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;;; base64.lisp -- The base64 encoding, defined in RFC 3548 and 4648.
(cl:in-package :binascii)
(defvar *base64-encode-table*
#.(coerce "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/" 'simple-base-string))
(defvar *base64url-encode-table*
#.(coerce "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_" 'simple-base-string))
(defstruct (base64-encode-state
(:constructor make-base64-encode-state
(&aux (descriptor (base64-format-descriptor))
(table *base64-encode-table*)))
(:constructor make-base64url-encode-state
(&aux (descriptor (base64-format-descriptor))
(table *base64url-encode-table*))))
(bits 0 :type (unsigned-byte 16))
(n-bits 0 :type (unsigned-byte 8))
(table *base64-encode-table* :read-only t :type (simple-array base-char (64)))
(padding-remaining 0 :type (integer 0 3)))
(declaim (notinline base64-encoder))
(defun base64-encoder (state output input
output-index output-end
input-index input-end lastp converter)
(declare (type (or simple-string simple-octet-vector) output))
(declare (type base64-encode-state state))
(declare (type simple-octet-vector input))
(declare (type index output-index output-end input-index input-end))
(declare (type function converter))
(let ((bits (base64-encode-state-bits state))
(n-bits (base64-encode-state-n-bits state))
(table (base64-encode-state-table state)))
(declare (type index input-index output-index))
(declare (type (unsigned-byte 16) bits))
(declare (type (integer 0 16) n-bits))
(when (base64-encode-state-finished-input-p state)
(go PAD))
INPUT-CHECK
(when (>= input-index input-end)
(go DONE))
DO-INPUT
(when (< n-bits 6)
(setf bits (ldb (byte 16 0)
(logior (ash bits 8) (aref input input-index))))
(incf input-index)
(incf n-bits 8))
OUTPUT-CHECK
(when (>= output-index output-end)
(go DONE))
DO-OUTPUT
(decf n-bits 6)
(setf (aref output output-index)
(funcall converter (aref table (ldb (byte 6 n-bits) bits))))
(incf output-index)
(if (>= n-bits 6)
(go OUTPUT-CHECK)
(go INPUT-CHECK))
DONE
(unless lastp
(go RESTORE-STATE))
(setf (base64-encode-state-finished-input-p state) t)
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(cond
((= n-bits 2)
(setf (base64-encode-state-padding-remaining state) 3))
((= n-bits 4)
(setf (base64-encode-state-padding-remaining state) 2)))
PAD
(cond
((or (zerop n-bits)
(zerop (base64-encode-state-padding-remaining state)))
(go RESTORE-STATE))
((= n-bits 2)
(go DO-PAD-FOR-2-BITS))
((= n-bits 4)
(go DO-PAD-FOR-4-BITS)))
DO-PAD-FOR-2-BITS
(let ((padding-remaining (base64-encode-state-padding-remaining state)))
(declare (type (integer 0 3) padding-remaining))
(when (and (>= padding-remaining 3)
(< output-index output-end))
(setf (aref output output-index)
(funcall converter
(aref table (ash (ldb (byte 2 0) bits) 4))))
(incf output-index)
(decf padding-remaining))
(when (and (>= padding-remaining 2)
(< output-index output-end))
(setf (aref output output-index) (funcall converter #\=))
(incf output-index)
(decf padding-remaining))
(when (and (>= padding-remaining 1)
(< output-index output-end))
(setf (aref output output-index) (funcall converter #\=))
(incf output-index)
(decf padding-remaining))
(when (zerop padding-remaining)
(setf n-bits 0))
(setf (base64-encode-state-padding-remaining state) padding-remaining)
(go RESTORE-STATE))
DO-PAD-FOR-4-BITS
(let ((padding-remaining (base64-encode-state-padding-remaining state)))
(declare (type (integer 0 3) padding-remaining))
(when (and (>= padding-remaining 2)
(< output-index output-end))
(setf (aref output output-index)
(funcall converter
(aref table (ash (ldb (byte 4 0) bits) 2))))
(incf output-index)
(decf padding-remaining))
(when (and (>= padding-remaining 1)
(< output-index output-end))
(setf (aref output output-index) (funcall converter #\=))
(incf output-index)
(decf padding-remaining))
(when (zerop padding-remaining)
(setf n-bits 0))
(setf (base64-encode-state-padding-remaining state) padding-remaining)
(go RESTORE-STATE))
RESTORE-STATE
(setf (base64-encode-state-bits state) bits
(base64-encode-state-n-bits state) n-bits))
(values input-index output-index)))
(defun encoded-length-base64 (count)
"Return the number of characters required to encode COUNT octets in Base64."
