codekingpro/portable-devtools

1// Copyright 2013 The Go Authors. All rights reserved.2// Use of this source code is governed by a BSD-style3// license that can be found in the LICENSE file.4 5package bufio_test6 7import (8	"bufio"9	"bytes"10	"fmt"11	"os"12	"strconv"13	"strings"14)15 16func ExampleWriter() {17	w := bufio.NewWriter(os.Stdout)18	fmt.Fprint(w, "Hello, ")19	fmt.Fprint(w, "world!")20	w.Flush() // Don't forget to flush!21	// Output: Hello, world!22}23 24func ExampleWriter_AvailableBuffer() {25	w := bufio.NewWriter(os.Stdout)26	for _, i := range []int64{1, 2, 3, 4} {27		b := w.AvailableBuffer()28		b = strconv.AppendInt(b, i, 10)29		b = append(b, ' ')30		w.Write(b)31	}32	w.Flush()33	// Output: 1 2 3 434}35 36// ExampleWriter_ReadFrom demonstrates how to use the ReadFrom method of Writer.37func ExampleWriter_ReadFrom() {38	var buf bytes.Buffer39	writer := bufio.NewWriter(&buf)40 41	data := "Hello, world!\nThis is a ReadFrom example."42	reader := strings.NewReader(data)43 44	n, err := writer.ReadFrom(reader)45	if err != nil {46		fmt.Println("ReadFrom Error:", err)47		return48	}49 50	if err = writer.Flush(); err != nil {51		fmt.Println("Flush Error:", err)52		return53	}54 55	fmt.Println("Bytes written:", n)56	fmt.Println("Buffer contents:", buf.String())57	// Output:58	// Bytes written: 4159	// Buffer contents: Hello, world!60	// This is a ReadFrom example.61}62 63// The simplest use of a Scanner, to read standard input as a set of lines.64func ExampleScanner_lines() {65	scanner := bufio.NewScanner(os.Stdin)66	for scanner.Scan() {67		fmt.Println(scanner.Text()) // Println will add back the final '\n'68	}69	if err := scanner.Err(); err != nil {70		fmt.Fprintln(os.Stderr, "reading standard input:", err)71	}72}73 74// Return the most recent call to Scan as a []byte.75func ExampleScanner_Bytes() {76	scanner := bufio.NewScanner(strings.NewReader("gopher"))77	for scanner.Scan() {78		fmt.Println(len(scanner.Bytes()) == 6)79	}80	if err := scanner.Err(); err != nil {81		fmt.Fprintln(os.Stderr, "shouldn't see an error scanning a string")82	}83	// Output:84	// true85}86 87// Use a Scanner to implement a simple word-count utility by scanning the88// input as a sequence of space-delimited tokens.89func ExampleScanner_words() {90	// An artificial input source.91	const input = "Now is the winter of our discontent,\nMade glorious summer by this sun of York.\n"92	scanner := bufio.NewScanner(strings.NewReader(input))93	// Set the split function for the scanning operation.94	scanner.Split(bufio.ScanWords)95	// Count the words.96	count := 097	for scanner.Scan() {98		count++99	}100	if err := scanner.Err(); err != nil {101		fmt.Fprintln(os.Stderr, "reading input:", err)102	}103	fmt.Printf("%d\n", count)104	// Output: 15105}106 107// Use a Scanner with a custom split function (built by wrapping ScanWords) to validate108// 32-bit decimal input.109func ExampleScanner_custom() {110	// An artificial input source.111	const input = "1234 5678 1234567901234567890"112	scanner := bufio.NewScanner(strings.NewReader(input))113	// Create a custom split function by wrapping the existing ScanWords function.114	split := func(data []byte, atEOF bool) (advance int, token []byte, err error) {115		advance, token, err = bufio.ScanWords(data, atEOF)116		if err == nil && token != nil {117			_, err = strconv.ParseInt(string(token), 10, 32)118		}119		return120	}121	// Set the split function for the scanning operation.122	scanner.Split(split)123	// Validate the input124	for scanner.Scan() {125		fmt.Printf("%s\n", scanner.Text())126	}127 128	if err := scanner.Err(); err != nil {129		fmt.Printf("Invalid input: %s", err)130	}131	// Output:132	// 1234133	// 5678134	// Invalid input: strconv.ParseInt: parsing "1234567901234567890": value out of range135}136 137// Use a Scanner with a custom split function to parse a comma-separated138// list with an empty final value.139func ExampleScanner_emptyFinalToken() {140	// Comma-separated list; last entry is empty.141	const input = "1,2,3,4,"142	scanner := bufio.NewScanner(strings.NewReader(input))143	// Define a split function that separates on commas.144	onComma := func(data []byte, atEOF bool) (advance int, token []byte, err error) {145		for i := 0; i < len(data); i++ {146			if data[i] == ',' {147				return i + 1, data[:i], nil148			}149		}150		if !atEOF {151			return 0, nil, nil152		}153		// There is one final token to be delivered, which may be the empty string.154		// Returning bufio.ErrFinalToken here tells Scan there are no more tokens after this155		// but does not trigger an error to be returned from Scan itself.156		return 0, data, bufio.ErrFinalToken157	}158	scanner.Split(onComma)159	// Scan.160	for scanner.Scan() {161		fmt.Printf("%q ", scanner.Text())162	}163	if err := scanner.Err(); err != nil {164		fmt.Fprintln(os.Stderr, "reading input:", err)165	}166	// Output: "1" "2" "3" "4" ""167}168 169// Use a Scanner with a custom split function to parse a comma-separated170// list with an empty final value but stops at the token "STOP".171func ExampleScanner_earlyStop() {172	onComma := func(data []byte, atEOF bool) (advance int, token []byte, err error) {173		i := bytes.IndexByte(data, ',')174		if i == -1 {175			if !atEOF {176				return 0, nil, nil177			}178			// If we have reached the end, return the last token.179			return 0, data, bufio.ErrFinalToken180		}181		// If the token is "STOP", stop the scanning and ignore the rest.182		if string(data[:i]) == "STOP" {183			return i + 1, nil, bufio.ErrFinalToken184		}185		// Otherwise, return the token before the comma.186		return i + 1, data[:i], nil187	}188	const input = "1,2,STOP,4,"189	scanner := bufio.NewScanner(strings.NewReader(input))190	scanner.Split(onComma)191	for scanner.Scan() {192		fmt.Printf("Got a token %q\n", scanner.Text())193	}194	if err := scanner.Err(); err != nil {195		fmt.Fprintln(os.Stderr, "reading input:", err)196	}197	// Output:198	// Got a token "1"199	// Got a token "2"200}201