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How to use read_tx method in wpt

Best JavaScript code snippet using wpt

blob-composite-blob-reads.any.js

Source:blob-composite-blob-reads.any.js

1// META: title=IDB-backed composite blobs maintain coherency2// META: script=resources/support-promises.js3// META: timeout=long4// This test file is intended to help validate browser handling of complex blob5// scenarios where one or more levels of multipart blobs are used and varying6// IPC serialization strategies may be used depending on various complexity7// heuristics.8//9// A variety of approaches of reading the blob's contents are attempted for10// completeness:11// - `fetch-blob-url`: fetch of a URL created via URL.createObjectURL12//   - Note that this is likely to involve multi-process behavior in a way that13//     the next 2 currently will not unless their Blobs are round-tripped14//     through a MessagePort.15// - `file-reader`: FileReader16// - `direct`: Blob.prototype.arrayBuffer()17function composite_blob_test({ blobCount, blobSize, name }) {18  // NOTE: In order to reduce the runtime of this test and due to the similarity19  // of the "file-reader" mechanism to the "direct", "file-reader" is commented20  // out, but if you are investigating failures detected by this test, you may21  // want to uncomment it.22  for (const mode of ["fetch-blob-url", /*"file-reader",*/ "direct"]) {23    promise_test(async testCase => {24      const key = "the-blobs";25      let memBlobs = [];26      for (let iBlob = 0; iBlob < blobCount; iBlob++) {27        memBlobs.push(new Blob([make_arraybuffer_contents(iBlob, blobSize)]));28      }29      const db = await createDatabase(testCase, db => {30        db.createObjectStore("blobs");31      });32      const write_tx = db.transaction("blobs", "readwrite");33      let store = write_tx.objectStore("blobs");34      store.put(memBlobs, key);35      // Make the blobs eligible for GC which is most realistic and most likely36      // to cause problems.37      memBlobs = null;38      await promiseForTransaction(testCase, write_tx);39      const read_tx = db.transaction("blobs");40      store = read_tx.objectStore("blobs");41      const read_req = store.get(key);42      await promiseForTransaction(testCase, read_tx);43      const diskBlobs = read_req.result;44      const compositeBlob = new Blob(diskBlobs);45      if (mode === "fetch-blob-url") {46        const blobUrl = URL.createObjectURL(compositeBlob);47        let urlResp = await fetch(blobUrl);48        let urlFetchArrayBuffer = await urlResp.arrayBuffer();49        urlResp = null;50        URL.revokeObjectURL(blobUrl);51        validate_arraybuffer_contents("fetched URL", urlFetchArrayBuffer, blobCount, blobSize);52        urlFetchArrayBuffer = null;53      } else if (mode === "file-reader") {54        let reader = new FileReader();55        let readerPromise = new Promise(resolve => {56          reader.onload = () => {57            resolve(reader.result);58          }59        })60        reader.readAsArrayBuffer(compositeBlob);61        let readArrayBuffer = await readerPromise;62        readerPromise = null;63        reader = null;64        validate_arraybuffer_contents("FileReader", readArrayBuffer, blobCount, blobSize);65        readArrayBuffer = null;66      } else if (mode === "direct") {67        let directArrayBuffer = await compositeBlob.arrayBuffer();68        validate_arraybuffer_contents("arrayBuffer", directArrayBuffer, blobCount, blobSize);69      }70    }, `Composite Blob Handling: ${name}: ${mode}`);71  }72}73// Create an ArrayBuffer whose even bytes are the index identifier and whose74// odd bytes are a sequence incremented by 3 (wrapping at 256) so that75// discontinuities at power-of-2 boundaries are more detectable.76function make_arraybuffer_contents(index, size) {77  const arr = new Uint8Array(size);78  for (let i = 0, counter = 0; i < size; i += 2, counter = (counter + 3) % 256) {79    arr[i] = index;80    arr[i + 1] = counter;81  }82  return arr.buffer;83}84function validate_arraybuffer_contents(source, buffer, blobCount, blobSize) {85  // Accumulate a list of problems we perceive so we can report what seems to86  // have happened all at once.87  const problems = [];88  const arr = new Uint8Array(buffer);89  const expectedLength = blobCount * blobSize;90  const actualCount = arr.length / blobSize;91  if (arr.length !== expectedLength) {92    problems.push(`ArrayBuffer only holds ${actualCount} blobs' worth instead of ${blobCount}.`);93    problems.push(`Actual ArrayBuffer is ${arr.length} bytes but expected ${expectedLength}`);94  }95  const counterBlobStep = (blobSize / 2 * 3) % 256;96  let expectedBlob = 0;97  let blobSeenSoFar = 0;98  let expectedCounter = 0;99  let counterDrift = 0;100  for (let i = 0; i < arr.length; i += 2) {101    if (arr[i] !== expectedBlob || blobSeenSoFar >= blobSize) {102      if (blobSeenSoFar !== blobSize) {103        problems.push(`Truncated blob ${expectedBlob} after ${blobSeenSoFar} bytes.`);104      } else {105        expectedBlob++;106      }107      if (expectedBlob !== arr[i]) {108        problems.push(`Expected blob ${expectedBlob} but found ${arr[i]}, compensating.`);109        expectedBlob = arr[i];110      }111      blobSeenSoFar = 0;112      expectedCounter = (expectedBlob * counterBlobStep) % 256;113      counterDrift = 0;114    }115    if (arr[i + 1] !== (expectedCounter + counterDrift) % 256) {116      const newDrift = expectedCounter - arr[i + 1];117      problems.push(`In blob ${expectedBlob} at ${blobSeenSoFar + 1} bytes in, counter drift now ${newDrift} was ${counterDrift}`);118      counterDrift = newDrift;119    }120    blobSeenSoFar += 2;121    expectedCounter = (expectedCounter + 3) % 256;122  }123  if (problems.length) {124    assert_true(false, `${source} blob payload problem: ${problems.join("\n")}`);125  } else {126    assert_true(true, `${source} blob payloads validated.`);127  }128}129composite_blob_test({130  blobCount: 16,131  blobSize: 256 * 1024,132  name: "Many blobs",...

Using AI Code Generation

1var wpttx = require('./wpttx.js');2var wpttx = new wpttx();3wpttx.read_tx('test.txt', function(err, data) {4    if (err) {5        console.log(err);6    } else {7        console.log(data);8    }9});

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