gecko/storage/src/mozStorageSQLFunctions.cpp

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 * vim: sw=2 ts=2 et lcs=trail\:.,tab\:>~ :
 * ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is unicode functions code.
 *
 * The Initial Developer of the Original Code is
 * Mozilla Corporation.
 * Portions created by the Initial Developer are Copyright (C) 2007
 * the Initial Developer. All Rights Reserved.
 *
 * This code is based off of icu.c from the sqlite code
 * whose original author is danielk1977
 *
 * Contributor(s):
 *   Shawn Wilsher <me@shawnwilsher.com> (Original Author)
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either the GNU General Public License Version 2 or later (the "GPL"), or
 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the MPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the MPL, the GPL or the LGPL.
 *
 * ***** END LICENSE BLOCK ***** */

#include "mozStorageSQLFunctions.h"
#include "nsUnicharUtils.h"

namespace mozilla {
namespace storage {

////////////////////////////////////////////////////////////////////////////////
//// Local Helper Functions

namespace {

/**
 * Performs the LIKE comparison of a string against a pattern.  For more detail
 * see http://www.sqlite.org/lang_expr.html#like.
 *
 * @param aPatternItr
 *        An iterator at the start of the pattern to check for.
 * @param aPatternEnd
 *        An iterator at the end of the pattern to check for.
 * @param aStringItr
 *        An iterator at the start of the string to check for the pattern.
 * @param aStringEnd
 *        An iterator at the end of the string to check for the pattern.
 * @param aEscapeChar
 *        The character to use for escaping symbols in the pattern.
 * @returns 1 if the pattern is found, 0 otherwise.
 */
int
likeCompare(nsAString::const_iterator aPatternItr,
            nsAString::const_iterator aPatternEnd,
            nsAString::const_iterator aStringItr,
            nsAString::const_iterator aStringEnd,
            PRUnichar aEscapeChar)
{
  const PRUnichar MATCH_ALL('%');
  const PRUnichar MATCH_ONE('_');

  PRBool lastWasEscape = PR_FALSE;
  while (aPatternItr != aPatternEnd) {
    /**
     * What we do in here is take a look at each character from the input
     * pattern, and do something with it.  There are 4 possibilities:
     * 1) character is an un-escaped match-all character
     * 2) character is an un-escaped match-one character
     * 3) character is an un-escaped escape character
     * 4) character is not any of the above
     */
    if (!lastWasEscape && *aPatternItr == MATCH_ALL) {
      // CASE 1
      /**
       * Now we need to skip any MATCH_ALL or MATCH_ONE characters that follow a
       * MATCH_ALL character.  For each MATCH_ONE character, skip one character
       * in the pattern string.
       */
      while (*aPatternItr == MATCH_ALL || *aPatternItr == MATCH_ONE) {
        if (*aPatternItr == MATCH_ONE) {
          // If we've hit the end of the string we are testing, no match
          if (aStringItr == aStringEnd)
            return 0;
          aStringItr++;
        }
        aPatternItr++;
      }

      // If we've hit the end of the pattern string, match
      if (aPatternItr == aPatternEnd)
        return 1;

      while (aStringItr != aStringEnd) {
        if (likeCompare(aPatternItr, aPatternEnd, aStringItr, aStringEnd,
                        aEscapeChar)) {
          // we've hit a match, so indicate this
          return 1;
        }
        aStringItr++;
      }

      // No match
      return 0;
    }
    else if (!lastWasEscape && *aPatternItr == MATCH_ONE) {
      // CASE 2
      if (aStringItr == aStringEnd) {
        // If we've hit the end of the string we are testing, no match
        return 0;
      }
      aStringItr++;
      lastWasEscape = PR_FALSE;
    }
    else if (!lastWasEscape && *aPatternItr == aEscapeChar) {
      // CASE 3
      lastWasEscape = PR_TRUE;
    }
    else {
      // CASE 4
      if (::ToUpperCase(*aStringItr) != ::ToUpperCase(*aPatternItr)) {
        // If we've hit a point where the strings don't match, there is no match
        return 0;
      }
      aStringItr++;
      lastWasEscape = PR_FALSE;
    }

