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Fix UTF-16 surrogate pair validation #52

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Fix UTF-16 surrogate pair validation #52

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4 changes: 2 additions & 2 deletions decode.lisp
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Original file line number Diff line number Diff line change
Expand Up @@ -363,7 +363,7 @@ the form which is used to obtain the next octet."
(declare (inline read-next-word))
(let ((word (read-next-word)))
(declare (type (unsigned-byte 16) word))
(cond ((<= #xd800 word #xdfff)
(cond ((<= #xd800 word #xdbff)
(let ((next-word (read-next-word)))
(declare (type (unsigned-byte 16) next-word))
(unless (<= #xdc00 next-word #xdfff)
Expand Down Expand Up @@ -394,7 +394,7 @@ the form which is used to obtain the next octet."
(declare (inline read-next-word))
(let ((word (read-next-word)))
(declare (type (unsigned-byte 16) word))
(cond ((<= #xd800 word #xdfff)
(cond ((<= #xd800 word #xdbff)
(let ((next-word (read-next-word)))
(declare (type (unsigned-byte 16) next-word))
(unless (<= #xdc00 next-word #xdfff)
Expand Down
16 changes: 15 additions & 1 deletion test/test.lisp
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Expand Up @@ -558,7 +558,21 @@ the external format EXTERNAL-FORMAT."
(format t "~&Illegal code points"))
(want-encoding-error #(#x00 #x00 #x11 #x00) :utf-32le)
(want-encoding-error #(#x00 #xd8) :utf-16le)
(want-encoding-error #(#xff #xdf) :utf-16le))
(want-encoding-error #(#xff #xdf) :utf-16le)
(when verbose
(format t "~&Low surrogates cannot be the first word of a surrogate pair"))
;; The bug: decode.lisp incorrectly accepts low surrogates (#xdc00-#xdfff)
;; as the first word. It should only accept high surrogates (#xd800-#xdbff).
;; These tests verify that low surrogates followed by valid low surrogates
;; are properly rejected (not incorrectly decoded as surrogate pairs).
(want-encoding-error #(#x00 #xdc #x00 #xdc) :utf-16le)
(want-encoding-error #(#x00 #xdc #xff #xdf) :utf-16le)
(want-encoding-error #(#xff #xdc #x00 #xdc) :utf-16le)
(want-encoding-error #(#x00 #xdd #x00 #xdd) :utf-16le)
(want-encoding-error #(#xff #xdf #xff #xdf) :utf-16le)
(want-encoding-error #(#xdc #x00 #xdc #x00) :utf-16be)
(want-encoding-error #(#xdf #xff #xdf #xff) :utf-16be)
(want-encoding-error #(#x00 #xdc #x41 #x00) :utf-16le))
(macrolet ((want-encoding-error (input format)
`(with-expected-error (external-format-encoding-error)
(read-flexi-line* ,input ,format))))
Expand Down