moved to CharReader everywhere

1 files changed, 665 insertions, 0 deletions

diff --git a/src/core/common/CharReader.hpp b/src/core/common/CharReader.hpp
new file mode 100644
index 0000000..3cbe4b4
--- /dev/null
+++ b/src/core/common/CharReader.hpp
@@ -0,0 +1,665 @@
+/*
+    Ousía
+    Copyright (C) 2014  Benjamin Paaßen, Andreas Stöckel
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+/**
+ * @file CharReader.hpp
+ *
+ * Used within all parsers to read single characters from an underlying stream.
+ *
+ * @author Andreas Stöckel (astoecke@techfak.uni-bielefeld.de)
+ */
+
+#ifndef _OUSIA_CHAR_READER_HPP_
+#define _OUSIA_CHAR_READER_HPP_
+
+#include <istream>
+#include <list>
+#include <memory>
+#include <vector>
+
+namespace ousia {
+
+/**
+ * A chunked ring buffer used in CharReader to provide access to an input stream
+ * with multiple read cursors. The Buffer automatically expands to the
+ * size of the spanned by the read cursors while reusing already allocated
+ * memory.
+ */
+class Buffer {
+public:
+	/**
+	 * Callback function which is called whenever new data is requested from the
+	 * input stream.
+	 *
+	 * @param buf is points a the target memory region.
+	 * @param size is the requested number of bytes.
+	 * @param userData is a pointer at some user defined data given in the
+	 * constructor.
+	 * @return the actual number of bytes read. If the result is smaller than
+	 * the requested size, this tells the Buffer that the end of the input
+	 * stream is reached.
+	 */
+	using ReadCallback = size_t (*)(char *buf, size_t size, void *userData);
+
+	/**
+	 * Handle used to identify a cursor.
+	 */
+	using CursorId = size_t;
+
+private:
+	/**
+	 * Number of bytes to request from the input stream. Set to 64 KiB because
+	 * this seems to be a nice value for I/O operations according to multiple
+	 * sources.
+	 */
+	static constexpr size_t REQUEST_SIZE = 64 * 1024;
+
+	/**
+	 * Number of bytes the buffer guarantees to be capable of looking back
+	 * for extracting the current context.
+	 */
+	static constexpr size_t LOOKBACK_SIZE = 128;
+
+	/**
+	 * Type used internally to represent one chunk of memory.
+	 */
+	using Bucket = std::vector<char>;
+
+	/**
+	 * Type used internally to represent a bucket container.
+	 */
+	using BucketList = std::list<Bucket>;
+
+	/**
+	 * Type used internally for representing iterators in the bucket list.
+	 */
+	using BucketIterator = BucketList::iterator;
+
+	/**
+	 * Type used internally to represent a read cursor.
+	 */
+	struct Cursor {
+		/**
+		 * Iterator pointing at the current bucket.
+		 */
+		BucketIterator bucket;
+
+		/**
+		 * Index of the bucket relative to the start bucket.
+		 */
+		size_t bucketIdx;
+
+		/**
+		 * Current offset within that bucket.
+		 */
+		size_t bucketOffs;
+	};
+
+	/**
+	 * List of buckets containing the buffered memory.
+	 */
+	BucketList buckets;
+
+	/**
+	 * List of cursors used to access the memory. Note that cursors can be
+	 * marked as inactive and reused lateron (to avoid having to resize the
+	 * vector).
+	 */
+	std::vector<Cursor> cursors;
+
+	/**
+	 * Bitfield specifying which of the cursors is actually valid.
+	 */
+	std::vector<bool> alive;
+
+	/**
+	 * Function to be called whenever new data is needed. Set to nullptr if the
+	 * Buffer is not backed by an input stream.
+	 */
+	const ReadCallback callback;
+
+	/**
+	 * User data given in the constructor.
+	 */
+	void *userData;
+
+	/**
+	 * Set to true if the input stream is at its end.
+	 */
+	bool reachedEnd;
+
+	/**
+	 * Iterator pointing at the current start bucket.
