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Rewrite LDB and friends in a way which can be reused by the compiler macros in src/cmp/cmpopt-bits.lsp

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Juan Jose Garcia Ripoll 2013-01-09 10:25:55 +01:00
parent 4b2e293a48
commit 84cb080e78
1 changed files with 16 additions and 10 deletions
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26
src/lsp/numlib.lsp
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@ -302,31 +302,37 @@ Returns the position part (in ECL, the cdr part) of the byte specifier BYTE."
"Args: (bytespec integer)
Extracts a byte from INTEGER at the specified byte position, right-justifies
the byte, and returns the result as an integer."
(logandc2 (ash integer (- (byte-position bytespec)))
(- (ash 1 (byte-size bytespec)))))
(logand (ash integer (- (byte-position bytespec)))
(lognot (ash -1 (byte-size bytespec)))))
(defun ldb-test (bytespec integer)
"Args: (bytespec integer)
Returns T if at least one bit of the specified byte is 1; NIL otherwise."
(not (zerop (ldb bytespec integer))))
(not (zerop (mask-field bytespec integer))))
(defun mask-field (bytespec integer)
"Args: (bytespec integer)
Extracts the specified byte from INTEGER and returns the result as an integer."
(ash (ldb bytespec integer) (byte-position bytespec)))
(logand (ash (lognot (ash -1 (byte-size bytespec)))
(byte-position bytespec))
integer))
(defun dpb (newbyte bytespec integer)
"Args: (newbyte bytespec integer)
Replaces the specified byte of INTEGER with NEWBYTE (an integer) and returns
the result."
(logxor integer
(mask-field bytespec integer)
(ash (logandc2 newbyte
(- (ash 1 (byte-size bytespec))))
(byte-position bytespec))))
(let* ((pos (byte-position bytespec))
(size (byte-size bytespec))
(mask (ash (lognot (ash -1 size)) pos)))
(logior (logandc2 integer mask)
(logand (ash newbyte pos) mask))))
(defun deposit-field (newbyte bytespec integer)
"Args: (integer1 bytespec integer2)
Returns an integer represented by the bit sequence obtained by replacing the
specified bits of INTEGER2 with the specified bits of INTEGER1."
(dpb (ash newbyte (- (byte-position bytespec))) bytespec integer))
(let* ((pos (byte-position bytespec))
(size (byte-size bytespec))
(mask (ash (lognot (ash -1 size)) pos)))
(logior (logandc2 integer mask)
(logand newbyte mask))))