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(in-package 3bz)
;; libz says these are enough entries for zlib as specified
(defconstant +max-tree-entries/len+ 852)
(defconstant +max-tree-entries/dist+ 592)
(defconstant +max-tree-size+ (+ +max-tree-entries/len+
+max-tree-entries/dist+))
;; max # of bits for an encoded huffman tree entry + and optional extra bits
;; (= 15 bits + 13 extra bits)
(defconstant +ht-max-bits+ 28)
;; low-bit tags for nodes in tree
(defconstant +ht-literal+ #b00)
(defconstant +ht-link/end+ #b01)
(defconstant +ht-len/dist+ #b10)
(defconstant +ht-invalid+ #b11)
;; 'end' code in lit/len alphabet
(defconstant +end-code+ 256)
;; first length code in lit/len alphabet
(defconstant +lengths-start+ 257)
;; last valid length (there are some extra unused values to fill tree)
(defconstant +lengths-end+ 285)
;; offset of length codes in extra-bits tables
(eval-when (:compile-toplevel :load-toplevel :execute)
(defconstant +lengths-extra-bits-offset+ 32))
(defconstant +adler32-prime+ 65521)
;; extra-bits and len/dist-bases store
(declaim (type (simple-array (unsigned-byte 4)
(#. (+ 29 +lengths-extra-bits-offset+)))
+extra-bits+)
(type (simple-array (unsigned-byte 16)
(#. (+ 29 +lengths-extra-bits-offset+)))
+len/dist-bases+))
(alexandria:define-constant +extra-bits+
(concatenate
'(simple-array (unsigned-byte 4) (61))
(replace (make-array +lengths-extra-bits-offset+ :initial-element 0)
#(0 0 0 0 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 10 10 11 11 12 12 13 13))
#(0 0 0 0 0 0 0 0 1 1 1 1 2 2 2 2 3 3 3 3 4 4 4 4 5 5 5 5 0))
:test 'equalp)
;; base length value for each length/distance code, add to extra bits
;; to get length
(alexandria:define-constant +len/dist-bases+
(concatenate '(simple-array (unsigned-byte 16) (61))
(replace (make-array +lengths-extra-bits-offset+ :initial-element 0)
#(1 2 3 4 5 7 9 13 17 25 33 49 65 97
129 193 257 385 513 769
1025 1537 2049 3073 4097 6145 8193
12289 16385 24577))
#(3 4 5 6 7 8 9 10 11 13 15 17 19 23 27 31 35 43 51 59 67 83 99
115 131 163 195 227 258))
:test 'equalp)
(declaim (type (simple-array (unsigned-byte 8) (19)) +len-code-order+))
(alexandria:define-constant +len-code-order+
(coerce #(16 17 18 0 8 7 9 6 10 5 11 4 12 3 13 2 14 1 15)
'(simple-array (unsigned-byte 8) (19)))
:test 'equalp)
(declaim (type (simple-array (unsigned-byte 4) (19)) +len-code-extra+))
(alexandria:define-constant +len-code-extra+
(coerce #(0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 3 7)
'(simple-array (unsigned-byte 4) (19)))
:test 'equalp)
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