add writability

[rrq/fusefile.git] / README.adoc

diff --git a/README.adoc b/README.adoc
index 6d9f7751ed3a6376ef5de4c6adb32c9e927a2218..a37d36d40c0e75d2409119e781fbc24923afe4e6 100644 (file)
--- a/README.adoc
+++ b/README.adoc
@@ -5,8 +5,8 @@ This project implements a "fuse" device to mount as a single file that
 is a concatenation of fragments of one or more files. By default the
 fused file is read-only.
 
-A writeable fused file is set up by
-associating the mount with a scratch-pad
+A writeable fused file is set up by associating the mount with a
+"scratch pad file"
 
 FUSE file mount for combining file fragments.
  
@@ -34,6 +34,13 @@ variations:
 
  * __filename/from-to__ include the file from the given start position, up to the given end position (not included). 
 
+ * *pad=*_filename_ when this is given as first argument, the fused
+ file is set up as a writable random-access file, where the write
+ events are captured appended to the nominated "pad" file. The new
+ content is inserted into the fused file but not the original files,
+ and fragments are split up and adjusted as needed so as to make the
+ write events appear as insertions inteo the fused file.
+
 ## EXAMPLES
 
 Insert file "y" into file "x" at position 1200:
@@ -58,6 +65,12 @@ file changes or reduces in size, anything may happen.
 If the mountpoint file doesn't exist, then **fusefile** creates it,
 and removes it when unmounted.
 
+When a "pad" file is used, it is updated as an "ar" archive where each
+write event is a new member appended at the end. The "pad" member has
+two additional, newline-terminated text lines with the insertion
+position and the member size (ascii decimal digits), before the actual
+insertion event content.
+
 ## AUTHOR
 
 Ralph Rönnquist <ralph.ronnquist@gmail.com>