Import Upstream version 3a5upstream/3a5

1 files changed, 32 insertions, 0 deletions

diff --git a/gambit.init b/gambit.init
index 07841e6..e431160 100644
--- a/gambit.init
+++ b/gambit.init
@@ -243,6 +243,38 @@
 (define (offset-time caltime offset)
   (seconds->time (+ (time->seconds caltime) offset)))
 
+;; procedure: input-port-byte-position port [position [whence]]
+;; procedure: output-port-byte-position port [position [whence]]
+;;
+;;     When called with a single argument these procedures return the
+;; byte position where the next I/O operation would take place in the
+;; file attached to the given port (relative to the beginning of the
+;; file).  When called with two or three arguments, the byte position
+;; for subsequent I/O operations on the given port is changed to
+;; position, which must be an exact integer.  When whence is omitted
+;; or is 0, the position is relative to the beginning of the file.
+;; When whence is 1, the position is relative to the current byte
+;; position of the file.  When whence is 2, the position is relative
+;; to the end of the file.  The return value is the new byte position.
+;; On most operating systems the byte position for reading and writing
+;; of a given bidirectional port are the same.
+;;
+;;     When input-port-byte-position is called to change the byte
+;; position of an input-port, all input buffers will be flushed so
+;; that the next byte read will be the one at the given position.
+;;
+;;     When output-port-byte-position is called to change the byte
+;; position of an output-port, there is an implicit call to
+;; force-output before the position is changed.
+
+;;@ (FILE-POSITION <port> . <k>)
+(define (file-position port . k)
+  (apply (if (output-port? port)
+	     output-port-byte-position
+	     input-port-byte-position)
+	 port
+	 k))
+
 ;;; (OUTPUT-PORT-WIDTH <port>)
 ;; (define (output-port-width . arg) 79)