Docs

docs.go

package main

import (
	"fmt"
	"strings"
)

type Doc struct {
	Off int
	Len int
	Nil bool
}

func (doc *Doc) String() string {
	isnil := "F"
	if doc.Nil {
		isnil = "T"
	}
	return fmt.Sprintf("Doc{%d, %d, %s}", doc.Off, doc.Len, isnil)
}

type Docs []*Doc

func NewDocs(n int) Docs {
	docs := make(Docs, n)
	for i := 0; i < n; i++ {
		docs[i] = new(Doc)
	}
	return docs
}

func (docs *Docs) String() string {
	if len(*docs) == 0 {
		return "Docs [ <nil> ]\n"
	}
	if len(*docs) == 1 {
		return "Docs [ " + (*docs)[0].String() + " ]\n"
	}
	var ss []string
	for i := 0; i < len(*docs); i++ {
		s := "%s"
		switch i {
		case 0:
			s = "Docs [ %s"
		case len(*docs) - 1:
			s = "%s ]\n"
		}
		ss = append(ss, fmt.Sprintf(s, (*docs)[i]))
	}
	return strings.Join(ss, ", ")
}

func (docs *Docs) InsertAt(doc *Doc, n int) {
	if n > len(*docs) || n < 0 {
		fmt.Printf("err: InsertAt(%d): %d is out of bounds!\n", n, n)
		return // out of bounds
	}
	if n <= len(*docs)-1 && (*docs)[n].Nil {
		fmt.Printf("Overwrote *Doc at index: %d\n", n)
		(*docs)[n] = doc
		return // overwrite if nil
	}
	*docs = append(*docs, new(Doc))
	copy((*docs)[n+1:], (*docs)[n:])
	(*docs)[n] = doc
	fmt.Printf("Inserted *Doc at index: %d\n", n)

}

func (docs *Docs) DeleteAt(n int) {
	if n > len(*docs)-1 || n < 0 {
		fmt.Printf("err: DeleteAt(%d): %d is out of bounds!\n", n, n)
		return // out of bounds
	}
	copy((*docs)[n:], (*docs)[n+1:])
	(*docs)[len(*docs)-1] = new(Doc)
	*docs = (*docs)[:len(*docs)-1]
	fmt.Printf("Deleted *Doc at index: %d\n", n)
}

func (docs *Docs) ClearAt(n int) {
	if n > len(*docs)-1 || n < 0 {
		fmt.Printf("err: ClearAt(%d): %d is out of bounds!\n", n, n)
		return // out of bounds
	}
	if (*docs)[n].Nil {
		fmt.Printf("err: ClearAt(%d): *Doc is already nil!\n", n)
		return // doc is already nil
	}
	(*docs)[n] = &Doc{Nil: true}
	fmt.Printf("Cleared *Doc at index: %d\n", n)
}

func (docs *Docs) Println() {
	fmt.Printf("len(docs) = %d\n%s\n", len(*docs), docs.String())
}

const COUNT = 8

func main() {

	docs := NewDocs(0)
	docs.Println()

	docs.InsertAt(&Doc{-1, -1, true}, 0)
	docs.Println()

	for i := 0; i < COUNT; i++ {
		docs.InsertAt(&Doc{i, i * 10, false}, i)
		docs.Println()
	}

	for i := COUNT - 1; i > 2; i-- {
		docs.DeleteAt(i)
		docs.Println()
	}

	docs.ClearAt(1)
	docs.Println()
	docs.ClearAt(2)
	docs.Println()
	docs.ClearAt(0)
	docs.Println()
}