mirror of
https://gitlab.winehq.org/wine/wine-gecko.git
synced 2024-09-13 09:24:08 -07:00
424 lines
12 KiB
C++
424 lines
12 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#include "mozilla/FloatingPoint.h"
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#include "Key.h"
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#include "nsIStreamBufferAccess.h"
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#include "jsfriendapi.h"
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#include "nsAlgorithm.h"
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#include "nsContentUtils.h"
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#include "nsJSUtils.h"
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#include "xpcpublic.h"
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USING_INDEXEDDB_NAMESPACE
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/*
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Here's how we encode keys:
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Basic strategy is the following
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Numbers: 1 n n n n n n n n ("n"s are encoded 64bit float)
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Dates: 2 n n n n n n n n ("n"s are encoded 64bit float)
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Strings: 3 s s s ... 0 ("s"s are encoded unicode bytes)
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Arrays: 4 i i i ... 0 ("i"s are encoded array items)
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When encoding floats, 64bit IEEE 754 are almost sortable, except that
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positive sort lower than negative, and negative sort descending. So we use
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the following encoding:
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value < 0 ?
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(-to64bitInt(value)) :
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(to64bitInt(value) | 0x8000000000000000)
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When encoding strings, we use variable-size encoding per the following table
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Chars 0 - 7E are encoded as 0xxxxxxx with 1 added
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Chars 7F - (3FFF+7F) are encoded as 10xxxxxx xxxxxxxx with 7F subtracted
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Chars (3FFF+80) - FFFF are encoded as 11xxxxxx xxxxxxxx xx000000
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This ensures that the first byte is never encoded as 0, which means that the
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string terminator (per basic-stategy table) sorts before any character.
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The reason that (3FFF+80) - FFFF is encoded "shifted up" 6 bits is to maximize
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the chance that the last character is 0. See below for why.
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When encoding Arrays, we use an additional trick. Rather than adding a byte
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containing the value '4' to indicate type, we instead add 4 to the next byte.
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This is usually the byte containing the type of the first item in the array.
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So simple examples are
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["foo"] 7 s s s 0 0 // 7 is 3 + 4
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[1, 2] 5 n n n n n n n n 1 n n n n n n n n 0 // 5 is 1 + 4
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Whe do this iteratively if the first item in the array is also an array
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[["foo"]] 11 s s s 0 0 0
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However, to avoid overflow in the byte, we only do this 3 times. If the first
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item in an array is an array, and that array also has an array as first item,
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we simply write out the total value accumulated so far and then follow the
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"normal" rules.
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[[["foo"]]] 12 3 s s s 0 0 0 0
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There is another edge case that can happen though, which is that the array
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doesn't have a first item to which we can add 4 to the type. Instead the
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next byte would normally be the array terminator (per basic-strategy table)
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so we simply add the 4 there.
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[[]] 8 0 // 8 is 4 + 4 + 0
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[] 4 // 4 is 4 + 0
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[[], "foo"] 8 3 s s s 0 0 // 8 is 4 + 4 + 0
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Note that the max-3-times rule kicks in before we get a chance to add to the
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array terminator
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[[[]]] 12 0 0 0 // 12 is 4 + 4 + 4
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We could use a much higher number than 3 at no complexity or performance cost,
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however it seems unlikely that it'll make a practical difference, and the low
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limit makes testing eaiser.
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As a final optimization we do a post-encoding step which drops all 0s at the
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end of the encoded buffer.
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"foo" // 3 s s s
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1 // 1 bf f0
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["a", "b"] // 7 s 3 s
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[1, 2] // 5 bf f0 0 0 0 0 0 0 1 c0
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[[]] // 8
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*/
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const int MaxArrayCollapse = 3;
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const int MaxRecursionDepth = 256;
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nsresult
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Key::EncodeJSValInternal(JSContext* aCx, const jsval aVal,
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PRUint8 aTypeOffset, PRUint16 aRecursionDepth)
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{
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NS_ENSURE_TRUE(aRecursionDepth < MaxRecursionDepth, NS_ERROR_DOM_INDEXEDDB_DATA_ERR);
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PR_STATIC_ASSERT(eMaxType * MaxArrayCollapse < 256);
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if (JSVAL_IS_STRING(aVal)) {
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nsDependentJSString str;
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if (!str.init(aCx, aVal)) {
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return NS_ERROR_DOM_INDEXEDDB_UNKNOWN_ERR;
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}
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EncodeString(str, aTypeOffset);
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return NS_OK;
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}
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if (JSVAL_IS_INT(aVal)) {
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EncodeNumber((double)JSVAL_TO_INT(aVal), eFloat + aTypeOffset);
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return NS_OK;
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}
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if (JSVAL_IS_DOUBLE(aVal)) {
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double d = JSVAL_TO_DOUBLE(aVal);
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if (MOZ_DOUBLE_IS_NaN(d)) {
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return NS_ERROR_DOM_INDEXEDDB_DATA_ERR;
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}
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EncodeNumber(d, eFloat + aTypeOffset);
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return NS_OK;
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}
