IndexedDB: Convert decoding functions to pass StringPieces vs. pointers

content/browser/indexed_db/indexed_db_leveldb_coding.cc

Index: content/browser/indexed_db/indexed_db_leveldb_coding.cc
diff --git a/content/browser/indexed_db/indexed_db_leveldb_coding.cc b/content/browser/indexed_db/indexed_db_leveldb_coding.cc
index 29ca0717d406eca46b580f88089568e98de7e074..c222c01f93fd8c85f78f9d166177a3506c136251 100644
--- a/content/browser/indexed_db/indexed_db_leveldb_coding.cc
+++ b/content/browser/indexed_db/indexed_db_leveldb_coding.cc
@@ -150,6 +150,7 @@
 //     IndexCursorImpl::load_current_row, and
 // IndexKeyCursorImpl::load_current_row).
 
+using base::StringPiece;
 using WebKit::WebIDBKey;
 using WebKit::WebIDBKeyPath;
 
@@ -193,19 +194,9 @@ static const unsigned char kIndexMetaDataTypeMaximum = 255;
 
 const unsigned char kMinimumIndexId = 30;
 
-void EncodeByte(unsigned char c, std::vector<char>* into) {
-  into->push_back(c);
-}
-
-const char* DecodeByte(const char* p,
-                       const char* limit,
-                       unsigned char& found_char) {
-  DCHECK_GE(limit, p);
-  if (p >= limit)
-    return 0;
-
-  found_char = *p++;
-  return p;
+inline void EncodeIntSafely(int64 nParam, int64 max, std::vector<char>* into) {
+  DCHECK_LE(nParam, max);
+  return EncodeInt(nParam, into);
 }
 
 std::vector<char> MaxIDBKey() {
@@ -220,19 +211,20 @@ std::vector<char> MinIDBKey() {
   return ret;
 }
 
-bool DecodeBool(const char* p, const char* limit) {
-  DCHECK_GT(limit, p);
-  return !!*p;
+void EncodeByte(unsigned char value, std::vector<char>* into) {
+  into->push_back(value);
 }
 
-void EncodeBool(bool b, std::vector<char>* into) { into->push_back(b ? 1 : 0); }
+void EncodeBool(bool value, std::vector<char>* into) {
+  into->push_back(value ? 1 : 0);
+}
 
-void EncodeInt(int64 nParam, std::vector<char>* into) {
+void EncodeInt(int64 value, std::vector<char>* into) {
 #ifndef NDEBUG
   // Exercised by unit tests in debug only.
-  DCHECK_GE(nParam, 0);
+  DCHECK_GE(value, 0);
 #endif
-  uint64 n = static_cast<uint64>(nParam);
+  uint64 n = static_cast<uint64>(value);
 
   do {
     unsigned char c = n;
@@ -241,26 +233,12 @@ void EncodeInt(int64 nParam, std::vector<char>* into) {
   } while (n);
 }
 
-static int CompareInts(int64 a, int64 b) {
-#ifndef NDEBUG
-  // Exercised by unit tests in debug only.
-  DCHECK_GE(a, 0);
-  DCHECK_GE(b, 0);
-#endif
-  int64 diff = a - b;
-  if (diff < 0)
-    return -1;
-  if (diff > 0)
-    return 1;
-  return 0;
-}
-
-void EncodeVarInt(int64 nParam, std::vector<char>* into) {
+void EncodeVarInt(int64 value, std::vector<char>* into) {
 #ifndef NDEBUG
   // Exercised by unit tests in debug only.
-  DCHECK_GE(nParam, 0);
+  DCHECK_GE(value, 0);
 #endif
-  uint64 n = static_cast<uint64>(nParam);
+  uint64 n = static_cast<uint64>(value);
 
   do {
     unsigned char c = n & 0x7f;
@@ -271,138 +249,35 @@ void EncodeVarInt(int64 nParam, std::vector<char>* into) {
   } while (n);
 }
 
-const char* DecodeVarInt(const char* p, const char* limit, int64& found_int) {
-  DCHECK_GE(limit, p);
-  found_int = 0;
-  int shift = 0;
-
-  do {
-    if (p >= limit)
-      return 0;
-
-    unsigned char c = *p;
-    found_int |= static_cast<int64>(c & 0x7f) << shift;
-    shift += 7;
-  } while (*p++ & 0x80);
-  return p;
-}
-
-void EncodeString(const string16& s, std::vector<char>* into) {
-  if (s.empty())
+void EncodeString(const string16& value, std::vector<char>* into) {
+  if (value.empty())
     return;
   // Backing store is UTF-16BE, convert from host endianness.
-  size_t length = s.length();
+  size_t length = value.length();
   size_t current = into->size();
   into->resize(into->size() + length * sizeof(char16));
 
-  const char16* src = s.c_str();
+  const char16* src = value.c_str();
   char16* dst = reinterpret_cast<char16*>(&*into->begin() + current);
   for (unsigned i = 0; i < length; ++i)
     *dst++ = htons(*src++);
 }
 
-string16 DecodeString(const char* p, const char* limit) {
-  // Backing store is UTF-16BE, convert to host endianness.
-  DCHECK_GE(limit, p);
-  DCHECK(!((limit - p) % sizeof(char16)));
-
-  size_t length = (limit - p) / sizeof(char16);
-  string16 decoded;
-  decoded.reserve(length);
-  const char16* encoded = reinterpret_cast<const char16*>(p);
-  for (unsigned i = 0; i < length; ++i)
-    decoded.push_back(ntohs(*encoded++));
-  return decoded;
-}
-
-void EncodeStringWithLength(const string16& s, std::vector<char>* into) {
-  EncodeVarInt(s.length(), into);
-  EncodeString(s, into);
-}
-
-const char* DecodeStringWithLength(const char* p,
-                                   const char* limit,
-                                   string16& found_string) {
-  DCHECK_GE(limit, p);
-  int64 len;
-  p = DecodeVarInt(p, limit, len);
-  if (!p || len < 0 || p + len * 2 > limit)
-    return 0;
-
-  found_string = DecodeString(p, p + len * 2);
-  p += len * 2;
-  return p;
+void EncodeStringWithLength(const string16& value, std::vector<char>* into) {
+  EncodeVarInt(value.length(), into);
+  EncodeString(value, into);
 }
 
