private void ParseInternal()

in src/log4net/Util/PatternParser.cs [183:302]
91 lines of code
21 McCabe index (conditional complexity)

		private void ParseInternal(string pattern, string[] matches)
		{
			int offset = 0;
			while(offset < pattern.Length)
			{
				int i = pattern.IndexOf('%', offset);
				if (i < 0 || i == pattern.Length - 1)
				{
					ProcessLiteral(pattern.Substring(offset));
					offset = pattern.Length;
				}
				else
				{
					if (pattern[i+1] == '%')
					{
						// Escaped
						ProcessLiteral(pattern.Substring(offset, i - offset + 1));
						offset = i + 2;
					}
					else
					{
						ProcessLiteral(pattern.Substring(offset, i - offset));
						offset = i + 1;

						FormattingInfo formattingInfo = new FormattingInfo();

						// Process formatting options

						// Look for the align flag
						if (offset < pattern.Length)
						{
							if (pattern[offset] == '-')
							{
								// Seen align flag
								formattingInfo.LeftAlign = true;
								offset++;
							}
						}
						// Look for the minimum length
						while (offset < pattern.Length && char.IsDigit(pattern[offset]))
						{
							// Seen digit
							if (formattingInfo.Min < 0)
							{
								formattingInfo.Min = 0;
							}

							formattingInfo.Min = (formattingInfo.Min * 10) + int.Parse(pattern[offset].ToString(), NumberFormatInfo.InvariantInfo);

							offset++;
						}
						// Look for the separator between min and max
						if (offset < pattern.Length)
						{
							if (pattern[offset] == '.')
							{
								// Seen separator
								offset++;
							}
						}
						// Look for the maximum length
						while (offset < pattern.Length && char.IsDigit(pattern[offset]))
						{
							// Seen digit
							if (formattingInfo.Max == int.MaxValue)
							{
								formattingInfo.Max = 0;
							}

							formattingInfo.Max = (formattingInfo.Max * 10) + int.Parse(pattern[offset].ToString(), NumberFormatInfo.InvariantInfo);

							offset++;
						}

						int remainingStringLength = pattern.Length - offset;

						// Look for pattern
						for(int m=0; m<matches.Length; m++)
						{
							string key = matches[m];

							if (key.Length <= remainingStringLength)
							{
								if (string.Compare(pattern, offset, key, 0, key.Length) == 0)
								{
									// Found match
									offset = offset + matches[m].Length;

									string option = null;

									// Look for option
									if (offset < pattern.Length)
									{
										if (pattern[offset] == '{')
										{
											// Seen option start
											offset++;
											
											int optEnd = pattern.IndexOf('}', offset);
											if (optEnd < 0)
											{
												// error
											}
											else
											{
												option = pattern.Substring(offset, optEnd - offset);
												offset = optEnd + 1;
											}
										}
									}

									ProcessConverter(matches[m], option, formattingInfo);
									break;
								}
							}
						}
					}
				}
			}
		}