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if (!JSVAL_IS_PRIMITIVE(aVal)) {
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JSObject* obj = JSVAL_TO_OBJECT(aVal);
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if (JS_IsArrayObject(aCx, obj)) {
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aTypeOffset += eMaxType;
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if (aTypeOffset == eMaxType * MaxArrayCollapse) {
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mBuffer.Append(aTypeOffset);
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aTypeOffset = 0;
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}
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NS_ASSERTION((aTypeOffset % eMaxType) == 0 &&
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aTypeOffset < (eMaxType * MaxArrayCollapse),
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"Wrong typeoffset");
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uint32_t length;
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if (!JS_GetArrayLength(aCx, obj, &length)) {
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return NS_ERROR_DOM_INDEXEDDB_UNKNOWN_ERR;
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}
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for (uint32_t index = 0; index < length; index++) {
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jsval val;
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if (!JS_GetElement(aCx, obj, index, &val)) {
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return NS_ERROR_DOM_INDEXEDDB_UNKNOWN_ERR;
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}
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nsresult rv = EncodeJSValInternal(aCx, val, aTypeOffset,
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aRecursionDepth + 1);
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if (NS_FAILED(rv)) {
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return rv;
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}
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aTypeOffset = 0;
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}
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mBuffer.Append(eTerminator + aTypeOffset);
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return NS_OK;
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}
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if (JS_ObjectIsDate(aCx, obj)) {
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if (!js_DateIsValid(aCx, obj)) {
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return NS_ERROR_DOM_INDEXEDDB_DATA_ERR;
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}
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EncodeNumber(js_DateGetMsecSinceEpoch(aCx, obj), eDate + aTypeOffset);
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return NS_OK;
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}
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}
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return NS_ERROR_DOM_INDEXEDDB_DATA_ERR;
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}
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// static
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nsresult
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Key::DecodeJSValInternal(const unsigned char*& aPos, const unsigned char* aEnd,
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JSContext* aCx, PRUint8 aTypeOffset, jsval* aVal,
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PRUint16 aRecursionDepth)
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{
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NS_ENSURE_TRUE(aRecursionDepth < MaxRecursionDepth, NS_ERROR_DOM_INDEXEDDB_DATA_ERR);
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if (*aPos - aTypeOffset >= eArray) {
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JSObject* array = JS_NewArrayObject(aCx, 0, nsnull);
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if (!array) {
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NS_WARNING("Failed to make array!");
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return NS_ERROR_DOM_INDEXEDDB_UNKNOWN_ERR;
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}
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aTypeOffset += eMaxType;
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if (aTypeOffset == eMaxType * MaxArrayCollapse) {
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++aPos;
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aTypeOffset = 0;
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}
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uint32_t index = 0;
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while (aPos < aEnd && *aPos - aTypeOffset != eTerminator) {
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jsval val;
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nsresult rv = DecodeJSValInternal(aPos, aEnd, aCx, aTypeOffset,
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&val, aRecursionDepth + 1);
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NS_ENSURE_SUCCESS(rv, rv);
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aTypeOffset = 0;
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if (!JS_SetElement(aCx, array, index++, &val)) {
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NS_WARNING("Failed to set array element!");
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return NS_ERROR_DOM_INDEXEDDB_UNKNOWN_ERR;
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}
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}
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NS_ASSERTION(aPos >= aEnd || (*aPos % eMaxType) == eTerminator,
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"Should have found end-of-array marker");
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++aPos;
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*aVal = OBJECT_TO_JSVAL(array);
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}
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else if (*aPos - aTypeOffset == eString) {
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nsString key;
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DecodeString(aPos, aEnd, key);
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if (!xpc::StringToJsval(aCx, key, aVal)) {
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return NS_ERROR_DOM_INDEXEDDB_UNKNOWN_ERR;
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}
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}
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else if (*aPos - aTypeOffset == eDate) {
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double msec = static_cast<double>(DecodeNumber(aPos, aEnd));
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JSObject* date = JS_NewDateObjectMsec(aCx, msec);
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if (!date) {
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NS_WARNING("Failed to make date!");
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return NS_ERROR_DOM_INDEXEDDB_UNKNOWN_ERR;
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}
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*aVal = OBJECT_TO_JSVAL(date);
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}
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else if (*aPos - aTypeOffset == eFloat) {
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*aVal = DOUBLE_TO_JSVAL(DecodeNumber(aPos, aEnd));
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}
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else {
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NS_NOTREACHED("Unknown key type!");
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}
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return NS_OK;
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}
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#define ONE_BYTE_LIMIT 0x7E
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#define TWO_BYTE_LIMIT (0x3FFF+0x7F)
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#define ONE_BYTE_ADJUST 1
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#define TWO_BYTE_ADJUST (-0x7F)
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#define THREE_BYTE_SHIFT 6
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void
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Key::EncodeString(const nsAString& aString, PRUint8 aTypeOffset)
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{
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// First measure how long the encoded string will be.
