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package rope
import (
"fmt"
"io"
)
// Reader is an io.Reader that reads from a Rope.
type Reader struct {
stack []*concat // The stack of internal nodes whose right subtrees we need to visit.
cur leaf // The unread part of the current leaf
}
// NewReader returns a Reader that reads from the specified Rope.
func NewReader(rope Rope) *Reader {
// Put the leftmost path on the stack.
var reader Reader
if rope.node != nil {
reader.stack = make([]*concat, 0, rope.node.depth())
reader.pushSubtree(rope.node)
}
return &reader
}
func (r *Reader) pushSubtree(n node) {
for {
if leaf, ok := n.(leaf); ok {
r.cur = leaf
return
}
conc := n.(*concat)
r.stack = append(r.stack, conc)
n = conc.Left
}
}
func (r *Reader) nextNode() {
last := r.stack[len(r.stack)-1]
r.stack = r.stack[:len(r.stack)-1]
r.pushSubtree(last.Right)
}
// Read implements io.Reader.
func (r *Reader) Read(p []byte) (n int, err error) {
if false && debug {
defer func(p []byte) {
fmt.Printf("Wrote %v bytes: %q (err=%v)\n", n, p[:n], err)
if err != nil {
fmt.Println()
}
}(p)
}
for len(p) > 0 {
if len(r.cur) == 0 {
if len(r.stack) == 0 {
// No more nodes to read.
return n, io.EOF
}
// Done reading this node.
r.nextNode()
}
m := copy(p, r.cur)
r.cur = r.cur[m:]
p = p[m:]
n += m
}
if len(r.cur) == 0 && len(r.stack) == 0 {
err = io.EOF
}
return
}
|
