/// <summary>
/// Given an expression and an optional comparator, build a tree of
/// InputFormats using the comparator to sort keys.
/// </summary>
/// <exception cref="System.IO.IOException"/>
internal static Parser.Node Parse(string expr, Configuration conf)
{
if (null == expr)
{
throw new IOException("Expression is null");
}
Type cmpcl = conf.GetClass <WritableComparator>(CompositeInputFormat.JoinComparator
, null);
Parser.Lexer lex = new Parser.Lexer(expr);
Stack <Parser.Token> st = new Stack <Parser.Token>();
Parser.Token tok;
while ((tok = lex.Next()) != null)
{
if (Parser.TType.Rparen.Equals(tok.GetType()))
{
st.Push(Reduce(st, conf));
}
else
{
st.Push(tok);
}
}
if (st.Count == 1 && Parser.TType.Cif.Equals(st.Peek().GetType()))
{
Parser.Node ret = st.Pop().GetNode();
if (cmpcl != null)
{
ret.SetKeyComparator(cmpcl);
}
return(ret);
}
throw new IOException("Missing ')'");
}
/// <exception cref="System.IO.IOException"/>
private static Parser.Token Reduce(Stack <Parser.Token> st, Configuration conf)
{
List <Parser.Token> args = new List <Parser.Token>();
while (!st.IsEmpty() && !Parser.TType.Lparen.Equals(st.Peek().GetType()))
{
args.AddFirst(st.Pop());
}
if (st.IsEmpty())
{
throw new IOException("Unmatched ')'");
}
st.Pop();
if (st.IsEmpty() || !Parser.TType.Ident.Equals(st.Peek().GetType()))
{
throw new IOException("Identifier expected");
}
Parser.Node n = Parser.Node.ForIdent(st.Pop().GetStr());
n.Parse(args, conf);
return(new Parser.NodeToken(n));
}
// expression parse tree to which IF requests are proxied
/// <summary>Interpret a given string as a composite expression.</summary>
/// <remarks>
/// Interpret a given string as a composite expression.
/// <c>
/// func ::= <ident>([<func>,]*<func>)
/// func ::= tbl(<class>,"<path>")
/// class ::= @see java.lang.Class#forName(java.lang.String)
/// path ::= @see org.apache.hadoop.fs.Path#Path(java.lang.String)
/// </c>
/// Reads expression from the <tt>mapreduce.join.expr</tt> property and
/// user-supplied join types from <tt>mapreduce.join.define.<ident></tt>
/// types. Paths supplied to <tt>tbl</tt> are given as input paths to the
/// InputFormat class listed.
/// </remarks>
/// <seealso cref="CompositeInputFormat{K}.Compose(string, System.Type{T}, string[])"
/// />
/// <exception cref="System.IO.IOException"/>
public virtual void SetFormat(Configuration conf)
{
AddDefaults();
AddUserIdentifiers(conf);
root = Parser.Parse(conf.Get(JoinExpr, null), conf);
}
internal NodeToken(Parser.Node node)
: base(Parser.TType.Cif)
{
this.node = node;
}