    aPatternItr++;
  }

  return aStringItr == aStringEnd;
}

} // anonymous namespace

////////////////////////////////////////////////////////////////////////////////
//// Exposed Functions

int
registerFunctions(sqlite3 *aDB)
{
  struct Functions {
    const char *zName;
    int nArg;
    int enc;
    void *pContext;
    void (*xFunc)(::sqlite3_context*, int, sqlite3_value**);
  } functions[] = {
    {"lower", 1, SQLITE_UTF16, 0,        caseFunction},
    {"lower", 1, SQLITE_UTF8,  0,        caseFunction},
    {"upper", 1, SQLITE_UTF16, (void*)1, caseFunction},
    {"upper", 1, SQLITE_UTF8,  (void*)1, caseFunction},

    {"like",  2, SQLITE_UTF16, 0,        likeFunction},
    {"like",  2, SQLITE_UTF8,  0,        likeFunction},
    {"like",  3, SQLITE_UTF16, 0,        likeFunction},
    {"like",  3, SQLITE_UTF8,  0,        likeFunction},
  };

  int rv = SQLITE_OK;
  for (size_t i = 0; SQLITE_OK == rv && i < NS_ARRAY_LENGTH(functions); ++i) {
    struct Functions *p = &functions[i];
    rv = ::sqlite3_create_function(aDB, p->zName, p->nArg, p->enc, p->pContext,
                                   p->xFunc, NULL, NULL);
  }

  return rv;
}

////////////////////////////////////////////////////////////////////////////////
//// SQL Functions

void
caseFunction(sqlite3_context *aCtx,
             int aArgc,
             sqlite3_value **aArgv)
{
  NS_ASSERTION(1 == aArgc, "Invalid number of arguments!");

  nsAutoString data(static_cast<const PRUnichar *>(::sqlite3_value_text16(aArgv[0])));
  PRBool toUpper = ::sqlite3_user_data(aCtx) ? PR_TRUE : PR_FALSE;

  if (toUpper)
    ::ToUpperCase(data);
  else
    ::ToLowerCase(data);

  // Set the result.
  ::sqlite3_result_text16(aCtx, data.get(), -1, SQLITE_TRANSIENT);
}

/**
 * This implements the like() SQL function.  This is used by the LIKE operator.
 * The SQL statement 'A LIKE B' is implemented as 'like(B, A)', and if there is
 * an escape character, say E, it is implemented as 'like(B, A, E)'.
 */
void
likeFunction(sqlite3_context *aCtx,
             int aArgc,
             sqlite3_value **aArgv)
{
  NS_ASSERTION(2 == aArgc || 3 == aArgc, "Invalid number of arguments!");

  if (::sqlite3_value_bytes(aArgv[0]) > SQLITE_MAX_LIKE_PATTERN_LENGTH) {
    ::sqlite3_result_error(aCtx, "LIKE or GLOB pattern too complex",
                           SQLITE_TOOBIG);
    return;
  }

  if (!::sqlite3_value_text16(aArgv[0]) || !::sqlite3_value_text16(aArgv[1]))
    return;

  nsDependentString A(static_cast<const PRUnichar *>(::sqlite3_value_text16(aArgv[1])));
  nsDependentString B(static_cast<const PRUnichar *>(::sqlite3_value_text16(aArgv[0])));
  NS_ASSERTION(!B.IsEmpty(), "LIKE string must not be null!");

  PRUnichar E = 0;
  if (3 == aArgc)
    E = static_cast<const PRUnichar *>(::sqlite3_value_text16(aArgv[2]))[0];

  nsAString::const_iterator itrString, endString;
  A.BeginReading(itrString);
  A.EndReading(endString);
  nsAString::const_iterator itrPattern, endPattern;
  B.BeginReading(itrPattern);
  B.EndReading(endPattern);
  ::sqlite3_result_int(aCtx, likeCompare(itrPattern, endPattern, itrString,
                                         endString, E));
}

} // namespace storage
} // namespace mozilla