diff --git a/freesia/__init__.py b/freesia/__init__.py
new file mode 100644
index 0000000..cf78f17
--- /dev/null
+++ b/freesia/__init__.py
@@ -0,0 +1,3 @@
+#!/usr/bin/env python
+
+from .freesia import *
diff --git a/freesia/__main__.py b/freesia/__main__.py
old mode 100755
new mode 100644
index 547c43f..547b421
--- a/freesia/__main__.py
+++ b/freesia/__main__.py
@@ -1,60 +1,5 @@
 #!/usr/bin/env python
 
-from __future__ import print_function
+import sys, freesia
 
-import argparse, sys, os.path
-
-argparser = argparse.ArgumentParser(description="Locates free space inside a GBA ROM.")
-argparser.add_argument("--rom", dest="ROM", required=True)
-argparser.add_argument("--needed-bytes", dest="NEEDED_BYTES", required=True)
-argparser.add_argument("--start-at", dest="START_AT", required=True)
-
-args = argparser.parse_args()
-args.NEEDED_BYTES = int(args.NEEDED_BYTES, 0)
-args.START_AT = int(args.START_AT, 0) & 0x1FFFFFF
-
-def round_up_to_4(x):
-    if x & 0x3 == 0:
-        return x
-    else:
-        return round_up_to_4(x + 1)
-
-def find_needed_bytes(rom, needed_bytes, start_at):
-    if needed_bytes == 0:
-        return 0
-
-    needed_words = round_up_to_4(needed_bytes) >> 2
-    start_at = round_up_to_4(start_at)
-    
-    with open(rom, "rb") as rom:
-        rom.seek(start_at)
-
-        record, start = 0, None
-
-        while record < needed_words:
-            val = rom.read(4)
-
-            if val == b"\xff\xff\xff\xff":
-                if start is None:
-                    assert record == 0
-                    record = 1
-                    
-                    start = rom.tell() - 4
-                else:
-                    record += 1
-            elif len(val) < 4:
-                print("{}: error: end of file reached before a suitable location was found".format(os.path.basename(sys.argv[0])), file=sys.stderr)
-                sys.exit(1)
-            else:
-                record, start = 0, None
-
-        # sanity check
-        rom.seek(start)
-        assert rom.read(round_up_to_4(needed_bytes)) == b"\xff\xff\xff\xff" * needed_words
-
-    return start
-
-
-addr = find_needed_bytes(rom=args.ROM, needed_bytes=args.NEEDED_BYTES, start_at=args.START_AT) | 0x08000000
-
-print("0x{0:08X}".format(addr))
+sys.exit(freesia.main())
diff --git a/freesia/freesia.py b/freesia/freesia.py
new file mode 100755
index 0000000..7238ec1
--- /dev/null
+++ b/freesia/freesia.py
@@ -0,0 +1,65 @@
+#!/usr/bin/env python
+
+from __future__ import print_function
+
+import argparse, sys
+
+def round_up_to_4(x):
+    if x & 0x3 == 0:
+        return x
+    else:
+        return round_up_to_4(x + 1)
+
+def find_needed_bytes(*, rom, needed_bytes, start_at):
+    if needed_bytes == 0:
+        return 0
+
+    needed_words = round_up_to_4(needed_bytes) >> 2
+    start_at = round_up_to_4(start_at)
+
+    rom.seek(start_at)
+
+    record, start = 0, None
+
+    while record < needed_words:
+        val = rom.read(4)
+
+        if val == b"\xff\xff\xff\xff":
+            if start is None:
+                assert record == 0
+                record = 1
+
+                start = rom.tell() - 4
+            else:
+                record += 1
+        elif len(val) < 4:
+            raise EOFError()
+        else:
+            record, start = 0, None
+
+    # sanity check
+    rom.seek(start)
+    assert rom.read(round_up_to_4(needed_bytes)) == b"\xff\xff\xff\xff" * needed_words
+
+    return start
+
+def main():
+    argparser = argparse.ArgumentParser(description="Locates free space inside a GBA ROM.")
+    argparser.add_argument("--rom", dest="ROM", required=True)
+    argparser.add_argument("--needed-bytes", dest="NEEDED_BYTES", required=True)
+    argparser.add_argument("--start-at", dest="START_AT", required=True)
+
+    args = argparser.parse_args()
+    args.NEEDED_BYTES = int(args.NEEDED_BYTES, 0)
+    args.START_AT = int(args.START_AT, 0) & 0x1FFFFFF
+
+    try:
+        with open(args.ROM, "rb") as rom:
+            addr = find_needed_bytes(rom=rom, needed_bytes=args.NEEDED_BYTES, start_at=args.START_AT) | 0x08000000
+            print("0x{0:08X}".format(addr))
+    except EOFError:
+        print("{}: error: end of file reached before a suitable location was found".format(argparser.prog), file=sys.stderr)
+        return 1
+
+if __name__ == "__main__":
+    sys.exit(main())