From e0e7e2aaffafd7969718f4e3d27c0bfb8c95faad Mon Sep 17 00:00:00 2001
From: Ralph Ronnquist <ralph.ronnquist@gmail.com>
Date: Wed, 21 Jun 2023 00:06:57 +1000
Subject: [PATCH] Added -dump function for dumping an overlay table.

---
 fusefile.8 | 12 ++++++++++++
 fusefile.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 64 insertions(+), 2 deletions(-)

diff --git a/fusefile.8 b/fusefile.8
index 3954389..2b116a9 100644
--- a/fusefile.8
+++ b/fusefile.8
@@ -35,6 +35,11 @@ any new written fused file regions followed by meta data to
 distinguish between new, written content and old content that comes
 from the fragments.
 
+The option \fB-dump\fR together with an overlay fusefile setup will
+print the current overlay table to standard output rather than
+establishing a fusefile mount. The table is printed as the series of
+fusefile fragments using the argments as given.
+
 .SH FRAGMENT ARGUMENTS
 
 The fragment arguments include the filename of a source file, and
@@ -100,6 +105,13 @@ The mount options \fI-ouid=...\fR and \fI-ogid=...\fR, where \fI...\fR
  \fBfusedisk\fR and thereby give user or group ownership for the mount
  to the nominated user or group.
 
+.TP
+\fI-dump\fR
+
+This "mount option" triggers fusefil to, instead of setting up a mount
+point, print out the applicable fusefile fragment sequence for the
+current setup as way of presenting the overlay table.
+
 .SH EXAMPLES
 This section illustrates uses of \fBfusefile\fR.
 
diff --git a/fusefile.c b/fusefile.c
index eeb0e72..d8729b9 100644
--- a/fusefile.c
+++ b/fusefile.c
@@ -1,8 +1,8 @@
 /***
     fusefile - overlay a file path with a concatenation of parts of
-    other files, read only.
+    other files.
 
-    Copyright (C) 2019  Ralph Ronnquist
+    Copyright (C) 2019-  Ralph Ronnquist
 
     This program is free software: you can redistribute it and/or
     modify it under the terms of the GNU General Public License as
@@ -775,8 +775,53 @@ void *fusefile_init(struct fuse_conn_info *fci) {
     return 0;
 }
 
+#define ENDSOURCE( S ) ( S.start + ( S.to - S.from ) )
+
+/**
+ * Dump the current fragmentation to stdout.
+ */
+static int dump_fragments() {
+    int oly = 0;
+    int src = 0;
+    size_t pos = 0;
+    while ( src < sources.count ) {
+	size_t x = ( oly < overlay.count )?
+	    overlay.table[ oly ].beg : sources.size;
+	for ( ; src < sources.count && 
+		  ENDSOURCE( sources.array[ src ] ) <= x; src++ ) {
+	    // Dump sources.array[src] in full
+	    fprintf( stdout, "%s/%ld:%ld\n",
+		     sources.array[ src ].filename,
+		     pos - sources.array[ src ].start,
+		     sources.array[ src ].to );
+	    pos = ENDSOURCE( sources.array[ src ] );
+	}
+	if ( sources.array[ src ].start < x ) {
+	    // Dump sources.array[src] up to x;
+	    fprintf( stdout, "%s/%ld:%ld\n",
+		     sources.array[ src ].filename,
+		     pos - sources.array[ src ].start,
+		     x - sources.array[ src ].start );
+	    pos = ENDSOURCE( sources.array[ src ] );
+	}
+	if ( oly < overlay.count ) {
+	    fprintf( stdout, "%s/%ld:%ld\n",
+		     overlay.source.filename,
+		     overlay.table[ oly ].beg,
+		     overlay.table[ oly ].end );
+	    pos = overlay.table[ oly++ ].end;
+	}
+	for ( ; src < sources.count &&
+		  ENDSOURCE( sources.array[ src ] ) <= pos; src++ ) {
+	    // Just skip these fragments.
+	}
+    }
+    return( 0 );
+}
+
 static struct fuse_operations fusefile_oper = {
     .getattr = fusefile_getattr,
+    // NYI .fgetattr = fusefile_fgetattr,
     .chmod = fusefile_chmod,
     .open = fusefile_open,
     .read = fusefile_read,
@@ -784,9 +829,11 @@ static struct fuse_operations fusefile_oper = {
     .write = fusefile_write,
     .write_buf = fusefile_write_buf,
     .destroy = fusefile_destroy,
+    // NYI .access = fusefile_access,
     .flush = fusefile_flush,
     .release = fusefile_release,
     .fsync = fusefile_fsync,
+    // NYI .ftruncate = fusefile_ftruncate,
     .truncate = fusefile_truncate,
     //.truncate = fusefile_truncate,
     //.release = fusefile_release,
@@ -903,6 +950,9 @@ int main(int argc, char *argv[])
 	}
     }
     fuseargc = setup_argv( fuseargc, &argv );
+    if ( strcmp( "-dump", argv[ 1 ] ) == 0 ) {
+	return dump_fragments();
+    }
     struct fuse_args args = FUSE_ARGS_INIT( fuseargc, argv );
     if ( fuse_parse_cmdline( &args, &mnt, &mt, &fg ) ) {
 	return 1;
-- 
2.39.2