3 files changed, 52 insertions, 8 deletions

diff --git a/src/core/common/CharReader.cpp b/src/core/common/CharReader.cpp
index edcaf76..5b9b1d4 100644
--- a/src/core/common/CharReader.cpp
+++ b/src/core/common/CharReader.cpp
@@ -329,6 +329,19 @@ ssize_t Buffer::moveCursor(CursorId cursor, ssize_t relativeOffs)
 	}
 }
 
+size_t Buffer::seekCursor(CursorId cursor, size_t offs)
+{
+	// Fetch the current offset
+	const ssize_t currentOffs = offset(cursor);
+	const ssize_t relativeOffs = offs - currentOffs;
+
+	// Perform the actual seeking, move the peek cursor to the read cursor
+	const ssize_t reachedOffs =  currentOffs + moveCursor(cursor, relativeOffs);
+
+	// Clamp to values larger or equal to zero
+	return reachedOffs < 0 ? 0 : reachedOffs;
+}
+
 bool Buffer::atEnd(Buffer::CursorId cursor) const
 {
 	const Cursor &c = cursors[cursor];
@@ -504,17 +517,17 @@ size_t CharReader::readRaw(char *buf, size_t size)
 
 size_t CharReader::seek(size_t requestedOffset)
 {
-	// Fetch the current offset
-	const ssize_t currentOffs = getOffset();
-	const ssize_t relativeOffs = requestedOffset - currentOffs;
-
-	// Perform the actual seeking, move the peek cursor to the read cursor
-	const ssize_t reachedOffs =  currentOffs + buffer->moveCursor(readCursor, relativeOffs);
+	const size_t res =  buffer->seekCursor(readCursor, requestedOffset);
 	buffer->copyCursor(readCursor, peekCursor);
 	coherent = true;
+	return res;
+}
 
-	// Clamp to values larger or equal to zero
-	return reachedOffs < 0 ? 0 : reachedOffs;
+size_t CharReader::seekPeekCursor(size_t requestedOffset)
+{
+	const size_t res =  buffer->seekCursor(peekCursor, requestedOffset);
+	coherent = (res == getOffset());
+	return res;
 }
 
 bool CharReader::atEnd() const { return buffer->atEnd(readCursor); }
@@ -526,6 +539,9 @@ size_t CharReader::getOffset() const
 
 size_t CharReader::getPeekOffset() const
 {
+	if (coherent) {
+		return getOffset();
+	}
 	return buffer->offset(peekCursor) + offs;
 }
 
diff --git a/src/core/common/CharReader.hpp b/src/core/common/CharReader.hpp
index cbd7b74..cbfeaf2 100644
--- a/src/core/common/CharReader.hpp
+++ b/src/core/common/CharReader.hpp
@@ -302,6 +302,15 @@ public:
 	ssize_t moveCursor(CursorId cursor, ssize_t relativeOffs);
 
 	/**
+	 * Moves the cursor to the given position.
+	 *
+	 * @param cursor is the cursor that should be moved.
+	 * @param offs is the offset to which the cursor should be moved.
+	 * @return the actual location that was reached.
+	 */
+	size_t seekCursor(CursorId cursor, size_t offs);
+
+	/**
 	 * Returns the current byte offset of the given cursor relative to the
 	 * beginning of the stream.
 	 *
@@ -533,6 +542,17 @@ public:
 	size_t seek(size_t requestedOffset);
 
 	/**
+	 * Moves the peek cursor to the requested offset. Returns the offse that wa
+	 * actually reached.
+	 *
+	 * @param requestedOffset is the requested offset. This offset may no longer
+	 * be reachable by the CharReader.
+	 * @return the actually reached offset. The operation was successful, if
+	 * the requested and reached offset are equal.
+	 */
+	size_t seekPeekCursor(size_t requestedOffset);
+
+	/**
 	 * Returns true if there are no more characters as the stream was closed.
 	 *
 	 * @return true if there is no more data.
diff --git a/src/core/common/Utils.hpp b/src/core/common/Utils.hpp
index fa3788a..457d446 100644
--- a/src/core/common/Utils.hpp
+++ b/src/core/common/Utils.hpp
@@ -58,6 +58,14 @@ public:
 	}
 
 	/**
+	 * Returns true if the given character is in [A-Za-z_]
+	 */
+	static bool isIdentifierStart(const char c)
+	{
+		return isAlphabetic(c) || (c == '_');
+	}
+
+	/**
 	 * Returns true if the given character is in [A-Za-z_][A-Za-z0-9_-]*
 	 */
 	static bool isIdentifier(const std::string &name);