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Add translate function for storage prefixed map. (#4555)

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* translace values for prefixed storages

* improve doc

* new impl

* update test
This commit is contained in:
thiolliere
2020-01-13 12:14:44 +01:00
committed by Gavin Wood
parent 5946d6f7a0
commit 4de8d5cef9
1 changed files with 72 additions and 0 deletions
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substrate/frame/support/src/storage/mod.rs
+72
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@@ -403,6 +403,7 @@ pub trait StoragePrefixedMap<Value: FullCodec> {
/// Storage prefix. Used for generating final key.
fn storage_prefix() -> &'static [u8];
/// Final full prefix that prefixes all keys.
fn final_prefix() -> [u8; 32] {
let mut final_key = [0u8; 32];
final_key[0..16].copy_from_slice(&Twox128::hash(Self::module_prefix()));
@@ -410,10 +411,12 @@ pub trait StoragePrefixedMap<Value: FullCodec> {
final_key
}
/// Remove all value of the storage.
fn remove_all() {
sp_io::storage::clear_prefix(&Self::final_prefix())
}
/// Iter over all value of the storage.
fn iter() -> PrefixIterator<Value> {
let prefix = Self::final_prefix();
PrefixIterator {
@@ -422,6 +425,51 @@ pub trait StoragePrefixedMap<Value: FullCodec> {
phantom_data: Default::default(),
}
}
/// Translate the values from some previous `OldValue` to the current type.
///
/// `TV` translates values.
///
/// Returns `Err` if the map could not be interpreted as the old type, and Ok if it could.
/// The `Err` contains the number of value that couldn't be interpreted, those value are
/// removed from the map.
///
/// # Warning
///
/// This function must be used with care, before being updated the storage still contains the
/// old type, thus other calls (such as `get`) will fail at decoding it.
///
/// # Usage
///
/// This would typically be called inside the module implementation of on_initialize, while
/// ensuring **no usage of this storage are made before the call to `on_initialize`**. (More
/// precisely prior initialized modules doesn't make use of this storage).
fn translate_values<OldValue, TV>(translate_val: TV) -> Result<(), u32>
where OldValue: Decode, TV: Fn(OldValue) -> Value
{
let prefix = Self::final_prefix();
let mut previous_key = prefix.to_vec();
let mut errors = 0;
while let Some(next_key) = sp_io::storage::next_key(&previous_key)
.filter(|n| n.starts_with(&prefix[..]))
{
if let Some(value) = unhashed::get(&next_key) {
unhashed::put(&next_key[..], &translate_val(value));
} else {
// We failed to read the value. Remove the key and increment errors.
unhashed::kill(&next_key[..]);
errors += 1;
}
previous_key = next_key;
}
if errors == 0 {
Ok(())
} else {
Err(errors)
}
}
}
#[cfg(test)]
@@ -463,6 +511,7 @@ mod test {
let k = [twox_128(b"MyModule"), twox_128(b"MyStorage")].concat();
assert_eq!(MyStorage::final_prefix().to_vec(), k);
// test iteration
assert_eq!(MyStorage::iter().collect::<Vec<_>>(), vec![]);
unhashed::put(&[&k[..], &vec![1][..]].concat(), &1u64);
@@ -472,9 +521,32 @@ mod test {
assert_eq!(MyStorage::iter().collect::<Vec<_>>(), vec![1, 2, 3, 4]);
// test removal
MyStorage::remove_all();
assert_eq!(MyStorage::iter().collect::<Vec<_>>(), vec![]);
// test migration
unhashed::put(&[&k[..], &vec![1][..]].concat(), &1u32);
unhashed::put(&[&k[..], &vec![8][..]].concat(), &2u32);
assert_eq!(MyStorage::iter().collect::<Vec<_>>(), vec![]);
MyStorage::translate_values(|v: u32| v as u64).unwrap();
assert_eq!(MyStorage::iter().collect::<Vec<_>>(), vec![1, 2]);
MyStorage::remove_all();
// test migration 2
unhashed::put(&[&k[..], &vec![1][..]].concat(), &1u128);
unhashed::put(&[&k[..], &vec![1, 1][..]].concat(), &2u64);
unhashed::put(&[&k[..], &vec![8][..]].concat(), &3u128);
unhashed::put(&[&k[..], &vec![10][..]].concat(), &4u32);
// (contains some value that successfully decoded to u64)
assert_eq!(MyStorage::iter().collect::<Vec<_>>(), vec![1, 2, 3]);
assert_eq!(MyStorage::translate_values(|v: u128| v as u64), Err(2));
assert_eq!(MyStorage::iter().collect::<Vec<_>>(), vec![1, 3]);
MyStorage::remove_all();
// test that other values are not modified.
assert_eq!(unhashed::get(&key_before[..]), Some(32u64));
assert_eq!(unhashed::get(&key_after[..]), Some(33u64));
});