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/* 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.
*/
#pragma once
#include "antlr4-common.h"
namespace antlr4 {
/// <summary>
/// A simple stream of symbols whose values are represented as integers. This
/// interface provides <em>marked ranges</em> with support for a minimum level
/// of buffering necessary to implement arbitrary lookahead during prediction.
/// For more information on marked ranges, see <seealso cref="#mark"/>.
/// <p/>
/// <strong>Initializing Methods:</strong> Some methods in this interface have
/// unspecified behavior if no call to an initializing method has occurred after
/// the stream was constructed. The following is a list of initializing methods:
///
/// <ul>
/// <li><seealso cref="#LA"/></li>
/// <li><seealso cref="#consume"/></li>
/// <li><seealso cref="#size"/></li>
/// </ul>
/// </summary>
class ANTLR4CPP_PUBLIC IntStream {
public:
static constexpr size_t EOF = std::numeric_limits<size_t>::max();
/// The value returned by <seealso cref="#LA LA()"/> when the end of the stream is
/// reached.
/// No explicit EOF definition. We got EOF on all platforms.
//static const size_t _EOF = std::ios::eofbit;
/// <summary>
/// The value returned by <seealso cref="#getSourceName"/> when the actual name of the
/// underlying source is not known.
/// </summary>
static const std::string UNKNOWN_SOURCE_NAME;
virtual ~IntStream();
/// <summary>
/// Consumes the current symbol in the stream. This method has the following
/// effects:
///
/// <ul>
/// <li><strong>Forward movement:</strong> The value of <seealso cref="#index index()"/>
/// before calling this method is less than the value of {@code index()}
/// after calling this method.</li>
/// <li><strong>Ordered lookahead:</strong> The value of {@code LA(1)} before
/// calling this method becomes the value of {@code LA(-1)} after calling
/// this method.</li>
/// </ul>
///
/// Note that calling this method does not guarantee that {@code index()} is
/// incremented by exactly 1, as that would preclude the ability to implement
/// filtering streams (e.g. <seealso cref="CommonTokenStream"/> which distinguishes
/// between "on-channel" and "off-channel" tokens).
/// </summary>
/// <exception cref="IllegalStateException"> if an attempt is made to consume the the
/// end of the stream (i.e. if {@code LA(1)==}<seealso cref="#EOF EOF"/> before calling
/// {@code consume}). </exception>
virtual void consume() = 0;
/// <summary>
/// Gets the value of the symbol at offset {@code i} from the current
/// position. When {@code i==1}, this method returns the value of the current
/// symbol in the stream (which is the next symbol to be consumed). When
/// {@code i==-1}, this method returns the value of the previously read
/// symbol in the stream. It is not valid to call this method with
/// {@code i==0}, but the specific behavior is unspecified because this
/// method is frequently called from performance-critical code.
/// <p/>
/// This method is guaranteed to succeed if any of the following are true:
///
/// <ul>
/// <li>{@code i>0}</li>
/// <li>{@code i==-1} and <seealso cref="#index index()"/> returns a value greater
/// than the value of {@code index()} after the stream was constructed
/// and {@code LA(1)} was called in that order. Specifying the current
/// {@code index()} relative to the index after the stream was created
/// allows for filtering implementations that do not return every symbol
/// from the underlying source. Specifying the call to {@code LA(1)}
/// allows for lazily initialized streams.</li>
/// <li>{@code LA(i)} refers to a symbol consumed within a marked region
/// that has not yet been released.</li>
/// </ul>
///
/// If {@code i} represents a position at or beyond the end of the stream,
/// this method returns <seealso cref="#EOF"/>.
/// <p/>
/// The return value is unspecified if {@code i<0} and fewer than {@code -i}
/// calls to <seealso cref="#consume consume()"/> have occurred from the beginning of
/// the stream before calling this method.
/// </summary>
/// <exception cref="UnsupportedOperationException"> if the stream does not support
/// retrieving the value of the specified symbol </exception>
virtual size_t LA(ssize_t i) = 0;
/// <summary>
/// A mark provides a guarantee that <seealso cref="#seek seek()"/> operations will be
/// valid over a "marked range" extending from the index where {@code mark()}
/// was called to the current <seealso cref="#index index()"/>. This allows the use of
/// streaming input sources by specifying the minimum buffering requirements
/// to support arbitrary lookahead during prediction.