+	 */
+	BucketIterator startBucket;
+
+	/**
+	 * Iterator pointing at the last bucket.
+	 */
+	BucketIterator endBucket;
+
+	/**
+	 * Byte offset of the start bucket relative to the beginning of the stream.
+	 */
+	size_t startOffset;
+
+	/**
+	 * Points at the smallest possible available cursor index, yet does not
+	 * guarantee that this cursor index actuall is free.
+	 */
+	CursorId firstDead;
+
+	/**
+	 * Advances the bucket iterator, cares about wrapping around in the ring.
+	 */
+	void advance(BucketIterator &it);
+
+	/**
+	 * Advances the bucket iterator, cares about wrapping around in the ring.
+	 */
+	void advance(BucketList::const_iterator &it) const;
+
+	/**
+	 * Internally used to find the next free cursor in the cursors vector. The
+	 * cursor is marked as active.
+	 *
+	 * @return the next free cursor index.
+	 */
+	CursorId nextCursor();
+
+	/**
+	 * Returns a reference at the next bucket into which data should be
+	 * inserted.
+	 *
+	 * @return a bucket into which the data can be inserted.
+	 */
+	Bucket &nextBucket();
+
+	/**
+	 * Reads data from the input stream and places it in the next free buffer.
+	 */
+	void stream();
+
+	/**
+	 * Moves the given cursor forward.
+	 */
+	size_t moveForward(CursorId cursor, size_t relativeOffs);
+
+	/**
+	 * Moves the given cursor backward.
+	 */
+	size_t moveBackward(CursorId cursor, size_t relativeOffs);
+
+	/**
+	 * Reads a character from the current cursor position and optionally
+	 * advances.
+	 */
+	bool fetchCharacter(CursorId cursor, char &c, bool incr);
+
+public:
+	/**
+	 * Intializes the Buffer with a reference to a ReadCallback that is used
+	 * to fetch data from an underlying input stream.
+	 *
+	 * @param callback is the function that will be called whenever data is read
+	 * from the ring buffer and the buffer does not hold enough data to fulfill
+	 * this read request.
+	 * @param userData is a pointer to user defined data which will be passed to
+	 * the callback function.
+	 */
+	Buffer(ReadCallback callback, void *userData);
+
+	/**
+	 * Initializes the Buffer with a reference to an std::istream from which
+	 * data will be read.
+	 *
+	 * @param istream is the input stream from which the data should be read.
+	 */
+	Buffer(std::istream &istream);
+
+	/**
+	 * Initializes the Buffer with the contents of the given string, after
+	 * this operation the Buffer has a fixed size.
+	 *
+	 * @param str is the string containing the data that should be copied into
+	 * the ring buffer.
+	 */
+	Buffer(const std::string &str);
+
+#ifndef NDEBUG
+	/**
+	 * Destructor of the Buffer class. Makes sure that all cursors have been
+	 * freed.
+	 */
+	~Buffer();
+#endif
+
+	// No copy
+	Buffer(const Buffer &) = delete;
+
+	// No assign
+	Buffer &operator=(const Buffer &) = delete;
+
+	/**
+	 * Creates a new read cursor positioned at the smallest possible position
+	 * in the ring buffer.
+	 */
+	CursorId createCursor();
+
+	/**
+	 * Creates a new read cursor positioned at the same position as the given
+	 * read cursor.
+	 *
+	 * @param ref is the read cursor that should be used as reference for the
+	 * new read cursor.
+	 */
+	CursorId createCursor(CursorId ref);
+
+	/**
+	 * Copies the position of one cursor to another cursor.
+	 *
+	 * @param from is the cursor id of which the position should be copied.
+	 * @param to is the cursor id to which the position should be copied.
+	 */
+	void copyCursor(CursorId from, CursorId to);
+
+	/**
+	 * Deletes the cursor with the given id. The cursor may no longer be used
+	 * after this function has been called.
+	 *
+	 * @param cursor is the id of the cursor that should be freed.
