英文:
How can I push bytes into a reader in Go?
问题
我需要将接收到的字节逐步追加到一个缓冲区中，以便以后可以再次读取。类似这样的代码：
type TwoPassReader struct {
someDataSource SomeDataReader
secondPassReader io.Reader
}
func (r *TwoPassReader) Read(b []byte) (n int, err error) {
n, err := r.someDataSource.Read(b)
if err == nil {
//XXX: 这个实际上不存在，对吗？
bytesAppended, writeErr := r.secondPassReader.Write(b)
}
return n, err
}
func (r *) ReadSecondPass(b []byte) (n int, err error) {
return r.secondPassReader.Read(b)
}
虽然最简单的解决方案是使用bufio.Reader.Peek，但我有一个无法修改的SomeDataReader对象，而不是一个Reader。将数据放入[]byte并在调用ReadSecondPass时返回，是最好的解决方案吗？
英文:
I need to incrementally append bytes as I receive them to a buffer where I can read them again later. Something like this:
type TwoPassReader struct {
someDataSource SomeDataReader
secondPassReader io.Reader
}
func (r *TwoPassReader) Read(b []byte) (n int, err error) {
n, err := r.someDataSource.Read(b)
if err == nil {
//XXX: this doesn't actually exist, right?
bytesAppended, writeErr := r.secondPassReader.Write(b)
}
return n, err
}
func (r *) ReadSecondPass(b []byte) (n int, err error) {
return r.secondPassReader.Read(b)
}
While the trivial answer for this would be to use bufio.Reader.Peek, I have a SomeDataReader object that I can't modify instead of a Reader. Is the best solution to just put the data into a []byte and return that when ReadSecondPass is called?
答案1
得分: 2
像这样吗？
package main
import (
"bytes"
"io"
)
type TwoPassReader struct {
firstPassReader io.Reader
secondPassBuffer io.ReadWriter
}
func NewTwoPassReader(firstPass io.Reader) *TwoPassReader {
return &TwoPassReader{
firstPassReader: firstPass,
secondPassBuffer: bytes.NewBuffer(nil),
}
}
func (r *TwoPassReader) Read(b []byte) (n int, err error) {
n1, err1 := r.firstPassReader.Read(b)
n2, err2 := r.secondPassBuffer.Write(b[:n1])
if err2 != nil {
return n2, err2
}
return n1, err1
}
func (r *TwoPassReader) ReadSecondPass(b []byte) (n int, err error) {
return r.secondPassBuffer.Read(b)
}
func main() {
}
这是一个示例的Go语言代码。它定义了一个名为TwoPassReader的结构体，该结构体具有两个字段：firstPassReader和secondPassBuffer。TwoPassReader结构体还有两个方法：Read和ReadSecondPass，用于读取数据。
NewTwoPassReader函数用于创建一个TwoPassReader对象，并初始化其字段。
在main函数中，你可以添加你的代码逻辑。
英文:
Something like this?
package main
import (
"bytes"
"io"
)
type TwoPassReader struct {
firstPassReader io.Reader
secondPassBuffer io.ReadWriter
}
func NewTwoPassReader(firstPass io.Reader) *TwoPassReader {
return &TwoPassReader{
firstPassReader: firstPass,
secondPassBuffer: bytes.NewBuffer(nil),
}
}
func (r *TwoPassReader) Read(b []byte) (n int, err error) {
n1, err1 := r.firstPassReader.Read(b)
n2, err2 := r.secondPassBuffer.Write(b[:n1])
if err2 != nil {
return n2, err2
}
return n1, err1
}
func (r *TwoPassReader) ReadSecondPass(b []byte) (n int, err error) {
return r.secondPassBuffer.Read(b)
}
func main() {
}
答案2
得分: 1
io.Reader只是一个接口。我们无法看到你将什么赋值给该结构字段（如果有的话），但是在这里使用bytes.Buffer可能是正确的类型。
英文:
io.Reader is just an interface. We can't see what you're assigning to that struct field (if anything), but a bytes.Buffer would probably be the correct type to use here.
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