add: io reader composition

interfaces/15-io-reader-composition/main.go

@@ -0,0 +1,97 @@
+// For more tutorials: https://blog.learngoprogramming.com
+//
+// Copyright © 2018 Inanc Gumus
+// Learn Go Programming Course
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+//
+
+package main
+
+import (
+	"compress/gzip"
+	"fmt"
+	"net/http"
+)
+
+func main() {
+	/*
+		store := list{
+			&book{product{"moby dick", 10}, toTimestamp(118281600)},
+			&book{product{"odyssey", 15}, toTimestamp("733622400")},
+			&book{product{"hobbit", 25}, unknown},
+			&puzzle{product{"rubik's cube", 5}},
+			&game{product{"minecraft", 20}},
+			&game{product{"tetris", 5}},
+			&toy{product{"yoda", 150}},
+		}
+
+		db := database{list: &store}
+
+		out, err := json.MarshalIndent(&db, "", "\t")
+		if err != nil {
+			log.Fatalln(err)
+		}
+
+		fmt.Println(string(out))
+
+		// store.discount(.5)
+		// fmt.Print(store)
+	*/
+
+	var store list
+
+	db := database{list: &store}
+	db.register("book", new(book))
+	db.register("book", new(book))
+	db.register("game", new(game))
+	db.register("puzzle", new(puzzle))
+	db.register("toy", new(toy))
+
+	// load from a file
+	// f, _ := os.Open("database.json")
+	// db.load(f)
+	// f.Close()
+
+	// load from a string
+	// const data = `[
+	// { "Type": "book", "Item": { "Title": "1984", "Price": 8, "Published": -649641600 } },
+	// { "Type": "game", "Item": { "Title": "paperboy", "Price": 20 } }]`
+	// r := strings.NewReader(data)
+	// db.load(r)
+
+	// load from a web server
+	// res, _ := http.Get("https://inancgumus.github.io/x/database.json")
+	// db.load(res.Body)
+	// res.Body.Close()
+
+	// decompress the reader while reading from it
+	// res, _ := http.Get("https://inancgumus.github.io/x/database.json.gz")
+	// gr, _ := gzip.NewReader(res.Body)
+	// db.load(gr)
+	// gr.Close()
+	// res.Body.Close()
+
+	// decompress and count the number of compressed bytes read
+	// res, _ := http.Get("https://inancgumus.github.io/x/database.json.gz")
+	// c := newCounter(res.Body) // count the bytes read
+	// gr, _ := gzip.NewReader(c)
+
+	// db.load(gr)
+	// fmt.Printf("%d bytes read.\n\n", c.total())
+
+	// gr.Close()
+	// res.Body.Close()
+
+	// count the number of compressed bytes read from the web server then decompress
+	res, _ := http.Get("https://inancgumus.github.io/x/database.json.gz")
+	gr, _ := gzip.NewReader(res.Body)
+	c := newCounter(gr)
+
+	db.load(c)
+	fmt.Printf("%d bytes read.\n\n", c.total())
+
+	gr.Close()
+	res.Body.Close()
+
+	fmt.Print(store)
+}