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author | upstream source tree <ports@midipix.org> | 2015-03-15 20:14:05 -0400 |
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committer | upstream source tree <ports@midipix.org> | 2015-03-15 20:14:05 -0400 |
commit | 554fd8c5195424bdbcabf5de30fdc183aba391bd (patch) | |
tree | 976dc5ab7fddf506dadce60ae936f43f58787092 /libgo/go/container/ring | |
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Diffstat (limited to 'libgo/go/container/ring')
-rw-r--r-- | libgo/go/container/ring/ring.go | 153 | ||||
-rw-r--r-- | libgo/go/container/ring/ring_test.go | 240 |
2 files changed, 393 insertions, 0 deletions
diff --git a/libgo/go/container/ring/ring.go b/libgo/go/container/ring/ring.go new file mode 100644 index 000000000..335afbc3c --- /dev/null +++ b/libgo/go/container/ring/ring.go @@ -0,0 +1,153 @@ +// Copyright 2009 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +// The ring package implements operations on circular lists. +package ring + +// A Ring is an element of a circular list, or ring. +// Rings do not have a beginning or end; a pointer to any ring element +// serves as reference to the entire ring. Empty rings are represented +// as nil Ring pointers. The zero value for a Ring is a one-element +// ring with a nil Value. +// +type Ring struct { + next, prev *Ring + Value interface{} // for use by client; untouched by this library +} + + +func (r *Ring) init() *Ring { + r.next = r + r.prev = r + return r +} + + +// Next returns the next ring element. r must not be empty. +func (r *Ring) Next() *Ring { + if r.next == nil { + return r.init() + } + return r.next +} + + +// Prev returns the previous ring element. r must not be empty. +func (r *Ring) Prev() *Ring { + if r.next == nil { + return r.init() + } + return r.prev +} + + +// Move moves n % r.Len() elements backward (n < 0) or forward (n >= 0) +// in the ring and returns that ring element. r must not be empty. +// +func (r *Ring) Move(n int) *Ring { + if r.next == nil { + return r.init() + } + switch { + case n < 0: + for ; n < 0; n++ { + r = r.prev + } + case n > 0: + for ; n > 0; n-- { + r = r.next + } + } + return r +} + + +// New creates a ring of n elements. +func New(n int) *Ring { + if n <= 0 { + return nil + } + r := new(Ring) + p := r + for i := 1; i < n; i++ { + p.next = &Ring{prev: p} + p = p.next + } + p.next = r + r.prev = p + return r +} + + +// Link connects ring r with with ring s such that r.Next() +// becomes s and returns the original value for r.Next(). +// r must not be empty. +// +// If r and s point to the same ring, linking +// them removes the elements between r and s from the ring. +// The removed elements form a subring and the result is a +// reference to that subring (if no elements were removed, +// the result is still the original value for r.Next(), +// and not nil). +// +// If r and s point to different rings, linking +// them creates a single ring with the elements of s inserted +// after r. The result points to the element following the +// last element of s after insertion. +// +func (r *Ring) Link(s *Ring) *Ring { + n := r.Next() + if s != nil { + p := s.Prev() + // Note: Cannot use multiple assignment because + // evaluation order of LHS is not specified. + r.next = s + s.prev = r + n.prev = p + p.next = n + } + return n +} + + +// Unlink removes n % r.Len() elements from the ring r, starting +// at r.Next(). If n % r.Len() == 0, r remains unchanged. +// The result is the removed subring. r must not be empty. +// +func (r *Ring) Unlink(n int) *Ring { + if n <= 0 { + return nil + } + return r.Link(r.Move(n + 1)) +} + + +// Len computes the number of elements in ring r. +// It executes in time proportional to the number of elements. +// +func (r *Ring) Len() int { + n := 0 + if r != nil { + n = 1 + for p := r.Next(); p != r; p = p.next { + n++ + } + } + return n +} + + +func (r *Ring) Iter() <-chan interface{} { + c := make(chan interface{}) + go func() { + if r != nil { + c <- r.Value + for p := r.Next(); p != r; p = p.next { + c <- p.Value + } + } + close(c) + }() + return c +} diff --git a/libgo/go/container/ring/ring_test.go b/libgo/go/container/ring/ring_test.go new file mode 100644 index 000000000..ee3c41128 --- /dev/null +++ b/libgo/go/container/ring/ring_test.go @@ -0,0 +1,240 @@ +// Copyright 2009 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package ring + +import ( + "fmt" + "testing" +) + + +// For debugging - keep around. +func dump(r *Ring) { + if r == nil { + fmt.Println("empty") + return + } + i, n := 0, r.Len() + for p := r; i < n; p = p.next { + fmt.Printf("%4d: %p = {<- %p | %p ->}\n", i, p, p.prev, p.next) + i++ + } + fmt.Println() +} + + +func verify(t *testing.T, r *Ring, N int, sum int) { + // Len + n := r.Len() + if n != N { + t.Errorf("r.Len() == %d; expected %d", n, N) + } + + // iteration + n = 0 + s := 0 + for p := range r.Iter() { + n++ + if p != nil { + s += p.(int) + } + } + if n != N { + t.Errorf("number of forward iterations == %d; expected %d", n, N) + } + if sum >= 0 && s != sum { + t.Errorf("forward ring sum = %d; expected %d", s, sum) + } + + if r == nil { + return + } + + // connections + if r.next != nil { + var p *Ring // previous element + for q := r; p == nil || q != r; q = q.next { + if p != nil && p != q.prev { + t.Errorf("prev = %p, expected q.prev = %p\n", p, q.prev) + } + p = q + } + if p != r.prev { + t.Errorf("prev = %p, expected r.prev = %p\n", p, r.prev) + } + } + + // Next, Prev + if r.Next() != r.next { + t.Errorf("r.Next() != r.next") + } + if r.Prev() != r.prev { + t.Errorf("r.Prev() != r.prev") + } + + // Move + if r.Move(0) != r { + t.Errorf("r.Move(0) != r") + } + if r.Move(N) != r { + t.Errorf("r.Move(%d) != r", N) + } + if r.Move(-N) != r { + t.Errorf("r.Move(%d) != r", -N) + } + for i := 0; i < 10; i++ { + ni := N + i + mi := ni % N + if r.Move(ni) != r.Move(mi) { + t.Errorf("r.Move(%d) != r.Move(%d)", ni, mi) + } + if r.Move(-ni) != r.Move(-mi) { + t.Errorf("r.Move(%d) != r.Move(%d)", -ni, -mi) + } + } +} + + +func TestCornerCases(t *testing.T) { + var ( + r0 *Ring + r1 Ring + ) + // Basics + verify(t, r0, 0, 0) + verify(t, &r1, 1, 0) + // Insert + r1.Link(r0) + verify(t, r0, 0, 0) + verify(t, &r1, 1, 0) + // Insert + r1.Link(r0) + verify(t, r0, 0, 0) + verify(t, &r1, 1, 0) + // Unlink + r1.Unlink(0) + verify(t, &r1, 1, 0) +} + + +func makeN(n int) *Ring { + r := New(n) + for i := 1; i <= n; i++ { + r.Value = i + r = r.Next() + } + return r +} + + +func sum(r *Ring) int { + s := 0 + for p := range r.Iter() { + s += p.(int) + } + return s +} + + +func sumN(n int) int { return (n*n + n) / 2 } + + +func TestNew(t *testing.T) { + for i := 0; i < 10; i++ { + r := New(i) + verify(t, r, i, -1) + } + for i := 0; i < 10; i++ { + r := makeN(i) + verify(t, r, i, sumN(i)) + } +} + + +func TestLink1(t *testing.T) { + r1a := makeN(1) + var r1b Ring + r2a := r1a.Link(&r1b) + verify(t, r2a, 2, 1) + if r2a != r1a { + t.Errorf("a) 2-element link failed") + } + + r2b := r2a.Link(r2a.Next()) + verify(t, r2b, 2, 1) + if r2b != r2a.Next() { + t.Errorf("b) 2-element link failed") + } + + r1c := r2b.Link(r2b) + verify(t, r1c, 1, 1) + verify(t, r2b, 1, 0) +} + + +func TestLink2(t *testing.T) { + var r0 *Ring + r1a := &Ring{Value: 42} + r1b := &Ring{Value: 77} + r10 := makeN(10) + + r1a.Link(r0) + verify(t, r1a, 1, 42) + + r1a.Link(r1b) + verify(t, r1a, 2, 42+77) + + r10.Link(r0) + verify(t, r10, 10, sumN(10)) + + r10.Link(r1a) + verify(t, r10, 12, sumN(10)+42+77) +} + + +func TestLink3(t *testing.T) { + var r Ring + n := 1 + for i := 1; i < 100; i++ { + n += i + verify(t, r.Link(New(i)), n, -1) + } +} + + +func TestUnlink(t *testing.T) { + r10 := makeN(10) + s10 := r10.Move(6) + + sum10 := sumN(10) + + verify(t, r10, 10, sum10) + verify(t, s10, 10, sum10) + + r0 := r10.Unlink(0) + verify(t, r0, 0, 0) + + r1 := r10.Unlink(1) + verify(t, r1, 1, 2) + verify(t, r10, 9, sum10-2) + + r9 := r10.Unlink(9) + verify(t, r9, 9, sum10-2) + verify(t, r10, 9, sum10-2) +} + + +func TestLinkUnlink(t *testing.T) { + for i := 1; i < 4; i++ { + ri := New(i) + for j := 0; j < i; j++ { + rj := ri.Unlink(j) + verify(t, rj, j, -1) + verify(t, ri, i-j, -1) + ri.Link(rj) + verify(t, ri, i, -1) + } + } +} |