Only makes sense for streams that buffer everything up probably, but might be useful to display the entire stream or for testing. This value includes a single EOF.
Return the current input symbol index 0..n where n indicates the last symbol has been read. The index is the symbol about to be read not the most recently read symbol.
How far ahead has the stream been asked to look? The return value is a valid index from 0..n-1.
Where are you getting symbols from? Normally, implementations will pass the buck all the way to the lexer who can ask its input stream for the file name or whatever.
Where is this stream pulling tokens from? This is not the name, but the object that provides Token objects.
Get a token at an absolute index i; 0..n-1. This is really only needed for profiling and debugging and token stream rewriting. If you don't want to buffer up tokens, then this method makes no sense for you. Naturally you can't use the rewrite stream feature. I believe DebugTokenStream can easily be altered to not use this method, removing the dependency.
Get int at current input pointer + i ahead where i=1 is next int. Negative indexes are allowed. LA(-1) is previous token (token just matched). LA(-i) where i is before first token should yield -1, invalid char / EOF.
Get Token at current input pointer + i ahead where i=1 is next Token. i<0 indicates tokens in the past. So -1 is previous token and -2 is two tokens ago. LT(0) is undefined. For i>=n, return Token.EOFToken. Return null for LT(0) and any index that results in an absolute address that is negative.
Tell the stream to start buffering if it hasn't already. Return current input position, Index, or some other marker so that when passed to rewind() you get back to the same spot. rewind(mark()) should not affect the input cursor. The Lexer track line/col info as well as input index so its markers are not pure input indexes. Same for tree node streams.
You may want to commit to a backtrack but don't want to force the stream to keep bookkeeping objects around for a marker that is no longer necessary. This will have the same behavior as rewind() except it releases resources without the backward seek. This must throw away resources for all markers back to the marker argument. So if you're nested 5 levels of mark(), and then release(2) you have to release resources for depths 2..5.
Reset the stream so that next call to index would return marker. The marker will usually be Index but it doesn't have to be. It's just a marker to indicate what state the stream was in. This is essentially calling release() and seek(). If there are markers created after this marker argument, this routine must unroll them like a stack. Assume the state the stream was in when this marker was created.
Set the input cursor to the position indicated by index. This is normally used to seek ahead in the input stream. No buffering is required to do this unless you know your stream will use seek to move backwards such as when backtracking.
This is different from rewind in its multi-directional requirement and in that its argument is strictly an input cursor (index).
For char streams, seeking forward must update the stream state such as line number. For seeking backwards, you will be presumably backtracking using the mark/rewind mechanism that restores state and so this method does not need to update state when seeking backwards.
Currently, this method is only used for efficient backtracking using memoization, but in the future it may be used for incremental parsing.
The index is 0..n-1. A seek to position i means that LA(1) will return the ith symbol. So, seeking to 0 means LA(1) will return the first element in the stream.
Return the text of all tokens from start to stop, inclusive. If the stream does not buffer all the tokens then it can just return "" or null; Users should not access $ruleLabel.text in an action of course in that case.
Because the user is not required to use a token with an index stored in it, we must provide a means for two token objects themselves to indicate the start/end location. Most often this will just delegate to the other toString(int,int). This is also parallel with the TreeNodeStream.toString(Object,Object).
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A simple stream of integers used when all I care about is the char or token type sequence (such as interpretation).