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package frame
import (
"bytes"
"fmt"
"sort"
"strings"
"gopkg.in/src-d/go-git.v4/utils/merkletrie/noder"
)
// A Frame is a collection of siblings in a trie, sorted alphabetically
// by name.
type Frame struct {
// siblings, sorted in reverse alphabetical order by name
stack []noder.Noder
}
type byName []noder.Noder
func (a byName) Len() int { return len(a) }
func (a byName) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
func (a byName) Less(i, j int) bool {
return strings.Compare(a[i].Name(), a[j].Name()) < 0
}
// New returns a frame with the children of the provided node.
func New(n noder.Noder) (*Frame, error) {
children, err := n.Children()
if err != nil {
return nil, err
}
sort.Sort(sort.Reverse(byName(children)))
return &Frame{
stack: children,
}, nil
}
// String returns the quoted names of the noders in the frame sorted in
// alphabetical order by name, surrounded by square brackets and
// separated by comas.
//
// Examples:
// []
// ["a", "b"]
func (f *Frame) String() string {
var buf bytes.Buffer
_ = buf.WriteByte('[')
sep := ""
for i := f.Len() - 1; i >= 0; i-- {
_, _ = buf.WriteString(sep)
sep = ", "
_, _ = buf.WriteString(fmt.Sprintf("%q", f.stack[i].Name()))
}
_ = buf.WriteByte(']')
return buf.String()
}
// First returns, but dont extract, the noder with the alphabetically
// smaller name in the frame and true if the frame was not empty.
// Otherwise it returns nil and false.
func (f *Frame) First() (noder.Noder, bool) {
if f.Len() == 0 {
return nil, false
}
top := f.Len() - 1
return f.stack[top], true
}
// Drop extracts the noder with the alphabetically smaller name in the
// frame or does nothing if the frame was empty.
func (f *Frame) Drop() {
if f.Len() == 0 {
return
}
top := f.Len() - 1
f.stack[top] = nil
f.stack = f.stack[:top]
}
// Len returns the number of noders in the frame.
func (f *Frame) Len() int {
return len(f.stack)
}
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