The Tor Browser: netwerk/cache2/CacheHashUtils.cpp@7e26c7da4463 (annotated)

netwerk/cache2/CacheHashUtils.cpp@7e26c7da4463 (annotated)

netwerk/cache2/CacheHashUtils.cpp

Wed, 31 Dec 2014 06:55:50 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:55:50 +0100
changeset 2: 7e26c7da4463
permissions: -rw-r--r--

Added tag UPSTREAM_283F7C6 for changeset ca08bd8f51b2

 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 #include "CacheHashUtils.h"
 #include "plstr.h"
 namespace mozilla {
 namespace net {
 /**
  *  CacheHash::Hash(const char * key, uint32_t initval)
  *
  *  See http://burtleburtle.net/bob/hash/evahash.html for more information
  *  about this hash function.
  *
  *  This algorithm is used to check the data integrity.
  */
 static inline void hashmix(uint32_t& a, uint32_t& b, uint32_t& c)
 {
   a -= b; a -= c; a ^= (c>>13);
   b -= c; b -= a; b ^= (a<<8);
   c -= a; c -= b; c ^= (b>>13);
   a -= b; a -= c; a ^= (c>>12);
   b -= c; b -= a; b ^= (a<<16);
   c -= a; c -= b; c ^= (b>>5);
   a -= b; a -= c; a ^= (c>>3);
   b -= c; b -= a; b ^= (a<<10);
   c -= a; c -= b; c ^= (b>>15);
 }
 CacheHash::Hash32_t
 CacheHash::Hash(const char *aData, uint32_t aSize, uint32_t aInitval)
 {
   const uint8_t *k = reinterpret_cast<const uint8_t*>(aData);
   uint32_t a, b, c, len;
 //  length = PL_strlen(key);
   /* Set up the internal state */
   len = aSize;
   a = b = 0x9e3779b9;  /* the golden ratio; an arbitrary value */
   c = aInitval;        /* variable initialization of internal state */
   /*---------------------------------------- handle most of the key */
   while (len >= 12)
   {
     a += k[0] + (uint32_t(k[1])<<8) + (uint32_t(k[2])<<16) + (uint32_t(k[3])<<24);
     b += k[4] + (uint32_t(k[5])<<8) + (uint32_t(k[6])<<16) + (uint32_t(k[7])<<24);
     c += k[8] + (uint32_t(k[9])<<8) + (uint32_t(k[10])<<16) + (uint32_t(k[11])<<24);
     hashmix(a, b, c);
     k += 12; len -= 12;
   }
   /*------------------------------------- handle the last 11 bytes */
   c += aSize;
   switch(len) {              /* all the case statements fall through */
     case 11: c += (uint32_t(k[10])<<24);
     case 10: c += (uint32_t(k[9])<<16);
     case 9 : c += (uint32_t(k[8])<<8);
     /* the low-order byte of c is reserved for the length */
     case 8 : b += (uint32_t(k[7])<<24);
     case 7 : b += (uint32_t(k[6])<<16);
     case 6 : b += (uint32_t(k[5])<<8);
     case 5 : b += k[4];
     case 4 : a += (uint32_t(k[3])<<24);
     case 3 : a += (uint32_t(k[2])<<16);
     case 2 : a += (uint32_t(k[1])<<8);
     case 1 : a += k[0];
     /* case 0: nothing left to add */
   }
   hashmix(a, b, c);
   return c;
 }
 CacheHash::Hash16_t
 CacheHash::Hash16(const char *aData, uint32_t aSize, uint32_t aInitval)
 {
   Hash32_t hash = Hash(aData, aSize, aInitval);
   return (hash & 0xFFFF);
 }
 NS_IMPL_ISUPPORTS0(CacheHash)
 CacheHash::CacheHash(uint32_t aInitval)
   : mA(0x9e3779b9)
   , mB(0x9e3779b9)
   , mC(aInitval)
   , mPos(0)
   , mBuf(0)
   , mBufPos(0)
   , mLength(0)
   , mFinalized(false)
 {}
 void
 CacheHash::Feed(uint32_t aVal, uint8_t aLen)
 {
   switch (mPos) {
   case 0:
     mA += aVal;
     mPos ++;
     break;
   case 1:
     mB += aVal;
     mPos ++;
     break;
   case 2:
     mPos = 0;
     if (aLen == 4) {
       mC += aVal;
       hashmix(mA, mB, mC);
     }
     else {
       mC += aVal << 8;
     }
   }
   mLength += aLen;
 }
 void
 CacheHash::Update(const char *aData, uint32_t aLen)
 {
   const uint8_t *data = reinterpret_cast<const uint8_t*>(aData);
   MOZ_ASSERT(!mFinalized);
   if (mBufPos) {
     while (mBufPos != 4 && aLen) {
       mBuf += uint32_t(*data) << 8*mBufPos;
       data++;
       mBufPos++;
       aLen--;
     }
     if (mBufPos == 4) {
       mBufPos = 0;
       Feed(mBuf);
       mBuf = 0;
     }
   }
   if (!aLen)
     return;
   while (aLen >= 4) {
     Feed(data[0] + (uint32_t(data[1]) << 8) + (uint32_t(data[2]) << 16) +
          (uint32_t(data[3]) << 24));
     data += 4;
     aLen -= 4;
   }
   switch (aLen) {
     case 3: mBuf += data[2] << 16;
     case 2: mBuf += data[1] << 8;
     case 1: mBuf += data[0];
   }
   mBufPos = aLen;
 }
 CacheHash::Hash32_t
 CacheHash::GetHash()
 {
   if (!mFinalized)
   {
     if (mBufPos) {
       Feed(mBuf, mBufPos);
     }
     mC += mLength;
     hashmix(mA, mB, mC);
     mFinalized = true;
   }
   return mC;
 }
 CacheHash::Hash16_t
 CacheHash::GetHash16()
 {
   Hash32_t hash = GetHash();
   return (hash & 0xFFFF);
 }
 } // net
 } // mozilla

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netwerk/cache2/CacheHashUtils.cpp@7e26c7da4463 (annotated)

netwerk/cache2/CacheHashUtils.cpp