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// The +2 is for initial 3 and trailing 0. We'll compensate for multi-byte
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// chars below.
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PRUint32 size = aString.Length() + 2;
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const PRUnichar* start = aString.BeginReading();
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const PRUnichar* end = aString.EndReading();
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for (const PRUnichar* iter = start; iter < end; ++iter) {
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if (*iter > ONE_BYTE_LIMIT) {
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size += *iter > TWO_BYTE_LIMIT ? 2 : 1;
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}
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}
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// Allocate memory for the new size
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PRUint32 oldLen = mBuffer.Length();
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char* buffer;
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if (!mBuffer.GetMutableData(&buffer, oldLen + size)) {
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return;
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}
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buffer += oldLen;
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// Write type marker
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*(buffer++) = eString + aTypeOffset;
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// Encode string
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for (const PRUnichar* iter = start; iter < end; ++iter) {
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if (*iter <= ONE_BYTE_LIMIT) {
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*(buffer++) = *iter + ONE_BYTE_ADJUST;
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}
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else if (*iter <= TWO_BYTE_LIMIT) {
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PRUnichar c = PRUnichar(*iter) + TWO_BYTE_ADJUST + 0x8000;
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*(buffer++) = (char)(c >> 8);
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*(buffer++) = (char)(c & 0xFF);
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}
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else {
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PRUint32 c = (PRUint32(*iter) << THREE_BYTE_SHIFT) | 0x00C00000;
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*(buffer++) = (char)(c >> 16);
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*(buffer++) = (char)(c >> 8);
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*(buffer++) = (char)c;
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}
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}
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// Write end marker
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*(buffer++) = eTerminator;
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NS_ASSERTION(buffer == mBuffer.EndReading(), "Wrote wrong number of bytes");
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}
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// static
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void
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Key::DecodeString(const unsigned char*& aPos, const unsigned char* aEnd,
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nsString& aString)
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{
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NS_ASSERTION(*aPos % eMaxType == eString, "Don't call me!");
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const unsigned char* buffer = aPos + 1;
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// First measure how big the decoded string will be.
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PRUint32 size = 0;
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const unsigned char* iter;
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for (iter = buffer; iter < aEnd && *iter != eTerminator; ++iter) {
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if (*iter & 0x80) {
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iter += (*iter & 0x40) ? 2 : 1;
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}
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++size;
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}
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// Set end so that we don't have to check for null termination in the loop
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// below
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if (iter < aEnd) {
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aEnd = iter;
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}
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PRUnichar* out;
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if (size && !aString.GetMutableData(&out, size)) {
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return;
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}
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for (iter = buffer; iter < aEnd;) {
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if (!(*iter & 0x80)) {
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*out = *(iter++) - ONE_BYTE_ADJUST;
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}
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else if (!(*iter & 0x40)) {
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PRUnichar c = (PRUnichar(*(iter++)) << 8);
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if (iter < aEnd) {
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c |= *(iter++);
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}
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*out = c - TWO_BYTE_ADJUST - 0x8000;
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}
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else {
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PRUint32 c = PRUint32(*(iter++)) << (16 - THREE_BYTE_SHIFT);
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if (iter < aEnd) {
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c |= PRUint32(*(iter++)) << (8 - THREE_BYTE_SHIFT);
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}
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if (iter < aEnd) {
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c |= *(iter++) >> THREE_BYTE_SHIFT;
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}
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*out = (PRUnichar)c;
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}
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++out;
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}
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NS_ASSERTION(!size || out == aString.EndReading(),
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"Should have written the whole string");
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aPos = iter + 1;
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}
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union Float64Union {
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double d;
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PRUint64 u;
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};
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void
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Key::EncodeNumber(double aFloat, PRUint8 aType)
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{
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// Allocate memory for the new size
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PRUint32 oldLen = mBuffer.Length();
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char* buffer;
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if (!mBuffer.GetMutableData(&buffer, oldLen + 1 + sizeof(double))) {
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return;
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}
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buffer += oldLen;
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*(buffer++) = aType;
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Float64Union pun;
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pun.d = aFloat;
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PRUint64 number = pun.u & PR_UINT64(0x8000000000000000) ?
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-pun.u :
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(pun.u | PR_UINT64(0x8000000000000000));
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number = NS_SWAP64(number);
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memcpy(buffer, &number, sizeof(number));
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}
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// static
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double
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Key::DecodeNumber(const unsigned char*& aPos, const unsigned char* aEnd)
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{
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NS_ASSERTION(*aPos % eMaxType == eFloat ||
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*aPos % eMaxType == eDate, "Don't call me!");
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++aPos;
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PRUint64 number = 0;
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memcpy(&number, aPos, NS_MIN<size_t>(sizeof(number), aEnd - aPos));
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number = NS_SWAP64(number);
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aPos += sizeof(number);
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Float64Union pun;
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pun.u = number & PR_UINT64(0x8000000000000000) ?
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(number & ~PR_UINT64(0x8000000000000000)) :
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-number;
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return pun.d;
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}
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