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This commit is contained in:
Kismet Hasanaj
+305
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"use strict";
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Object.defineProperty(exports, "__esModule", {
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value: true
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});
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0 && (module.exports = {
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Fallback: null,
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createCacheMap: null,
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deleteFromCacheMap: null,
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deleteMapEntry: null,
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getFromCacheMap: null,
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isValueExpired: null,
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setInCacheMap: null,
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setSizeInCacheMap: null
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});
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function _export(target, all) {
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for(var name in all)Object.defineProperty(target, name, {
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enumerable: true,
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get: all[name]
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});
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}
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_export(exports, {
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Fallback: function() {
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return Fallback;
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},
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createCacheMap: function() {
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return createCacheMap;
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},
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deleteFromCacheMap: function() {
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return deleteFromCacheMap;
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},
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deleteMapEntry: function() {
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return deleteMapEntry;
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},
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getFromCacheMap: function() {
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return getFromCacheMap;
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},
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isValueExpired: function() {
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return isValueExpired;
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},
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setInCacheMap: function() {
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return setInCacheMap;
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},
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setSizeInCacheMap: function() {
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return setSizeInCacheMap;
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}
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});
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const _lru = require("./lru");
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const Fallback = {};
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// This is a special internal key that is used for "revalidation" entries. It's
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// an implementation detail that shouldn't leak outside of this module.
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const Revalidation = {};
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function createCacheMap() {
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const cacheMap = {
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parent: null,
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key: null,
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value: null,
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map: null,
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// LRU-related fields
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prev: null,
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next: null,
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size: 0
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};
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return cacheMap;
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}
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function getOrInitialize(cacheMap, keys, isRevalidation) {
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// Go through each level of keys until we find the entry that matches, or
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// create a new entry if one doesn't exist.
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//
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// This function will only return entries that match the keypath _exactly_.
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// Unlike getWithFallback, it will not access fallback entries unless it's
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// explicitly part of the keypath.
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let entry = cacheMap;
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let remainingKeys = keys;
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let key = null;
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while(true){
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const previousKey = key;
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if (remainingKeys !== null) {
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key = remainingKeys.value;
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remainingKeys = remainingKeys.parent;
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} else if (isRevalidation && previousKey !== Revalidation) {
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// During a revalidation, we append an internal "Revalidation" key to
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// the end of the keypath. The "normal" entry is its parent.
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// However, if the parent entry is currently empty, we don't need to store
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// this as a revalidation entry. Just insert the revalidation into the
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// normal slot.
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if (entry.value === null) {
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return entry;
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}
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// Otheriwse, create a child entry.
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key = Revalidation;
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} else {
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break;
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}
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let map = entry.map;
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if (map !== null) {
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const existingEntry = map.get(key);
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if (existingEntry !== undefined) {
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// Found a match. Keep going.
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entry = existingEntry;
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continue;
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}
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} else {
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map = new Map();
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entry.map = map;
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}
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// No entry exists yet at this level. Create a new one.
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const newEntry = {
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parent: entry,
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key,
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value: null,
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map: null,
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// LRU-related fields
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prev: null,
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next: null,
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size: 0
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};
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map.set(key, newEntry);
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entry = newEntry;
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}
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return entry;
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}
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function getFromCacheMap(now, currentCacheVersion, rootEntry, keys, isRevalidation) {
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const entry = getEntryWithFallbackImpl(now, currentCacheVersion, rootEntry, keys, isRevalidation, 0);
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if (entry === null || entry.value === null) {
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return null;
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}
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// This is an LRU access. Move the entry to the front of the list.
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(0, _lru.lruPut)(entry);
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return entry.value;
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}
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function isValueExpired(now, currentCacheVersion, value) {
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return value.staleAt <= now || value.version < currentCacheVersion;
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}
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function lazilyEvictIfNeeded(now, currentCacheVersion, entry) {
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// We have a matching entry, but before we can return it, we need to check if
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// it's still fresh. Otherwise it should be treated the same as a cache miss.
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if (entry.value === null) {
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// This entry has no value, so there's nothing to evict.
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return entry;
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}
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const value = entry.value;
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if (isValueExpired(now, currentCacheVersion, value)) {
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// The value expired. Lazily evict it from the cache, and return null. This
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// is conceptually the same as a cache miss.
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deleteMapEntry(entry);
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return null;
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}
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// The matched entry has not expired. Return it.
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return entry;
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}
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function getEntryWithFallbackImpl(now, currentCacheVersion, entry, keys, isRevalidation, previousKey) {
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// This is similar to getExactEntry, but if an exact match is not found for
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// a key, it will return the fallback entry instead. This is recursive at
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// every level, e.g. an entry with keypath [a, Fallback, c, Fallback] is
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// valid match for [a, b, c, d].
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//
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// It will return the most specific match available.
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let key;
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let remainingKeys;
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if (keys !== null) {
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key = keys.value;
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remainingKeys = keys.parent;
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} else if (isRevalidation && previousKey !== Revalidation) {
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// During a revalidation, we append an internal "Revalidation" key to
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// the end of the keypath.
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key = Revalidation;
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remainingKeys = null;
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} else {
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// There are no more keys. This is the terminal entry.
