Function sp_io::default_child_storage::read

pub fn read(
    storage_key: &[u8], 
    key: &[u8], 
    value_out: &mut [u8], 
    value_offset: u32
) -> Option<u32>

Allocation efficient variant of get.

Get key from child storage, placing the value into value_out and return the number of bytes that the entry in storage has beyond the offset or None if the storage entry doesn’t exist at all. If value_out length is smaller than the returned length, only value_out length bytes are copied into value_out.