/// <p/>
/// The returned mark is an opaque handle (type {@code int}) which is passed
/// to <seealso cref="#release release()"/> when the guarantees provided by the marked
/// range are no longer necessary. When calls to
/// {@code mark()}/{@code release()} are nested, the marks must be released
/// in reverse order of which they were obtained. Since marked regions are
/// used during performance-critical sections of prediction, the specific
/// behavior of invalid usage is unspecified (i.e. a mark is not released, or
/// a mark is released twice, or marks are not released in reverse order from
/// which they were created).
/// <p/>
/// The behavior of this method is unspecified if no call to an
/// <seealso cref="IntStream initializing method"/> has occurred after this stream was
/// constructed.
/// <p/>
/// This method does not change the current position in the input stream.
/// <p/>
/// The following example shows the use of <seealso cref="#mark mark()"/>,
/// <seealso cref="#release release(mark)"/>, <seealso cref="#index index()"/>, and
/// <seealso cref="#seek seek(index)"/> as part of an operation to safely work within a
/// marked region, then restore the stream position to its original value and
/// release the mark.
/// <pre>
/// IntStream stream = ...;
/// int index = -1;
/// int mark = stream.mark();
/// try {
/// index = stream.index();
/// // perform work here...
/// } finally {
/// if (index != -1) {
/// stream.seek(index);
/// }
/// stream.release(mark);
/// }
/// </pre>
/// </summary>
/// <returns> An opaque marker which should be passed to
/// <seealso cref="#release release()"/> when the marked range is no longer required. </returns>
virtual ssize_t mark() = 0;
/// <summary>
/// This method releases a marked range created by a call to
/// <seealso cref="#mark mark()"/>. Calls to {@code release()} must appear in the
/// reverse order of the corresponding calls to {@code mark()}. If a mark is
/// released twice, or if marks are not released in reverse order of the
/// corresponding calls to {@code mark()}, the behavior is unspecified.
/// <p/>
/// For more information and an example, see <seealso cref="#mark"/>.
/// </summary>
/// <param name="marker"> A marker returned by a call to {@code mark()}. </param>
/// <seealso cref= #mark </seealso>
virtual void release(ssize_t marker) = 0;
/// <summary>
/// Return the index into the stream of the input symbol referred to by
/// {@code LA(1)}.
/// <p/>
/// The behavior of this method is unspecified if no call to an
/// <seealso cref="IntStream initializing method"/> has occurred after this stream was
/// constructed.
/// </summary>
virtual size_t index() = 0;
/// <summary>
/// Set the input cursor to the position indicated by {@code index}. If the
/// specified index lies past the end of the stream, the operation behaves as
/// though {@code index} was the index of the EOF symbol. After this method
/// returns without throwing an exception, the at least one of the following
/// will be true.
///
/// <ul>
/// <li><seealso cref="#index index()"/> will return the index of the first symbol
/// appearing at or after the specified {@code index}. Specifically,
/// implementations which filter their sources should automatically
/// adjust {@code index} forward the minimum amount required for the
/// operation to target a non-ignored symbol.</li>
/// <li>{@code LA(1)} returns <seealso cref="#EOF"/></li>
/// </ul>
///
/// This operation is guaranteed to not throw an exception if {@code index}
/// lies within a marked region. For more information on marked regions, see
/// <seealso cref="#mark"/>. The behavior of this method is unspecified if no call to
/// an <seealso cref="IntStream initializing method"/> has occurred after this stream
/// was constructed.
/// </summary>
/// <param name="index"> The absolute index to seek to.
/// </param>
/// <exception cref="IllegalArgumentException"> if {@code index} is less than 0 </exception>
/// <exception cref="UnsupportedOperationException"> if the stream does not support
/// seeking to the specified index </exception>
virtual void seek(size_t index) = 0;
/// <summary>
/// Returns the total number of symbols in the stream, including a single EOF
/// symbol.
/// </summary>
/// <exception cref="UnsupportedOperationException"> if the size of the stream is
/// unknown. </exception>
virtual size_t size() = 0;
/// <summary>
/// Gets the name of the underlying symbol source. This method returns a
/// non-null, non-empty string. If such a name is not known, this method
/// returns <seealso cref="#UNKNOWN_SOURCE_NAME"/>.
/// </summary>
virtual std::string getSourceName() const = 0;
};
} // namespace antlr4
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