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// TODO: When performing a lookup during a navigation, as opposed to a
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// prefetch, we may want to skip entries that are Pending if there's also
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// a Fulfilled fallback entry. Tricky to say, though, since if it's
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// already pending, it's likely to stream in soon. Maybe we could do this
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// just on slow connections and offline mode.
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return lazilyEvictIfNeeded(now, currentCacheVersion, entry);
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}
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const map = entry.map;
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if (map !== null) {
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const existingEntry = map.get(key);
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if (existingEntry !== undefined) {
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// Found an exact match for this key. Keep searching.
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const result = getEntryWithFallbackImpl(now, currentCacheVersion, existingEntry, remainingKeys, isRevalidation, key);
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if (result !== null) {
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return result;
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}
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}
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// No match found for this key. Check if there's a fallback.
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const fallbackEntry = map.get(Fallback);
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if (fallbackEntry !== undefined) {
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// Found a fallback for this key. Keep searching.
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return getEntryWithFallbackImpl(now, currentCacheVersion, fallbackEntry, remainingKeys, isRevalidation, key);
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}
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}
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return null;
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}
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function setInCacheMap(cacheMap, keys, value, isRevalidation) {
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// Add a value to the map at the given keypath. If the value is already
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// part of the map, it's removed from its previous keypath. (NOTE: This is
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// unlike a regular JS map, but the behavior is intentional.)
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const entry = getOrInitialize(cacheMap, keys, isRevalidation);
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setMapEntryValue(entry, value);
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// This is an LRU access. Move the entry to the front of the list.
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(0, _lru.lruPut)(entry);
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(0, _lru.updateLruSize)(entry, value.size);
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}
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function setMapEntryValue(entry, value) {
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if (entry.value !== null) {
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// There's already a value at the given keypath. Disconnect the old value
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// from the map. We're not calling `deleteMapEntry` here because the
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// entry itself is still in the map. We just want to overwrite its value.
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dropRef(entry.value);
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entry.value = null;
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}
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// This value may already be in the map at a different keypath.
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// Grab a reference before we overwrite it.
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const oldEntry = value.ref;
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entry.value = value;
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value.ref = entry;
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(0, _lru.updateLruSize)(entry, value.size);
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if (oldEntry !== null && oldEntry !== entry && oldEntry.value === value) {
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// This value is already in the map at a different keypath in the map.
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// Values only exist at a single keypath at a time. Remove it from the
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// previous keypath.
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//
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// Note that only the internal map entry is garbage collected; we don't
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// call `dropRef` here because it's still in the map, just
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// at a new keypath (the one we just set, above).
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deleteMapEntry(oldEntry);
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}
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}
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function deleteFromCacheMap(value) {
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const entry = value.ref;
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if (entry === null) {
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// This value is not a member of any map.
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return;
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}
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dropRef(value);
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deleteMapEntry(entry);
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}
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function dropRef(value) {
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// Drop the value from the map by setting its `ref` backpointer to
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// null. This is a separate operation from `deleteMapEntry` because when
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// re-keying a value we need to be able to delete the old, internal map
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// entry without garbage collecting the value itself.
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value.ref = null;
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}
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function deleteMapEntry(entry) {
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// Delete the entry from the cache.
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entry.value = null;
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(0, _lru.deleteFromLru)(entry);
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// Check if we can garbage collect the entry.
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const map = entry.map;
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if (map === null) {
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// Since this entry has no value, and also no child entries, we can
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// garbage collect it. Remove it from its parent, and keep garbage
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// collecting the parents until we reach a non-empty entry.
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let parent = entry.parent;
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let key = entry.key;
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while(parent !== null){
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const parentMap = parent.map;
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if (parentMap !== null) {
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parentMap.delete(key);
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if (parentMap.size === 0) {
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// We just removed the last entry in the parent map.
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parent.map = null;
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if (parent.value === null) {
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// The parent node has no child entries, nor does it have a value
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// on itself. It can be garbage collected. Keep going.
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key = parent.key;
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parent = parent.parent;
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continue;
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}
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}
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}
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break;
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}
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} else {
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// Check if there's a revalidating entry. If so, promote it to a
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// "normal" entry, since the normal one was just deleted.
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const revalidatingEntry = map.get(Revalidation);
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if (revalidatingEntry !== undefined && revalidatingEntry.value !== null) {
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setMapEntryValue(entry, revalidatingEntry.value);
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}
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}
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}
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function setSizeInCacheMap(value, size) {
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const entry = value.ref;
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if (entry === null) {
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// This value is not a member of any map.
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return;
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}
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// Except during initialization (when the size is set to 0), this is the only
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// place the `size` field should be updated, to ensure it's in sync with the
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// the LRU.
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value.size = size;
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(0, _lru.updateLruSize)(entry, size);
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}
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if ((typeof exports.default === 'function' || (typeof exports.default === 'object' && exports.default !== null)) && typeof exports.default.__esModule === 'undefined') {
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Object.defineProperty(exports.default, '__esModule', { value: true });
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Object.assign(exports.default, exports);
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module.exports = exports.default;
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}
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//# sourceMappingURL=cache-map.js.map
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