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With inspiration from other libraries
/*
* Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
* Use of this file is governed by the BSD 3-clause license that
* can be found in the LICENSE.txt file in the project root.
*/
package org.antlr.v4.runtime;
import org.antlr.v4.runtime.misc.Interval;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
/**
* This implementation of {@link TokenStream} loads tokens from a
* {@link TokenSource} on-demand, and places the tokens in a buffer to provide
* access to any previous token by index.
*
*
* This token stream ignores the value of {@link Token#getChannel}. If your
* parser requires the token stream filter tokens to only those on a particular
* channel, such as {@link Token#DEFAULT_CHANNEL} or
* {@link Token#HIDDEN_CHANNEL}, use a filtering token stream such a
* {@link CommonTokenStream}.
*/
public class BufferedTokenStream implements TokenStream {
/**
* The {@link TokenSource} from which tokens for this stream are fetched.
*/
protected TokenSource tokenSource;
/**
* A collection of all tokens fetched from the token source. The list is
* considered a complete view of the input once {@link #fetchedEOF} is set
* to {@code true}.
*/
protected List tokens = new ArrayList(100);
/**
* The index into {@link #tokens} of the current token (next token to
* {@link #consume}). {@link #tokens}{@code [}{@link #p}{@code ]} should be
* {@link #LT LT(1)}.
*
* This field is set to -1 when the stream is first constructed or when
* {@link #setTokenSource} is called, indicating that the first token has
* not yet been fetched from the token source. For additional information,
* see the documentation of {@link IntStream} for a description of
* Initializing Methods.
*/
protected int p = -1;
/**
* Indicates whether the {@link Token#EOF} token has been fetched from
* {@link #tokenSource} and added to {@link #tokens}. This field improves
* performance for the following cases:
*
*
* - {@link #consume}: The lookahead check in {@link #consume} to prevent
* consuming the EOF symbol is optimized by checking the values of
* {@link #fetchedEOF} and {@link #p} instead of calling {@link #LA}.
* - {@link #fetch}: The check to prevent adding multiple EOF symbols into
* {@link #tokens} is trivial with this field.
*
*/
protected boolean fetchedEOF;
public BufferedTokenStream(TokenSource tokenSource) {
if (tokenSource == null) {
throw new NullPointerException("tokenSource cannot be null");
}
this.tokenSource = tokenSource;
}
@Override
public TokenSource getTokenSource() { return tokenSource; }
@Override
public int index() { return p; }
@Override
public int mark() {
return 0;
}
@Override
public void release(int marker) {
// no resources to release
}
/**
* This method resets the token stream back to the first token in the
* buffer. It is equivalent to calling {@link #seek}{@code (0)}.
*
* @see #setTokenSource(TokenSource)
* @deprecated Use {@code seek(0)} instead.
*/
@Deprecated
public void reset() {
seek(0);
}
@Override
public void seek(int index) {
lazyInit();
p = adjustSeekIndex(index);
}
@Override
public int size() { return tokens.size(); }
@Override
public void consume() {
boolean skipEofCheck;
if (p >= 0) {
if (fetchedEOF) {
// the last token in tokens is EOF. skip check if p indexes any
// fetched token except the last.
skipEofCheck = p < tokens.size() - 1;
}
else {
// no EOF token in tokens. skip check if p indexes a fetched token.
skipEofCheck = p < tokens.size();
}
}
else {
// not yet initialized
skipEofCheck = false;
}
if (!skipEofCheck && LA(1) == EOF) {
throw new IllegalStateException("cannot consume EOF");
}
if (sync(p + 1)) {
p = adjustSeekIndex(p + 1);
}
}
/** Make sure index {@code i} in tokens has a token.
*
* @return {@code true} if a token is located at index {@code i}, otherwise
* {@code false}.
* @see #get(int i)
*/
protected boolean sync(int i) {
assert i >= 0;
int n = i - tokens.size() + 1; // how many more elements we need?
//System.out.println("sync("+i+") needs "+n);
if ( n > 0 ) {
int fetched = fetch(n);
return fetched >= n;
}
return true;
}
/** Add {@code n} elements to buffer.
*
* @return The actual number of elements added to the buffer.
