X-Git-Url: https://git.rrq.au/?a=blobdiff_plain;f=fusefile.c;h=99424c5fd8ea7f8b1247d404da41cd8be7f06280;hb=6637283f63bfa51cbf0ae0746a6702cb2b6014e7;hp=0936da92219a0e5877679c1bdbae2fc91d1680e6;hpb=bcaeffd9fc73b359636ff32629fc07374c50cf16;p=rrq%2Ffusefile.git

diff --git a/fusefile.c b/fusefile.c
index 0936da9..99424c5 100644
--- a/fusefile.c
+++ b/fusefile.c
@@ -34,6 +34,11 @@
 #include <time.h>
 #include <errno.h>
 
+struct Region {
+    off_t pos;
+    size_t size;
+};
+
 struct Source {
     char *filename;
     ssize_t from;
@@ -53,7 +58,123 @@ static struct {
     time_t mtime;
     time_t ctime;
 } times;
-    
+
+/**
+ * Overlay
+ */
+static struct {
+    struct Source source;
+    struct Region *table;
+    size_t count;
+    size_t limit;
+} overlay;
+
+#define FRAG(m) (overlay.table+m)
+#define BEG(m) (FRAG(m)->pos)
+#define END(m) (FRAG(m)->pos + FRAG(m)->size)
+
+static ssize_t overlay_prior_fragment(off_t pos) {
+    size_t lo = 0, hi = overlay.count;
+    while ( lo < hi ) {
+	size_t m = ( lo + hi ) / 2;
+	if ( m == lo ) {
+	    return BEG( m ) < pos? m : -1;
+	}
+	if ( BEG( m ) <= pos ) {
+	    lo = m;
+	} else {
+	    hi = m;
+	}
+    }
+    return -1;
+}
+
+static void overlay_save_count() {
+    lseek( overlay.source.fd, overlay.source.to, SEEK_SET );
+    size_t size = sizeof( overlay.count );
+    char *p = (char *) &overlay.count ;
+    while ( size > 0 ) {
+	size_t n = write( overlay.source.fd, p, size );
+	if ( n < 0 ) {
+	    perror( overlay.source.filename );
+	    exit( 1 );
+	}
+	size -= n;
+	p += n;
+    }
+}
+
+static void overlay_save_table(size_t lo,size_t hi) {
+    char *p = (char *) FRAG(lo);
+    size_t pos =  overlay.source.to + sizeof( overlay.count ) +
+	lo * sizeof( struct Region );
+    size_t size = ( hi - lo ) * sizeof( struct Region );
+    if ( pos != lseek( overlay.source.fd, pos, SEEK_SET ) ) {
+	fprintf( stderr, "%s: seek error\n", overlay.source.filename );
+	exit( 1 );
+    }
+    while ( size > 0 ) {
+	size_t n = write( overlay.source.fd, p, size );
+	if ( n < 0 ) {
+	    perror( overlay.source.filename );
+	    exit( 1 );
+	}
+	size -= n;
+	p += n;
+    }
+}
+
+static void overlay_insert(size_t p,off_t pos,size_t size) {
+    size_t bytes;
+    if ( overlay.count >= overlay.limit ) {
+	overlay.limit = overlay.count + 10;
+	bytes = overlay.limit * sizeof( struct Region );
+	overlay.table = overlay.table?
+	    realloc( overlay.table, bytes ) : malloc( bytes );
+    }
+    bytes = ( overlay.count++ - p ) * sizeof( struct Region );
+    if ( bytes ) {
+	memmove( FRAG( p+1 ), FRAG( p ), bytes );
+    }
+    FRAG( p )->pos = pos;
+    FRAG( p )->size = size;
+    overlay_save_count();
+}
+
+static void overlay_delete(size_t p) {
+    if ( p < --overlay.count ) {
+	size_t size = ( overlay.count - p ) * sizeof( struct Region );
+	memmove( FRAG(p), FRAG(p+1), size );
+    }
+    overlay_save_count();
+}
+
+static void overlay_mark(off_t pos,size_t size) {
+    ssize_t p = overlay_prior_fragment( pos );
+    if ( p >= 0 && pos <= END(p) ) {
+	// Merge new marks with fragment p
+	FRAG(p)->size = pos + size - BEG(p);
+	if ( p+1 < overlay.count && BEG(p+1) <= END(p) ) {
+	    FRAG(p)->size = END(p+1) - BEG(p);
+	    overlay_delete( p+1 );
+	    overlay_save_table( p, overlay.count );
+	} else {
+	    overlay_save_table( p, p+1 );
+	}
+	return;
+    }
+    p++; // index of subsequent fragment
+    if ( p < overlay.count && BEG(p) < pos + size ) {
+	// Merge new marks with pragment p+1
+	FRAG(p)->size = END(p) - pos;
+	FRAG(p)->pos = pos;
+	overlay_save_table( p, p+1 );
+    } else {
+	overlay_insert( p, pos, size);
+	overlay_save_table( p, overlay.count );
+    }
+}
+
 #if DEBUG
 static void print_source(struct Source *p) {
     fprintf( stderr, "%p { %s, %ld, %ld, %ld, %d }\n",
@@ -67,6 +188,17 @@ static int RANGE(int s,int n ) {
     return ( s == n ) && *(range+c) == 0;
 }
 
