spec: bytevectors (make-bytevector/u8-ref/u8-set!/utf8->string/etc)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

spec/primitives.sx

@@ -1252,3 +1252,77 @@
   :params ((re :as regexp) (str :as string))
   :returns "list"
   :doc "Split str on every match of re; returns list of strings.")
+
+(define-module :stdlib.bytevectors)
+
+(define-primitive
+  "make-bytevector"
+  :params (n &rest fill)
+  :returns "bytevector"
+  :doc "Create a bytevector of n bytes, all initialised to fill (default 0).")
+
+(define-primitive
+  "bytevector?"
+  :params (v)
+  :returns "boolean"
+  :doc "True if v is a bytevector.")
+
+(define-primitive
+  "bytevector-length"
+  :params ((bv :as bytevector))
+  :returns "number"
+  :doc "Number of bytes in bv.")
+
+(define-primitive
+  "bytevector-u8-ref"
+  :params ((bv :as bytevector) (i :as number))
+  :returns "number"
+  :doc "Byte value 0-255 at index i.")
+
+(define-primitive
+  "bytevector-u8-set!"
+  :params ((bv :as bytevector) (i :as number) (byte :as number))
+  :returns "nil"
+  :doc "Set byte at index i to byte 0-255. Mutates bv.")
+
+(define-primitive
+  "bytevector-copy"
+  :params ((bv :as bytevector) &rest bounds)
+  :returns "bytevector"
+  :doc "Fresh copy of bv, optionally sliced to [start, end).")
+
+(define-primitive
+  "bytevector-copy!"
+  :params ((dst :as bytevector) (at :as number) (src :as bytevector) &rest bounds)
+  :returns "nil"
+  :doc "Copy bytes from src[start..end) into dst starting at at. Mutates dst.")
+
+(define-primitive
+  "bytevector-append"
+  :params (&rest bvs)
+  :returns "bytevector"
+  :doc "Concatenate bytevectors into a new bytevector.")
+
+(define-primitive
+  "utf8->string"
+  :params ((bv :as bytevector) &rest bounds)
+  :returns "string"
+  :doc "Decode bv[start..end) as UTF-8 and return the string.")
+
+(define-primitive
+  "string->utf8"
+  :params ((s :as string) &rest bounds)
+  :returns "bytevector"
+  :doc "Encode s[start..end) as UTF-8 and return a bytevector.")
+
+(define-primitive
+  "bytevector->list"
+  :params ((bv :as bytevector))
+  :returns "list"
+  :doc "Convert bytevector to a list of byte integers.")
+
+(define-primitive
+  "list->bytevector"
+  :params ((lst :as list))
+  :returns "bytevector"
+  :doc "Build a bytevector from a list of byte integers 0-255.")