// Infrastructure shared by interleaved-cursors-{small,large}.html
// Number of objects that each iterator goes over.
const itemCount = 10;
// Ratio of small objects to large objects.
const largeObjectRatio = 5;
// Size of large objects. This should exceed the size of a block in the storage
// method underlying the browser's IndexedDB implementation. For example, this
// needs to exceed the LevelDB block size on Chrome, and the SQLite block size
// on Firefox.
const largeObjectSize = 48 * 1024;
function objectKey(cursorIndex, itemIndex) {
return `${cursorIndex}-key-${itemIndex}`;
}
function objectValue(cursorIndex, itemIndex) {
if ((cursorIndex * itemCount + itemIndex) % largeObjectRatio === 0) {
// We use a typed array (as opposed to a string) because IndexedDB
// implementations may serialize strings using UTF-8 or UTF-16, yielding
// larger IndexedDB entries than we'd expect. It's very unlikely that an
// IndexedDB implementation would use anything other than the raw buffer to
// serialize a typed array.
const buffer = new Uint8Array(largeObjectSize);
// Some IndexedDB implementations, like LevelDB, compress their data blocks
// before storing them to disk. We use a simple 32-bit xorshift PRNG, which
// should be sufficient to foil any fast generic-purpose compression scheme.
// 32-bit xorshift - the seed can't be zero
let state = 1000 + (cursorIndex * itemCount + itemIndex);
for (let i = 0; i < largeObjectSize; ++i) {
state ^= state << 13;
state ^= state >> 17;
state ^= state << 5;
buffer[i] = state & 0xff;
}
return buffer;
}
return [cursorIndex, 'small', itemIndex];
}
// Writes the objects to be read by one cursor. Returns a promise that resolves
// when the write completes.
//
// We want to avoid creating a large transaction, because that is outside the
// test's scope, and it's a bad practice. So we break up the writes across
// multiple transactions. For simplicity, each transaction writes all the
// objects that will be read by a cursor.
function writeCursorObjects(database, cursorIndex) {
return new Promise((resolve, reject) => {
const transaction = database.transaction('cache', 'readwrite', {durability: 'relaxed'});
transaction.onabort = () => { reject(transaction.error); };
const store = transaction.objectStore('cache');
for (let i = 0; i < itemCount; ++i) {
store.put({
key: objectKey(cursorIndex, i), value: objectValue(cursorIndex, i)});
}
transaction.oncomplete = resolve;
});
}
// Returns a promise that resolves when the store has been populated.
function populateTestStore(testCase, database, cursorCount) {
let promiseChain = Promise.resolve();
for (let i = 0; i < cursorCount; ++i)
promiseChain = promiseChain.then(() => writeCursorObjects(database, i));
return promiseChain;
}
// Reads cursors in an interleaved fashion, as shown below.
//
// Given N cursors, each of which points to the beginning of a K-item sequence,
// the following accesses will be made.
//
// OC(i) = open cursor i
// RD(i, j) = read result of cursor i, which should be at item j
// CC(i) = continue cursor i
// | = wait for onsuccess on the previous OC or CC
//
// OC(1) | RD(1, 1) OC(2) | RD(2, 1) OC(3) | ... | RD(n-1, 1) CC(n) |
// RD(n, 1) CC(1) | RD(1, 2) CC(2) | RD(2, 2) CC(3) | ... | RD(n-1, 2) CC(n) |
// RD(n, 2) CC(1) | RD(1, 3) CC(2) | RD(2, 3) CC(3) | ... | RD(n-1, 3) CC(n) |
// ...
// RD(n, k-1) CC(1) | RD(1, k) CC(2) | RD(2, k) CC(3) | ... | RD(n-1, k) CC(n) |
// RD(n, k) done
function interleaveCursors(testCase, store, cursorCount) {
return new Promise((resolve, reject) => {
// The cursors used for iteration are stored here so each cursor's onsuccess
// handler can call continue() on the next cursor.
const cursors = [];
// The results of IDBObjectStore.openCursor() calls are stored here so we
// we can change the requests' onsuccess handler after every
// IDBCursor.continue() call.
const requests = [];
const checkCursorState = (cursorIndex, itemIndex) => {
const cursor = cursors[cursorIndex];
assert_equals(cursor.key, objectKey(cursorIndex, itemIndex));
assert_equals(cursor.value.key, objectKey(cursorIndex, itemIndex));
assert_equals(
cursor.value.value.join('-'),
objectValue(cursorIndex, itemIndex).join('-'));
};
const openCursor = (cursorIndex, callback) => {
const request = store.openCursor(
IDBKeyRange.lowerBound(objectKey(cursorIndex, 0)));
requests[cursorIndex] = request;
request.onsuccess = testCase.step_func(() => {
const cursor = request.result;
cursors[cursorIndex] = cursor;
checkCursorState(cursorIndex, 0);
callback();
});
request.onerror = event => reject(request.error);
};
const readItemFromCursor = (cursorIndex, itemIndex, callback) => {
const request = requests[cursorIndex];
request.onsuccess = testCase.step_func(() => {
const cursor = request.result;
cursors[cursorIndex] = cursor;
checkCursorState(cursorIndex, itemIndex);
callback();
});
const cursor = cursors[cursorIndex];
cursor.continue();
};
// We open all the cursors one at a time, then cycle through the cursors and
// call continue() on each of them. This access pattern causes maximal
// trashing to an LRU cursor cache. Eviction scheme aside, any cache will
// have to evict some cursors, and this access pattern verifies that the
// cache correctly restores the state of evicted cursors.
const steps = [];
for (let cursorIndex = 0; cursorIndex < cursorCount; ++cursorIndex)
steps.push(openCursor.bind(null, cursorIndex));
for (let itemIndex = 1; itemIndex < itemCount; ++itemIndex) {
for (let cursorIndex = 0; cursorIndex < cursorCount; ++cursorIndex)
steps.push(readItemFromCursor.bind(null, cursorIndex, itemIndex));
}
const runStep = (stepIndex) => {
if (stepIndex === steps.length) {
resolve();
return;
}
steps[stepIndex](() => { runStep(stepIndex + 1); });
};
runStep(0);
});
}
function cursorTest(cursorCount) {
promise_test(testCase => {
return createDatabase(testCase, (database, transaction) => {
const store = database.createObjectStore('cache',
{ keyPath: 'key', autoIncrement: true });
}).then(database => {
return populateTestStore(testCase, database, cursorCount).then(
() => database);
}).then(database => {
database.close();
}).then(() => {
return openDatabase(testCase);
}).then(database => {
const transaction = database.transaction('cache', 'readonly', {durability: 'relaxed'});
transaction.onabort = () => { reject(transaction.error); };
const store = transaction.objectStore('cache');
return interleaveCursors(testCase, store, cursorCount).then(
() => database);
}).then(database => {
database.close();
});
}, `${cursorCount} cursors`);
}
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