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https://github.com/ashinn/chibi-scheme.git
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8b5eb68238
They can be close()d explicitly with close-file-descriptor, and will close() on gc, but only explicitly closing the last port on them will close the fileno. Notably needed for network sockets where we open separate input and output ports on the same socket.
61 lines
2 KiB
Scheme
61 lines
2 KiB
Scheme
;; bitwise.scm -- high-level bitwise functions
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;; Copyright (c) 2009 Alex Shinn. All rights reserved.
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;; BSD-style license: http://synthcode.com/license.txt
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(define (bitwise-not i) (- -1 i))
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(define (bitwise-complement f) (lambda args (bitwise-not (apply f args))))
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(define (make-nary proc2 default)
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(lambda args
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(if (null? args)
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default
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(let lp ((i (car args)) (ls (cdr args)))
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(if (null? ls)
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i
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(lp (proc2 i (car ls)) (cdr ls)))))))
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(define bitwise-and (make-nary bit-and -1))
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(define bitwise-ior (make-nary bit-ior 0))
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(define bitwise-xor (make-nary bit-xor 0))
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(define bitwise-eqv (bitwise-complement (make-nary bit-xor -1)))
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(define bitwise-nand (bitwise-complement (make-nary bit-and 0)))
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(define bitwise-nor (bitwise-complement (make-nary bit-ior -1)))
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(define (bitwise-andc1 i j) (bit-and (bitwise-not i) j))
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(define (bitwise-andc2 i j) (bit-and i (bitwise-not j)))
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(define (bitwise-orc1 i j) (bit-ior (bitwise-not i) j))
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(define (bitwise-orc2 i j) (bit-ior i (bitwise-not j)))
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(define (any-bits-set? test-bits i)
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(not (zero? (bitwise-and test-bits i))))
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(define (all-bits-set? test-bits i)
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(= test-bits (bitwise-and test-bits i)))
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(define (first-set-bit i)
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(if (zero? i)
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-1
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(integer-length (- i (bit-and i (- i 1))))))
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(define (mask len) (- (arithmetic-shift 1 len) 1))
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(define (bitwise-merge mask n m)
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(bit-ior (bit-and mask n) (bit-and (bitwise-not mask) m)))
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(define (extract-bit-field size position n)
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(bit-and (arithmetic-shift n (- position)) (mask size)))
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(define (test-bit-field? size position n)
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(not (zero? (bit-and (arithmetic-shift n (- position)) (mask size)))))
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(define (replace-bit-field size position newfield n)
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(bit-ior (bit-and n (bitwise-not (arithmetic-shift (mask size) position)))
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(arithmetic-shift newfield position)))
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(define (clear-bit-field size position n)
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(replace-bit-field size position 0 n))
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(define (copy-bit-field size position from to)
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(bitwise-merge (arithmetic-shift (mask size) position) to from))
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