mirror of
https://github.com/protomaps/PMTiles.git
synced 2026-02-04 10:51:07 +00:00
add second implementation of Cache for environments where promises cannot be shared between requests
This commit is contained in:
Brandon Liu
322
js/v3.ts
322
js/v3.ts
@@ -295,12 +295,6 @@ export class FetchSource implements Source {
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}
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}
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interface CacheEntry {
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lastUsed: number;
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size: number; // 0 if the promise has not resolved
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data: Promise<Header | Entry[] | ArrayBuffer>;
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}
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export function bytesToHeader(bytes: ArrayBuffer, etag?: string): Header {
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const v = new DataView(bytes);
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if (v.getUint16(0, true) !== 0x4d50) {
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@@ -378,54 +372,30 @@ export interface Cache {
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length: number,
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header: Header
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) => Promise<Entry[]>;
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getArrayBuffer: (
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source: Source,
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offset: number,
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length: number,
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header: Header
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) => Promise<ArrayBuffer>;
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invalidate: (source: Source) => void;
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}
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// a "dumb" bag of bytes.
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// only caches headers and directories
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// deduplicates simultaneous responses
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// (estimates) the maximum size of the cache.
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export class SharedPromiseCache {
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cache: Map<string, CacheEntry>;
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sizeBytes: number;
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maxSizeBytes: number;
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counter: number;
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prefetch: boolean;
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constructor(maxSizeBytes = 64000000, prefetch = true) {
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this.cache = new Map<string, CacheEntry>();
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this.sizeBytes = 0;
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this.maxSizeBytes = maxSizeBytes;
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this.counter = 1;
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this.prefetch = prefetch;
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}
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async getHeader(source: Source): Promise<Header> {
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const cacheKey = source.getKey();
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if (this.cache.has(cacheKey)) {
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this.cache.get(cacheKey)!.lastUsed = this.counter++;
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const data = await this.cache.get(cacheKey)!.data;
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return data as Header;
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}
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const p = new Promise<Header>((resolve, reject) => {
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source
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.getBytes(0, 16384)
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.then((resp) => {
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if (this.cache.has(cacheKey)) {
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this.cache.get(cacheKey)!.size = HEADER_SIZE_BYTES;
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this.sizeBytes += HEADER_SIZE_BYTES;
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}
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async function getHeaderAndRoot(
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source: Source,
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prefetch: boolean
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): Promise<[Header, [string, number, Entry[] | ArrayBuffer]?]> {
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let resp = await source.getBytes(0, 16384);
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// check spec revision
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if (false) {
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} else {
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const headerData = resp.data.slice(0, HEADER_SIZE_BYTES);
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if (headerData.byteLength !== HEADER_SIZE_BYTES) {
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throw new Error("Invalid PMTiles header");
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}
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const header = bytesToHeader(headerData, resp.etag);
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// optimistically set the root directory
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// TODO check root bounds
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if (this.prefetch) {
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if (prefetch) {
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const rootDirData = resp.data.slice(
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header.rootDirectoryOffset,
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header.rootDirectoryOffset + header.rootDirectoryLength
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@@ -442,15 +412,206 @@ export class SharedPromiseCache {
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const rootDir = deserializeIndex(
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tryDecompress(rootDirData, header.internalCompression)
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);
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return [header, [dirKey, ENTRY_SIZE_BYTES * rootDir.length, rootDir]];
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}
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this.cache.set(dirKey, {
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return [header, undefined];
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}
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}
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async function getDirectory(
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source: Source,
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offset: number,
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length: number,
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header: Header
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): Promise<Entry[]> {
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let resp = await source.getBytes(offset, length);
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if (header.etag && header.etag !== resp.etag) {
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throw new VersionMismatch("ETag mismatch: " + header.etag);
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}
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const data = tryDecompress(resp.data, header.internalCompression);
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const directory = deserializeIndex(data);
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if (directory.length === 0) {
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throw new Error("Empty directory is invalid");
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}
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return directory;
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}
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interface ResolvedValue {
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lastUsed: number;
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size: number;
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data: Header | Entry[] | ArrayBuffer;
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}
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export class ResolvedValueCache {
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cache: Map<string, ResolvedValue>;
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sizeBytes: number;
