From 4de8d5cef9cfb6e41c79be4ee63e6017a445e1b2 Mon Sep 17 00:00:00 2001
From: thiolliere <gui.thiolliere@gmail.com>
Date: Mon, 13 Jan 2020 12:14:44 +0100
Subject: [PATCH] Add translate function for storage prefixed map. (#4555)
* translace values for prefixed storages
* improve doc
* new impl
* update test
---
substrate/frame/support/src/storage/mod.rs | 72 ++++++++++++++++++++++
1 file changed, 72 insertions(+)
diff --git a/substrate/frame/support/src/storage/mod.rs b/substrate/frame/support/src/storage/mod.rs
index 53e7ceb45df..0908adae3b6 100644
--- a/substrate/frame/support/src/storage/mod.rs
+++ b/substrate/frame/support/src/storage/mod.rs
@@ -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));
});
--
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