CharStream.h

/*
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 *
 * This file is derived from the file "scanner.h", which was part of the
 * V8 project. The original copyright header follows:
 *
 * Copyright 2006-2012, the V8 project authors. All rights reserved.
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*/
/**
 * Character stream / input file.
 */

#pragma once

#include <cstdint>
#include <string>
#include <tuple>
#include <utility>

namespace solidity::langutil
{

struct SourceLocation;

/**
 * Bidirectional stream of characters.
 *
 * This CharStream is used by lexical analyzers as the source.
 */
class CharStream
{
public:
	CharStream() = default;
	CharStream(std::string _source, std::string _name):
		m_source(std::move(_source)), m_name(std::move(_name)) {}

	size_t position() const { return m_position; }
	bool isPastEndOfInput(size_t _charsForward = 0) const { return (m_position + _charsForward) >= m_source.size(); }

	char get(size_t _charsForward = 0) const { return m_source[m_position + _charsForward]; }
	char advanceAndGet(size_t _chars = 1);
	/// Sets scanner position to @ _amount characters backwards in source text.
	/// @returns The character of the current location after update is returned.
	char rollback(size_t _amount);
	/// Sets scanner position to @ _location if it refers a valid offset in m_source.
	/// If not, nothing is done.
	/// @returns The character of the current location after update is returned.
	char setPosition(size_t _location);

	void reset() { m_position = 0; }

	std::string const& source() const noexcept { return m_source; }
	std::string const& name() const noexcept { return m_name; }

	size_t size() const { return m_source.size(); }

	///@{
	///@name Error printing helper functions
	/// Functions that help pretty-printing parse errors
	/// Do only use in error cases, they are quite expensive.
	std::string lineAtPosition(int _position) const;
	std::tuple<int, int> translatePositionToLineColumn(int _position) const;
	///@}

	/// Tests whether or not given octet sequence is present at the current position in stream.
	/// @returns true if the sequence could be found, false otherwise.
	bool prefixMatch(std::string_view _sequence)
	{
		if (isPastEndOfInput(_sequence.size()))
			return false;

		for (size_t i = 0; i < _sequence.size(); ++i)
			if (_sequence[i] != get(i))
				return false;

		return true;
	}

	/// @returns the substring of the source that the source location references.
	/// Returns an empty string view if the source location does not `hasText()`.
	std::string_view text(SourceLocation const& _location) const;

	/// @returns the first line of the referenced source fragment. If the fragment is longer than
	/// one line, appends an ellipsis to indicate that.
	std::string singleLineSnippet(SourceLocation const& _location) const
	{
		return singleLineSnippet(m_source, _location);
	}

	static std::string singleLineSnippet(std::string const& _sourceCode, SourceLocation const& _location);

private:
	std::string m_source;
	std::string m_name;
	size_t m_position{0};
};

}