+	 */
+	void deleteCursor(CursorId cursor);
+
+	/**
+	 * Moves a cursor by offs bytes. Note that moving backwards is theoretically
+	 * limited by the LOOKBACK_SIZE of the Buffer, practically it will most
+	 * likely be limited by the REQUEST_SIZE, so you can got at most 64 KiB
+	 * backwards.
+	 *
+	 * @param cursor is the cursor that should be moved.
+	 * @param relativeOffs is a positive or negative integer number specifying
+	 * the number of bytes the cursor should be moved forward (positive numbers)
+	 * or backwards (negative numbers).
+	 * @return the actual number of bytes the cursor was moved. This number is
+	 * smaller than the relativeOffs given in the constructor if the
+	 */
+	ssize_t moveCursor(CursorId cursor, ssize_t relativeOffs);
+
+	/**
+	 * Returns the current byte offset of the given cursor relative to the
+	 * beginning of the stream.
+	 *
+	 * @param cursor is the cursor for which the byte offset relative to the
+	 * beginning of the stream should be returned.
+	 * @return the number of bytes since the beginning of the stream for the
+	 * given cursor.
+	 */
+	size_t offset(CursorId cursor) const;
+
+	/**
+	 * Returns true if the given cursor currently is at the end of the stream.
+	 *
+	 * @param cursor is the cursor for which the atEnd flag should be returned.
+	 * @return true if the there are no more bytes for this cursor. If false
+	 * is returned, this means that there may be more bytes in the stream,
+	 * nevertheless the end of the stream may be hit once the next read function
+	 * is called.
+	 */
+	bool atEnd(CursorId cursor) const;
+
+	/**
+	 * Reads a single character from the ring buffer from the given cursor and
+	 * moves to the next character.
+	 *
+	 * @param cursor specifies the cursor from which the data should be read.
+	 * The cursor will be advanced by one byte.
+	 * @param c is the character into which the data needs to be read.
+	 * @return true if a character was read, false if the end of the stream has
+	 * been reached.
+	 */
+	bool read(CursorId cursor, char &c);
+
+	/**
+	 * Returns a single character from the ring buffer from the current cursor
+	 * position and stays at that position.
+	 *
+	 * @param cursor specifies the cursor from which the data should be read.
+	 * The cursor will be advanced by one byte.
+	 * @param c is the character into which the data needs to be read.
+	 * @return true if a character could be fetched, false if the end of the
+	 * stream has been reached.
+	 */
+	bool fetch(CursorId cursor, char &c);
+};
+
+// Forward declaration
+class CharReaderFork;
+
+/**
+ * Used within parsers for convenient access to single characters in an input
+ * stream or buffer. It allows reading and peeking single characters from a
+ * buffer. Additionally it counts the current column/row (with correct handling
+ * for UTF-8) and contains an internal state machine that handles the detection
+ * of linebreaks and converts these to a single '\n'.
+ */
+class CharReader {
+public:
+	/**
+	 * The context struct is used to represent the current context the char
+	 * reader is in. This context can for example be used when building error
+	 * messages.
+	 */
+	struct Context {
+		/**
+		 * Set to the content of the current line.
+		 */
+		std::string line;
+
+		/**
+		 * Relative position (in characters) within that line.
+		 */
+		size_t relPos;
+
+		/**
+		 * Set to true if the beginning of the line has been truncated (because
+		 * the reader position is too far away from the actual position of the
+		 * line).
+		 */
+		bool truncatedStart;
+
+		/**
+		 * Set to true if the end of the line has been truncated (because the
+		 * reader position is too far away from the actual end position of the
+		 * line.
+		 */
+		bool truncatedEnd;
+
+		Context()
+		    : line(), relPos(0), truncatedStart(false), truncatedEnd(false)
+		{
+		}
+
+		Context(std::string line, size_t relPos, bool truncatedStart,
+		        bool truncatedEnd)
+		    : line(std::move(line)),
+		      relPos(relPos),
+		      truncatedStart(truncatedStart),
+		      truncatedEnd(truncatedEnd)
+		{
+		}
+	};
+
+protected:
+	/**
+	 * Internally used cursor structure for managing the read and the peek
+	 * cursor.
