Experimental alternative implementation of the vector p...

src/pkg/exp/vector/intvector.go

Index: src/pkg/exp/vector/intvector.go
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+// 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 vector
+
+
+func (p *IntVector) realloc(length, capacity int) (b []int) {
+	if capacity < initialSize {
+		capacity = initialSize
+	}
+	b = make(IntVector, length, capacity)
+	copy(b, *p)
+	*p = b
+	return
+}
+
+
+// Insert n elements at position i.
+func (p *IntVector) Expand(i, n int) {
+	a := *p
+
+	// make sure we have enough space
+	len0 := len(a)
+	len1 := len0 + n
+	if len1 <= cap(a) {
+		// enough space - just expand
+		a = a[0:len1]
+	} else {
+		// not enough space - double capacity
+		capb := cap(a) * 2
+		if capb < len1 {
+			// still not enough - use required length
+			capb = len1
+		}
+		// capb >= len1
+		a = p.realloc(len1, capb)
+	}
+
+	// make a hole
+	for j := len0 - 1; j >= i; j-- {
+		a[j+n] = a[j]
+	}
+
+	*p = a
+}
+
+
+// Insert n elements at the end of a vector.
+func (p *IntVector) Extend(n int) { p.Expand(len(*p), n) }
+
+
+// Resize changes the length and capacity of a vector.
+// If the new length is shorter than the current length, Resize discards
+// trailing elements. If the new length is longer than the current length,
+// Resize adds the respective zero values for the additional elements. The capacity
+// parameter is ignored unless the new length or capacity is longer than the current
+// capacity. The resized vector's capacity may be larger than the requested capacity.
+func (p *IntVector) Resize(length, capacity int) *IntVector {
+	a := *p
+
+	if length > cap(a) || capacity > cap(a) {
+		// not enough space or larger capacity requested explicitly
+		a = p.realloc(length, capacity)
+	} else if length < len(a) {
+		// clear trailing elements
+		for i := range a[length:] {
+			var zero int
+			a[length+i] = zero
+		}
+	}
+
+	*p = a[0:length]
+	return p
+}
+
+
+// Len returns the number of elements in the vector.
+// Same as len(*p).
+func (p *IntVector) Len() int { return len(*p) }
+
+
+// Cap returns the capacity of the vector; that is, the
+// maximum length the vector can grow without resizing.
+// Same as cap(*p).
+func (p *IntVector) Cap() int { return cap(*p) }
+
+
+// At returns the i'th element of the vector.
+func (p *IntVector) At(i int) int { return (*p)[i] }
+
+
+// Set sets the i'th element of the vector to value x.
+func (p *IntVector) Set(i int, x int) { (*p)[i] = x }
+
+
+// Last returns the element in the vector of highest index.
+func (p *IntVector) Last() int { return (*p)[len(*p)-1] }
+
+
+// Data returns all the elements as a slice.
+func (p *IntVector) Data() []int {
+	arr := make(IntVector, len(*p))
+	copy(arr, *p)
+	return arr
+}
+
+
+// Insert inserts into the vector an element of value x before
+// the current element at index i.
+func (p *IntVector) Insert(i int, x int) {
+	p.Expand(i, 1)
+	(*p)[i] = x
+}
+
+
+// Delete deletes the i'th element of the vector.  The gap is closed so the old
+// element at index i+1 has index i afterwards.
+func (p *IntVector) Delete(i int) {
+	a := *p
+	n := len(a)
+
+	copy(a[i:n-1], a[i+1:n])
+	var zero int
+	a[n-1] = zero // support GC, zero out entry
+	*p = a[0 : n-1]
+}
+
+
+// InsertVector inserts into the vector the contents of the vector
+// x such that the 0th element of x appears at index i after insertion.
+func (p *IntVector) InsertVector(i int, x *IntVector) {
+	b := *x
+
+	p.Expand(i, len(b))
+	copy((*p)[i:i+len(b)], b)
+}
+
+
+// Cut deletes elements i through j-1, inclusive.
+func (p *IntVector) Cut(i, j int) {
+	a := *p
+	n := len(a)
+	m := n - (j - i)
+
+	copy(a[i:m], a[j:n])
+	for k := m; k < n; k++ { //TODO(bflm) don't zero out the elements unless it's a Vector.
+		var zero int
+		a[k] = zero // support GC, zero out entries
+	}
+
+	*p = a[0:m]
+}
+
+
+// Slice returns a new sub-vector by slicing the old one to extract slice [i:j].
+// The elements are copied. The original vector is unchanged.
+func (p *IntVector) Slice(i, j int) *IntVector {
+	var s IntVector
+	s.realloc(j-i, 0) // will fail in Init() if j < i
+	copy(s, (*p)[i:j])
+	return &s
+}
+
+
+// Convenience wrappers
+
+// Push appends x to the end of the vector.
+func (p *IntVector) Push(x int) { p.Insert(len(*p), x) }
+
+
+// Pop deletes the last element of the vector.
+func (p *IntVector) Pop() int {
+	a := *p
+
+	i := len(a) - 1
+	x := a[i]
+	var zero int
+	a[i] = zero // support GC, zero out entry
+	*p = a[0:i]
+	return x
+}
+
+
+// AppendVector appends the entire vector x to the end of this vector.
+func (p *IntVector) AppendVector(x *IntVector) {
+	p.InsertVector(len(*p), x)
+}
+
+
+// Swap exchanges the elements at indexes i and j.
+func (p *IntVector) Swap(i, j int) {
+	a := *p
+	a[i], a[j] = a[j], a[i]
+}
+
+
+// Iterate over all elements; driver for range
+func (p *IntVector) iterate(c chan<- int) {
+	for _, v := range *p {
+		c <- v
+	}
+	close(c)
+}
+
+
+// Channel iterator for range.
+func (p *IntVector) Iter() <-chan int {
+	c := make(chan int)
+	go p.iterate(c)
+	return c
+}