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data/bit-vector: change implementation to fxvectors

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There are minor benefits to using fxvectors instead of vectors:
the GC knows that an fxvector has no pointers inside, and the
bytecode compiler knows that `fxvector-ref' produces a fixnum.

BTW, a benefit of fxvectors over byte strings is the lack of an
indirection internally. (Unlike a byte string, the content of
an fxvector is "inlined" into the vector object.)
This commit is contained in:
Matthew Flatt 2012-11-27 07:19:10 -07:00
parent 4ed45a6aef
commit 054a52f547
1 changed files with 12 additions and 12 deletions
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24
collects/data/bit-vector.rkt
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@ -4,7 +4,7 @@
racket/match
racket/dict
racket/contract/base
racket/vector
racket/fixnum
racket/unsafe/ops)
(define bits-in-a-word
@ -20,7 +20,7 @@
(define (make-bit-vector size [fill #f])
(define word-size (add1 (quotient size bits-in-a-word)))
(define words (make-vector word-size (if fill largest-fixnum 0)))
(define words (make-fxvector word-size (if fill largest-fixnum 0)))
(bit-vector words size word-size))
(define (bit-vector* . init-bits)
@ -46,7 +46,7 @@
(define-values (wi bi) (quotient/remainder n bits-in-a-word))
(match bv
[(struct bit-vector (words size word-size))
(define word (vector-ref words wi))
(define word (fxvector-ref words wi))
(define bit (bitwise-bit-set? word bi))
bit]))
@ -68,10 +68,10 @@
(define-values (wi bi) (quotient/remainder n bits-in-a-word))
(match bv
[(struct bit-vector (words size word-size))
(define word (vector-ref words wi))
(define word (fxvector-ref words wi))
(define bit (bitwise-bit-set? word bi))
(unless (eq? bit b)
(vector-set! words wi (bitwise-xor word (expt 2 bi))))]))
(fxvector-set! words wi (bitwise-xor word (expt 2 bi))))]))
(define (bit-vector-length bv)
(bit-vector-size bv))
@ -80,7 +80,7 @@
(let ([bit-vector-copy
(case-lambda
[(bv)
(bit-vector (vector-copy (bit-vector-words bv))
(bit-vector (fxvector-copy (bit-vector-words bv))
(bit-vector-size bv)
(bit-vector-word-size bv))]
[(bv start)
@ -102,7 +102,7 @@
; A bit vector is represented as a vector of words.
; Each word contains 30 or 62 bits depending on the size of a fixnum.
(struct bit-vector (words size word-size)
; words is the vector of words
; words is the fxvector of words
; size is the number of bits in bitvector
; word-size is the number of words in words
#:property prop:dict/contract
@ -129,9 +129,9 @@
[wsx (bit-vector-word-size x)]
[wsy (bit-vector-word-size y)])
(and (= nx ny) (= wsx wsy)
(for/and ([index (in-range (- (vector-length vx) 1))])
(eqv? (vector-ref vx index)
(vector-ref vy index)))
(for/and ([index (in-range (- (fxvector-length vx) 1))])
(eq? (fxvector-ref vx index)
(fxvector-ref vy index)))
; TODO: check last word
)))
(define (hash-code x hc)
@ -140,8 +140,8 @@
[ws (bit-vector-word-size x)])
(bitwise-xor
(hc ws) (hc n)
(for/fold ([h 1]) ([i (in-range (vector-length v))])
(bitwise-xor h (hc (vector-ref v i)))))))
(for/fold ([h 1]) ([i (in-range (fxvector-length v))])
(bitwise-xor h (hc (fxvector-ref v i)))))))
(define hash-proc hash-code)
(define hash2-proc hash-code)]
#:property prop:sequence in-bit-vector)