1 files changed, 24 insertions, 0 deletions
diff --git a/src/base/io/offset.c b/src/base/io/offset.c
new file mode 100644
index 0000000..81ef994
--- /dev/null
+++ b/src/base/io/offset.c
@@ -0,0 +1,24 @@
+#include "internal.h"
+
+intptr
+io·offset(io·Header *io)
+{
+    intptr n;
+    switch(io->state){
+    default:
+        fmt·fprint(2, "offset: unknown state %d\n", io->state);
+        n = io·BufEof;
+        break;
+
+    case io·BufEnd:
+    case io·BufRdr:
+        n = io->pos + io->ilen;
+        break;
+
+    case io·BufWtr:
+        n = io->pos + (io->cap + io->olen);
+        break;
+    }
+
+    return n;
+}