diff --git a/extra/yaml/yaml.factor b/extra/yaml/yaml.factor
index 687555f515..67e51e4601 100644
--- a/extra/yaml/yaml.factor
+++ b/extra/yaml/yaml.factor
@@ -1,5 +1,163 @@
 ! Copyright (C) 2013 Jon Harper.
 ! See http://factorcode.org/license.txt for BSD license.
-USING: ;
+USING: accessors alien.c-types alien.data alien.syntax assocs
+classes.struct combinators continuations destructors
+io.encodings.string io.encodings.utf8 kernel libc locals make
+math namespaces prettyprint sequences strings yaml.ffi ;
 IN: yaml
 
+: yaml-assert-ok ( n -- ) 0 = [ "yaml error" throw ] when ;
+: event>scalar ( event -- obj ) data>> scalar>> [ value>> ] [ length>> ] bi memory>byte-array utf8 decode ;
+: ?scalar-value ( event -- scalar/f f/type )
+  dup type>> YAML_SCALAR_EVENT = [ event>scalar f ] [ type>> clone f swap ] if ;
+
+! Must not reuse the event struct before with-destructors scope ends
+: next-event ( parser event -- event )
+    [ yaml_parser_parse yaml-assert-ok ] [ &yaml_event_delete ] bi ;
+
+DEFER: parse-sequence
+DEFER: parse-mapping
+: next-complex-value ( parser event type -- obj )
+  {
+    { YAML_SEQUENCE_START_EVENT [ parse-sequence ] }
+    { YAML_MAPPING_START_EVENT [ parse-mapping ] }
+    [ throw ]
+  } case ;
+:: next-value ( parser event -- obj )
+  parser event [ next-event ?scalar-value ] with-destructors
+  [ [ drop parser event ] dip next-complex-value ] when* ;
+
+:: parse-mapping ( parser event -- map ) [
+  f :> done!
+  [ done ] [ [
+    parser event next-event type>>
+    YAML_MAPPING_END_EVENT = [
+      t done! f f
+    ] [
+      event event>scalar t
+    ] if
+  ] with-destructors [ parser event next-value swap ,, ] [ drop ] if ] until
+] H{ } make ;
+:: parse-sequence ( parser event -- seq ) [
+  f :> done!
+  [ done ] [ [
+    parser event next-event type>>
+    YAML_SEQUENCE_END_EVENT = [
+      t done! f
+    ] [
+      event ?scalar-value dup [ nip ] [ [ , ] dip ] if
+    ] if
+  ] with-destructors [ [ parser event ] dip next-complex-value , ] when* ] until
+] { } make ;
+
+: expect-event ( parser event type -- )
+[
+  [ next-event type>> ] dip =
+  [ "wrong event" throw ] unless
+] with-destructors ;
+
+
+:: yaml> ( str -- obj )
+[
+yaml_parser_t (malloc-struct) &free :> parser
+parser yaml_parser_initialize yaml-assert-ok
+parser &yaml_parser_delete drop
+
+str utf8 encode [ malloc-byte-array &free ] [ length ] bi :> ( input length )
+parser input length yaml_parser_set_input_string
+
+yaml_event_t (malloc-struct) &free :> event
+
+parser event YAML_STREAM_START_EVENT expect-event
+parser event YAML_DOCUMENT_START_EVENT expect-event
+
+parser event next-value
+
+parser event YAML_DOCUMENT_END_EVENT expect-event
+parser event YAML_STREAM_END_EVENT expect-event
+
+] with-destructors
+
+;
+
+! TODO We can also pass some data when registering the write handler,
+! use this to have several buffers if it can be interrupted.
+! For now, only do operations on strings that are in memory
+! so we don't need to be reentrant.
+SYMBOL: yaml-write-buffer
+: yaml-write-handler ( -- alien )
+  [
+    memory>byte-array yaml-write-buffer get-global
+    push-all drop 1
+  ] yaml_write_handler_t ;
+
+GENERIC: emit-value ( emitter event obj -- )
+M:: string emit-value ( emitter event string -- )
+[
+  string utf8 encode [ malloc-byte-array &free ] [ length ] bi :> ( value length )
+  "tag:yaml.org,2002:str" utf8 malloc-string &free :> tag
+  event f tag value length 0 0 0 yaml_scalar_event_initialize yaml-assert-ok
+  emitter event yaml_emitter_emit yaml-assert-ok
+] with-destructors ;
+:: emit-sequence-start ( emitter event -- )
+[
+  "tag:yaml.org,2002:seq" utf8 malloc-string &free :> tag
+  event f tag 0 0 yaml_sequence_start_event_initialize yaml-assert-ok
+  emitter event yaml_emitter_emit yaml-assert-ok
+] with-destructors ;
+: emit-sequence-end ( emitter event -- )
+  dup yaml_sequence_end_event_initialize yaml-assert-ok
+  yaml_emitter_emit yaml-assert-ok ;
+
+: emit-sequence ( emitter event seq -- )
+  [ emit-value ] with with each ;
+
+M: sequence emit-value ( emitter event seq -- )
+  [ drop emit-sequence-start ] [ emit-sequence ] [ drop emit-sequence-end ] 3tri ;
+
+:: emit-assoc-start ( emitter event -- )
+[
+  "tag:yaml.org,2002:map" utf8 malloc-string &free :> tag
+  event f tag 0 0 yaml_mapping_start_event_initialize yaml-assert-ok
+  emitter event yaml_emitter_emit yaml-assert-ok
+] with-destructors ;
+: emit-assoc-end ( emitter event -- )
+  dup yaml_mapping_end_event_initialize yaml-assert-ok
+  yaml_emitter_emit yaml-assert-ok ;
+
+: emit-assoc ( emitter event assoc -- )
+  [ [ emit-value ] with with bi@ ] with with assoc-each ;
+
+M: assoc emit-value ( emitter event seq -- )
+  [ drop emit-assoc-start ] [ emit-assoc ] [ drop emit-assoc-end ] 3tri ;
+
+:: >yaml ( obj -- str )
+[
+yaml_emitter_t (malloc-struct) &free :> emitter
+emitter yaml_emitter_initialize yaml-assert-ok
+emitter &yaml_emitter_delete drop
+
+BV{ } clone :> output
+output yaml-write-buffer set-global
+emitter yaml-write-handler f yaml_emitter_set_output
+
+yaml_event_t (malloc-struct) &free :> event
+
+event YAML_UTF8_ENCODING yaml_stream_start_event_initialize yaml-assert-ok
+emitter event yaml_emitter_emit yaml-assert-ok
+event f f f 0 yaml_document_start_event_initialize yaml-assert-ok
+emitter event yaml_emitter_emit yaml-assert-ok
+
+emitter event obj emit-value
+
+event 0 yaml_document_end_event_initialize yaml-assert-ok
+emitter event yaml_emitter_emit yaml-assert-ok
+event yaml_stream_end_event_initialize yaml-assert-ok
+emitter event yaml_emitter_emit yaml-assert-ok
+
+emitter yaml_emitter_flush yaml-assert-ok
+yaml-write-buffer get utf8 decode
+
+] with-destructors
+
+;