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- // Copyright 2013 The Go Authors. All rights reserved.
- // Use of this source code is governed by a BSD-style
- // license that can be found in the LICENSE file.
- package bufio_test
- import (
- "bufio"
- "fmt"
- "os"
- "strconv"
- "strings"
- )
- func ExampleWriter() {
- w := bufio.NewWriter(os.Stdout)
- fmt.Fprint(w, "Hello, ")
- fmt.Fprint(w, "world!")
- w.Flush() // Don't forget to flush!
- // Output: Hello, world!
- }
- func ExampleWriter_AvailableBuffer() {
- w := bufio.NewWriter(os.Stdout)
- for _, i := range []int64{1, 2, 3, 4} {
- b := w.AvailableBuffer()
- b = strconv.AppendInt(b, i, 10)
- b = append(b, ' ')
- w.Write(b)
- }
- w.Flush()
- // Output: 1 2 3 4
- }
- // The simplest use of a Scanner, to read standard input as a set of lines.
- func ExampleScanner_lines() {
- scanner := bufio.NewScanner(os.Stdin)
- for scanner.Scan() {
- fmt.Println(scanner.Text()) // Println will add back the final '\n'
- }
- if err := scanner.Err(); err != nil {
- fmt.Fprintln(os.Stderr, "reading standard input:", err)
- }
- }
- // Return the most recent call to Scan as a []byte.
- func ExampleScanner_Bytes() {
- scanner := bufio.NewScanner(strings.NewReader("gopher"))
- for scanner.Scan() {
- fmt.Println(len(scanner.Bytes()) == 6)
- }
- if err := scanner.Err(); err != nil {
- fmt.Fprintln(os.Stderr, "shouldn't see an error scanning a string")
- }
- // Output:
- // true
- }
- // Use a Scanner to implement a simple word-count utility by scanning the
- // input as a sequence of space-delimited tokens.
- func ExampleScanner_words() {
- // An artificial input source.
- const input = "Now is the winter of our discontent,\nMade glorious summer by this sun of York.\n"
- scanner := bufio.NewScanner(strings.NewReader(input))
- // Set the split function for the scanning operation.
- scanner.Split(bufio.ScanWords)
- // Count the words.
- count := 0
- for scanner.Scan() {
- count++
- }
- if err := scanner.Err(); err != nil {
- fmt.Fprintln(os.Stderr, "reading input:", err)
- }
- fmt.Printf("%d\n", count)
- // Output: 15
- }
- // Use a Scanner with a custom split function (built by wrapping ScanWords) to validate
- // 32-bit decimal input.
- func ExampleScanner_custom() {
- // An artificial input source.
- const input = "1234 5678 1234567901234567890"
- scanner := bufio.NewScanner(strings.NewReader(input))
- // Create a custom split function by wrapping the existing ScanWords function.
- split := func(data []byte, atEOF bool) (advance int, token []byte, err error) {
- advance, token, err = bufio.ScanWords(data, atEOF)
- if err == nil && token != nil {
- _, err = strconv.ParseInt(string(token), 10, 32)
- }
- return
- }
- // Set the split function for the scanning operation.
- scanner.Split(split)
- // Validate the input
- for scanner.Scan() {
- fmt.Printf("%s\n", scanner.Text())
- }
- if err := scanner.Err(); err != nil {
- fmt.Printf("Invalid input: %s", err)
- }
- // Output:
- // 1234
- // 5678
- // Invalid input: strconv.ParseInt: parsing "1234567901234567890": value out of range
- }
- // Use a Scanner with a custom split function to parse a comma-separated
- // list with an empty final value.
- func ExampleScanner_emptyFinalToken() {
- // Comma-separated list; last entry is empty.
- const input = "1,2,3,4,"
- scanner := bufio.NewScanner(strings.NewReader(input))
- // Define a split function that separates on commas.
- onComma := func(data []byte, atEOF bool) (advance int, token []byte, err error) {
- for i := 0; i < len(data); i++ {
- if data[i] == ',' {
- return i + 1, data[:i], nil
- }
- }
- if !atEOF {
- return 0, nil, nil
- }
- // There is one final token to be delivered, which may be the empty string.
- // Returning bufio.ErrFinalToken here tells Scan there are no more tokens after this
- // but does not trigger an error to be returned from Scan itself.
- return 0, data, bufio.ErrFinalToken
- }
- scanner.Split(onComma)
- // Scan.
- for scanner.Scan() {
- fmt.Printf("%q ", scanner.Text())
- }
- if err := scanner.Err(); err != nil {
- fmt.Fprintln(os.Stderr, "reading input:", err)
- }
- // Output: "1" "2" "3" "4" ""
- }
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