dom/localstorage/SnappyUtils.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
   5  * You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #include "SnappyUtils.h"
   8
   9 #include <stddef.h>
  10 #include "mozilla/Assertions.h"
  11 #include "mozilla/CheckedInt.h"
  12 #include "mozilla/fallible.h"
  13 #include "nsDebug.h"
  14 #include "nsString.h"
  15 #include "snappy/snappy.h"
  16
  17 namespace mozilla::dom {
  18
  19 static_assert(SNAPPY_VERSION == 0x010109);
  20
  21 bool SnappyCompress(const nsACString& aSource, nsACString& aDest) {
  22   MOZ_ASSERT(!aSource.IsVoid());
  23
  24   size_t uncompressedLength = aSource.Length();
  25
  26   if (uncompressedLength <= 16) {
  27     aDest.SetIsVoid(true);
  28     return true;
  29   }
  30
  31   size_t compressedLength = snappy::MaxCompressedLength(uncompressedLength);
  32
  33   if (NS_WARN_IF(!aDest.SetLength(compressedLength, fallible))) {
  34     return false;
  35   }
  36
  37   snappy::RawCompress(aSource.BeginReading(), uncompressedLength,
  38                       aDest.BeginWriting(), &compressedLength);
  39
  40   if (compressedLength >= uncompressedLength) {
  41     aDest.SetIsVoid(true);
  42     return true;
  43   }
  44
  45   if (NS_WARN_IF(!aDest.SetLength(compressedLength, fallible))) {
  46     return false;
  47   }
  48
  49   return true;
  50 }
  51
  52 bool SnappyUncompress(const nsACString& aSource, nsACString& aDest) {
  53   MOZ_ASSERT(!aSource.IsVoid());
  54
  55   const char* compressed = aSource.BeginReading();
  56
  57   auto compressedLength = static_cast<size_t>(aSource.Length());
  58
  59   size_t uncompressedLength = 0u;
  60   if (!snappy::GetUncompressedLength(compressed, compressedLength,
  61                                      &uncompressedLength)) {
  62     return false;
  63   }
  64
  65   CheckedUint32 checkedLength(uncompressedLength);
  66   if (!checkedLength.isValid()) {
  67     return false;
  68   }
  69
  70   aDest.SetLength(checkedLength.value());
  71
  72   if (!snappy::RawUncompress(compressed, compressedLength,
  73                              aDest.BeginWriting())) {
  74     return false;
  75   }
  76
  77   return true;
  78 }
  79
  80 }  // namespace mozilla::dom