-int CompareEncodedStringsWithLength(const char*& p,
-                                    const char* limit_p,
-                                    const char*& q,
-                                    const char* limit_q,
-                                    bool& ok) {
-  DCHECK_NE(&p, &q);
-  DCHECK_GT(limit_p, p);
-  DCHECK_GT(limit_q, q);
-  int64 len_p, len_q;
-  p = DecodeVarInt(p, limit_p, len_p);
-  q = DecodeVarInt(q, limit_q, len_q);
-  if (!p || !q || len_p < 0 || len_q < 0) {
-    ok = false;
-    return 0;
-  }
-  DCHECK(p && q);
-  DCHECK_GE(len_p, 0);
-  DCHECK_GE(len_q, 0);
-  DCHECK_LE(p + len_p * 2, limit_p);
-  DCHECK_LE(q + len_q * 2, limit_q);
-
-  const char* start_p = p;
-  const char* start_q = q;
-  p += len_p * 2;
-  q += len_q * 2;
-
-  if (p > limit_p || q > limit_q) {
-    ok = false;
-    return 0;
-  }
-
-  ok = true;
-  const size_t lmin = static_cast<size_t>(len_p < len_q ? len_p : len_q);
-  if (int x = memcmp(start_p, start_q, lmin * 2))
-    return x;
-
-  if (len_p == len_q)
-    return 0;
-
-  return (len_p > len_q) ? 1 : -1;
-}
-
-void EncodeDouble(double x, std::vector<char>* into) {
-  // TODO(jsbell): It would be nice if we could be byte order independent.
-  const char* p = reinterpret_cast<char*>(&x);
-  into->insert(into->end(), p, p + sizeof(x));
+void EncodeDouble(double value, std::vector<char>* into) {
+  // This always has host endianness.
+  const char* p = reinterpret_cast<char*>(&value);
+  into->insert(into->end(), p, p + sizeof(value));
 }
 
-const char* DecodeDouble(const char* p, const char* limit, double* d) {
-  if (p + sizeof(*d) > limit)
-    return 0;
-
-  char* x = reinterpret_cast<char*>(d);
-  for (size_t i = 0; i < sizeof(*d); ++i)
-    *x++ = *p++;
-  return p;
-}
-
-std::vector<char> EncodeIDBKey(const IndexedDBKey& key) {
-  std::vector<char> buffer;
-  buffer.reserve(kDefaultInlineBufferSize);
-  EncodeIDBKey(key, &buffer);
-  return buffer;
-}
-
-void EncodeIDBKey(const IndexedDBKey& key, std::vector<char>* into) {
+void EncodeIDBKey(const IndexedDBKey& value, std::vector<char>* into) {
   size_t previous_size = into->size();
-  DCHECK(key.IsValid());
-  switch (key.type()) {
+  DCHECK(value.IsValid());
+  switch (value.type()) {
     case WebIDBKey::NullType:
     case WebIDBKey::InvalidType:
     case WebIDBKey::MinType: {
@@ -412,29 +287,29 @@ void EncodeIDBKey(const IndexedDBKey& key, std::vector<char>* into) {
     }
     case WebIDBKey::ArrayType: {
       EncodeByte(kIndexedDBKeyArrayTypeByte, into);
-      size_t length = key.array().size();
+      size_t length = value.array().size();
       EncodeVarInt(length, into);
       for (size_t i = 0; i < length; ++i)
-        EncodeIDBKey(key.array()[i], into);
+        EncodeIDBKey(value.array()[i], into);
       DCHECK_GT(into->size(), previous_size);
       return;
     }
     case WebIDBKey::StringType: {
       EncodeByte(kIndexedDBKeyStringTypeByte, into);
-      EncodeStringWithLength(key.string(), into);
+      EncodeStringWithLength(value.string(), into);
       DCHECK_GT(into->size(), previous_size);
       return;
     }
     case WebIDBKey::DateType: {
       EncodeByte(kIndexedDBKeyDateTypeByte, into);
-      EncodeDouble(key.date(), into);
+      EncodeDouble(value.date(), into);
       DCHECK_EQ(static_cast<size_t>(9),
                 static_cast<size_t>(into->size() - previous_size));
       return;
     }
     case WebIDBKey::NumberType: {
       EncodeByte(kIndexedDBKeyNumberTypeByte, into);
-      EncodeDouble(key.number(), into);
+      EncodeDouble(value.number(), into);
       DCHECK_EQ(static_cast<size_t>(9),
                 static_cast<size_t>(into->size() - previous_size));
       return;
@@ -444,115 +319,287 @@ void EncodeIDBKey(const IndexedDBKey& key, std::vector<char>* into) {
   NOTREACHED();
 }
 
