fixed chunk offset calculation

src/lib/io/zffwriter.rs

@@ -23,7 +23,6 @@ use crate::{
 	FILE_EXTENSION_INITIALIZER,
 	ERROR_MISMATCH_ZFF_VERSION,
 	ERROR_MISSING_SEGMENT_MAIN_FOOTER,
-	ERROR_INVALID_OPTION_ZFFEXTEND,
 	ERROR_INVALID_OPTION_ZFFCREATE,
 };
 use crate::{
@@ -565,9 +564,15 @@ impl<R: Read> ZffWriter<R> {
 			output.seek(SeekFrom::End(-8))?;
 			let footer_offset = u64::decode_directly(output)?;
 			output.seek(SeekFrom::Start(footer_offset))?;
-			SegmentFooter::decode_directly(output)?
+			let segment_footer = SegmentFooter::decode_directly(output)?;
+			//move the seek position to the footer start, to overwrite the old footer.
+			output.seek(SeekFrom::Start(footer_offset))?;
+			segment_footer
+
 		} else {
-			SegmentFooter::new_empty(DEFAULT_FOOTER_VERSION_SEGMENT_FOOTER)
+			let mut segment_footer = SegmentFooter::new_empty(DEFAULT_FOOTER_VERSION_SEGMENT_FOOTER);
+			segment_footer.first_chunk_number = self.current_object_encoder.current_chunk_number();
+			segment_footer
 		};
 
 		// prepare output
@@ -754,9 +759,11 @@ impl<R: Read> ZffWriter<R> {
 
 	    	current_offset = match self.write_next_segment(&mut output_file, seek_value, &mut chunk_map, extend) {
 	    		Ok(written_bytes) => {
+	    			//adds the seek value to the written bytes
 	    			extend = false;
-	    			seek_value = 0;
-	    			written_bytes
+	    			current_offset = seek_value + written_bytes;
+	    			seek_value = current_offset;
+	    			current_offset
 	    		},
 	    		Err(e) => match e.get_kind() {
 	    			ZffErrorKind::ReadEOF => {

src/lib/segment.rs

@@ -93,6 +93,8 @@ impl<R: Read + Seek> Segment<R> {
 					      DEFAULT_LENGTH_HEADER_IDENTIFIER as u64 + //skip the chunk header identifier
 						  DEFAULT_LENGTH_VALUE_HEADER_LENGTH as u64 + //skip the header length value
 						  1 + // skip the ChunkMap header version
+						  8 + // skip the length of the map
+						  8 + // skip the chunk number itself
 						  ((chunk_number - first_chunk_number_of_map) * 2 * 8); //skip the other chunk entries
 
 		//go to the appropriate chunk map.
@@ -283,7 +285,7 @@ fn get_first_chunknumber(map: &BTreeMap<u64, u64>, chunk_number: u64, first_segm
     let mut range = map.range(..chunk_number).rev();
     match range.next() {
         Some((&k, _)) => Ok(k + 1),
-        None => if chunk_number > first_segment_chunk_number {
+        None => if chunk_number >= first_segment_chunk_number {
         	Ok(first_segment_chunk_number)
         } else {
         	Err(ZffError::new(ZffErrorKind::ValueNotInMap, chunk_number.to_string()))