        if( pPrev && (
            (eType==FTSQUERY_NEAR && !isPhrase && pPrev->eType!=FTSQUERY_PHRASE)
         || (eType!=FTSQUERY_PHRASE && isPhrase && pPrev->eType==FTSQUERY_NEAR)
        )){
          sqlite3Fts3ExprFree(p);
          rc = SQLITE_ERROR;
          goto exprparse_out;
        }
  
        if( isPhrase ){
          if( pRet ){
            assert( pPrev && pPrev->pLeft && pPrev->pRight==0 );
            pPrev->pRight = p;
            p->pParent = pPrev;
          }else{
            pRet = p;
          }
        }else{
          insertBinaryOperator(&pRet, pPrev, p);
        }
        isRequirePhrase = !isPhrase;
      }
      assert( nByte>0 );
    }
    assert( rc!=SQLITE_OK || (nByte>0 && nByte<=nIn) );
    nIn -= nByte;
    zIn += nByte;
    pPrev = p;
  }

  if( rc==SQLITE_DONE && pRet && isRequirePhrase ){
    rc = SQLITE_ERROR;
  }

  if( rc==SQLITE_DONE ){
    rc = SQLITE_OK;
    if( !sqlite3_fts3_enable_parentheses && pNotBranch ){
      if( !pRet ){
        rc = SQLITE_ERROR;
      }else{
        Fts3Expr *pIter = pNotBranch;
        while( pIter->pLeft ){
          pIter = pIter->pLeft;
        }
        pIter->pLeft = pRet;
        pRet = pNotBranch;
      }
    }
  }
  *pnConsumed = n - nIn;

exprparse_out:
  if( rc!=SQLITE_OK ){
    sqlite3Fts3ExprFree(pRet);
    sqlite3Fts3ExprFree(pNotBranch);
    pRet = 0;
  }
  *ppExpr = pRet;
  return rc;
}

/*
** Parameters z and n contain a pointer to and length of a buffer containing
** an fts3 query expression, respectively. This function attempts to parse the
** query expression and create a tree of Fts3Expr structures representing the
** parsed expression. If successful, *ppExpr is set to point to the head
** of the parsed expression tree and SQLITE_OK is returned. If an error
** occurs, either SQLITE_NOMEM (out-of-memory error) or SQLITE_ERROR (parse
** error) is returned and *ppExpr is set to 0.
**
** If parameter n is a negative number, then z is assumed to point to a
** nul-terminated string and the length is determined using strlen().
**
** The first parameter, pTokenizer, is passed the fts3 tokenizer module to
** use to normalize query tokens while parsing the expression. The azCol[]
** array, which is assumed to contain nCol entries, should contain the names
** of each column in the target fts3 table, in order from left to right. 
** Column names must be nul-terminated strings.
**
** The iDefaultCol parameter should be passed the index of the table column
** that appears on the left-hand-side of the MATCH operator (the default
** column to match against for tokens for which a column name is not explicitly
** specified as part of the query string), or -1 if tokens may by default
** match any table column.
*/
int sqlite3Fts3ExprParse(
  sqlite3_tokenizer *pTokenizer,      /* Tokenizer module */
  char **azCol,                       /* Array of column names for fts3 table */
  int nCol,                           /* Number of entries in azCol[] */
  int iDefaultCol,                    /* Default column to query */
  const char *z, int n,               /* Text of MATCH query */
  Fts3Expr **ppExpr                   /* OUT: Parsed query structure */
){
  int nParsed;
  int rc;
  ParseContext sParse;
  sParse.pTokenizer = pTokenizer;
  sParse.azCol = (const char **)azCol;
  sParse.nCol = nCol;
  sParse.iDefaultCol = iDefaultCol;
  sParse.nNest = 0;
  if( z==0 ){
    *ppExpr = 0;
    return SQLITE_OK;
  }
  if( n<0 ){
    n = (int)strlen(z);
  }
  rc = fts3ExprParse(&sParse, z, n, ppExpr, &nParsed);

  /* Check for mismatched parenthesis */
  if( rc==SQLITE_OK && sParse.nNest ){
    rc = SQLITE_ERROR;
    sqlite3Fts3ExprFree(*ppExpr);
    *ppExpr = 0;
  }

  return rc;
}

/*
** Free a parsed fts3 query expression allocated by sqlite3Fts3ExprParse().
*/
void sqlite3Fts3ExprFree(Fts3Expr *p){
  if( p ){
    sqlite3Fts3ExprFree(p->pLeft);
    sqlite3Fts3ExprFree(p->pRight);
    sqlite3_free(p->aDoclist);
    sqlite3_free(p);
  }
}

/****************************************************************************
*****************************************************************************
** Everything after this point is just test code.
*/

#ifdef SQLITE_TEST

#include <stdio.h>

/*
** Function to query the hash-table of tokenizers (see README.tokenizers).
*/
static int queryTestTokenizer(
  sqlite3 *db, 
  const char *zName,  
  const sqlite3_tokenizer_module **pp
){
  int rc;
  sqlite3_stmt *pStmt;
  const char zSql[] = "SELECT fts3_tokenizer(?)";