-const char* DecodeIDBKey(const char* p,
-                         const char* limit,
-                         scoped_ptr<IndexedDBKey>* found_key) {
-  DCHECK_GE(limit, p);
-  if (p >= limit)
-    return 0;
+void EncodeIDBKeyPath(const IndexedDBKeyPath& value, std::vector<char>* into) {
+  // May be typed, or may be a raw string. An invalid leading
+  // byte is used to identify typed coding. New records are
+  // always written as typed.
+  EncodeByte(kIndexedDBKeyPathTypeCodedByte1, into);
+  EncodeByte(kIndexedDBKeyPathTypeCodedByte2, into);
+  EncodeByte(static_cast<char>(value.type()), into);
+  switch (value.type()) {
+    case WebIDBKeyPath::NullType:
+      break;
+    case WebIDBKeyPath::StringType: {
+      EncodeStringWithLength(value.string(), into);
+      break;
+    }
+    case WebIDBKeyPath::ArrayType: {
+      const std::vector<string16>& array = value.array();
+      size_t count = array.size();
+      EncodeVarInt(count, into);
+      for (size_t i = 0; i < count; ++i) {
+        EncodeStringWithLength(array[i], into);
+      }
+      break;
+    }
+  }
+}
+
+bool DecodeByte(StringPiece* slice, unsigned char* value) {
+  if (slice->empty())
+    return false;
+
+  *value = (*slice)[0];
+  slice->remove_prefix(1);
+  return true;
+}
+
+bool DecodeBool(StringPiece* slice, bool* value) {
+  if (slice->empty())
+    return false;
+
+  *value = !!(*slice)[0];
+  slice->remove_prefix(1);
+  return true;
+}
+
+bool DecodeInt(StringPiece* slice, int64* value) {
+  if (slice->empty())
+    return false;
+
+  StringPiece::const_iterator it = slice->begin();
+  int shift = 0;
+  int64 ret = 0;
+  while (it != slice->end()) {
+    unsigned char c = *it++;
+    ret |= static_cast<int64>(c) << shift;
+    shift += 8;
+  }
+  *value = ret;
+  slice->remove_prefix(it - slice->begin());
+  return true;
+}
+
+bool DecodeVarInt(StringPiece* slice, int64* value) {
+  if (slice->empty())
+    return false;
+
+  StringPiece::const_iterator it = slice->begin();
+  int shift = 0;
+  int64 ret = 0;
+  do {
+    if (it == slice->end())
+      return false;
+
+    unsigned char c = *it;
+    ret |= static_cast<int64>(c & 0x7f) << shift;
+    shift += 7;
+  } while (*it++ & 0x80);
+  *value = ret;
+  slice->remove_prefix(it - slice->begin());
+  return true;
+}
+
+bool DecodeString(StringPiece* slice, string16* value) {
+  if (slice->empty()) {
+    value->clear();
+    return true;
+  }
+
+  // Backing store is UTF-16BE, convert to host endianness.
+  DCHECK(!(slice->size() % sizeof(char16)));
+  size_t length = slice->size() / sizeof(char16);
+  string16 decoded;
+  decoded.reserve(length);
+  const char16* encoded = reinterpret_cast<const char16*>(slice->begin());
+  for (unsigned i = 0; i < length; ++i)
+    decoded.push_back(ntohs(*encoded++));
+
+  *value = decoded;
+  slice->remove_prefix(length * sizeof(char16));
+  return true;
+}
+
+bool DecodeStringWithLength(StringPiece* slice, string16* value) {
+  if (slice->empty())
+    return false;
 
-  unsigned char type = *p++;
+  int64 len;
+  if (!DecodeVarInt(slice, &len) || len < 0)
+    return false;
+  size_t bytes = len * sizeof(char16);
+  if (slice->size() < bytes)
+    return false;
+
+  StringPiece subpiece(slice->begin(), bytes);
+  slice->remove_prefix(bytes);
+  if (!DecodeString(&subpiece, value))
+    return false;
+
+  return true;
+}
+
+bool DecodeIDBKey(StringPiece* slice, scoped_ptr<IndexedDBKey>* value) {
+  if (slice->empty())
+    return false;
+
+  unsigned char type = (*slice)[0];
+  slice->remove_prefix(1);
 
   switch (type) {
     case kIndexedDBKeyNullTypeByte:
-      *found_key = make_scoped_ptr(new IndexedDBKey());
-      return p;
+      *value = make_scoped_ptr(new IndexedDBKey());
+      return true;
 
     case kIndexedDBKeyArrayTypeByte: {
       int64 length;
-      p = DecodeVarInt(p, limit, length);
-      if (!p || length < 0)
-        return 0;
+      if (!DecodeVarInt(slice, &length) || length < 0)
+        return false;
       IndexedDBKey::KeyArray array;
       while (length--) {
         scoped_ptr<IndexedDBKey> key;
-        p = DecodeIDBKey(p, limit, &key);
-        if (!p)
-          return 0;
+        if (!DecodeIDBKey(slice, &key))
+          return false;
         array.push_back(*key);
       }
-      *found_key = make_scoped_ptr(new IndexedDBKey(array));
-      return p;
+      *value = make_scoped_ptr(new IndexedDBKey(array));
+      return true;
     }
     case kIndexedDBKeyStringTypeByte: {
       string16 s;
-      p = DecodeStringWithLength(p, limit, s);
-      if (!p)
-        return 0;
-      *found_key = make_scoped_ptr(new IndexedDBKey(s));
-      return p;
+      if (!DecodeStringWithLength(slice, &s))
+        return false;
+      *value = make_scoped_ptr(new IndexedDBKey(s));
+      return true;
     }
     case kIndexedDBKeyDateTypeByte: {
       double d;
-      p = DecodeDouble(p, limit, &d);
-      if (!p)
-        return 0;
-      *found_key = make_scoped_ptr(new IndexedDBKey(d, WebIDBKey::DateType));
-      return p;
+      if (!DecodeDouble(slice, &d))
+        return false;
+      *value = make_scoped_ptr(new IndexedDBKey(d, WebIDBKey::DateType));
+      return true;
     }
     case kIndexedDBKeyNumberTypeByte: {
       double d;
-      p = DecodeDouble(p, limit, &d);
-      if (!p)
-        return 0;
-      *found_key = make_scoped_ptr(new IndexedDBKey(d, WebIDBKey::NumberType));
-      return p;
+      if (!DecodeDouble(slice, &d))
+        return false;
+      *value = make_scoped_ptr(new IndexedDBKey(d, WebIDBKey::NumberType));
+      return true;
     }
   }
 
   NOTREACHED();
-  return 0;
+  return false;
 }
 
-const char* ExtractEncodedIDBKey(const char* start,
-                                 const char* limit,
-                                 std::vector<char>* result = 0) {
-  DCHECK_GT(limit, start);
-  const char* p = start;
-  if (p >= limit)
-    return 0;
+bool DecodeDouble(StringPiece* slice, double* value) {
+  if (slice->size() < sizeof(*value))
+    return false;
+
+  memcpy(value, slice->begin(), sizeof(*value));
+  slice->remove_prefix(sizeof(*value));
+  return true;
+}
 
