/// <summary> /// Parses a regular expression from the specified <see cref="ParseContext"/> /// </summary> /// <param name="pc">The parse context to use</param> /// <returns>A new abstract syntax tree representing the expression</returns> public static RegexExpression Parse(ParseContext pc) { RegexExpression result = null, next = null; int ich; pc.EnsureStarted(); var line = pc.Line; var column = pc.Column; var position = pc.Position; while (true) { switch (pc.Current) { case -1: return(result); case '.': var nset = new RegexCharsetExpression(new RegexCharsetEntry[] { new RegexCharsetRangeEntry(char.MinValue, char.MaxValue) }, false); nset.SetLocation(line, column, position); if (null == result) { result = nset; } else { result = new RegexConcatExpression(result, nset); result.SetLocation(line, column, position); } pc.Advance(); result = _ParseModifier(result, pc); line = pc.Line; column = pc.Column; position = pc.Position; break; case '\\': pc.Advance(); pc.Expecting(); switch (pc.Current) { case 'd': next = new RegexCharsetExpression(new RegexCharsetEntry[] { new RegexCharsetClassEntry("digit") }); pc.Advance(); break; case 'D': next = new RegexCharsetExpression(new RegexCharsetEntry[] { new RegexCharsetClassEntry("digit") }, true); pc.Advance(); break; case 'h': next = new RegexCharsetExpression(new RegexCharsetEntry[] { new RegexCharsetClassEntry("blank") }); pc.Advance(); break; case 'l': next = new RegexCharsetExpression(new RegexCharsetEntry[] { new RegexCharsetClassEntry("lower") }); pc.Advance(); break; case 's': next = new RegexCharsetExpression(new RegexCharsetEntry[] { new RegexCharsetClassEntry("space") }); pc.Advance(); break; case 'S': next = new RegexCharsetExpression(new RegexCharsetEntry[] { new RegexCharsetClassEntry("space") }, true); pc.Advance(); break; case 'u': next = new RegexCharsetExpression(new RegexCharsetEntry[] { new RegexCharsetClassEntry("upper") }); pc.Advance(); break; case 'w': next = new RegexCharsetExpression(new RegexCharsetEntry[] { new RegexCharsetClassEntry("word") }); pc.Advance(); break; case 'W': next = new RegexCharsetExpression(new RegexCharsetEntry[] { new RegexCharsetClassEntry("word") }, true); pc.Advance(); break; default: if (-1 != (ich = _ParseEscapePart(pc))) { next = new RegexLiteralExpression((char)ich); } else { pc.Expecting(); // throw an error return(null); // doesn't execute } break; } next.SetLocation(line, column, position); next = _ParseModifier(next, pc); if (null != result) { result = new RegexConcatExpression(result, next); result.SetLocation(line, column, position); } else { result = next; } line = pc.Line; column = pc.Column; position = pc.Position; break; case ')': return(result); case '(': pc.Advance(); pc.Expecting(); next = Parse(pc); pc.Expecting(')'); pc.Advance(); next = _ParseModifier(next, pc); if (null == result) { result = next; } else { result = new RegexConcatExpression(result, next); result.SetLocation(line, column, position); } line = pc.Line; column = pc.Column; position = pc.Position; break; case '|': if (-1 != pc.Advance()) { next = Parse(pc); result = new RegexOrExpression(result, next); result.SetLocation(line, column, position); } else { result = new RegexOrExpression(result, null); result.SetLocation(line, column, position); } line = pc.Line; column = pc.Column; position = pc.Position; break; case '[': pc.ClearCapture(); pc.Advance(); pc.Expecting(); bool not = false; if ('^' == pc.Current) { not = true; pc.Advance(); pc.Expecting(); } var ranges = _ParseRanges(pc); if (ranges.Count == 0) { System.Diagnostics.Debugger.Break(); } pc.Expecting(']'); pc.Advance(); next = new RegexCharsetExpression(ranges, not); next.SetLocation(line, column, position); next = _ParseModifier(next, pc); if (null == result) { result = next; } else { result = new RegexConcatExpression(result, next); result.SetLocation(pc.Line, pc.Column, pc.Position); } line = pc.Line; column = pc.Column; position = pc.Position; break; default: ich = pc.Current; next = new RegexLiteralExpression((char)ich); next.SetLocation(line, column, position); pc.Advance(); next = _ParseModifier(next, pc); if (null == result) { result = next; } else { result = new RegexConcatExpression(result, next); result.SetLocation(line, column, position); } line = pc.Line; column = pc.Column; position = pc.Position; break; } } }