Imported Upstream version 60upstream/60

1 files changed, 93 insertions, 0 deletions

diff --git a/src/libbio/bseek.c b/src/libbio/bseek.c
new file mode 100644
index 000000000..291498108
--- /dev/null
+++ b/src/libbio/bseek.c
@@ -0,0 +1,93 @@
+/*
+http://code.google.com/p/inferno-os/source/browse/libbio/bseek.c
+
+	Copyright © 1994-1999 Lucent Technologies Inc.  All rights reserved.
+	Revisions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com).  All rights reserved.
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
+*/
+
+#include	<u.h>
+#include	<libc.h>
+#include	<bio.h>
+
+vlong
+Bseek(Biobuf *bp, vlong offset, int base)
+{
+	vlong n, d;
+	int bufsz;
+
+#ifndef _WIN32
+	if(sizeof(offset) != sizeof(off_t)) {
+		fprint(2, "Bseek: libbio compiled with %d-byte offset\n", sizeof(off_t));
+		abort();
+	}
+#endif
+
+	switch(bp->state) {
+	default:
+		fprint(2, "Bseek: unknown state %d\n", bp->state);
+		return Beof;
+
+	case Bracteof:
+		bp->state = Bractive;
+		bp->icount = 0;
+		bp->gbuf = bp->ebuf;
+
+	case Bractive:
+		n = offset;
+		if(base == 1) {
+			n += Boffset(bp);
+			base = 0;
+		}
+
+		/*
+		 * try to seek within buffer
+		 */
+		if(base == 0) {
+			d = n - Boffset(bp);
+			bufsz = bp->ebuf - bp->gbuf;
+			if(-bufsz <= d && d <= bufsz){
+				bp->icount += d;
+				if(d >= 0) {
+					if(bp->icount <= 0)
+						return n;
+				} else {
+					if(bp->ebuf - bp->gbuf >= -bp->icount)
+						return n;
+				}
+			}
+		}
+
+		/*
+		 * reset the buffer
+		 */
+		n = lseek(bp->fid, n, base);
+		bp->icount = 0;
+		bp->gbuf = bp->ebuf;
+		break;
+
+	case Bwactive:
+		Bflush(bp);
+		n = lseek(bp->fid, offset, base);
+		break;
+	}
+	bp->offset = n;
+	return n;
+}