-  unsigned char type = *p++;
+bool DecodeIDBKeyPath(StringPiece* slice, IndexedDBKeyPath* value) {
+  // May be typed, or may be a raw string. An invalid leading
+  // byte sequence is used to identify typed coding. New records are
+  // always written as typed.
+  if (slice->size() < 3 || (*slice)[0] != kIndexedDBKeyPathTypeCodedByte1 ||
+      (*slice)[1] != kIndexedDBKeyPathTypeCodedByte2) {
+    string16 s;
+    if (!DecodeString(slice, &s))
+      return false;
+    *value = IndexedDBKeyPath(s);
+    return true;
+  }
+
+  slice->remove_prefix(2);
+  DCHECK(!slice->empty());
+  WebIDBKeyPath::Type type = static_cast<WebIDBKeyPath::Type>((*slice)[0]);
+  slice->remove_prefix(1);
+
+  switch (type) {
+    case WebIDBKeyPath::NullType:
+      DCHECK(slice->empty());
+      *value = IndexedDBKeyPath();
+      return true;
+    case WebIDBKeyPath::StringType: {
+      string16 string;
+      if (!DecodeStringWithLength(slice, &string))
+        return false;
+      DCHECK(slice->empty());
+      *value = IndexedDBKeyPath(string);
+      return true;
+    }
+    case WebIDBKeyPath::ArrayType: {
+      std::vector<string16> array;
+      int64 count;
+      if (!DecodeVarInt(slice, &count))
+        return false;
+      DCHECK_GE(count, 0);
+      while (count--) {
+        string16 string;
+        if (!DecodeStringWithLength(slice, &string))
+          return false;
+        array.push_back(string);
+      }
+      DCHECK(slice->empty());
+      *value = IndexedDBKeyPath(array);
+      return true;
+    }
+  }
+  NOTREACHED();
+  return false;
+}
+
+bool ExtractEncodedIDBKey(StringPiece* slice) {
+
+  unsigned char type = (*slice)[0];
+  slice->remove_prefix(1);
 
   switch (type) {
     case kIndexedDBKeyNullTypeByte:
     case kIndexedDBKeyMinKeyTypeByte:
-      break;
+      return true;
     case kIndexedDBKeyArrayTypeByte: {
       int64 length;
-      p = DecodeVarInt(p, limit, length);
-      if (!p || length < 0)
-        return 0;
+      if (!DecodeVarInt(slice, &length))
+        return false;
       while (length--) {
-        p = ExtractEncodedIDBKey(p, limit);
-        if (!p)
-          return 0;
+        if (!ExtractEncodedIDBKey(slice))
+          return false;
       }
-      break;
+      return true;
     }
     case kIndexedDBKeyStringTypeByte: {
       int64 length;
-      p = DecodeVarInt(p, limit, length);
-      if (!p || length < 0 || p + length * 2 > limit)
-        return 0;
-      p += length * 2;
-      break;
+      if (!DecodeVarInt(slice, &length) || length < 0)
+        return false;
+      if (slice->size() < static_cast<size_t>(length) * sizeof(char16))
+        return false;
+      slice->remove_prefix(length * sizeof(char16));
+      return true;
     }
     case kIndexedDBKeyDateTypeByte:
     case kIndexedDBKeyNumberTypeByte:
-      if (p + sizeof(double) > limit)
-        return 0;
-      p += sizeof(double);
-      break;
+      if (slice->size() < sizeof(double))
+        return false;
+      slice->remove_prefix(sizeof(double));
+      return true;
   }
+  NOTREACHED();
+  return false;
+}
 
-  if (result) {
-    DCHECK(p);
-    DCHECK_LE(p, limit);
-    result->assign(start, p);
-  }
+bool ExtractEncodedIDBKey(StringPiece* slice, std::vector<char>* result) {
+  const char* start = slice->begin();
+  if (!ExtractEncodedIDBKey(slice))
+    return 0;
 
-  return p;
+  if (result)
+    result->assign(start, slice->begin());
+  return true;
 }
 
 static WebIDBKey::Type KeyTypeByteToKeyType(unsigned char type) {
@@ -575,19 +622,62 @@ static WebIDBKey::Type KeyTypeByteToKeyType(unsigned char type) {
   return WebIDBKey::InvalidType;
 }
 
+int CompareEncodedStringsWithLength(StringPiece* slice1,
+                                    StringPiece* slice2,
+                                    bool& ok) {
+  int64 len1, len2;
+  if (!DecodeVarInt(slice1, &len1) || !DecodeVarInt(slice2, &len2)) {
+    ok = false;
+    return 0;
+  }
+  DCHECK_GE(len1, 0);
+  DCHECK_GE(len2, 0);
+  if (len1 < 0 || len2 < 0) {
+    ok = false;
+    return 0;
+  }
+  DCHECK_GE(slice1->size(), len1 * sizeof(char16));
+  DCHECK_GE(slice2->size(), len2 * sizeof(char16));
+  if (slice1->size() < len1 * sizeof(char16) ||
+      slice2->size() < len2 * sizeof(char16)) {
+    ok = false;
+    return 0;
+  }
+
+  StringPiece string1(slice1->begin(), len1 * sizeof(char16));
+  StringPiece string2(slice2->begin(), len2 * sizeof(char16));
+  slice1->remove_prefix(len1 * sizeof(char16));
+  slice2->remove_prefix(len2 * sizeof(char16));
+
+  ok = true;
+  // Strings are UTF-16BE encoded, so a simple memcmp is sufficient.
+  return string1.compare(string2);
+}
+
+static int CompareInts(int64 a, int64 b) {
+#ifndef NDEBUG
+  // Exercised by unit tests in debug only.
+  DCHECK_GE(a, 0);
+  DCHECK_GE(b, 0);
+#endif
+  int64 diff = a - b;
+  if (diff < 0)
+    return -1;
+  if (diff > 0)
+    return 1;
+  return 0;
+}
+
 static int CompareTypes(WebIDBKey::Type a, WebIDBKey::Type b) { return b - a; }
 
