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;;; -*- Mode: LISP; Syntax: COMMON-LISP; Package: FLEXI-STREAMS; Base: 10 -*-
;;; $Header: /usr/local/cvsrep/flexi-streams/length.lisp,v 1.6 2008/05/29 10:25:14 edi Exp $
;;; Copyright (c) 2005-2008, Dr. Edmund Weitz. All rights reserved.
;;; Redistribution and use in source and binary forms, with or without
;;; modification, are permitted provided that the following conditions
;;; are met:
;;; * Redistributions of source code must retain the above copyright
;;; notice, this list of conditions and the following disclaimer.
;;; * Redistributions in binary form must reproduce the above
;;; copyright notice, this list of conditions and the following
;;; disclaimer in the documentation and/or other materials
;;; provided with the distribution.
;;; THIS SOFTWARE IS PROVIDED BY THE AUTHOR 'AS IS' AND ANY EXPRESSED
;;; OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
;;; WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
;;; ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
;;; DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
;;; DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
;;; GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
;;; INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
;;; WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
;;; NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
;;; SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
(in-package :flexi-streams)
(defgeneric encoding-factor (format)
(:documentation "Given an external format FORMAT, returns a factor
which denotes the octets to characters ratio to expect when
encoding/decoding. If the returned value is an integer, the factor is
assumed to be exact. If it is a \(double) float, the factor is
supposed to be based on heuristics and usually not exact.
This factor is used in string.lisp.")
(declare #.*standard-optimize-settings*))
(defmethod encoding-factor ((format flexi-8-bit-format))
(declare #.*standard-optimize-settings*)
;; 8-bit encodings map octets to characters in an exact one-to-one
;; fashion
1)
(defmethod encoding-factor ((format flexi-utf-8-format))
(declare #.*standard-optimize-settings*)
;; UTF-8 characters can be anything from one to six octets, but we
;; assume that the "overhead" is only about 5 percent - this
;; estimate is obviously very much dependant on the content
1.05d0)
(defmethod encoding-factor ((format flexi-utf-16-format))
(declare #.*standard-optimize-settings*)
;; usually one character maps to two octets, but characters with
;; code points above #x10000 map to four octets - we assume that we
;; usually don't see these characters but of course have to return a
;; float
2.0d0)
(defmethod encoding-factor ((format flexi-utf-32-format))
(declare #.*standard-optimize-settings*)
;; UTF-32 always matches every character to four octets
4)
(defmethod encoding-factor ((format flexi-crlf-mixin))
(declare #.*standard-optimize-settings*)
;; if the sequence #\Return #\Linefeed is the line-end marker, this
;; obviously makes encodings potentially longer and definitely makes
;; the estimate unexact
(* 1.02d0 (call-next-method)))
(defgeneric check-end (format start end i)
(declare #.*fixnum-optimize-settings*)
(:documentation "Helper function used below to determine if we tried
to read past the end of the sequence.")
(:method (format start end i)
(declare #.*fixnum-optimize-settings*)
(declare (ignore start))
(declare (fixnum end i))
(when (> i end)
(signal-encoding-error format "This sequence can't be decoded ~
using ~A as it is too short. ~A octet~:P missing at the end."
(external-format-name format)
(- i end))))
(:method ((format flexi-utf-16-format) start end i)
(declare #.*fixnum-optimize-settings*)
(declare (fixnum start end i))
(declare (ignore i))
;; don't warn twice
(when (evenp (- end start))
(call-next-method))))
(defgeneric compute-number-of-chars (format sequence start end)
(declare #.*standard-optimize-settings*)
(:documentation "Computes the exact number of characters required to
decode the sequence of octets in SEQUENCE from START to END using the
external format FORMAT."))
