Package org.antlr.v4.runtime

Class TokenStreamRewriter

  • public class TokenStreamRewriter
extends Object
    Useful for rewriting out a buffered input token stream after doing some augmentation or other manipulations on it.

    You can insert stuff, replace, and delete chunks. Note that the operations are done lazily--only if you convert the buffer to a String with TokenStream.getText(). This is very efficient because you are not moving data around all the time. As the buffer of tokens is converted to strings, the getText() method(s) scan the input token stream and check to see if there is an operation at the current index. If so, the operation is done and then normal String rendering continues on the buffer. This is like having multiple Turing machine instruction streams (programs) operating on a single input tape. :)

    This rewriter makes no modifications to the token stream. It does not ask the stream to fill itself up nor does it advance the input cursor. The token stream IntStream.index() will return the same value before and after any getText() call.

    The rewriter only works on tokens that you have in the buffer and ignores the current input cursor. If you are buffering tokens on-demand, calling getText() halfway through the input will only do rewrites for those tokens in the first half of the file.

    Since the operations are done lazily at getText()-time, operations do not screw up the token index values. That is, an insert operation at token index i does not change the index values for tokens i+1..n-1.

    Because operations never actually alter the buffer, you may always get the original token stream back without undoing anything. Since the instructions are queued up, you can easily simulate transactions and roll back any changes if there is an error just by removing instructions. For example,

     CharStream input = new ANTLRFileStream("input");
 TLexer lex = new TLexer(input);
 CommonTokenStream tokens = new CommonTokenStream(lex);
 T parser = new T(tokens);
 TokenStreamRewriter rewriter = new TokenStreamRewriter(tokens);
 parser.startRule();

    Then in the rules, you can execute (assuming rewriter is visible):

     Token t,u;
 ...
 rewriter.insertAfter(t, "text to put after t");}
 rewriter.insertAfter(u, "text after u");}
 System.out.println(rewriter.getText());

    You can also have multiple "instruction streams" and get multiple rewrites from a single pass over the input. Just name the instruction streams and use that name again when printing the buffer. This could be useful for generating a C file and also its header file--all from the same buffer:

     rewriter.insertAfter("pass1", t, "text to put after t");}
 rewriter.insertAfter("pass2", u, "text after u");}
 System.out.println(rewriter.getText("pass1"));
 System.out.println(rewriter.getText("pass2"));

    If you don't use named rewrite streams, a "default" stream is used as the first example shows.

    • Constructor Detail

      • TokenStreamRewriter

        public TokenStreamRewriter​(TokenStream tokens)

    • Method Detail

      • getTokenStream

        public final TokenStream getTokenStream()

      • rollback

        public void rollback​(int instructionIndex)

      • rollback

        public void rollback​(String programName,
                     int instructionIndex)
        Rollback the instruction stream for a program so that the indicated instruction (via instructionIndex) is no longer in the stream. UNTESTED!

      • deleteProgram

        public void deleteProgram()

      • deleteProgram

        public void deleteProgram​(String programName)
        Reset the program so that no instructions exist

      • insertAfter

        public void insertAfter​(Token t,
                        Object text)

      • insertAfter

        public void insertAfter​(int index,
                        Object text)

      • insertAfter

        public void insertAfter​(String programName,
                        Token t,
                        Object text)

      • insertAfter

        public void insertAfter​(String programName,
                        int index,
                        Object text)

      • insertBefore

        public void insertBefore​(Token t,
                         Object text)

      • insertBefore

        public void insertBefore​(int index,
                         Object text)

      • insertBefore

        public void insertBefore​(String programName,
                         Token t,
                         Object text)

      • insertBefore

        public void insertBefore​(String programName,
                         int index,
                         Object text)

      • replace

        public void replace​(int index,
                    Object text)

      • replace

        public void replace​(int from,
                    int to,
                    Object text)

      • replace

        public void replace​(Token indexT,
                    Object text)

      • replace

        public void replace​(String programName,
                    int from,
                    int to,
                    Object text)

      • delete

        public void delete​(int index)

      • delete

        public void delete​(int from,
                   int to)

      • delete

        public void delete​(Token indexT)

      • delete

        public void delete​(Token from,
                   Token to)

      • delete

        public void delete​(String programName,
                   int from,
                   int to)

      • getLastRewriteTokenIndex

        public int getLastRewriteTokenIndex()

      • getLastRewriteTokenIndex

        protected int getLastRewriteTokenIndex​(String programName)

      • setLastRewriteTokenIndex

        protected void setLastRewriteTokenIndex​(String programName,
                                        int i)

      • getText

        public String getText()
        Return the text from the original tokens altered per the instructions given to this rewriter.

      • getText

        public String getText​(String programName)
        Return the text from the original tokens altered per the instructions given to this rewriter in programName.

      • getText

        public String getText​(Interval interval)
        Return the text associated with the tokens in the interval from the original token stream but with the alterations given to this rewriter. The interval refers to the indexes in the original token stream. We do not alter the token stream in any way, so the indexes and intervals are still consistent. Includes any operations done to the first and last token in the interval. So, if you did an insertBefore on the first token, you would get that insertion. The same is true if you do an insertAfter the stop token.

      • reduceToSingleOperationPerIndex

        protected Map<Integer,​TokenStreamRewriter.RewriteOperation> reduceToSingleOperationPerIndex​(List<TokenStreamRewriter.RewriteOperation> rewrites)
        We need to combine operations and report invalid operations (like overlapping replaces that are not completed nested). Inserts to same index need to be combined etc... Here are the cases: I.i.u I.j.v leave alone, nonoverlapping I.i.u I.i.v combine: Iivu R.i-j.u R.x-y.v | i-j in x-y delete first R R.i-j.u R.i-j.v delete first R R.i-j.u R.x-y.v | x-y in i-j ERROR R.i-j.u R.x-y.v | boundaries overlap ERROR Delete special case of replace (text==null): D.i-j.u D.x-y.v | boundaries overlap combine to max(min)..max(right) I.i.u R.x-y.v | i in (x+1)-y delete I (since insert before we're not deleting i) I.i.u R.x-y.v | i not in (x+1)-y leave alone, nonoverlapping R.x-y.v I.i.u | i in x-y ERROR R.x-y.v I.x.u R.x-y.uv (combine, delete I) R.x-y.v I.i.u | i not in x-y leave alone, nonoverlapping I.i.u = insert u before op @ index i R.x-y.u = replace x-y indexed tokens with u First we need to examine replaces. For any replace op: 1. wipe out any insertions before op within that range. 2. Drop any replace op before that is contained completely within that range. 3. Throw exception upon boundary overlap with any previous replace. Then we can deal with inserts: 1. for any inserts to same index, combine even if not adjacent. 2. for any prior replace with same left boundary, combine this insert with replace and delete this replace. 3. throw exception if index in same range as previous replace Don't actually delete; make op null in list. Easier to walk list. Later we can throw as we add to index → op map. Note that I.2 R.2-2 will wipe out I.2 even though, technically, the inserted stuff would be before the replace range. But, if you add tokens in front of a method body '{' and then delete the method body, I think the stuff before the '{' you added should disappear too. Return a map from token index to operation.