// ReadBytes reads bytes from a data object at the specified position and length, returns []byte slice and error.
func (obj *DataObj) ReadBytes(pos int64, length int) ([]byte, error) {
if er := obj.init(); er != nil {
return nil, er
}
var (
buffer C.bytesBuf_t
err *C.char
bytesRead C.int
)
if er := obj.LSeek(pos); er != nil {
return nil, er
}
ccon := obj.con.GetCcon()
defer obj.con.ReturnCcon(ccon)
if status := C.gorods_read_dataobject(obj.chandle, C.rodsLong_t(length), &buffer, &bytesRead, ccon, &err); status != 0 {
return nil, newError(Fatal, fmt.Sprintf("iRODS ReadBytes DataObject Failed: %v, %v", obj.path, C.GoString(err)))
}
buf := unsafe.Pointer(buffer.buf)
defer C.free(buf)
data := C.GoBytes(buf, bytesRead)
return data, nil
}
// ReadChunk reads the entire data object in chunks (size of chunk specified by size parameter), passing the data into a callback function for each chunk. Use this to read/write large files.
func (obj *DataObj) ReadChunk(size int64, callback func([]byte)) error {
if er := obj.init(); er != nil {
return er
}
var (
buffer C.bytesBuf_t
err *C.char
bytesRead C.int
)
if er := obj.LSeek(0); er != nil {
return er
}
for obj.offset < obj.size {
ccon := obj.con.GetCcon()
if status := C.gorods_read_dataobject(obj.chandle, C.rodsLong_t(size), &buffer, &bytesRead, ccon, &err); status != 0 {
obj.con.ReturnCcon(ccon)
return newError(Fatal, fmt.Sprintf("iRODS Read DataObject Failed: %v, %v", obj.path, C.GoString(err)))
}
obj.con.ReturnCcon(ccon)
buf := unsafe.Pointer(buffer.buf)
chunk := C.GoBytes(buf, bytesRead)
C.free(buf)
callback(chunk)
if er := obj.LSeek(obj.offset + size); er != nil {
return er
}
}
if er := obj.LSeek(0); er != nil {
return er
}
return obj.Close()
}