next
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The React Framework
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JavaScript
;
Object.defineProperty(exports, "__esModule", {
value: true
});
0 && (module.exports = {
Fallback: null,
createCacheMap: null,
deleteFromCacheMap: null,
getFromCacheMap: null,
isValueExpired: null,
setInCacheMap: null,
setSizeInCacheMap: null
});
function _export(target, all) {
for(var name in all)Object.defineProperty(target, name, {
enumerable: true,
get: all[name]
});
}
_export(exports, {
Fallback: function() {
return Fallback;
},
createCacheMap: function() {
return createCacheMap;
},
deleteFromCacheMap: function() {
return deleteFromCacheMap;
},
getFromCacheMap: function() {
return getFromCacheMap;
},
isValueExpired: function() {
return isValueExpired;
},
setInCacheMap: function() {
return setInCacheMap;
},
setSizeInCacheMap: function() {
return setSizeInCacheMap;
}
});
const _lru = require("./lru");
const Fallback = {};
// This is a special internal key that is used for "revalidation" entries. It's
// an implementation detail that shouldn't leak outside of this module.
const Revalidation = {};
function createCacheMap() {
const cacheMap = {
parent: null,
key: null,
value: null,
map: null,
// LRU-related fields
prev: null,
next: null,
size: 0
};
return cacheMap;
}
function getOrInitialize(cacheMap, keys, isRevalidation) {
// Go through each level of keys until we find the entry that matches, or
// create a new entry if one doesn't exist.
//
// This function will only return entries that match the keypath _exactly_.
// Unlike getWithFallback, it will not access fallback entries unless it's
// explicitly part of the keypath.
let entry = cacheMap;
let remainingKeys = keys;
let key = null;
while(true){
const previousKey = key;
if (remainingKeys !== null) {
key = remainingKeys.value;
remainingKeys = remainingKeys.parent;
} else if (isRevalidation && previousKey !== Revalidation) {
// During a revalidation, we append an internal "Revalidation" key to
// the end of the keypath. The "normal" entry is its parent.
// However, if the parent entry is currently empty, we don't need to store
// this as a revalidation entry. Just insert the revalidation into the
// normal slot.
if (entry.value === null) {
return entry;
}
// Otheriwse, create a child entry.
key = Revalidation;
} else {
break;
}
let map = entry.map;
if (map !== null) {
const existingEntry = map.get(key);
if (existingEntry !== undefined) {
// Found a match. Keep going.
entry = existingEntry;
continue;
}
} else {
map = new Map();
entry.map = map;
}
// No entry exists yet at this level. Create a new one.
const newEntry = {
parent: entry,
key,
value: null,
map: null,
// LRU-related fields
prev: null,
next: null,
size: 0
};
map.set(key, newEntry);
entry = newEntry;
}
return entry;
}
function getFromCacheMap(now, currentCacheVersion, rootEntry, keys, isRevalidation) {
const entry = getEntryWithFallbackImpl(now, currentCacheVersion, rootEntry, keys, isRevalidation, 0);
if (entry === null || entry.value === null) {
return null;
}
// This is an LRU access. Move the entry to the front of the list.
(0, _lru.lruPut)(entry);
return entry.value;
}
function isValueExpired(now, currentCacheVersion, value) {
return value.staleAt <= now || value.version < currentCacheVersion;
}
function lazilyEvictIfNeeded(now, currentCacheVersion, entry) {
// We have a matching entry, but before we can return it, we need to check if
// it's still fresh. Otherwise it should be treated the same as a cache miss.
if (entry.value === null) {
// This entry has no value, so there's nothing to evict.
return entry;
}
const value = entry.value;
if (isValueExpired(now, currentCacheVersion, value)) {
// The value expired. Lazily evict it from the cache, and return null. This
// is conceptually the same as a cache miss.
deleteMapEntry(entry);
return null;
}
// The matched entry has not expired. Return it.
return entry;
}
function getEntryWithFallbackImpl(now, currentCacheVersion, entry, keys, isRevalidation, previousKey) {
// This is similar to getExactEntry, but if an exact match is not found for
// a key, it will return the fallback entry instead. This is recursive at
// every level, e.g. an entry with keypath [a, Fallback, c, Fallback] is
// valid match for [a, b, c, d].
//
// It will return the most specific match available.
let key;
let remainingKeys;
if (keys !== null) {
key = keys.value;
remainingKeys = keys.parent;
} else if (isRevalidation && previousKey !== Revalidation) {
// During a revalidation, we append an internal "Revalidation" key to
// the end of the keypath.
key = Revalidation;
remainingKeys = null;
} else {
// There are no more keys. This is the terminal entry.
