From f2a64b0bd6a5624ec37ec31a07747bfb063a7bb6 Mon Sep 17 00:00:00 2001
From: Ralph Ronnquist <ralph.ronnquist@gmail.com>
Date: Sun, 31 Jul 2022 17:51:41 +1000
Subject: [PATCH] Seek on the mount target to register fused size. More
 debugging.

---
 fusefile.c | 41 ++++++++++++++++++++++++++++++++++++-----
 1 file changed, 36 insertions(+), 5 deletions(-)

diff --git a/fusefile.c b/fusefile.c
index 0936da9..59dcaa5 100644
--- a/fusefile.c
+++ b/fusefile.c
@@ -200,14 +200,28 @@ static int find_source(off_t offset) {
     if ( offset >= sources.size ) {
 	return -1;
     }
+#if DEBUG
+    fprintf( stderr, "find_source( %ld )\n", offset );
+#endif
     while ( lo + 1 < hi ) {
 	int m = ( lo + hi ) / 2;
 	if ( offset < sources.array[ m ].start ) {
+#if DEBUG
+	    fprintf( stderr, "  offset < [%d].start: %ld\n",
+		     m, sources.array[ m ].start );
+#endif
 	    hi = m;
 	} else {
+#if DEBUG
+	    fprintf( stderr, "  offset >= [%d].start: %ld\n",
+		     m, sources.array[ m ].start );
+#endif
 	    lo = m;
 	}
     }
+#if DEBUG
+    fprintf( stderr, "found %d\n", lo );
+#endif
     return lo;
 }
 
@@ -224,10 +238,10 @@ static int fusefile_read(const char *path, char *buf, size_t size,
 #if DEBUG
     fprintf( stderr, "read %ld %ld\n", off, size );
 #endif
-    size_t rr = 0;
+    size_t rr = 0; // total reading
     while ( size > 0 ) {
 #if DEBUG
-	fprintf( stderr, "find_source %ld %ld\n", off, size );
+	fprintf( stderr, "  find_source %ld %ld\n", off, size );
 #endif
 	int i = find_source( off );
 	if ( i < 0 ) {
@@ -245,16 +259,20 @@ static int fusefile_read(const char *path, char *buf, size_t size,
 	if ( n > size ) {
 	    n = size;
 	}
+#if DEBUG
+	fprintf( stderr, "  seek fd=%d to %ld\n", sources.array[i].fd, b );
+#endif
 	if ( lseek( sources.array[i].fd, b, SEEK_SET ) < 0 ) {
 	    perror( sources.array[i].filename );
 	    return -ENOENT;
 	}
 #if DEBUG
-	fprintf( stderr, "get %ld bytes at %ld\n", n, rr );
+	fprintf( stderr, "  now read %ld from fd=%d\n",
+		 n, sources.array[i].fd );
 #endif
 	ssize_t r = read( sources.array[i].fd, buf + rr, n );
 #if DEBUG
-	fprintf( stderr, "got %ld bytes\n", r );
+	fprintf( stderr, "  got %ld bytes\n", r );
 #endif
 	if ( r < 0 ) {
 	    perror( sources.array[i].filename );
@@ -267,6 +285,9 @@ static int fusefile_read(const char *path, char *buf, size_t size,
 	off += r;
 	size -= r;
     }
+#if DEBUG
+    fprintf( stderr, "  total reading %ld bytes\n", rr );
+#endif
     return rr;
 }
 
@@ -459,7 +480,7 @@ static struct fuse_operations fusefile_oper = {
 static void usage() {
     char *usage =
 "Usage: fusefile [ <fuse options> ] <mount> <file/from-to> ... \n"
-"Mounts a virtual, read-only file that is a concatenation of file fragments\n"
+"Mounts a virtual, file that is a concatenation of file fragments\n"
 	;
     fprintf( stderr, "%s", usage );
     exit( 1 );
@@ -542,6 +563,16 @@ int main(int argc, char *argv[])
 	times.ctime = stbuf.st_ctime;
     }
 
+    {
+	int fd = open( mnt, O_RDWR, S_IRUSR | S_IWUSR );
+	if ( fd < 0 ) {
+	    perror( mnt );
+	    return 1;
+	}
+	if ( lseek( fd, sources.size, SEEK_SET ) < 0 ) {
+	    return -EIO;
+	}
+    }
     fuseargc = setup_argv( fuseargc, &argv );
     struct fuse_args args = FUSE_ARGS_INIT( fuseargc, argv );
     if ( fuse_parse_cmdline( &args, &mnt, &mt, &fg ) ) {
-- 
2.39.2