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maxSizeBytes: number;
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counter: number;
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prefetch: boolean;
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constructor(maxSizeBytes = 64000000, prefetch = true) {
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this.cache = new Map<string, ResolvedValue>();
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this.sizeBytes = 0;
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this.maxSizeBytes = maxSizeBytes;
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this.counter = 1;
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this.prefetch = prefetch;
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}
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async getHeader(source: Source): Promise<Header> {
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const cacheKey = source.getKey();
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if (this.cache.has(cacheKey)) {
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this.cache.get(cacheKey)!.lastUsed = this.counter++;
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const data = this.cache.get(cacheKey)!.data;
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return data as Header;
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}
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let res = await getHeaderAndRoot(source, this.prefetch);
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if (res[1]) {
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this.cache.set(res[1][0], {
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lastUsed: this.counter++,
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data: Promise.resolve(rootDir),
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size: ENTRY_SIZE_BYTES * rootDir.length,
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size: res[1][1],
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data: res[1][2],
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});
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}
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resolve(header);
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this.cache.set(cacheKey, {
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lastUsed: this.counter++,
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data: res[0],
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size: HEADER_SIZE_BYTES,
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});
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this.sizeBytes += HEADER_SIZE_BYTES;
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this.prune();
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return res[0];
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}
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async getDirectory(
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source: Source,
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offset: number,
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length: number,
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header: Header
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): Promise<Entry[]> {
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const cacheKey =
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source.getKey() + "|" + (header.etag || "") + "|" + offset + "|" + length;
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if (this.cache.has(cacheKey)) {
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this.cache.get(cacheKey)!.lastUsed = this.counter++;
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const data = this.cache.get(cacheKey)!.data;
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return data as Entry[];
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}
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const directory = await getDirectory(source, offset, length, header);
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this.cache.set(cacheKey, {
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lastUsed: this.counter++,
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data: directory,
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size: ENTRY_SIZE_BYTES * directory.length,
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});
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this.sizeBytes += ENTRY_SIZE_BYTES * directory.length;
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this.prune();
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return directory;
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}
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// for v2 backwards compatibility
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async getArrayBuffer(
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source: Source,
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offset: number,
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length: number,
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header: Header
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): Promise<ArrayBuffer> {
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const cacheKey =
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source.getKey() + "|" + (header.etag || "") + "|" + offset + "|" + length;
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if (this.cache.has(cacheKey)) {
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this.cache.get(cacheKey)!.lastUsed = this.counter++;
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const data = await this.cache.get(cacheKey)!.data;
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return data as ArrayBuffer;
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}
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let resp = await source.getBytes(offset, length);
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if (header.etag && header.etag !== resp.etag) {
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throw new VersionMismatch("ETag mismatch: " + header.etag);
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}
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this.cache.set(cacheKey, {
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lastUsed: this.counter++,
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data: resp.data,
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size: resp.data.byteLength,
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});
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this.sizeBytes += resp.data.byteLength;
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this.prune();
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return resp.data;
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}
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prune() {
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while (this.sizeBytes > this.maxSizeBytes) {
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let minUsed = Infinity;
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let minKey = undefined;
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this.cache.forEach((cache_value: ResolvedValue, key: string) => {
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if (cache_value.lastUsed < minUsed) {
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minUsed = cache_value.lastUsed;
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minKey = key;
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}
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});
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if (minKey) {
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this.sizeBytes -= this.cache.get(minKey)!.size;
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this.cache.delete(minKey);
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}
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}
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}
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invalidate(source: Source) {
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this.cache.delete(source.getKey());
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}
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}
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interface SharedPromiseCacheValue {
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lastUsed: number;
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size: number; // 0 if the promise has not resolved
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data: Promise<Header | Entry[] | ArrayBuffer>;
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}
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// a "dumb" bag of bytes.
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// only caches headers and directories
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// deduplicates simultaneous responses
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// (estimates) the maximum size of the cache.
