I am trying to write a program to read a binary file into a struct in golang, the approach is to use the binary package to read a binary file to populate a struct that contains arrays, I am using arrays and not slices because I want to specify the field length, this seems to work fine but when I try to use reflection to print our the values of the fields I am getting this error
panic: reflect: call of reflect.Value.Bytes on array Value
Here is the code
package main
import (
"encoding/binary"
"fmt"
"log"
"os"
"reflect"
)
type SomeStruct struct {
Field1 [4]byte
Field2 [2]byte
Field3 [1]byte
}
func main() {
f, err := os.Open("/Users/user/Downloads/file.bin")
if err != nil {
log.Fatalln(err)
}
defer f.Close()
s := SomeStruct{}
err = binary.Read(f, binary.LittleEndian, &s)
numOfFields := reflect.TypeOf(s).NumField()
ps := reflect.ValueOf(&s).Elem()
for i := 0; i < numOfFields; i {
value := ps.Field(i).Bytes()
for j := 0; j < len(value); j {
fmt.Print(value[j])
}
}
}
when I change the code to this
package main
import (
"encoding/binary"
"fmt"
"log"
"os"
"reflect"
)
type SomeStruct struct {
Field1 [4]byte
Field2 [2]byte
Field3 [1]byte
}
func main() {
f, err := os.Open("/Users/user/Downloads/file.bin")
if err != nil {
log.Fatalln(err)
}
defer f.Close()
s := SomeStruct{}
err = binary.Read(f, binary.LittleEndian, &s)
numOfFields := reflect.TypeOf(s).NumField()
ps := reflect.ValueOf(&s).Elem()
for i := 0; i < numOfFields; i {
value := ps.Field(i)
fmt.Print(value)
}
}
it prints the arrays with their ascii representation, I need to print the char representation of the ascii and that when I get the panic
thoughts?
CodePudding user response:
The Bytes documentation says:
Bytes returns v's underlying value. It panics if v's underlying value is not a slice of bytes.
Slice the array to get a slice of bytes:
field := ps.Field(i)
value := field.Slice(0, field.Len()).Bytes()
for j := 0; j < len(value); j {
fmt.Print(value[j])
}
You can also iterate through the array:
value := ps.Field(i)
for j := 0; j < value.Len(); j {
fmt.Print(byte(value.Index(j).Uint()))
}