+	 */
+	struct Cursor {
+		/**
+		 * Corresponding cursor in the underlying buffer instance.
+		 */
+		const Buffer::CursorId cursor;
+
+		/**
+		 * Current line the cursor is in.
+		 */
+		uint32_t line;
+
+		/**
+		 * Current column the cursor is in.
+		 */
+		uint32_t column;
+
+		/**
+		 * Constructor of the Cursor class.
+		 *
+		 * @param cursor is the underlying cursor in the Buffer instance.
+		 */
+		Cursor(Buffer::CursorId cursor, size_t line, size_t column)
+		    : cursor(cursor), line(line), column(column)
+		{
+		}
+
+		/**
+		 * Assigns one cursor to another.
+		 *
+		 * @param buffer is the underlying buffer instance the internal cursor
+		 * belongs to.
+		 * @param cursor is the cursor from which the state should be copied.
+		 */
+		void assign(std::shared_ptr<Buffer> buffer, Cursor &cursor);
+	};
+
+private:
+	/**
+	 * Substitutes "\r", "\n\r", "\r\n" with a single "\n".
+	 *
+	 * @param cursor is the cursor from which the character should be read.
+	 * @param c a reference to the character that should be written.
+	 * @return true if another character needs to be read.
+	 */
+	bool substituteLinebreaks(Cursor &cursor, char &c);
+
+	/**
+	 * Reads a single character from the given cursor.
+	 *
+	 * @param cursor is the cursor from which the character should be read.
+	 * @param c a reference to the character that should be written.
+	 * @return true if a character was read, false if the end of the stream has
+	 * been reached.
+	 */
+	bool readAtCursor(Cursor &cursor, char &c);
+
+protected:
+	/**
+	 * Reference pointing at the underlying buffer.
+	 */
+	std::shared_ptr<Buffer> buffer;
+
+	/**
+	 * Cursor used for reading.
+	 */
+	Cursor readCursor;
+
+	/**
+	 * Cursor used for peeking.
+	 */
+	Cursor peekCursor;
+
+	/**
+	 * Set to true as long the underlying Buffer cursor is at the same position
+	 * for the read and the peek cursor. This is only used for optimization
+	 * purposes and makes consecutive reads a bit faster.
+	 */
+	bool coherent;
+
+	/**
+	 * Protected constructor of the CharReader base class. Creates new read
+	 * and peek cursors for the given buffer.
+	 *
+	 * @param buffer is a reference to the underlying Buffer class responsible
+	 * for allowing to read from a single input stream from multiple locations.
+	 */
+	CharReader(std::shared_ptr<Buffer> buffer, size_t line, size_t column);
+
+public:
+	/**
+	 * Creates a new CharReader instance from a string.
+	 *
+	 * @param str is a string containing the input data.
+	 * @param line is the start line.
+	 * @param column is the start column.
+	 */
+	CharReader(const std::string &str, size_t line = 1, size_t column = 1);
+
+	/**
+	 * Creates a new CharReader instance for an input stream.
+	 *
+	 * @param istream is the input stream from which incomming data should be
+	 * read.
+	 * @param line is the start line.
+	 * @param column is the start column.
+	 */
+	CharReader(std::istream &istream, size_t line = 1, size_t column = 1);
+
+	/**
+	 * Deletes the used cursors from the underlying buffer instance.
+	 */
+	~CharReader();
+
+	// No copy
+	CharReader(const Buffer &) = delete;
+
+	// No assign
+	CharReader &operator=(const Buffer &) = delete;
+
+	/**
+	 * Peeks a single character. If called multiple times, returns the
+	 * character after the previously peeked character.
+	 *
+	 * @param c is a reference to the character to which the result should be
+	 * written.