(defmethod compute-number-of-chars :around (format (list list) start end)
(declare #.*standard-optimize-settings*)
(call-next-method format (coerce list 'vector) start end))
(defmethod compute-number-of-chars ((format flexi-8-bit-format) sequence start end)
(declare #.*fixnum-optimize-settings*)
(declare (fixnum start end))
(declare (ignore sequence))
(- end start))
(defmethod compute-number-of-chars ((format flexi-crlf-mixin) sequence start end)
;; this method only applies to the 8-bit formats as all other
;; formats with CRLF line endings have their own specialized methods
;; below
(declare #.*fixnum-optimize-settings*)
(declare (fixnum start end) (vector sequence))
(let ((i start)
(length (- end start)))
(declare (fixnum i length))
(loop
(when (>= i end)
(return))
(let ((position (search #.(vector +cr+ +lf+) sequence :start2 i :end2 end :test #'=)))
(unless position
(return))
(setq i (1+ position))
(decf length)))
length))
(defmethod compute-number-of-chars ((format flexi-utf-8-format) sequence start end)
(declare #.*fixnum-optimize-settings*)
(declare (fixnum start end) (vector sequence))
(let ((sum 0)
(i start))
(declare (fixnum i sum))
(loop
(when (>= i end)
(return))
(let* ((octet (aref sequence i))
;; note that there are no validity checks here
(length (cond ((not (logbitp 7 octet)) 1)
((= #b11000000 (logand* octet #b11100000)) 2)
((= #b11100000 (logand* octet #b11110000)) 3)
(t 4))))
(declare (fixnum length) (type octet octet))
(incf sum)
(incf i length)))
(check-end format start end i)
sum))
(defmethod compute-number-of-chars ((format flexi-crlf-utf-8-format) sequence start end)
(declare #.*fixnum-optimize-settings*)
(declare (fixnum start end) (vector sequence))
(let ((sum 0)
(i start)
(last-octet 0))
(declare (fixnum i sum) (type octet last-octet))
(loop
(when (>= i end)
(return))
(let* ((octet (aref sequence i))
;; note that there are no validity checks here
(length (cond ((not (logbitp 7 octet)) 1)
((= #b11000000 (logand* octet #b11100000)) 2)
((= #b11100000 (logand* octet #b11110000)) 3)
(t 4))))
(declare (fixnum length) (type octet octet))
(unless (and (= octet +lf+) (= last-octet +cr+))
(incf sum))
(incf i length)
(setq last-octet octet)))
(check-end format start end i)
sum))
(defmethod compute-number-of-chars :before ((format flexi-utf-16-format) sequence start end)
(declare #.*fixnum-optimize-settings*)
(declare (fixnum start end) (vector sequence))
(declare (ignore sequence))
(when (oddp (- end start))
(signal-encoding-error format "~A octet~:P cannot be decoded ~
using UTF-16 as ~:*~A is not even."
(- end start))))
(defmethod compute-number-of-chars ((format flexi-utf-16-le-format) sequence start end)
(declare #.*fixnum-optimize-settings*)
(declare (fixnum start end))
(let ((sum 0)
(i start))
(declare (fixnum i sum))
(decf end 2)
(loop
(when (> i end)
(return))
(let* ((high-octet (aref sequence (1+ i)))
(length (cond ((<= #xd8 high-octet #xdf) 4)
(t 2))))
(declare (fixnum length) (type octet high-octet))
(incf sum)
(incf i length)))
(check-end format start (+ end 2) i)
sum))
(defmethod compute-number-of-chars ((format flexi-utf-16-be-format) sequence start end)
(declare #.*fixnum-optimize-settings*)
(declare (fixnum start end) (vector sequence))
(let ((sum 0)
(i start))
(declare (fixnum i sum))
(decf end 2)
(loop
(when (> i end)
(return))
