源码 WriteString unsafeheader.Slice

src\os\file.go

 

// WriteString is like Write, but writes the contents of string s rather than

// a slice of bytes.

func (f *File) WriteString(s string) (n int, err error) {

    var b []byte

    hdr := (*unsafeheader.Slice)(unsafe.Pointer(&b))

    hdr.Data = (*unsafeheader.String)(unsafe.Pointer(&s)).Data

    hdr.Cap = len(s)

    hdr.Len = len(s)

    return f.Write(b)

}

 

// Write writes len(b) bytes from b to the File.

// It returns the number of bytes written and an error, if any.

// Write returns a non-nil error when n != len(b).

func (f *File) Write(b []byte) (n int, err error) {

    if err := f.checkValid("write"); err != nil {

        return 0, err

    }

    n, e := f.write(b)

    if n < 0 {

        n = 0

    }

    if n != len(b) {

        err = io.ErrShortWrite

    }

    epipecheck(f, e)

    if e != nil {

        err = f.wrapErr("write", e)

    }

    return n, err

}