adding simple header validation

src/shell.zig

@@ -7,8 +7,8 @@ const BoundedArray = std.BoundedArray;
 const StringContext = std.hash_map.StringContext;
 
 // MaxShells is the maximum number of "popular" shells.
-const MaxShells = 63;
-const MaxShellLen = 64;
+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
@@ -22,7 +22,7 @@ const ShellIndex = struct {
 };
 
 // ShellReader interprets "Shell Index" and "Shell Blob" sections.
-const ShellReader = struct {
+pub const ShellReader = struct {
     sectionIndex: []const ShellIndex,
     sectionBlob: []const u8,
 
@@ -44,7 +44,7 @@ const ShellReader = struct {
 
 // ShellWriter is a shell popularity contest: collect shells and return the
 // popular ones, sorted by score. score := len(shell) * number_of_shells.
-const ShellWriter = struct {
+pub const ShellWriter = struct {
     counts: std.StringHashMap(u32),
     allocator: Allocator,
     const KV = struct { shell: []const u8, score: u32 };