gecko-dev/netwerk/cache2/CacheHashUtils.cpp

/* 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 "mozilla/BasePrincipal.h"
#include "mozilla/EndianUtils.h"
#include "mozilla/SHA1.h"
#include "plstr.h"

namespace mozilla::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;

  /* 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);
      [[fallthrough]];
    case 10:
      c += (uint32_t(k[9]) << 16);
      [[fallthrough]];
    case 9:
      c += (uint32_t(k[8]) << 8);
      [[fallthrough]];
    /* the low-order byte of c is reserved for the length */
    case 8:
      b += (uint32_t(k[7]) << 24);
      [[fallthrough]];
    case 7:
      b += (uint32_t(k[6]) << 16);
      [[fallthrough]];
    case 6:
      b += (uint32_t(k[5]) << 8);
      [[fallthrough]];
    case 5:
      b += k[4];
      [[fallthrough]];
    case 4:
      a += (uint32_t(k[3]) << 24);
      [[fallthrough]];
    case 3:
      a += (uint32_t(k[2]) << 16);
      [[fallthrough]];
    case 2:
      a += (uint32_t(k[1]) << 8);
      [[fallthrough]];
    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) : mC(aInitval) {}

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;
      [[fallthrough]];
    case 2:
      mBuf += data[1] << 8;
      [[fallthrough]];
    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);
}

OriginAttrsHash GetOriginAttrsHash(const mozilla::OriginAttributes& aOA) {
  nsAutoCString suffix;
  aOA.CreateSuffix(suffix);

  SHA1Sum sum;
  SHA1Sum::Hash hash;
  sum.update(suffix.BeginReading(), suffix.Length());
  sum.finish(hash);

  return BigEndian::readUint64(&hash);
}

}  // namespace mozilla::net