// TODO: When performing a lookup during a navigation, as opposed to a
// prefetch, we may want to skip entries that are Pending if there's also
// a Fulfilled fallback entry. Tricky to say, though, since if it's
// already pending, it's likely to stream in soon. Maybe we could do this
// just on slow connections and offline mode.
return lazilyEvictIfNeeded(now, currentCacheVersion, entry);
}
const map = entry.map;
if (map !== null) {
const existingEntry = map.get(key);
if (existingEntry !== undefined) {
// Found an exact match for this key. Keep searching.
const result = getEntryWithFallbackImpl(now, currentCacheVersion, existingEntry, remainingKeys, isRevalidation, key);
if (result !== null) {
return result;
}
}
// No match found for this key. Check if there's a fallback.
const fallbackEntry = map.get(Fallback);
if (fallbackEntry !== undefined) {
// Found a fallback for this key. Keep searching.
return getEntryWithFallbackImpl(now, currentCacheVersion, fallbackEntry, remainingKeys, isRevalidation, key);
}
}
return null;
}
function setInCacheMap(cacheMap, keys, value, isRevalidation) {
// Add a value to the map at the given keypath. If the value is already
// part of the map, it's removed from its previous keypath. (NOTE: This is
// unlike a regular JS map, but the behavior is intentional.)
const entry = getOrInitialize(cacheMap, keys, isRevalidation);
setMapEntryValue(entry, value);
// This is an LRU access. Move the entry to the front of the list.
(0, _lru.lruPut)(entry);
(0, _lru.updateLruSize)(entry, value.size);
}
function setMapEntryValue(entry, value) {
if (entry.value !== null) {
// There's already a value at the given keypath. Disconnect the old value
// from the map. We're not calling `deleteMapEntry` here because the
// entry itself is still in the map. We just want to overwrite its value.
dropRef(entry.value);
// Fill the entry with the updated value.
const emptyEntry = entry;
emptyEntry.value = null;
fillEmptyReference(emptyEntry, value);
} else {
fillEmptyReference(entry, value);
}
}
function fillEmptyReference(entry, value) {
// This value may already be in the map at a different keypath.
// Grab a reference before we overwrite it.
const oldEntry = value.ref;
const fullEntry = entry;
fullEntry.value = value;
value.ref = fullEntry;
(0, _lru.updateLruSize)(fullEntry, value.size);
if (oldEntry !== null && oldEntry !== entry && oldEntry.value === value) {
// This value is already in the map at a different keypath in the map.
// Values only exist at a single keypath at a time. Remove it from the
// previous keypath.
//
// Note that only the internal map entry is garbage collected; we don't
// call `dropRef` here because it's still in the map, just
// at a new keypath (the one we just set, above).
deleteMapEntry(oldEntry);
}
}
function deleteFromCacheMap(value) {
const entry = value.ref;
if (entry === null) {
// This value is not a member of any map.
return;
}
dropRef(value);
deleteMapEntry(entry);
}
function dropRef(value) {
// Drop the value from the map by setting its `ref` backpointer to
// null. This is a separate operation from `deleteMapEntry` because when
// re-keying a value we need to be able to delete the old, internal map
// entry without garbage collecting the value itself.
value.ref = null;
}
function deleteMapEntry(entry) {
// Delete the entry from the cache.
const emptyEntry = entry;
emptyEntry.value = null;
(0, _lru.deleteFromLru)(entry);
// Check if we can garbage collect the entry.
const map = emptyEntry.map;
if (map === null) {
// Since this entry has no value, and also no child entries, we can
// garbage collect it. Remove it from its parent, and keep garbage
// collecting the parents until we reach a non-empty entry.
let parent = emptyEntry.parent;
let key = emptyEntry.key;
while(parent !== null){
const parentMap = parent.map;
if (parentMap !== null) {
parentMap.delete(key);
if (parentMap.size === 0) {
// We just removed the last entry in the parent map.
parent.map = null;
if (parent.value === null) {
// The parent node has no child entries, nor does it have a value
// on itself. It can be garbage collected. Keep going.
key = parent.key;
parent = parent.parent;
continue;
}
}
}
break;
}
} else {
// Check if there's a revalidating entry. If so, promote it to a
// "normal" entry, since the normal one was just deleted.
const revalidatingEntry = map.get(Revalidation);
if (revalidatingEntry !== undefined && revalidatingEntry.value !== null) {
setMapEntryValue(emptyEntry, revalidatingEntry.value);
}
}
}
function setSizeInCacheMap(value, size) {
const entry = value.ref;
if (entry === null) {
// This value is not a member of any map.
return;
}
// Except during initialization (when the size is set to 0), this is the only
// place the `size` field should be updated, to ensure it's in sync with the
// the LRU.
value.size = size;
(0, _lru.updateLruSize)(entry, size);
}
if ((typeof exports.default === 'function' || (typeof exports.default === 'object' && exports.default !== null)) && typeof exports.default.__esModule === 'undefined') {
Object.defineProperty(exports.default, '__esModule', { value: true });
Object.assign(exports.default, exports);
module.exports = exports.default;
}
//# sourceMappingURL=cache-map.js.map