*/
protected int fetch(int n) {
if (fetchedEOF) {
return 0;
}
for (int i = 0; i < n; i++) {
Token t = tokenSource.nextToken();
if ( t instanceof WritableToken ) {
((WritableToken)t).setTokenIndex(tokens.size());
}
tokens.add(t);
if ( t.getType()==Token.EOF ) {
fetchedEOF = true;
return i + 1;
}
}
return n;
}
@Override
public Token get(int i) {
if ( i < 0 || i >= tokens.size() ) {
throw new IndexOutOfBoundsException("token index "+i+" out of range 0.."+(tokens.size()-1));
}
return tokens.get(i);
}
/** Get all tokens from start..stop inclusively */
public List get(int start, int stop) {
if ( start<0 || stop<0 ) return null;
lazyInit();
List subset = new ArrayList();
if ( stop>=tokens.size() ) stop = tokens.size()-1;
for (int i = start; i <= stop; i++) {
Token t = tokens.get(i);
if ( t.getType()==Token.EOF ) break;
subset.add(t);
}
return subset;
}
@Override
public int LA(int i) { return LT(i).getType(); }
protected Token LB(int k) {
if ( (p-k)<0 ) return null;
return tokens.get(p-k);
}
@Override
public Token LT(int k) {
lazyInit();
if ( k==0 ) return null;
if ( k < 0 ) return LB(-k);
int i = p + k - 1;
sync(i);
if ( i >= tokens.size() ) { // return EOF token
// EOF must be last token
return tokens.get(tokens.size()-1);
}
// if ( i>range ) range = i;
return tokens.get(i);
}
/**
* Allowed derived classes to modify the behavior of operations which change
* the current stream position by adjusting the target token index of a seek
* operation. The default implementation simply returns {@code i}. If an
* exception is thrown in this method, the current stream index should not be
* changed.
*
* For example, {@link CommonTokenStream} overrides this method to ensure that
* the seek target is always an on-channel token.
*
* @param i The target token index.
* @return The adjusted target token index.
*/
protected int adjustSeekIndex(int i) {
return i;
}
protected final void lazyInit() {
if (p == -1) {
setup();
}
}
protected void setup() {
sync(0);
p = adjustSeekIndex(0);
}
/** Reset this token stream by setting its token source. */
public void setTokenSource(TokenSource tokenSource) {
this.tokenSource = tokenSource;
tokens.clear();
p = -1;
fetchedEOF = false;
}
public List getTokens() { return tokens; }
public List getTokens(int start, int stop) {
return getTokens(start, stop, null);
}
/** Given a start and stop index, return a List of all tokens in
* the token type BitSet. Return null if no tokens were found. This
* method looks at both on and off channel tokens.
*/
public List getTokens(int start, int stop, Set types) {
lazyInit();
if ( start<0 || stop>=tokens.size() ||
stop<0 || start>=tokens.size() )
{
throw new IndexOutOfBoundsException("start "+start+" or stop "+stop+
" not in 0.."+(tokens.size()-1));
}
if ( start>stop ) return null;
// list = tokens[start:stop]:{T t, t.getType() in types}
List filteredTokens = new ArrayList();
for (int i=start; i<=stop; i++) {
Token t = tokens.get(i);
if ( types==null || types.contains(t.getType()) ) {
filteredTokens.add(t);
}
}
if ( filteredTokens.isEmpty() ) {
filteredTokens = null;
}
return filteredTokens;
}
public List getTokens(int start, int stop, int ttype) {
HashSet s = new HashSet(ttype);
s.add(ttype);
return getTokens(start,stop, s);
}
/**
* Given a starting index, return the index of the next token on channel.
* Return {@code i} if {@code tokens[i]} is on channel. Return the index of
* the EOF token if there are no tokens on channel between {@code i} and
* EOF.
*/
protected int nextTokenOnChannel(int i, int channel) {
sync(i);
if (i >= size()) {
return size() - 1;
}
Token token = tokens.get(i);
while ( token.getChannel()!=channel ) {
if ( token.getType()==Token.EOF ) {
return i;
}
i++;
sync(i);
token = tokens.get(i);
}
return i;
}
/**
* Given a starting index, return the index of the previous token on
* channel. Return {@code i} if {@code tokens[i]} is on channel. Return -1
* if there are no tokens on channel between {@code i} and 0.
*
*
* If {@code i} specifies an index at or after the EOF token, the EOF token
* index is returned. This is due to the fact that the EOF token is treated
* as though it were on every channel.