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export class SharedPromiseCache {
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cache: Map<string, SharedPromiseCacheValue>;
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sizeBytes: number;
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maxSizeBytes: number;
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counter: number;
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prefetch: boolean;
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constructor(maxSizeBytes = 64000000, prefetch = true) {
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this.cache = new Map<string, SharedPromiseCacheValue>();
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this.sizeBytes = 0;
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this.maxSizeBytes = maxSizeBytes;
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this.counter = 1;
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this.prefetch = prefetch;
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}
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async getHeader(source: Source): Promise<Header> {
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const cacheKey = source.getKey();
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if (this.cache.has(cacheKey)) {
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this.cache.get(cacheKey)!.lastUsed = this.counter++;
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const data = await this.cache.get(cacheKey)!.data;
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return data as Header;
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}
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const p = new Promise<Header>((resolve, reject) => {
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getHeaderAndRoot(source, this.prefetch)
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.then((res) => {
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if (this.cache.has(cacheKey)) {
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this.cache.get(cacheKey)!.size = HEADER_SIZE_BYTES;
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this.sizeBytes += HEADER_SIZE_BYTES;
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}
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if (res[1]) {
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this.cache.set(res[1][0], {
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lastUsed: this.counter++,
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size: res[1][1],
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data: Promise.resolve(res[1][2]),
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});
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}
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resolve(res[0]);
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this.prune();
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})
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.catch((e) => {
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@@ -476,21 +637,9 @@ export class SharedPromiseCache {
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}
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const p = new Promise<Entry[]>((resolve, reject) => {
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source
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.getBytes(offset, length)
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.then((resp) => {
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if (header.etag && header.etag !== resp.etag) {
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throw new VersionMismatch("ETag mismatch: " + header.etag);
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}
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const data = tryDecompress(resp.data, header.internalCompression);
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const directory = deserializeIndex(data);
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if (directory.length === 0) {
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return reject(new Error("Empty directory is invalid"));
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}
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getDirectory(source, offset, length, header)
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.then((directory) => {
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resolve(directory);
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if (this.cache.has(cacheKey)) {
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this.cache.get(cacheKey)!.size =
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ENTRY_SIZE_BYTES * directory.length;
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@@ -506,16 +655,55 @@ export class SharedPromiseCache {
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return p;
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}
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// for v2 backwards compatibility
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async getArrayBuffer(
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source: Source,
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offset: number,
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length: number,
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header: Header
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): Promise<ArrayBuffer> {
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const cacheKey =
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source.getKey() + "|" + (header.etag || "") + "|" + offset + "|" + length;
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if (this.cache.has(cacheKey)) {
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this.cache.get(cacheKey)!.lastUsed = this.counter++;
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const data = await this.cache.get(cacheKey)!.data;
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return data as ArrayBuffer;
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}
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const p = new Promise<ArrayBuffer>((resolve, reject) => {
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source
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.getBytes(offset, length)
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.then((resp) => {
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if (header.etag && header.etag !== resp.etag) {
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throw new VersionMismatch("ETag mismatch: " + header.etag);
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}
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resolve(resp.data);
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if (this.cache.has(cacheKey)) {
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this.cache.get(cacheKey)!.size = resp.data.byteLength;
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this.sizeBytes += resp.data.byteLength;
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}
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this.prune();
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})
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.catch((e) => {
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reject(e);
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});
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});
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this.cache.set(cacheKey, { lastUsed: this.counter++, data: p, size: 0 });
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return p;
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}
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prune() {
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while (this.sizeBytes > this.maxSizeBytes) {
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let minUsed = Infinity;
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let minKey = undefined;
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this.cache.forEach((cache_entry: CacheEntry, key: string) => {
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if (cache_entry.lastUsed < minUsed) {
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minUsed = cache_entry.lastUsed;
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this.cache.forEach(
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(cache_value: SharedPromiseCacheValue, key: string) => {
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if (cache_value.lastUsed < minUsed) {
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minUsed = cache_value.lastUsed;
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minKey = key;
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}
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});
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}
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);
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if (minKey) {
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this.sizeBytes -= this.cache.get(minKey)!.size;
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this.cache.delete(minKey);
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