Support seeking past the end of writable file streams as Bocfel needs…

… it (see iftechfoundation/ifarchive-if-specs#17)

Support non-existent files in `glkunix_stream_open_pathname_gen`
Wrap glkstart.h in `extern "C"`

remglk/src/glkapi/mod.rs

@@ -1632,9 +1632,13 @@ where S: Default + GlkSystem {
 
 #[derive(Default)]
 pub struct Directories {
+    /** The storyfile directory, used by `garglk_add_resource_from_file` */
     pub storyfile: PathBuf,
+    /** The system current working directory, used by `glkunix_stream_open_pathname` */
     pub system_cwd: PathBuf,
+    /** Temp folder */
     pub temp: PathBuf,
+    /** The Glk "current directory", used by `glk_fileref_create_by_name`/`glk_fileref_create_by_prompt` */
     pub working: PathBuf,
 }
 

remglk/src/glkapi/streams.rs

@@ -331,6 +331,16 @@ where T: Clone + Default, Box<[T]>: GlkArray {
     }
 
     fn set_position(&mut self, mode: SeekMode, pos: i32) {
+        // Despite the Glk spec saying that it's illegal to specify a position after the end of a file (5.4) this is needed by Bocfel, and seemingly supported by all libc based Glk interpreters, so we might need to expand first
+        // See https://github.com/iftechfoundation/ifarchive-if-specs/issues/17
+        let new_pos = match mode {
+            SeekMode::Current => self.str.pos as i32 + pos,
+            SeekMode::End => self.str.len as i32 + pos,
+            SeekMode::Start => pos,
+        } as usize;
+        if new_pos > self.str.len {
+            self.expand(new_pos - self.str.len);
+        }
         self.str.set_position(mode, pos);
     }
 

remglk_capi/src/glk/glkstart.h

@@ -18,6 +18,10 @@
 #ifndef GT_START_H
 #define GT_START_H
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /* We define our own TRUE and FALSE and NULL, because ANSI
     is a strange world. */
 #ifndef TRUE
@@ -115,5 +119,9 @@ extern void glkunix_fileref_set_dispatch_rock(frefid_t fref, glk_objrock_u rock)
 
 #endif /* GLKUNIX_AUTOSAVE_FEATURES */
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* GT_START_H */
 

remglk_capi/src/glkstart.rs

@@ -202,11 +202,10 @@ unsafe fn glkunix_arguments() -> Vec<GlkUnixArgument> {
 
 #[no_mangle]
 pub extern "C" fn glkunix_fileref_create_by_name_uncleaned(usage: u32, filename_ptr: *const i8, rock: u32) -> FileRefPtr {
-    let mut glkapi = glkapi().lock().unwrap();
     let filename_cstr = unsafe {CStr::from_ptr(filename_ptr)};
     let filename = filename_cstr.to_string_lossy().to_string();
-    let fileref = glkapi.glkunix_fileref_create_by_name_uncleaned(usage, filename, rock);
-    to_owned(fileref)
+    let result = glkapi().lock().unwrap().glkunix_fileref_create_by_name_uncleaned(usage, filename, rock);
+    to_owned(result)
 }
 
 #[no_mangle]
@@ -242,7 +241,7 @@ pub extern "C" fn glkunix_stream_open_pathname_gen(filename_ptr: *const i8, writ
     let fileref = glkunix_fileref_create_by_name_uncleaned(fileusage_Data | if textmode > 0 {fileusage_TextMode} else {fileusage_BinaryMode}, filename_ptr, 0);
     let fileref = reclaim(fileref);
     let mut glkapi = glkapi().lock().unwrap();
-    let str = glkapi.glk_stream_open_file(&fileref, if writemode > 0 {FileMode::Write} else {FileMode::Read}, rock).unwrap().unwrap();
+    let result = glkapi.glk_stream_open_file(&fileref, if writemode > 0 {FileMode::Write} else {FileMode::Read}, rock);
     glkapi.glk_fileref_destroy(fileref);
-    to_owned(str)
+    to_owned_opt(result.unwrap())
 }