(* (ceiling count 3) 4))
(defvar *base64-decode-table*
(make-decode-table *base64-encode-table*))
(declaim (type decode-table *base64-decode-table*))
(defvar *base64url-decode-table*
(make-decode-table *base64url-encode-table*))
(declaim (type decode-table *base64url-decode-table*))
(defstruct (base64-decode-state
(:include decode-state)
(:copier nil)
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(:constructor %make-base64-decode-state
(table
&aux (descriptor (base64-format-descriptor)))))
(bits 0 :type (unsigned-byte 16))
(n-bits 0 :type (unsigned-byte 8))
(padding-remaining 0 :type (integer 0 3))
(table *base64-decode-table* :read-only t :type decode-table))
(defun make-base64-decode-state (case-fold map01)
(declare (ignore case-fold map01))
(%make-base64-decode-state *base64-decode-table*))
(defun make-base64url-decode-state (case-fold map01)
(declare (ignore case-fold map01))
(%make-base64-decode-state *base64url-decode-table*))
(defun base64-decoder (state output input
output-index output-end
input-index input-end lastp converter)
(declare (type base64-decode-state state))
(declare (type simple-octet-vector output))
(declare (type index output-index output-end input-index input-end))
(declare (type function converter))
(let ((bits (base64-decode-state-bits state))
(n-bits (base64-decode-state-n-bits state))
(padding-remaining (base64-decode-state-padding-remaining state))
(table (base64-decode-state-table state)))
(declare (type (unsigned-byte 16) bits))
(declare (type fixnum n-bits))
(declare (type (integer 0 6) padding-remaining))
(tagbody
PAD-CHECK
(when (base64-decode-state-finished-input-p state)
(go EAT-EQUAL-CHECK-PAD))
OUTPUT-AVAILABLE-CHECK
(when (< n-bits 8)
(go INPUT-AVAILABLE-CHECK))
OUTPUT-SPACE-CHECK
(when (>= output-index output-end)
(go DONE))
DO-OUTPUT
(decf n-bits 8)
(setf (aref output output-index) (logand (ash bits (- n-bits)) #xff)
bits (logand bits #xff))
(incf output-index)
(go INPUT-AVAILABLE-CHECK)
INPUT-AVAILABLE-CHECK
(when (>= input-index input-end)
(go DONE))
DO-INPUT
(let* ((c (aref input input-index))
(v (funcall converter c))
(d (dtref table v)))
(when (= v (if (typep input 'simple-octet-vector)
(char-code #\=)
(funcall converter #\=)))
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(go SAW-EQUAL))
(when (= d +dt-invalid+)
(error "invalid base64 character ~A at position ~D" c input-index))
(incf input-index)
(setf bits (ldb (byte 16 0) (logior (ash bits 6) d)))
(incf n-bits 6)
(go OUTPUT-AVAILABLE-CHECK))
DONE
(unless lastp
(go RESTORE-STATE))
SAW-EQUAL
(setf (base64-decode-state-finished-input-p state) t)
(cond
((zerop n-bits)
(go RESTORE-STATE))
((= n-bits 2)
(setf padding-remaining 3))
((= n-bits 4)
(setf padding-remaining 2)))
EAT-EQUAL-CHECK-PAD
(when (zerop padding-remaining)
(go RESTORE-STATE))
EAT-EQUAL-CHECK-INPUT
(when (>= input-index input-end)
(go RESTORE-STATE))
EAT-EQUAL
(let ((v (aref input input-index)))
(unless (= (funcall converter v)
(if (typep input 'simple-octet-vector)
(char-code #\=)
(funcall converter #\=)))
(error "invalid base64 input ~A at position ~D" v input-index))
(incf input-index)
(decf padding-remaining)
(go EAT-EQUAL-CHECK-PAD))
RESTORE-STATE
(setf (base64-decode-state-n-bits state) n-bits
(base64-decode-state-bits state) bits
(base64-decode-state-padding-remaining state) padding-remaining))
(values input-index output-index)))
(defun decoded-length-base64 (length)
(* (ceiling length 4) 3))
(define-format :base64
:encode-state-maker make-base64-encode-state
:decode-state-maker make-base64-decode-state
:encode-length-fun encoded-length-base64
:decode-length-fun decoded-length-base64
:encoder-fun base64-encoder
:decoder-fun base64-decoder)
(define-format :base64url
:encode-state-maker make-base64url-encode-state
:decode-state-maker make-base64url-decode-state
:encode-length-fun encoded-length-base64
:decode-length-fun decoded-length-base64
:encoder-fun base64-encoder
:decoder-fun base64-decoder)