diff -r 7a6abdd00ab5 -r 6904e4448807 src/lib/AbstractParser.cpp
--- a/src/lib/AbstractParser.cpp	Sat Jun 12 22:37:44 2021 +0200
+++ b/src/lib/AbstractParser.cpp	Sat Jun 19 12:59:07 2021 +0200
@@ -16,6 +16,7 @@
  */
 
 #include "AbstractParser.h"
+#include "TransactionalBuffer.h"
 
 namespace relpipe {
 namespace in {
@@ -24,7 +25,9 @@
 
 class AbstractParserImpl {
 private:
+	friend AbstractParser;
 	AbstractParser* interface;
+	TransactionalBuffer buffer;
 public:
 
 	AbstractParserImpl(AbstractParser* interface) : interface(interface) {
@@ -43,12 +46,15 @@
 }
 
 void AbstractParser::write(const char* buffer, const size_t length) {
-	// TODO: update pointers and positions
 	try {
+		// TODO: do not write to the buffer, just append in read()/peek() and write just the part that was not read during this cycle
+		implementation->buffer.write(buffer, length);
+
 		// TODO: call an overridable method to get preferred minimum block size and run cycle only if we have enough data or EOF
+		// and/or remember the length of last failed (rollbacked) read() call
 		update();
 		commit();
-	} catch (const AbstractParser::ReadBufferUnderflowException& e) {
+	} catch (const TransactionalBuffer::ReadBufferUnderflowException& e) {
 		rollback();
 	} catch (const AbstractParser::ExplicitRollbackException& e) {
 		rollback();
@@ -56,20 +62,24 @@
 }
 
 void AbstractParser::close() {
+	// TODO: check remaining data + call update() or just let parsers override this method?
 }
 
 void AbstractParser::rollback() {
-	// FIXME: store content of the current buffer + update pointers and positions
 	// TODO: notify rollback listeners? (they can monitor the performance / frequency of rollbacks)
+	implementation->buffer.rollbackRead();
 }
 
 void AbstractParser::commit() {
+	implementation->buffer.commitRead();
 }
 
 void AbstractParser::read(char* buffer, const size_t length) {
+	implementation->buffer.read(buffer, length);
 }
 
 void AbstractParser::peek(char* buffer, const size_t length) {
+	implementation->buffer.read(buffer, length);
 }
 
 }