properly report and handle EOF when handling input HEAD main

this should be a robust fix for the double-termination issue when compiling

Force-Push: yes
Change-Id: Ieaacdc232ea7e3036916d81139fc5c5a41087c64

1 files changed, 12 insertions, 6 deletions

diff --git a/input.e b/input.e
index 3d8fabb..16fa836 100644
--- a/input.e
+++ b/input.e
@@ -134,16 +134,20 @@
   swap buffer-logical-start ! ;
 
 
-~ (metadata pointer -- byte or 0)
+~   We use -1 as a return value to indicate end-of-file. This can be
+~ distinguished from valid data, because it's a full 64 bits, whereas a byte
+~ of 0xFF wouldn't be.
+~
+~ (metadata pointer -- byte or -1)
 : peek-from
   dup buffer-logical-length @ {
     ~ If the length is zero, there is no input, but we can still try calling
     ~ the "refill" word.
     ~ (metadata pointer)
     dup input-buffer-refill @ dup {
-      ~ If the refill word is zero, we can't help, just return null.
+      ~ If the refill word is zero, we can't help, just return EOF.
       ~ (metadata pointer, refill word)
-      drop drop 0 exit
+      drop drop -1 exit
     } unless
 
     ~ If the refill word is nonzero, call it. It expects a copy of the metadata
@@ -153,9 +157,9 @@
     ~ (metadata pointer)
     ~ Now we check if the length is still zero.
     dup buffer-logical-length @ {
-      ~ The length is zero even after calling the refill word, so return null.
+      ~ The length is zero even after calling the refill word, so return EOF.
       ~ (metadata pointer)
-      drop 0 exit
+      drop -1 exit
     } unless
   } unless
 
@@ -171,7 +175,9 @@
   buffer-logical-start @ 8@ ;
 
 
-~ (metadata pointer -- byte or 0)
+~   Just as with peek-from, we use -1 for EOF.
+~
+~ (metadata pointer -- byte or -1)
 : key-from
   dup peek-from
   ~ (metadata pointer, result byte)