+	 * @return true if the character was successfully read, false if there are
+	 * no more characters to be read in the buffer.
+	 */
+	bool peek(char &c);
+
+	/**
+	 * Reads a character from the input data. If "peek" was called
+	 * beforehand resets the peek pointer.
+	 *
+	 * @param c is a reference to the character to which the result should be
+	 * written.
+	 * @return true if the character was successfully read, false if there are
+	 * no more characters to be read in the buffer.
+	 */
+	bool read(char &c);
+
+	/**
+	 * Resets the peek pointer to the "read" pointer.
+	 */
+	void resetPeek();
+
+	/**
+	 * Advances the read pointer to the peek pointer -- so if the "peek"
+	 * function was called, "read" will now return the character after
+	 * the last peeked character.
+	 */
+	void consumePeek();
+
+	/**
+	 * Moves the read cursor to the next non-whitespace character. Returns
+	 * false, if the end of the stream was reached.
+	 *
+	 * @return false if the end of the stream was reached, false othrwise.
+	 */
+	bool consumeWhitespace();
+
+	/**
+	 * Creates a new CharReader located at the same position as this CharReader
+	 * instance, yet the new CharReader can be used independently of this
+	 * CharReader. Use the "commit" function of the returned CharReader to
+	 * copy the state of the forked CharReaderFork to this CharReader.
+	 *
+	 * @return a CharReaderFork instance positioned at the same location as this
+	 * CharReader instance.
+	 */
+	CharReaderFork fork();
+
+	/**
+	 * Returns true if there are no more characters as the stream was
+	 * closed.
+	 *
+	 * @return true if there is no more data.
+	 */
+	bool atEnd() const { return buffer->atEnd(readCursor.cursor); }
+
+	/**
+	 * Returns the current line (starting with one).
+	 *
+	 * @return the current line number.
+	 */
+	uint32_t getLine() const { return readCursor.line; }
+
+	/**
+	 * Returns the current column (starting with one).
+	 *
+	 * @return the current column number.
+	 */
+	uint32_t getColumn() const { return readCursor.column; }
+
+	/**
+	 * Returns the current byte offset of the read cursor.
+	 *
+	 * @return the byte position within the stream.
+	 */
+	size_t getOffset() const { return buffer->offset(readCursor.cursor); };
+
+	/**
+	 * Returns the line the read cursor currently is in, but at most the
+	 * given number of characters in the form of a Context structure.
+	 */
+	Context getContext(ssize_t maxSize);
+};
+
+/**
+ * A CharReaderFork is returned whenever the "fork" function of the CharReader
+ * class is used. Its "commit" function can be used to move the underlying
+ * CharReader instance to the location of the CharReaderFork instance. Otherwise
+ * the read location of the underlying CharReader is left unchanged.
+ */
+class CharReaderFork : public CharReader {
+private:
+	friend CharReader;
+
+	/**
+	 * The reader cursor of the underlying CharReader instance.
+	 */
+	CharReader::Cursor &parentReadCursor;
+
+	/**
+	 * The peek cursor of the underlying CharReader instance.
+	 */
+	CharReader::Cursor &parentPeekCursor;
+
+	/**
+	 * Constructor of the CharReaderFork class.
+	 *
+	 * @param buffer is a reference at the parent Buffer instance.
+	 * @param parentPeekCursor is a reference at the parent read cursor.
+	 * @param parentPeekCursor is a reference at the parent peek cursor.
+	 * @param coherent specifies whether the char reader cursors are initialized
+	 * coherently.
+	 */
+	CharReaderFork(std::shared_ptr<Buffer> buffer,
+	               CharReader::Cursor &parentReadCursor,
+	               CharReader::Cursor &parentPeekCursor, bool coherent);
+
+public:
+	/**
+	 * Moves the read and peek cursor of the parent CharReader to the location
+	 * of the read and peek cursor in the fork.
+	 */
+	void commit();
+};
+
+}
+
+#endif /* _OUSIA_CHAR_READER_HPP_ */
+