Function sp_io::storage::child_read

pub fn child_read(
    child_storage_key: &[u8], 
    child_definition: &[u8], 
    child_type: u32, 
    key: &[u8], 
    value_out: &mut [u8], 
    value_offset: u32
) -> Option<u32>

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.

See child_get for common child api parameters.