fix casting functions, add some tests

src/shell.zig

@@ -10,17 +10,6 @@ const StringContext = std.hash_map.StringContext;
 pub const MaxShells = 63;
 pub const MaxShellLen = 64;
 
-// ShellIndex is an index to the shell strings. As shell can be up to 64 bytes
-// (1<<6), maximum number of shells is 63 (1<<6-1), the maximum location offset
-// is 1<<12. To make location resolvable in 10 bits, all shells will be padded
-// to 4 bytes.
-// The actual shell length is len+1: we don't allow empty shells, and the real
-// length of the shell is 1-64 bytes.
-const ShellIndex = struct {
-    offset: u10,
-    len: u6,
-};
-
 // ShellReader interprets "Shell Index" and "Shell Blob" sections.
 pub const ShellReader = struct {
     sectionIndex: []const ShellIndex,
@@ -81,7 +70,7 @@ pub const ShellWriter = struct {
                 const padding = roundUp4Padding(fullOffset);
                 fullOffset += padding;
                 //const stderr = std.io.getStdErr().writer();
-                //try stderr.print("\n", .{});
+                //stderr.print("\n", .{}) catch unreachable;
                 try self.blob.appendNTimes(0, padding);
                 idx += 1;
             }
@@ -181,6 +170,17 @@ inline fn roundUp4Padding(n: u12) u12 {
     return ((n + 3) & ~@intCast(u12, 3)) - n;
 }
 
+// ShellIndex is an index to the shell strings. As shell can be up to 64 bytes
+// (1<<6), maximum number of shells is 63 (1<<6-1), the maximum location offset
+// is 1<<12. To make location resolvable in 10 bits, all shells will be padded
+// to 4 bytes.
+// The actual shell length is len+1: we don't allow empty shells, and the real
+// length of the shell is 1-64 bytes.
+const ShellIndex = struct {
+    offset: u10,
+    len: u6,
+};
+
 const testing = std.testing;
 
 test "basic shellpopcon" {