-int CompareEncodedIDBKeys(const char*& ptr_a,
-                          const char* limit_a,
-                          const char*& ptr_b,
-                          const char* limit_b,
+int CompareEncodedIDBKeys(StringPiece* slice_a,
+                          StringPiece* slice_b,
                           bool& ok) {
   ok = true;
-  DCHECK_NE(&ptr_a, &ptr_b);
-  DCHECK_LT(ptr_a, limit_a);
-  DCHECK_LT(ptr_b, limit_b);
-  unsigned char type_a = *ptr_a++;
-  unsigned char type_b = *ptr_b++;
+  unsigned char type_a = (*slice_a)[0];
+  unsigned char type_b = (*slice_b)[0];
+  slice_a->remove_prefix(1);
+  slice_b->remove_prefix(1);
 
   if (int x = CompareTypes(KeyTypeByteToKeyType(type_a),
                            KeyTypeByteToKeyType(type_b)))
@@ -600,34 +690,24 @@ int CompareEncodedIDBKeys(const char*& ptr_a,
       return 0;
     case kIndexedDBKeyArrayTypeByte: {
       int64 length_a, length_b;
-      ptr_a = DecodeVarInt(ptr_a, limit_a, length_a);
-      ptr_b = DecodeVarInt(ptr_b, limit_b, length_b);
-      if (!ptr_a || !ptr_b || length_a < 0 || length_b < 0) {
+      if (!DecodeVarInt(slice_a, &length_a) ||
+          !DecodeVarInt(slice_b, &length_b)) {
         ok = false;
         return 0;
       }
       for (int64 i = 0; i < length_a && i < length_b; ++i) {
-        int result = CompareEncodedIDBKeys(ptr_a, limit_a, ptr_b, limit_b, ok);
+        int result = CompareEncodedIDBKeys(slice_a, slice_b, ok);
         if (!ok || result)
           return result;
       }
-      if (length_a < length_b)
-        return -1;
-      if (length_a > length_b)
-        return 1;
-      return 0;
+      return length_a - length_b;
     }
     case kIndexedDBKeyStringTypeByte:
-      return CompareEncodedStringsWithLength(
-          ptr_a, limit_a, ptr_b, limit_b, ok);
+      return CompareEncodedStringsWithLength(slice_a, slice_b, ok);
     case kIndexedDBKeyDateTypeByte:
     case kIndexedDBKeyNumberTypeByte: {
       double d, e;
-      ptr_a = DecodeDouble(ptr_a, limit_a, &d);
-      ptr_b = DecodeDouble(ptr_b, limit_b, &e);
-      DCHECK(ptr_a);
-      DCHECK(ptr_b);
-      if (!ptr_a || !ptr_b) {
+      if (!DecodeDouble(slice_a, &d) || !DecodeDouble(slice_b, &e)) {
         ok = false;
         return 0;
       }
@@ -646,84 +726,12 @@ int CompareEncodedIDBKeys(const char*& ptr_a,
 int CompareEncodedIDBKeys(const std::vector<char>& key_a,
                           const std::vector<char>& key_b,
                           bool& ok) {
-  DCHECK_GE(key_a.size(), static_cast<size_t>(1));
-  DCHECK_GE(key_b.size(), static_cast<size_t>(1));
-
-  const char* ptr_a = &*key_a.begin();
-  const char* limit_a = &*key_a.rbegin() + 1;
-  const char* ptr_b = &*key_b.begin();
-  const char* limit_b = &*key_b.rbegin() + 1;
+  DCHECK(!key_a.empty());
+  DCHECK(!key_b.empty());
 
-  return CompareEncodedIDBKeys(ptr_a, limit_a, ptr_b, limit_b, ok);
-}
-
-void EncodeIDBKeyPath(const IndexedDBKeyPath& key_path,
-                      std::vector<char>* into) {
-  // May be typed, or may be a raw string. An invalid leading
-  // byte is used to identify typed coding. New records are
-  // always written as typed.
-  EncodeByte(kIndexedDBKeyPathTypeCodedByte1, into);
-  EncodeByte(kIndexedDBKeyPathTypeCodedByte2, into);
-  EncodeByte(static_cast<char>(key_path.type()), into);
-  switch (key_path.type()) {
-    case WebIDBKeyPath::NullType:
-      break;
-    case WebIDBKeyPath::StringType: {
-      EncodeStringWithLength(key_path.string(), into);
-      break;
-    }
-    case WebIDBKeyPath::ArrayType: {
-      const std::vector<string16>& array = key_path.array();
-      size_t count = array.size();
-      EncodeVarInt(count, into);
-      for (size_t i = 0; i < count; ++i) {
-        EncodeStringWithLength(array[i], into);
-      }
-      break;
-    }
-  }
-}
-
-IndexedDBKeyPath DecodeIDBKeyPath(const char* p, const char* limit) {
-  // May be typed, or may be a raw string. An invalid leading
-  // byte sequence is used to identify typed coding. New records are
-  // always written as typed.
-  if (p == limit ||
-      (limit - p >= 2 && (*p != kIndexedDBKeyPathTypeCodedByte1 ||
-                          *(p + 1) != kIndexedDBKeyPathTypeCodedByte2)))
-    return IndexedDBKeyPath(DecodeString(p, limit));
-  p += 2;
-
-  DCHECK_NE(p, limit);
-  WebIDBKeyPath::Type type = static_cast<WebIDBKeyPath::Type>(*p++);
-  switch (type) {
-    case WebIDBKeyPath::NullType:
-      DCHECK_EQ(p, limit);
-      return IndexedDBKeyPath();
-    case WebIDBKeyPath::StringType: {
-      string16 string;
-      p = DecodeStringWithLength(p, limit, string);
-      DCHECK_EQ(p, limit);
-      return IndexedDBKeyPath(string);
-    }
-    case WebIDBKeyPath::ArrayType: {
-      std::vector<string16> array;
-      int64 count;
-      p = DecodeVarInt(p, limit, count);
-      DCHECK(p);
-      DCHECK_GE(count, 0);
-      while (count--) {
-        string16 string;
-        p = DecodeStringWithLength(p, limit, string);
-        DCHECK(p);
-        array.push_back(string);
-      }
-      DCHECK_EQ(p, limit);
-      return IndexedDBKeyPath(array);
-    }
-  }
-  NOTREACHED();
-  return IndexedDBKeyPath();
+  StringPiece slice_a(&*key_a.begin(), key_a.size());
+  StringPiece slice_b(&*key_b.begin(), key_b.size());
+  return CompareEncodedIDBKeys(&slice_a, &slice_b, ok);
 }
 
 namespace {
@@ -772,7 +780,9 @@ int Compare<ExistsEntryKey>(const LevelDBSlice& a,
   // Prefixes are not compared - it is assumed this was already done.
   DCHECK(!prefix_a.Compare(prefix_b));
 
