SqlStringExtensions.cs

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// 
//  Copyright 2010-2015 Deveel
// 
//    Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
// 
//    Unless required by applicable law or agreed to in writing, software
//    distributed under the License is distributed on an "AS IS" BASIS,
//    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
//    See the License for the specific language governing permissions and
//    limitations under the License.
//

using System;
using System.Text;

namespace Deveel.Data.Sql.Objects {
    public static class SqlStringExtensions {
        // Statics for the tokens.
        private const char ZeroOrMoreChars = '%';
        private const char OneChar = '_';

        private static bool IsWildCard(char ch) {
            return (ch == OneChar || ch == ZeroOrMoreChars);
        }

        public static SqlBoolean PatternMatch(this ISqlString pattern, string expression, char escapeChar) {
            throw new NotImplementedException();
        }

        public static SqlString Substring(this ISqlString source, int offset) {
            return Substring(source, offset, (int)source.Length - offset);
        }

        public static SqlString Substring(this ISqlString source, int offset, int count) {
            if (source == null || source.IsNull)
                return SqlString.Null;

            var en = source.GetEnumerator();
            var sb = new StringBuilder(count);

            int index = -1;
            while (en.MoveNext()) {
                if (++index < offset)
                    continue;

                sb.Append(en.Current);

                if (index == count - 1)
                    break;
            }

#if PCL
            var s = sb.ToString();
            return new SqlString(s);
#else
            var chars = new char[count];
            sb.CopyTo(0, chars, 0, count);
            return new SqlString(chars);
#endif
        }

        public static SqlNumber IndexOf(this ISqlString pattern, SqlString expression) {
            // TODO: Implement a version of the Boyer-Moore algorithm over a SQL String
            throw new NotImplementedException();
        }
    }
}