Unpack.peek: remove bound checking

Author: thislight

src/Unpack.zig

@@ -75,15 +75,14 @@ pub fn setAppend(self: *Unpack, olen: usize, new: []const u8) void {
 }
 
 pub const PeekError = error{
-    BufferEmpty,
+    /// The type could not be recongized.
     UnrecognizedType,
 };
 
+/// Peek the next value.
+///
+/// The inner buffer must have at least 1 byte.
 pub fn peek(self: *const Unpack) PeekError!HeaderType {
-    if (self.rest.len == 0) {
-        return PeekError.BufferEmpty;
-    }
-
     return HeaderType.from(self.rest[0]) orelse PeekError.UnrecognizedType;
 }
 

src/io.zig

@@ -148,15 +148,10 @@ pub const UnpackReader = struct {
 
     /// Peek the next value's type
     fn peek(self: *UnpackReader, reader: anytype) !fmt.HeaderType {
-        while (true) {
-            return self.unpack.peek() catch |err| switch (err) {
-                error.BufferEmpty => {
-                    try self.readMore(reader);
-                    continue;
-                },
-                else => err,
-            };
+        while (self.unpack.rest.len == 0) {
+            try self.readMore(reader);
         }
+        return try self.unpack.peek();
     }
 
     fn resetUnreadToStart(self: *UnpackReader) usize {