-  return CompareEncodedIDBKeys(ptr_a, a.end(), ptr_b, b.end(), ok);
+  StringPiece slice_a(ptr_a, a.end() - ptr_a);
+  StringPiece slice_b(ptr_b, b.end() - ptr_b);
+  return CompareEncodedIDBKeys(&slice_a, &slice_b, ok);
 }
 
 template <>
@@ -797,7 +807,9 @@ int Compare<ObjectStoreDataKey>(const LevelDBSlice& a,
   // Prefixes are not compared - it is assumed this was already done.
   DCHECK(!prefix_a.Compare(prefix_b));
 
-  return CompareEncodedIDBKeys(ptr_a, a.end(), ptr_b, b.end(), ok);
+  StringPiece slice_a(ptr_a, a.end() - ptr_a);
+  StringPiece slice_b(ptr_b, b.end() - ptr_b);
+  return CompareEncodedIDBKeys(&slice_a, &slice_b, ok);
 }
 
 template <>
@@ -823,7 +835,10 @@ int Compare<IndexDataKey>(const LevelDBSlice& a,
   DCHECK(!prefix_a.Compare(prefix_b));
 
   // index key
-  int result = CompareEncodedIDBKeys(ptr_a, a.end(), ptr_b, b.end(), ok);
+
+  StringPiece slice_a(ptr_a, a.end() - ptr_a);
+  StringPiece slice_b(ptr_b, b.end() - ptr_b);
+  int result = CompareEncodedIDBKeys(&slice_a, &slice_b, ok);
   if (!ok || result)
     return result;
   if (ignore_duplicates)
@@ -832,22 +847,24 @@ int Compare<IndexDataKey>(const LevelDBSlice& a,
   // sequence number [optional]
   int64 sequence_number_a = -1;
   int64 sequence_number_b = -1;
-  if (ptr_a != a.end())
-    ptr_a = DecodeVarInt(ptr_a, a.end(), sequence_number_a);
-  if (ptr_b != b.end())
-    ptr_b = DecodeVarInt(ptr_b, b.end(), sequence_number_b);
+  if (!slice_a.empty()) {
+    if (!DecodeVarInt(&slice_a, &sequence_number_a))
+      return 0;
+  }
+  if (!slice_b.empty()) {
+    if (!DecodeVarInt(&slice_b, &sequence_number_b))
+      return 0;
+  }
 
   // primary key [optional]
-  if (!ptr_a || !ptr_b)
-    return 0;
-  if (ptr_a == a.end() && ptr_b == b.end())
+  if (slice_a.empty() && slice_b.empty())
     return 0;
-  if (ptr_a == a.end())
+  if (slice_a.empty())
     return -1;
-  if (ptr_b == b.end())
+  if (slice_b.empty())
     return 1;
 
-  result = CompareEncodedIDBKeys(ptr_a, a.end(), ptr_b, b.end(), ok);
+  result = CompareEncodedIDBKeys(&slice_a, &slice_b, ok);
   if (!ok || result)
     return result;
 
@@ -937,6 +954,7 @@ int Compare(const LevelDBSlice& a,
     const bool ignore_duplicates = false;
     return Compare<ObjectStoreDataKey>(a, b, ignore_duplicates, ok);
   }
+
   if (prefix_a.type() == KeyPrefix::EXISTS_ENTRY) {
     if (ptr_a == end_a && ptr_b == end_b)
       return 0;
@@ -949,6 +967,7 @@ int Compare(const LevelDBSlice& a,
     const bool ignore_duplicates = false;
     return Compare<ExistsEntryKey>(a, b, ignore_duplicates, ok);
   }
+
   if (prefix_a.type() == KeyPrefix::INDEX_DATA) {
     if (ptr_a == end_a && ptr_b == end_b)
       return 0;
@@ -1055,11 +1074,23 @@ const char* KeyPrefix::Decode(const char* start,
       limit)
     return 0;
 
-  result->database_id_ = DecodeInt(start, start + database_id_bytes);
+  {
+    StringPiece slice(start, database_id_bytes);
+    if (!DecodeInt(&slice, &result->database_id_))
+      return 0;
+  }
   start += database_id_bytes;
-  result->object_store_id_ = DecodeInt(start, start + object_store_id_bytes);
+  {
+    StringPiece slice(start, object_store_id_bytes);
+    if (!DecodeInt(&slice, &result->object_store_id_))
+      return 0;
+  }
   start += object_store_id_bytes;
-  result->index_id_ = DecodeInt(start, start + index_id_bytes);
+  {
+    StringPiece slice(start, index_id_bytes);
+    if (!DecodeInt(&slice, &result->index_id_))
+      return 0;
+  }
   start += index_id_bytes;
 
   return start;
@@ -1181,11 +1212,15 @@ const char* DatabaseFreeListKey::Decode(const char* start,
   if (p == limit)
     return 0;
   unsigned char type_byte = 0;
-  p = DecodeByte(p, limit, type_byte);
+  StringPiece slice(p, limit - p);
+  if (!DecodeByte(&slice, &type_byte))
+    return 0;
   DCHECK_EQ(type_byte, kDatabaseFreeListTypeByte);
-  if (p == limit)
+  if (slice.empty())
     return 0;
-  return DecodeVarInt(p, limit, result->database_id_);
+  if (!DecodeVarInt(&slice, &result->database_id_))
+    return 0;
+  return slice.begin();
 }
 
 std::vector<char> DatabaseFreeListKey::Encode(int64 database_id) {
@@ -1222,14 +1257,15 @@ const char* DatabaseNameKey::Decode(const char* start,
   if (p == limit)
     return 0;
   unsigned char type_byte = 0;
-  p = DecodeByte(p, limit, type_byte);
+  StringPiece slice(p, limit - p);
+  if (!DecodeByte(&slice, &type_byte))
+    return 0;
   DCHECK_EQ(type_byte, kDatabaseNameTypeByte);
-  if (p == limit)
+  if (!DecodeStringWithLength(&slice, &result->origin_))
     return 0;
-  p = DecodeStringWithLength(p, limit, result->origin_);
-  if (!p)
+  if (!DecodeStringWithLength(&slice, &result->database_name_))
     return 0;
-  return DecodeStringWithLength(p, limit, result->database_name_);
+  return slice.begin();
 }
 