  *pp = 0;
  rc = sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0);
  if( rc!=SQLITE_OK ){
    return rc;
  }

  sqlite3_bind_text(pStmt, 1, zName, -1, SQLITE_STATIC);
  if( SQLITE_ROW==sqlite3_step(pStmt) ){
    if( sqlite3_column_type(pStmt, 0)==SQLITE_BLOB ){
      memcpy((void *)pp, sqlite3_column_blob(pStmt, 0), sizeof(*pp));
    }
  }

  return sqlite3_finalize(pStmt);
}

/*
** Return a pointer to a buffer containing a text representation of the
** expression passed as the first argument. The buffer is obtained from
** sqlite3_malloc(). It is the responsibility of the caller to use 
** sqlite3_free() to release the memory. If an OOM condition is encountered,
** NULL is returned.
**
** If the second argument is not NULL, then its contents are prepended to 
** the returned expression text and then freed using sqlite3_free().
*/
static char *exprToString(Fts3Expr *pExpr, char *zBuf){
  switch( pExpr->eType ){
    case FTSQUERY_PHRASE: {
      Fts3Phrase *pPhrase = pExpr->pPhrase;
      int i;
      zBuf = sqlite3_mprintf(
          "%zPHRASE %d %d", zBuf, pPhrase->iColumn, pPhrase->isNot);
      for(i=0; zBuf && i<pPhrase->nToken; i++){
        zBuf = sqlite3_mprintf("%z %.*s%s", zBuf, 
            pPhrase->aToken[i].n, pPhrase->aToken[i].z,
            (pPhrase->aToken[i].isPrefix?"+":"")
        );
      }
      return zBuf;
    }

    case FTSQUERY_NEAR:
      zBuf = sqlite3_mprintf("%zNEAR/%d ", zBuf, pExpr->nNear);
      break;
    case FTSQUERY_NOT:
      zBuf = sqlite3_mprintf("%zNOT ", zBuf);
      break;
    case FTSQUERY_AND:
      zBuf = sqlite3_mprintf("%zAND ", zBuf);
      break;
    case FTSQUERY_OR:
      zBuf = sqlite3_mprintf("%zOR ", zBuf);
      break;
  }

  if( zBuf ) zBuf = sqlite3_mprintf("%z{", zBuf);
  if( zBuf ) zBuf = exprToString(pExpr->pLeft, zBuf);
  if( zBuf ) zBuf = sqlite3_mprintf("%z} {", zBuf);

  if( zBuf ) zBuf = exprToString(pExpr->pRight, zBuf);
  if( zBuf ) zBuf = sqlite3_mprintf("%z}", zBuf);

  return zBuf;
}

/*
** This is the implementation of a scalar SQL function used to test the 
** expression parser. It should be called as follows:
**
**   fts3_exprtest(<tokenizer>, <expr>, <column 1>, ...);
**
** The first argument, <tokenizer>, is the name of the fts3 tokenizer used
** to parse the query expression (see README.tokenizers). The second argument
** is the query expression to parse. Each subsequent argument is the name
** of a column of the fts3 table that the query expression may refer to.
** For example:
**
**   SELECT fts3_exprtest('simple', 'Bill col2:Bloggs', 'col1', 'col2');
*/
static void fts3ExprTest(
  sqlite3_context *context,
  int argc,
  sqlite3_value **argv
){
  sqlite3_tokenizer_module const *pModule = 0;
  sqlite3_tokenizer *pTokenizer = 0;
  int rc;
  char **azCol = 0;
  const char *zExpr;
  int nExpr;
  int nCol;
  int ii;
  Fts3Expr *pExpr;
  char *zBuf = 0;
  sqlite3 *db = sqlite3_context_db_handle(context);

  if( argc<3 ){
    sqlite3_result_error(context, 
        "Usage: fts3_exprtest(tokenizer, expr, col1, ...", -1
    );
    return;
  }

  rc = queryTestTokenizer(db,
                          (const char *)sqlite3_value_text(argv[0]), &pModule);
  if( rc==SQLITE_NOMEM ){
    sqlite3_result_error_nomem(context);
    goto exprtest_out;
  }else if( !pModule ){
    sqlite3_result_error(context, "No such tokenizer module", -1);
    goto exprtest_out;
  }

  rc = pModule->xCreate(0, 0, &pTokenizer);
  assert( rc==SQLITE_NOMEM || rc==SQLITE_OK );
  if( rc==SQLITE_NOMEM ){
    sqlite3_result_error_nomem(context);
    goto exprtest_out;
  }
  pTokenizer->pModule = pModule;

  zExpr = (const char *)sqlite3_value_text(argv[1]);
  nExpr = sqlite3_value_bytes(argv[1]);
  nCol = argc-2;
  azCol = (char **)sqlite3_malloc(nCol*sizeof(char *));
  if( !azCol ){
    sqlite3_result_error_nomem(context);
    goto exprtest_out;
  }
  for(ii=0; ii<nCol; ii++){
    azCol[ii] = (char *)sqlite3_value_text(argv[ii+2]);
  }

  rc = sqlite3Fts3ExprParse(
      pTokenizer, azCol, nCol, nCol, zExpr, nExpr, &pExpr
  );
  if( rc!=SQLITE_OK && rc!=SQLITE_NOMEM ){
    sqlite3_result_error(context, "Error parsing expression", -1);
  }else if( rc==SQLITE_NOMEM || !(zBuf = exprToString(pExpr, 0)) ){
    sqlite3_result_error_nomem(context);
  }else{
    sqlite3_result_text(context, zBuf, -1, SQLITE_TRANSIENT);
    sqlite3_free(zBuf);
  }

  sqlite3Fts3ExprFree(pExpr);

exprtest_out:
  if( pModule && pTokenizer ){
    rc = pModule->xDestroy(pTokenizer);
  }
  sqlite3_free(azCol);
}

/*
** Register the query expression parser test function fts3_exprtest() 
** with database connection db. 
*/
int sqlite3Fts3ExprInitTestInterface(sqlite3* db){
  return sqlite3_create_function(
      db, "fts3_exprtest", -1, SQLITE_UTF8, 0, fts3ExprTest, 0, 0
  );
}

#endif
#endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3) */

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