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Replace the AnnotationStorage.lastModified-getter with a proper hash-method

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The current `lastModified`-getter, which only contains a time-stamp, is a fairly crude way of detecting if the stored data has actually been changed. In particular, when the `getRawValue`-method is used, the `lastModified`-getter doesn't cope with data being modified from the "outside".

To fix these issues[1], and to prevent any future bugs in this code, this patch introduces a new `AnnotationStorage.hash`-getter which computes a hash of the currently stored data. To simplify things this re-uses the existing `MurmurHash3_64`-implementation, which required moving that file into the `src/shared/`-folder, since its performance should be good enough here.

---
[1] Given how the `AnnotationStorage.lastModified`-getter was used, this would have been limited to *printing* of forms.
This commit is contained in:
Jonas Jenwald 2022-05-04 15:03:46 +02:00
parent 8135d7ccf6
commit 8267fd8a52
5 changed files with 14 additions and 10 deletions
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2
src/core/evaluator.js
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@ -75,7 +75,7 @@ import { DecodeStream } from "./decode_stream.js";
import { getGlyphsUnicode } from "./glyphlist.js";
import { getLookupTableFactory } from "./core_utils.js";
import { getMetrics } from "./metrics.js";
import { MurmurHash3_64 } from "./murmurhash3.js";
import { MurmurHash3_64 } from "../shared/murmurhash3.js";
import { OperatorList } from "./operator_list.js";
import { PDFImage } from "./image.js";

139
src/core/murmurhash3.js
View file

@ -1,139 +0,0 @@
/* Copyright 2014 Opera Software ASA
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*
* Based on https://code.google.com/p/smhasher/wiki/MurmurHash3.
* Hashes roughly 100 KB per millisecond on i7 3.4 GHz.
*/
import { isArrayBuffer } from "../shared/util.js";
const SEED = 0xc3d2e1f0;
// Workaround for missing math precision in JS.
const MASK_HIGH = 0xffff0000;
const MASK_LOW = 0xffff;
class MurmurHash3_64 {
constructor(seed) {
this.h1 = seed ? seed & 0xffffffff : SEED;
this.h2 = seed ? seed & 0xffffffff : SEED;
}
update(input) {
let data, length;
if (typeof input === "string") {
data = new Uint8Array(input.length * 2);
length = 0;
for (let i = 0, ii = input.length; i < ii; i++) {
const code = input.charCodeAt(i);
if (code <= 0xff) {
data[length++] = code;
} else {
data[length++] = code >>> 8;
data[length++] = code & 0xff;
}
}
} else if (isArrayBuffer(input)) {
data = input.slice();
length = data.byteLength;
} else {
throw new Error(
"Wrong data format in MurmurHash3_64_update. " +
"Input must be a string or array."
);
}
const blockCounts = length >> 2;
const tailLength = length - blockCounts * 4;
// We don't care about endianness here.
const dataUint32 = new Uint32Array(data.buffer, 0, blockCounts);
let k1 = 0,
k2 = 0;
let h1 = this.h1,
h2 = this.h2;
const C1 = 0xcc9e2d51,
C2 = 0x1b873593;
const C1_LOW = C1 & MASK_LOW,
C2_LOW = C2 & MASK_LOW;
for (let i = 0; i < blockCounts; i++) {
if (i & 1) {
k1 = dataUint32[i];
k1 = ((k1 * C1) & MASK_HIGH) | ((k1 * C1_LOW) & MASK_LOW);
k1 = (k1 << 15) | (k1 >>> 17);
k1 = ((k1 * C2) & MASK_HIGH) | ((k1 * C2_LOW) & MASK_LOW);
h1 ^= k1;
h1 = (h1 << 13) | (h1 >>> 19);
h1 = h1 * 5 + 0xe6546b64;
} else {
k2 = dataUint32[i];
k2 = ((k2 * C1) & MASK_HIGH) | ((k2 * C1_LOW) & MASK_LOW);
k2 = (k2 << 15) | (k2 >>> 17);
k2 = ((k2 * C2) & MASK_HIGH) | ((k2 * C2_LOW) & MASK_LOW);
h2 ^= k2;
h2 = (h2 << 13) | (h2 >>> 19);
h2 = h2 * 5 + 0xe6546b64;
}
}
k1 = 0;
switch (tailLength) {
case 3:
k1 ^= data[blockCounts * 4 + 2] << 16;
/* falls through */
case 2:
k1 ^= data[blockCounts * 4 + 1] << 8;
/* falls through */
case 1:
k1 ^= data[blockCounts * 4];
/* falls through */
k1 = ((k1 * C1) & MASK_HIGH) | ((k1 * C1_LOW) & MASK_LOW);
k1 = (k1 << 15) | (k1 >>> 17);
k1 = ((k1 * C2) & MASK_HIGH) | ((k1 * C2_LOW) & MASK_LOW);
if (blockCounts & 1) {
h1 ^= k1;
} else {
h2 ^= k1;
}
}
this.h1 = h1;
this.h2 = h2;
}
hexdigest() {
let h1 = this.h1,
h2 = this.h2;
h1 ^= h2 >>> 1;
h1 = ((h1 * 0xed558ccd) & MASK_HIGH) | ((h1 * 0x8ccd) & MASK_LOW);
h2 =
((h2 * 0xff51afd7) & MASK_HIGH) |
(((((h2 << 16) | (h1 >>> 16)) * 0xafd7ed55) & MASK_HIGH) >>> 16);
h1 ^= h2 >>> 1;
h1 = ((h1 * 0x1a85ec53) & MASK_HIGH) | ((h1 * 0xec53) & MASK_LOW);
h2 =
((h2 * 0xc4ceb9fe) & MASK_HIGH) |
(((((h2 << 16) | (h1 >>> 16)) * 0xb9fe1a85) & MASK_HIGH) >>> 16);
h1 ^= h2 >>> 1;
const hex1 = (h1 >>> 0).toString(16),
hex2 = (h2 >>> 0).toString(16);
return hex1.padStart(8, "0") + hex2.padStart(8, "0");
}
}
export { MurmurHash3_64 };