 std::vector<char> DatabaseNameKey::Encode(const string16& origin,
@@ -1282,17 +1318,16 @@ const char* ObjectStoreMetaDataKey::Decode(const char* start,
   if (p == limit)
     return 0;
   unsigned char type_byte = 0;
-  p = DecodeByte(p, limit, type_byte);
-  DCHECK_EQ(type_byte, kObjectStoreMetaDataTypeByte);
-  if (p == limit)
+  StringPiece slice(p, limit - p);
+  if (!DecodeByte(&slice, &type_byte))
     return 0;
-  p = DecodeVarInt(p, limit, result->object_store_id_);
-  if (!p)
+  DCHECK_EQ(type_byte, kObjectStoreMetaDataTypeByte);
+  if (!DecodeVarInt(&slice, &result->object_store_id_))
     return 0;
   DCHECK(result->object_store_id_);
-  if (p == limit)
+  if (!DecodeByte(&slice, &result->meta_data_type_))
     return 0;
-  return DecodeByte(p, limit, result->meta_data_type_);
+  return slice.begin();
 }
 
 std::vector<char> ObjectStoreMetaDataKey::Encode(int64 database_id,
@@ -1351,19 +1386,17 @@ const char* IndexMetaDataKey::Decode(const char* start,
   if (p == limit)
     return 0;
   unsigned char type_byte = 0;
-  p = DecodeByte(p, limit, type_byte);
-  DCHECK_EQ(type_byte, kIndexMetaDataTypeByte);
-  if (p == limit)
+  StringPiece slice(p, limit - p);
+  if (!DecodeByte(&slice, &type_byte))
     return 0;
-  p = DecodeVarInt(p, limit, result->object_store_id_);
-  if (!p)
+  DCHECK_EQ(type_byte, kIndexMetaDataTypeByte);
+  if (!DecodeVarInt(&slice, &result->object_store_id_))
     return 0;
-  p = DecodeVarInt(p, limit, result->index_id_);
-  if (!p)
+  if (!DecodeVarInt(&slice, &result->index_id_))
     return 0;
-  if (p == limit)
+  if (!DecodeByte(&slice, &result->meta_data_type_))
     return 0;
-  return DecodeByte(p, limit, result->meta_data_type_);
+  return slice.begin();
 }
 
 std::vector<char> IndexMetaDataKey::Encode(int64 database_id,
@@ -1425,11 +1458,13 @@ const char* ObjectStoreFreeListKey::Decode(const char* start,
   if (p == limit)
     return 0;
   unsigned char type_byte = 0;
-  p = DecodeByte(p, limit, type_byte);
+  StringPiece slice(p, limit - p);
+  if (!DecodeByte(&slice, &type_byte))
+    return 0;
   DCHECK_EQ(type_byte, kObjectStoreFreeListTypeByte);
-  if (p == limit)
+  if (!DecodeVarInt(&slice, &result->object_store_id_))
     return 0;
-  return DecodeVarInt(p, limit, result->object_store_id_);
+  return slice.begin();
 }
 
 std::vector<char> ObjectStoreFreeListKey::Encode(int64 database_id,
@@ -1473,14 +1508,15 @@ const char* IndexFreeListKey::Decode(const char* start,
   if (p == limit)
     return 0;
   unsigned char type_byte = 0;
-  p = DecodeByte(p, limit, type_byte);
+  StringPiece slice(p, limit - p);
+  if (!DecodeByte(&slice, &type_byte))
+    return 0;
   DCHECK_EQ(type_byte, kIndexFreeListTypeByte);
-  if (p == limit)
+  if (!DecodeVarInt(&slice, &result->object_store_id_))
     return 0;
-  p = DecodeVarInt(p, limit, result->object_store_id_);
-  if (!p)
+  if (!DecodeVarInt(&slice, &result->index_id_))
     return 0;
-  return DecodeVarInt(p, limit, result->index_id_);
+  return slice.begin();
 }
 
 std::vector<char> IndexFreeListKey::Encode(int64 database_id,
@@ -1534,9 +1570,13 @@ const char* ObjectStoreNamesKey::Decode(const char* start,
   if (p == limit)
     return 0;
   unsigned char type_byte = 0;
-  p = DecodeByte(p, limit, type_byte);
+  StringPiece slice(p, limit - p);
+  if (!DecodeByte(&slice, &type_byte))
+    return 0;
   DCHECK_EQ(type_byte, kObjectStoreNamesTypeByte);
-  return DecodeStringWithLength(p, limit, result->object_store_name_);
+  if (!DecodeStringWithLength(&slice, &result->object_store_name_))
+    return 0;
+  return slice.begin();
 }
 
 std::vector<char> ObjectStoreNamesKey::Encode(
@@ -1570,14 +1610,15 @@ const char* IndexNamesKey::Decode(const char* start,
   if (p == limit)
     return 0;
   unsigned char type_byte = 0;
-  p = DecodeByte(p, limit, type_byte);
+  StringPiece slice(p, limit - p);
+  if (!DecodeByte(&slice, &type_byte))
+    return 0;
   DCHECK_EQ(type_byte, kIndexNamesKeyTypeByte);
-  if (p == limit)
+  if (!DecodeVarInt(&slice, &result->object_store_id_))
     return 0;
-  p = DecodeVarInt(p, limit, result->object_store_id_);
-  if (!p)
+  if (!DecodeStringWithLength(&slice, &result->index_name_))
     return 0;
-  return DecodeStringWithLength(p, limit, result->index_name_);
+  return slice.begin();
 }
 
 std::vector<char> IndexNamesKey::Encode(int64 database_id,
@@ -1613,7 +1654,10 @@ const char* ObjectStoreDataKey::Decode(const char* start,
   DCHECK_EQ(prefix.index_id_, kSpecialIndexNumber);
   if (p == end)
     return 0;
-  return ExtractEncodedIDBKey(p, end, &result->encoded_user_key_);
+  StringPiece slice(p, end - p);
+  if (!ExtractEncodedIDBKey(&slice, &result->encoded_user_key_))
+    return 0;
+  return slice.begin();
 }
 
