ioutil

Documentation

Overview

Package ioutil contains extensions and utilities for package io from the standard library.

Index

• func LimitReader(r io.Reader, n uint64) (limited io.Reader)
• type LimitError
  • func (err *LimitError) Error() (msg string)
• type LockedBuffer
  • func NewLockedBuffer(bufSize uint) (b *LockedBuffer)
  • func (b *LockedBuffer) Buffer() (buf *bytes.Buffer)
  • func (b *LockedBuffer) Bytes() (bytes []byte)
  • func (b *LockedBuffer) Read(p []byte) (n int, err error)
  • func (b *LockedBuffer) Write(p []byte) (n int, err error)
• type TruncatedWriter
  • func NewTruncatedWriter(w io.Writer, limit uint64) (tw *TruncatedWriter)
  • func (w *TruncatedWriter) Write(b []byte) (n int, err error)

Examples

• LockedBuffer
• TruncatedWriter

Functions

func LimitReader

func LimitReader(r io.Reader, n uint64) (limited io.Reader)

LimitReader returns an io.Reader that reads up to n bytes. Once that limit is reached, [ErrLimit] is returned from the Read method. The Read method is not safe for concurrent use.

Types

type LimitError

type LimitError struct {
	// Limit is the limit that triggered the error.
	Limit uint64
}

LimitError is returned when the Limit is reached.

func (*LimitError) Error

func (err *LimitError) Error() (msg string)

Error implements the error interface for *LimitError.

type LockedBuffer

type LockedBuffer struct {
	// contains filtered or unexported fields
}

LockedBuffer is a wrapper around bytes.Buffer that makes it safe for concurrent use.

Example

package main

import (
	"fmt"
	"slices"
	"sync"

	"github.com/AdguardTeam/golibs/errors"
	"github.com/AdguardTeam/golibs/ioutil"
)

func main() {
	const goroutineCount = 5

	b := ioutil.NewLockedBuffer(goroutineCount)

	var wg sync.WaitGroup

	for i := range goroutineCount {
		wg.Go(func() {
			_, err := b.Write([]byte{byte(i)})
			errors.Check(err)
		})
	}

	wg.Wait()

	readBuffer := make([]byte, goroutineCount)

	for i := range goroutineCount {
		wg.Go(func() {
			_, err := b.Read(readBuffer[i : i+1])
			errors.Check(err)
		})
	}

	wg.Wait()

	slices.Sort(readBuffer)

	fmt.Printf("%x\n", readBuffer)

}

Output:

0001020304

func NewLockedBuffer

func NewLockedBuffer(bufSize uint) (b *LockedBuffer)

NewLockedBuffer creates a new instance of *LockedBuffer. The size of the underlying buffer is set to bufSize.

func (*LockedBuffer) Buffer

func (b *LockedBuffer) Buffer() (buf *bytes.Buffer)

Buffer returns the underlying bytes buffer.

func (*LockedBuffer) Bytes

func (b *LockedBuffer) Bytes() (bytes []byte)

Bytes returns a copy of the buffer contents.

func (*LockedBuffer) Read

func (b *LockedBuffer) Read(p []byte) (n int, err error)

Read implements the io.Reader interface for *LockedBuffer.

func (*LockedBuffer) Write

func (b *LockedBuffer) Write(p []byte) (n int, err error)

Write implements the io.Writer interface for *LockedBuffer.

type TruncatedWriter

type TruncatedWriter struct {
	// contains filtered or unexported fields
}

TruncatedWriter is an io.Writer that writes up to a certain limit of bytes to its underlying writer and then ignores the rest.

Example

package main

import (
	"bytes"
	"fmt"

	"github.com/AdguardTeam/golibs/ioutil"
)

func main() {
	data := []byte("hello")

	buf := &bytes.Buffer{}
	fmt.Println(ioutil.NewTruncatedWriter(buf, 1).Write(data))
	fmt.Println(buf)

	buf = &bytes.Buffer{}
	fmt.Println(ioutil.NewTruncatedWriter(buf, 2).Write(data))
	fmt.Println(buf)

	buf = &bytes.Buffer{}
	fmt.Println(ioutil.NewTruncatedWriter(buf, 10).Write(data))
	fmt.Println(buf)

}

Output:

5 <nil>
h
5 <nil>
he
5 <nil>
hello

func NewTruncatedWriter

func NewTruncatedWriter(w io.Writer, limit uint64) (tw *TruncatedWriter)

NewTruncatedWriter returns a new truncated writer. It wraps w so that it writes up to limit bytes and then ignores the rest.

func (*TruncatedWriter) Write

func (w *TruncatedWriter) Write(b []byte) (n int, err error)

Write implements the io.Writer interface for *TruncatedWriter. n is always len(b).