(let* ((high-octet (aref sequence i))
(length (cond ((<= #xd8 high-octet #xdf) 4)
(t 2))))
(declare (fixnum length) (type octet high-octet))
(incf sum)
(incf i length)))
(check-end format start (+ end 2) i)
sum))
(defmethod compute-number-of-chars ((format flexi-crlf-utf-16-le-format) sequence start end)
(declare #.*fixnum-optimize-settings*)
(declare (fixnum start end) (vector sequence))
(let ((sum 0)
(i start)
(last-octet 0))
(declare (fixnum i sum) (type octet last-octet))
(decf end 2)
(loop
(when (> i end)
(return))
(let* ((high-octet (aref sequence (1+ i)))
(length (cond ((<= #xd8 high-octet #xdf) 4)
(t 2))))
(declare (fixnum length) (type octet high-octet))
(unless (and (zerop high-octet)
(= (the octet (aref sequence i)) +lf+)
(= last-octet +cr+))
(incf sum))
(setq last-octet (if (zerop high-octet)
(aref sequence i)
0))
(incf i length)))
(check-end format start (+ end 2) i)
sum))
(defmethod compute-number-of-chars ((format flexi-crlf-utf-16-be-format) sequence start end)
(declare #.*fixnum-optimize-settings*)
(declare (fixnum start end) (vector sequence))
(let ((sum 0)
(i start)
(last-octet 0))
(declare (fixnum i sum) (type octet last-octet))
(decf end 2)
(loop
(when (> i end)
(return))
(let* ((high-octet (aref sequence i))
(length (cond ((<= #xd8 high-octet #xdf) 4)
(t 2))))
(declare (fixnum length) (type octet high-octet))
(unless (and (zerop high-octet)
(= (the octet (aref sequence (1+ i))) +lf+)
(= last-octet +cr+))
(incf sum))
(setq last-octet (if (zerop high-octet)
(aref sequence (1+ i))
0))
(incf i length)))
(check-end format start (+ end 2) i)
sum))
(defmethod compute-number-of-chars :before ((format flexi-utf-32-format) sequence start end)
(declare #.*fixnum-optimize-settings*)
(declare (fixnum start end))
(declare (ignore sequence))
(let ((length (- end start)))
(when (plusp (mod length 4))
(signal-encoding-error format "~A octet~:P cannot be decoded ~
using UTF-32 as ~:*~A is not a multiple-value of four."
length))))
(defmethod compute-number-of-chars ((format flexi-utf-32-format) sequence start end)
(declare #.*fixnum-optimize-settings*)
(declare (fixnum start end))
(declare (ignore sequence))
(ceiling (- end start) 4))
(defmethod compute-number-of-chars ((format flexi-crlf-utf-32-le-format) sequence start end)
(declare #.*fixnum-optimize-settings*)
(declare (fixnum start end) (vector sequence))
(let ((i start)
(length (ceiling (- end start) 4)))
(decf end 8)
(loop
(when (> i end)
(return))
(cond ((loop for j of-type fixnum from i
for octet across #.(vector +cr+ 0 0 0 +lf+ 0 0 0)
always (= octet (aref sequence j)))
(decf length)
(incf i 8))
(t (incf i 4))))
length))
(defmethod compute-number-of-chars ((format flexi-crlf-utf-32-be-format) sequence start end)
(declare #.*fixnum-optimize-settings*)
(declare (fixnum start end) (vector sequence))
(let ((i start)
(length (ceiling (- end start) 4)))
(decf end 8)
(loop
(when (> i end)
(return))
(cond ((loop for j of-type fixnum from i
for octet across #.(vector 0 0 0 +cr+ 0 0 0 +lf+)
always (= octet (aref sequence j)))
(decf length)
(incf i 8))
(t (incf i 4))))
length))
(defgeneric compute-number-of-octets (format sequence start end)
(declare #.*standard-optimize-settings*)
(:documentation "Computes the exact number of octets required to
encode the sequence of characters in SEQUENCE from START to END using
the external format FORMAT."))