+static void usage();
+
+static void setup_overlay(char *filename) {
+    overlay.source.filename = filename;
+    overlay.source.fd = open( filename, O_RDWR | O_CREAT, S_IRUSR | S_IWUSR );
+    if ( overlay.source.fd < 0 ) {
+	perror( filename );
+	usage();
+    }
+}
+
 static int setup_sources(char **argv,int i,int n) {
     sources.array = calloc( n, sizeof( struct Source ) );
     if ( sources.array == 0 ) {
@@ -200,17 +332,68 @@ 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;
 }
 
+static int overlay_merge(char *buf,off_t off,size_t size) {
+#if DEBUG
+    fprintf( stderr, "merge %ld %ld\n", off, size );
+#endif
+    // Find nearest overlay data before or at off
+    ssize_t p = overlay_prior_fragment( off );
+    if ( p < 0 ) {
+	p = 0;
+    }
+    for ( ; p < overlay.count && BEG(p) < off+size; p++ ) {
+	size_t delta = FRAG(p)->size;
+	if ( BEG(p) > off ) {
+	    size_t skip = BEG(p) - off;
+	    off += skip;
+	    size -= skip;
+	    buf += skip;
+	} else {
+	    delta = off - BEG(p);
+	}
+	if ( delta > size ) {
+	    delta = size;
+	}
+	lseek( overlay.source.fd, off, SEEK_SET );
+	while ( delta > 0 ) {
+	    size_t n = read( overlay.source.fd, buf, delta );
+	    off += n;
+	    size -= n;
+	    delta -= n;
+	    buf += n;
+	}
+    }
+#if DEBUG
+    fprintf( stderr, "merged\n" );
+#endif
+    return 0;
+}
+
 // Read <size> bytes from <offset> in file
 static int fusefile_read(const char *path, char *buf, size_t size,
 			 off_t off, struct fuse_file_info *fi)
@@ -224,10 +407,10 @@ 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 +428,26 @@ 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 ( overlay.source.filename ) {
+	    int x = overlay_merge( buf + rr, off + rr, r );
+	    if ( x ) {
+		return x;
+	    }
+	}
 #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 +460,9 @@ 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;
 }
 
@@ -288,6 +484,30 @@ int fusefile_poll(const char *path, struct fuse_file_info *fi,
     return 0;
 }
 
+static void overlay_load() {
+    lseek( overlay.source.fd, overlay.source.to, SEEK_SET );
+    size_t x = 0;
+    size_t size = sizeof( overlay.count );
+    if ( read( overlay.source.fd, &x, size ) != size ) {
+	return;
+    }
+#if DEBUG
+    fprintf( stderr, "overlay: %s with %ld regions\n",
+	     overlay.source.filename, x );
+#endif
+    struct Region f = { 0, 0 };
+    size = sizeof( struct Region );
+    while ( x-- > 0 ) {
+	if ( read( overlay.source.fd, &f, size ) != size ) {
+	    fprintf( stderr, "%s: bad meta data\n", overlay.source.filename );
+	    exit( 1 );
+	}
+#if DEBUG
+	fprintf( stderr, "overlay region: %ld %ld\n", f.pos, f.size );
+#endif
+	overlay_mark( f.pos, f.size );
+    }
+}
 
 /**
  * Write a full block of data over the sources at the offset
@@ -301,7 +521,13 @@ static int write_block(off_t off,const char *buf,size_t size) {
 	if ( index < 0 ) {
 	    return -EIO; // past EOF
 	}
-	struct Source *source = &sources.array[ index ];
+	struct Source *source;
+	if ( overlay.source.filename ) {
+	    source = &overlay.source;
+	    overlay_mark( off, size ); // Mark region as written
+	} else {
+	    source = &sources.array[ index ];
+	}
 	off_t from = off - source->start + source->from;
 	off_t max = source->to - from;
 	if ( lseek( source->fd, from, SEEK_SET ) < 0 ) {
@@ -459,7 +685,7 @@ 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 );
@@ -518,9 +744,22 @@ int main(int argc, char *argv[])
     }
     fuseargc = i;
     mnt = argv[ i++ ]; // First non-option argument is the mount pount
+    char *overlaytag = "-overlay:";
+    int overlaytagsize = strlen( overlaytag );
+    if ( strncmp( argv[i], overlaytag, overlaytagsize ) == 0 ) {
+	// consume "-overlay:filename"
+	setup_overlay( argv[i++] + overlaytagsize ); // Need a writable file
+	if ( i >= argc ) {
+	    usage();
+	}
+    }
     if ( setup_sources( argv, i, argc-i ) ) {
 	return 1;
     }
+    if ( overlay.source.filename ) {
+	overlay.source.to = sources.size; // Register total size.
+	overlay_load();
+    }
     if ( stat( mnt, &stbuf ) == -1 ) {
 	int fd = open( mnt, O_CREAT | O_RDWR, S_IRUSR | S_IWUSR );
 	if ( fd < 0 ) {
@@ -542,6 +781,16 @@ 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 ) ) {