io.SectionReader.Read() Function in Golang with Examples
Last Updated :
03 May, 2020
In Go language, io packages supply fundamental interfaces to the I/O primitives. And its principal job is to enclose the ongoing implementations of such king of primitives. The SectionReader.Read() function in Go language is used to return the number of bytes as read by NewSectionReader method. This method holds a buffer as its parameter. Moreover, this function is defined under the io package. Here, you need to import the “io” package in order to use these functions.
Syntax:
func (s *SectionReader) Read(p []byte) (n int, err error)
Here, “s” is a pointer to the SectionReader which is returned by the NewSectionReader method, and “p” is a buffer of stated byte length.
Return value: It returns the number of bytes of the content returned from the stated buffer of specified length and also returns an error if any but if no error occurred then “nil” is returned.
Below examples illustrates the use of above method:
Example 1:
package main
import (
"fmt"
"io"
"strings"
)
func main() {
reader := strings.NewReader( "Geeks\n" )
r := io.NewSectionReader(reader, 2, 4)
buf := make([]byte, 3)
n, err := r.Read(buf)
if err != nil {
panic(err)
}
fmt.Printf( "Content in buffer: %s\n" , buf)
fmt.Printf( "n: %v\n" , n)
}
|
Output:
Content in buffer: eks
n: 3
In the above example, the content of the buffer has only three bytes so, “3” is returned and there is no error thrown while reading the stated content so the error is “nil”.
Example 2:
package main
import (
"fmt"
"io"
"strings"
)
func main() {
reader := strings.NewReader( "GeeksforGeeks\nis\na\nCS-Portal." )
r := io.NewSectionReader(reader, 6, 34)
buf := make([]byte, 25)
n, err := r.Read(buf)
if err != nil {
panic(err)
}
fmt.Printf( "Content in buffer: %s\n" , buf)
fmt.Printf( "n: %v\n" , n)
}
|
Output:
panic: EOF
goroutine 1 [running]:
main.main()
/tmp/sandbox125171693/prog.go:31 +0x25a
Here, the content in the buffer used in above code has less number of bytes than stated so, EOF error is thrown.
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