英文:
*strings.Reader leaving target buffer blank
问题
我正在尝试将一个*strings.Reader从一个函数传递给另一个函数。读者的内容是"Foo"。这是创建/传递读者的代码：
_, err = funcNum2(strings.NewReader("Foo"))
...以及从中读取的代码...
buf := []byte{}
_, err := reader.Read(buf)
if err != nil {
fmt.Printf("从读者中读取错误：%v\n", err)
}
当我运行调试器并查看method2中reader的值时，我发现reader仍然包含"Foo"。然而，为什么当我尝试读取到buf时，buf是空的，请帮助我理解这个问题。
英文:
I am attempting to pass an *strings.Reader from one function to another. The content of the reader is "Foo". This is the code that creates/passes the reader:
_, err = funcNum2(strings.NewReader("Foo"))
... and the code that reads from it...
buf := []byte{}
_, err := reader.Read(buf)
if err != nil {
fmt.Printf("Error reading from reader: %v\n", err)
}
When I run the debugger and look at the value of reader in method2, I find that reader still contains "Foo". However, can you please help me understand why, when I try to read into buf, buf is empty?
答案1
得分: 0
当分配buf:=[]byte{}时，分配了一个大小为0的字节切片。为了从缓冲区读取，您可以获取读取器的缓冲区大小reader.Size()，创建一个相同大小的字节切片，并将数据写入其中。
以下代码可以工作：
package main
import (
"fmt"
"strings"
)
func print_reader(read *strings.Reader) {
buf := make([]byte, read.Size()) //在这里使用read.Size()
n, err := read.Read(buf)
fmt.Println(n, err, string(buf), read.Size())
}
func main() {
rd := strings.NewReader("test")
print_reader(rd)
}
希望对您有所帮助！
英文:
when assigning buf:=[]byte{}, a byte slice of size 0 is assigned. In order to read from buffer you can take size of the reader's buffer, reader.Size(), create a byte slice of that size. Write to it.
following code works
package main
import (
"fmt"
"strings"
)
func print_reader(read *strings.Reader) {
buf := make([]byte, 4) //give read.Size() here
n, err := read.Read(buf)
fmt.Println(n, err, string(buf), read.Size())
}
func main() {
rd := strings.NewReader("test")
print_reader(rd)
}
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