 std::vector<char> ObjectStoreDataKey::Encode(
@@ -1631,7 +1675,9 @@ std::vector<char> ObjectStoreDataKey::Encode(
 std::vector<char> ObjectStoreDataKey::Encode(int64 database_id,
                                              int64 object_store_id,
                                              const IndexedDBKey& user_key) {
-  return Encode(database_id, object_store_id, EncodeIDBKey(user_key));
+  std::vector<char> encoded_key;
+  EncodeIDBKey(user_key, &encoded_key);
+  return Encode(database_id, object_store_id, encoded_key);
 }
 
 int ObjectStoreDataKey::Compare(const ObjectStoreDataKey& other, bool& ok) {
@@ -1640,9 +1686,10 @@ int ObjectStoreDataKey::Compare(const ObjectStoreDataKey& other, bool& ok) {
 
 scoped_ptr<IndexedDBKey> ObjectStoreDataKey::user_key() const {
   scoped_ptr<IndexedDBKey> key;
-  DecodeIDBKey(&encoded_user_key_[0],
-               &encoded_user_key_[0] + encoded_user_key_.size(),
-               &key);
+  StringPiece slice(&encoded_user_key_[0], encoded_user_key_.size());
+  if (!DecodeIDBKey(&slice, &key)) {
+    // TODO(jsbell): Return error.
+  }
   return key.Pass();
 }
 
@@ -1663,7 +1710,10 @@ const char* ExistsEntryKey::Decode(const char* start,
   DCHECK_EQ(prefix.index_id_, kSpecialIndexNumber);
   if (p == end)
     return 0;
-  return ExtractEncodedIDBKey(p, end, &result->encoded_user_key_);
+  StringPiece slice(p, end - p);
+  if (!ExtractEncodedIDBKey(&slice, &result->encoded_user_key_))
+    return 0;
+  return slice.begin();
 }
 
 std::vector<char> ExistsEntryKey::Encode(int64 database_id,
@@ -1679,7 +1729,9 @@ std::vector<char> ExistsEntryKey::Encode(int64 database_id,
 std::vector<char> ExistsEntryKey::Encode(int64 database_id,
                                          int64 object_store_id,
                                          const IndexedDBKey& user_key) {
-  return Encode(database_id, object_store_id, EncodeIDBKey(user_key));
+  std::vector<char> encoded_key;
+  EncodeIDBKey(user_key, &encoded_key);
+  return Encode(database_id, object_store_id, encoded_key);
 }
 
 int ExistsEntryKey::Compare(const ExistsEntryKey& other, bool& ok) {
@@ -1688,9 +1740,10 @@ int ExistsEntryKey::Compare(const ExistsEntryKey& other, bool& ok) {
 
 scoped_ptr<IndexedDBKey> ExistsEntryKey::user_key() const {
   scoped_ptr<IndexedDBKey> key;
-  DecodeIDBKey(&encoded_user_key_[0],
-               &encoded_user_key_[0] + encoded_user_key_.size(),
-               &key);
+  StringPiece slice(&encoded_user_key_[0], encoded_user_key_.size());
+  if (!DecodeIDBKey(&slice, &key)) {
+    // TODO(jsbell): Return error.
+  }
   return key.Pass();
 }
 
@@ -1720,25 +1773,23 @@ const char* IndexDataKey::Decode(const char* start,
   result->sequence_number_ = -1;
   result->encoded_primary_key_ = MinIDBKey();
 
-  p = ExtractEncodedIDBKey(p, limit, &result->encoded_user_key_);
-  if (!p)
+  StringPiece slice(p, limit - p);
+  if (!ExtractEncodedIDBKey(&slice, &result->encoded_user_key_))
     return 0;
 
   // [optional] sequence number
-  if (p == limit)
-    return p;
-  p = DecodeVarInt(p, limit, result->sequence_number_);
-  if (!p)
+  if (slice.empty())
+    return slice.begin();
+  if (!DecodeVarInt(&slice, &result->sequence_number_))
     return 0;
 
   // [optional] primary key
-  if (p == limit)
-    return p;
-  p = ExtractEncodedIDBKey(p, limit, &result->encoded_primary_key_);
-  if (!p)
+  if (slice.empty())
+    return slice.begin();
+  if (!ExtractEncodedIDBKey(&slice, &result->encoded_primary_key_))
     return 0;
 
-  return p;
+  return slice.begin();
 }
 
 std::vector<char> IndexDataKey::Encode(
@@ -1760,11 +1811,10 @@ std::vector<char> IndexDataKey::Encode(int64 database_id,
                                        int64 object_store_id,
                                        int64 index_id,
                                        const IndexedDBKey& user_key) {
-  return Encode(database_id,
-                object_store_id,
-                index_id,
-                EncodeIDBKey(user_key),
-                MinIDBKey());
+  std::vector<char> encoded_key;
+  EncodeIDBKey(user_key, &encoded_key);
+  return Encode(
+      database_id, object_store_id, index_id, encoded_key, MinIDBKey());
 }
 
 std::vector<char> IndexDataKey::EncodeMinKey(int64 database_id,
@@ -1821,17 +1871,19 @@ int64 IndexDataKey::IndexId() const {
 
 scoped_ptr<IndexedDBKey> IndexDataKey::user_key() const {
   scoped_ptr<IndexedDBKey> key;
-  DecodeIDBKey(&encoded_user_key_[0],
-               &encoded_user_key_[0] + encoded_user_key_.size(),
-               &key);
+  StringPiece slice(&encoded_user_key_[0], encoded_user_key_.size());
+  if (!DecodeIDBKey(&slice, &key)) {
+    // TODO(jsbell): Return error.
+  }
   return key.Pass();
 }
 
 scoped_ptr<IndexedDBKey> IndexDataKey::primary_key() const {
   scoped_ptr<IndexedDBKey> key;
-  DecodeIDBKey(&encoded_primary_key_[0],
-               &encoded_primary_key_[0] + encoded_primary_key_.size(),
-               &key);
+  StringPiece slice(&encoded_primary_key_[0], encoded_primary_key_.size());
+  if (!DecodeIDBKey(&slice, &key)) {
+    // TODO(jsbell): Return error.
+  }
   return key.Pass();
 }