/
util.go
54 lines (48 loc) · 1.17 KB
/
util.go
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package main
import (
"crypto/rand"
"errors"
"fmt"
"io"
"os"
)
func fatal(txt string, formatter ...interface{}) {
fmt.Fprintf(os.Stderr, txt, formatter)
os.Exit(1)
}
// RandomBytes fills buff from the given reader or crypto.Rand(omness) if reader
// == nil. If there is any problem or the read did not take len(buff) bytes,
// it returns an error.
func randomBytes(reader io.Reader, buff []byte) error {
if reader == nil {
return fillBuff(rand.Read, buff)
}
return fillBuff(reader.Read, buff)
}
func fillBuff(fn func(b []byte) (int, error), buff []byte) error {
n, err := fn(buff)
if err != nil {
return err
} else if n != len(buff) {
return fmt.Errorf("Could not read %d bytes from reader")
}
return nil
}
// Reverse computes the reverse of src into dst. Both buffers can be the same
// but must not be overlapping otherwise.
func reverse(src, dst []byte) error {
if len(src) != len(dst) {
return errors.New("Reverse can't operate on two different size buffer")
}
n := len(src)
for i := 0; i < n; i++ {
dst[n-i-1] = src[i]
}
return nil
}
func exists(fname string) bool {
if _, err := os.Stat(fname); os.IsNotExist(err) {
return false
}
return true
}