add proper functionality for opening files for reading HEAD main

the overall file API is not yet stable, this is subject to change, but it felt like the time had come for this first step

Force-Push: yes
Change-Id: Idad271b975748b67b5bb9a82fe22337080447e97

1 files changed, 30 insertions, 1 deletions

diff --git a/language/dynamic/files.e b/language/dynamic/files.e
index 4822c2f..e0ef533 100644
--- a/language/dynamic/files.e
+++ b/language/dynamic/files.e
@@ -150,7 +150,7 @@
   ~ (filename, file descriptor)
 
   ~   Notice that we deferred this allocation until after we know that opening
-  ~ the file succeeded. We can't leave it any longer thaan this;
+  ~ the file succeeded. We can't leave it any longer than this;
   ~ push-input-buffer will allocate memory, which will overwrite the scratch
   ~ space.
   swap allocate-string-if-temporary swap
@@ -176,3 +176,32 @@
 : current-input-file-name
   main-input-buffer buffer-filename @ ;
 
+
+: open-file-for-reading
+~ (filename -- metadata pointer or 0)
+  dup 0 0 sys-open
+  dup 0 > {
+    ." Couldn't open " swap emitstring space
+    ." because " space . ." ." newline
+    drop 0 exit
+  } if
+  ~ (filename, file descriptor)
+
+  ~ As with include, we deferred this allocation until after successful open.
+  swap allocate-string-if-temporary swap
+
+  allocate-input-buffer-metadata dup zero-input-buffer-metadata
+  ~ (filename, file descriptor)
+
+  dup 3unroll swap attach-input-buffer-to-file-descriptor ;
+
+
+~ Note that this doesn't clear data that's already in the buffer.
+~
+~ (metadata pointer --)
+: close-file
+  dup buffer-file-descriptor @ sys-close drop
+  ~ Ignore a failed close.
+
+  buffer-file-descriptor -1 swap ! ;
+