lib: Changed istream.abs_start_offset to be relative start_offset

i_stream_get_absolute_offset() walks through the stream's parents to get the
absolute offset. This allows streams to change their start_offset after
they have already created (e.g. istream-metawrap).

src/lib-compression/istream-bzlib.c

@@ -41,8 +41,7 @@ static void bzlib_read_error(struct bzlib_istream *zstream, const char *error)
 	io_stream_set_error(&zstream->istream.iostream,
 			    "bzlib.read(%s): %s at %"PRIuUOFF_T,
 			    i_stream_get_name(&zstream->istream.istream), error,
-			    zstream->istream.abs_start_offset +
-			    zstream->istream.istream.v_offset);
+			    i_stream_get_absolute_offset(&zstream->istream.istream));
 	if (zstream->log_errors)
 		i_error("%s", zstream->istream.iostream.error);
 }

src/lib-compression/istream-lz4.c

@@ -40,8 +40,7 @@ static void lz4_read_error(struct lz4_istream *zstream, const char *error)
 	io_stream_set_error(&zstream->istream.iostream,
 			    "lz4.read(%s): %s at %"PRIuUOFF_T,
 			    i_stream_get_name(&zstream->istream.istream), error,
-			    zstream->istream.abs_start_offset +
-			    zstream->istream.istream.v_offset);
+			    i_stream_get_absolute_offset(&zstream->istream.istream));
 	if (zstream->log_errors)
 		i_error("%s", zstream->istream.iostream.error);
 }

src/lib-compression/istream-lzma.c

@@ -43,8 +43,7 @@ static void lzma_read_error(struct lzma_istream *zstream, const char *error)
 	io_stream_set_error(&zstream->istream.iostream,
 			    "lzma.read(%s): %s at %"PRIuUOFF_T,
 			    i_stream_get_name(&zstream->istream.istream), error,
-			    zstream->istream.abs_start_offset +
-			    zstream->istream.istream.v_offset);
+			    i_stream_get_absolute_offset(&zstream->istream.istream));
 	if (zstream->log_errors)
 		i_error("%s", zstream->istream.iostream.error);
 }

src/lib-compression/istream-zlib.c

@@ -58,8 +58,7 @@ static void zlib_read_error(struct zlib_istream *zstream, const char *error)
 	io_stream_set_error(&zstream->istream.iostream,
 			    "zlib.read(%s): %s at %"PRIuUOFF_T,
 			    i_stream_get_name(&zstream->istream.istream), error,
-			    zstream->istream.abs_start_offset +
-			    zstream->istream.istream.v_offset);
+			    i_stream_get_absolute_offset(&zstream->istream.istream));
 	if (zstream->log_errors)
 		i_error("%s", zstream->istream.iostream.error);
 }

src/lib-fs/istream-metawrap.c

@@ -64,7 +64,7 @@ static ssize_t i_stream_metawrap_read(struct istream_private *stream)
 		if (ret <= 0)
 			return ret;
 		/* this stream is kind of silently skipping over the metadata */
-		stream->abs_start_offset += mstream->start_offset;
+		stream->start_offset += mstream->start_offset;
 		mstream->in_metadata = FALSE;
 		if (mstream->pending_seek != 0) {
 			i_stream_seek(&stream->istream, mstream->pending_seek);

src/lib/iostream-temp.c

@@ -296,7 +296,8 @@ struct istream *iostream_temp_finish(struct ostream **output,
 		for_path = t_strdup_printf(" for %s", tstream->name);
 
 	if (tstream->dupstream != NULL && !tstream->dupstream->closed) {
-		abs_offset = tstream->dupstream->real_stream->abs_start_offset +
+		abs_offset = i_stream_get_absolute_offset(tstream->dupstream) -
+			tstream->dupstream->v_offset +
 			tstream->dupstream_start_offset;
 		size = tstream->dupstream_offset -
 			tstream->dupstream_start_offset;

src/lib/istream-mmap.c

@@ -230,7 +230,7 @@ struct istream *i_stream_create_mmap(int fd, size_t block_size,
 	mstream->istream.stat = i_stream_mmap_stat;
 
 	mstream->istream.istream.readable_fd = TRUE;
-	mstream->istream.abs_start_offset = start_offset;
+	mstream->istream.start_offset = start_offset;
 	istream = i_stream_create(&mstream->istream, NULL, fd);
 	istream->mmaped = TRUE;
 	istream->blocking = TRUE;

src/lib/istream-private.h

@@ -25,7 +25,7 @@ struct istream_private {
 	struct istream istream;
 
 	int fd;
-	uoff_t abs_start_offset;
+	uoff_t start_offset;
 	struct stat statbuf;
 	/* added by io_add_istream() -> i_stream_set_io() */
 	struct io *io;

src/lib/istream.c

@@ -367,7 +367,12 @@ bool i_stream_is_eof(struct istream *stream)
 
 uoff_t i_stream_get_absolute_offset(struct istream *stream)
 {
-	return stream->real_stream->abs_start_offset + stream->v_offset;
+	uoff_t abs_offset = stream->v_offset;
+	while (stream != NULL) {
+		abs_offset += stream->real_stream->start_offset;
+		stream = stream->real_stream->parent;
+	}
+	return abs_offset;
 }
 
 static char *i_stream_next_line_finish(struct istream_private *stream, size_t i)
@@ -827,8 +832,7 @@ void i_stream_init_parent(struct istream_private *_stream,
 	_stream->parent = parent;
 	_stream->parent_start_offset = parent->v_offset;
 	_stream->parent_expected_offset = parent->v_offset;
-	_stream->abs_start_offset = parent->v_offset +
-		parent->real_stream->abs_start_offset;
+	_stream->start_offset = parent->v_offset;
 	/* if parent stream is an istream-error, copy the error */
 	_stream->istream.stream_errno = parent->stream_errno;
 	_stream->istream.eof = parent->eof;

src/lib/ostream-file.c

@@ -692,7 +692,7 @@ static int io_stream_sendfile(struct ostream_private *outstream,
 			      bool *sendfile_not_supported_r)
 {
 	struct file_ostream *foutstream = (struct file_ostream *)outstream;
-	uoff_t in_size, offset, send_size, v_offset;
+	uoff_t in_size, offset, send_size, v_offset, abs_start_offset;
 	ssize_t ret;
 
 	*sendfile_not_supported_r = FALSE;
@@ -713,9 +713,10 @@ static int io_stream_sendfile(struct ostream_private *outstream,
 	if (o_stream_lseek(foutstream) < 0)
 		return -1;
 
-        v_offset = instream->v_offset;
+	v_offset = instream->v_offset;
+	abs_start_offset = i_stream_get_absolute_offset(instream) - v_offset;
 	while (v_offset < in_size) {
-		offset = instream->real_stream->abs_start_offset + v_offset;
+		offset = abs_start_offset + v_offset;
 		send_size = in_size - v_offset;
 
 		ret = safe_sendfile(foutstream->fd, in_fd, &offset,
@@ -862,8 +863,7 @@ static int io_stream_copy_same_stream(struct ostream_private *outstream,
 	}
 	i_assert(instream->v_offset <= in_size);
 
-	in_abs_offset = instream->real_stream->abs_start_offset +
-		instream->v_offset;
+	in_abs_offset = i_stream_get_absolute_offset(instream);
 	ret = (off_t)outstream->ostream.offset - in_abs_offset;
 	if (ret == 0) {
 		/* copying data over itself. we don't really