unix support for stream seeking

basis/io/backend/unix/unix.factor

@@ -46,6 +46,9 @@ M: fd cancel-operation ( fd -- )
         2bi
     ] if ;
 
+M: unix (stream-seek)
+    handle>> fd>> swap SEEK_SET lseek io-error ;
+
 SYMBOL: +retry+ ! just try the operation again without blocking
 SYMBOL: +input+
 SYMBOL: +output+

basis/io/buffers/buffers.factor

@@ -27,6 +27,9 @@ M: buffer dispose* ptr>> free ;
 : buffer-empty? ( buffer -- ? )
     fill>> zero? ; inline
 
+: buffer-seek ( n buffer -- )
+    (>>pos) ; inline
+
 : buffer-consume ( n buffer -- )
     [ + ] change-pos
     dup [ pos>> ] [ fill>> ] bi <

basis/io/ports/ports.factor

@@ -4,7 +4,7 @@ USING: math kernel io sequences io.buffers io.timeouts generic
 byte-vectors system io.encodings math.order io.backend
 continuations classes byte-arrays namespaces splitting
 grouping dlists assocs io.encodings.binary summary accessors
-destructors combinators ;
+destructors combinators unix ;
 IN: io.ports
 
 SYMBOL: default-buffer-size
@@ -93,6 +93,12 @@ M: input-port stream-read-until ( seps port -- str/f sep/f )
         ] [ [ 2drop ] 2dip ] if
     ] if ;
 
+HOOK: (stream-seek) os ( n stream -- )
+
+M: input-port stream-seek ( n stream -- )
+    dup check-disposed
+    2dup buffer>> buffer-seek (stream-seek) ;
+
 TUPLE: output-port < buffered-port ;
 
 : <output-port> ( handle -- output-port )

core/io/encodings/encodings.factor

@@ -50,6 +50,8 @@ M: object <decoder> f decoder boa ;
 M: decoder stream-read1
     dup >decoder< decode-char fix-read1 ;
 
+M: decoder stream-seek stream>> stream-seek ;
+
 : fix-read ( stream string -- string )
     over cr>> [
         over cr-

core/io/io.factor

@@ -15,6 +15,8 @@ GENERIC: stream-write ( seq stream -- )
 GENERIC: stream-flush ( stream -- )
 GENERIC: stream-nl ( stream -- )
 
+GENERIC: stream-seek ( n stream -- )
+
 : stream-print ( str stream -- ) [ stream-write ] keep stream-nl ;
 
 ! Default streams
@@ -27,6 +29,7 @@ SYMBOL: error-stream
 : read ( n -- seq ) input-stream get stream-read ;
 : read-until ( seps -- seq sep/f ) input-stream get stream-read-until ;
 : read-partial ( n -- seq ) input-stream get stream-read-partial ;
+: seek ( n -- ) input-stream get stream-seek ;
 
 : write1 ( elt -- ) output-stream get stream-write1 ;
 : write ( seq -- ) output-stream get stream-write ;
@@ -82,4 +85,4 @@ PRIVATE>
 
 : stream-copy ( in out -- )
     [ [ [ write ] each-block ] with-output-stream ]
-    curry with-input-stream ;
+    curry with-input-stream ;