(defmethod compute-number-of-octets :around (format (list list) start end)
(declare #.*standard-optimize-settings*)
(call-next-method format (coerce list 'string*) start end))
(defmethod compute-number-of-octets ((format flexi-8-bit-format) string start end)
(declare #.*fixnum-optimize-settings*)
(declare (fixnum start end))
(declare (ignore string))
(- end start))
(defmethod compute-number-of-octets ((format flexi-utf-8-format) string start end)
(declare #.*fixnum-optimize-settings*)
(declare (fixnum start end) (string string))
(let ((sum 0)
(i start))
(declare (fixnum i sum))
(loop
(when (>= i end)
(return))
(let* ((char-code (char-code (char string i)))
(char-length (cond ((< char-code #x80) 1)
((< char-code #x800) 2)
((< char-code #x10000) 3)
(t 4))))
(declare (fixnum char-length) (type char-code-integer char-code))
(incf sum char-length)
(incf i)))
sum))
(defmethod compute-number-of-octets ((format flexi-crlf-utf-8-format) string start end)
(declare #.*fixnum-optimize-settings*)
(declare (fixnum start end) (string string))
(let ((sum 0)
(i start))
(declare (fixnum i sum))
(loop
(when (>= i end)
(return))
(let* ((char-code (char-code (char string i)))
(char-length (cond ((= char-code #.(char-code #\Newline)) 2)
((< char-code #x80) 1)
((< char-code #x800) 2)
((< char-code #x10000) 3)
(t 4))))
(declare (fixnum char-length) (type char-code-integer char-code))
(incf sum char-length)
(incf i)))
sum))
(defmethod compute-number-of-octets ((format flexi-utf-16-format) string start end)
(declare #.*fixnum-optimize-settings*)
(declare (fixnum start end) (string string))
(let ((sum 0)
(i start))
(declare (fixnum i sum))
(loop
(when (>= i end)
(return))
(let* ((char-code (char-code (char string i)))
(char-length (cond ((< char-code #x10000) 2)
(t 4))))
(declare (fixnum char-length) (type char-code-integer char-code))
(incf sum char-length)
(incf i)))
sum))
(defmethod compute-number-of-octets ((format flexi-crlf-utf-16-le-format) string start end)
(declare #.*fixnum-optimize-settings*)
(declare (fixnum start end) (string string))
(let ((sum 0)
(i start))
(declare (fixnum i sum))
(loop
(when (>= i end)
(return))
(let* ((char-code (char-code (char string i)))
(char-length (cond ((= char-code #.(char-code #\Newline)) 4)
((< char-code #x10000) 2)
(t 4))))
(declare (fixnum char-length) (type char-code-integer char-code))
(incf sum char-length)
(incf i)))
sum))
(defmethod compute-number-of-octets ((format flexi-crlf-utf-16-be-format) string start end)
(declare #.*fixnum-optimize-settings*)
(declare (fixnum start end) (string string))
(let ((sum 0)
(i start))
(declare (fixnum i sum))
(loop
(when (>= i end)
(return))
(let* ((char-code (char-code (char string i)))
(char-length (cond ((= char-code #.(char-code #\Newline)) 4)
((< char-code #x10000) 2)
(t 4))))
(declare (fixnum char-length) (type char-code-integer char-code))
(incf sum char-length)
(incf i)))
sum))
(defmethod compute-number-of-octets ((format flexi-utf-32-format) string start end)
(declare #.*fixnum-optimize-settings*)
(declare (fixnum start end))
(declare (ignore string))
(* 4 (- end start)))
(defmethod compute-number-of-octets ((format flexi-crlf-mixin) string start end)
(declare #.*fixnum-optimize-settings*)
(declare (fixnum start end) (string string))
(+ (call-next-method)
(* (case (external-format-name format)
(:utf-32 4)
(otherwise 1))
(count #\Newline string :start start :end end :test #'char=))))
(defgeneric character-length (format char)
(declare #.*fixnum-optimize-settings*)
(:documentation "Returns the number of octets needed to encode the
single character CHAR.")
(:method (format char)
(compute-number-of-octets format (string char) 0 1)))
(defmethod character-length :around ((format flexi-crlf-mixin) (char (eql #\Newline)))
(declare #.*fixnum-optimize-settings*)
(+ (call-next-method format +cr+)
(call-next-method format +lf+)))
(defmethod character-length ((format flexi-8-bit-format) char)
(declare #.*fixnum-optimize-settings*)
(declare (ignore char))
1)
(defmethod character-length ((format flexi-utf-32-format) char)
(declare #.*fixnum-optimize-settings*)
(declare (ignore char))
4)
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