*/
protected int previousTokenOnChannel(int i, int channel) {
sync(i);
if (i >= size()) {
// the EOF token is on every channel
return size() - 1;
}
while (i >= 0) {
Token token = tokens.get(i);
if (token.getType() == Token.EOF || token.getChannel() == channel) {
return i;
}
i--;
}
return i;
}
/** Collect all tokens on specified channel to the right of
* the current token up until we see a token on DEFAULT_TOKEN_CHANNEL or
* EOF. If channel is -1, find any non default channel token.
*/
public List getHiddenTokensToRight(int tokenIndex, int channel) {
lazyInit();
if ( tokenIndex<0 || tokenIndex>=tokens.size() ) {
throw new IndexOutOfBoundsException(tokenIndex+" not in 0.."+(tokens.size()-1));
}
int nextOnChannel =
nextTokenOnChannel(tokenIndex + 1, Lexer.DEFAULT_TOKEN_CHANNEL);
int to;
int from = tokenIndex+1;
// if none onchannel to right, nextOnChannel=-1 so set to = last token
if ( nextOnChannel == -1 ) to = size()-1;
else to = nextOnChannel;
return filterForChannel(from, to, channel);
}
/** Collect all hidden tokens (any off-default channel) to the right of
* the current token up until we see a token on DEFAULT_TOKEN_CHANNEL
* or EOF.
*/
public List getHiddenTokensToRight(int tokenIndex) {
return getHiddenTokensToRight(tokenIndex, -1);
}
/** Collect all tokens on specified channel to the left of
* the current token up until we see a token on DEFAULT_TOKEN_CHANNEL.
* If channel is -1, find any non default channel token.
*/
public List getHiddenTokensToLeft(int tokenIndex, int channel) {
lazyInit();
if ( tokenIndex<0 || tokenIndex>=tokens.size() ) {
throw new IndexOutOfBoundsException(tokenIndex+" not in 0.."+(tokens.size()-1));
}
if (tokenIndex == 0) {
// obviously no tokens can appear before the first token
return null;
}
int prevOnChannel =
previousTokenOnChannel(tokenIndex - 1, Lexer.DEFAULT_TOKEN_CHANNEL);
if ( prevOnChannel == tokenIndex - 1 ) return null;
// if none onchannel to left, prevOnChannel=-1 then from=0
int from = prevOnChannel+1;
int to = tokenIndex-1;
return filterForChannel(from, to, channel);
}
/** Collect all hidden tokens (any off-default channel) to the left of
* the current token up until we see a token on DEFAULT_TOKEN_CHANNEL.
*/
public List getHiddenTokensToLeft(int tokenIndex) {
return getHiddenTokensToLeft(tokenIndex, -1);
}
protected List filterForChannel(int from, int to, int channel) {
List hidden = new ArrayList();
for (int i=from; i<=to; i++) {
Token t = tokens.get(i);
if ( channel==-1 ) {
if ( t.getChannel()!= Lexer.DEFAULT_TOKEN_CHANNEL ) hidden.add(t);
}
else {
if ( t.getChannel()==channel ) hidden.add(t);
}
}
if ( hidden.size()==0 ) return null;
return hidden;
}
@Override
public String getSourceName() { return tokenSource.getSourceName(); }
/** Get the text of all tokens in this buffer. */
@Override
public String getText() {
return getText(Interval.of(0,size()-1));
}
@Override
public String getText(Interval interval) {
int start = interval.a;
int stop = interval.b;
if ( start<0 || stop<0 ) return "";
fill();
if ( stop>=tokens.size() ) stop = tokens.size()-1;
StringBuilder buf = new StringBuilder();
for (int i = start; i <= stop; i++) {
Token t = tokens.get(i);
if ( t.getType()==Token.EOF ) break;
buf.append(t.getText());
}
return buf.toString();
}
@Override
public String getText(RuleContext ctx) {
return getText(ctx.getSourceInterval());
}
@Override
public String getText(Token start, Token stop) {
if ( start!=null && stop!=null ) {
return getText(Interval.of(start.getTokenIndex(), stop.getTokenIndex()));
}
return "";
}
/** Get all tokens from lexer until EOF */
public void fill() {
lazyInit();
final int blockSize = 1000;
while (true) {
int fetched = fetch(blockSize);
if (fetched < blockSize) {
return;
}
}
}
}