mozStorageStatement.cpp

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 * vim: sw=2 ts=2 et lcs=trail\:.,tab\:>~ :
 * 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 <limits.h>
#include <stdio.h>

#include "nsError.h"
#include "nsMemory.h"
#include "nsThreadUtils.h"
#include "nsIClassInfoImpl.h"
#include "Variant.h"

#include "mozIStorageError.h"

#include "mozStorageBindingParams.h"
#include "mozStorageConnection.h"
#include "mozStorageStatementJSHelper.h"
#include "mozStoragePrivateHelpers.h"
#include "mozStorageStatementParams.h"
#include "mozStorageStatementRow.h"
#include "mozStorageStatement.h"
#include "GeckoProfiler.h"
#include "nsDOMClassInfo.h"

#include "mozilla/Logging.h"


extern mozilla::LazyLogModule gStorageLog;

namespace mozilla {
namespace storage {

////////////////////////////////////////////////////////////////////////////////
//// nsIClassInfo

NS_IMPL_CI_INTERFACE_GETTER(Statement,
                            mozIStorageStatement,
                            mozIStorageBaseStatement,
                            mozIStorageBindingParams,
                            mozIStorageValueArray,
                            mozilla::storage::StorageBaseStatementInternal)

class StatementClassInfo : public nsIClassInfo
{
public:
  constexpr StatementClassInfo() {}

  NS_DECL_ISUPPORTS_INHERITED

  NS_IMETHOD
  GetInterfaces(uint32_t *_count, nsIID ***_array) override
  {
    return NS_CI_INTERFACE_GETTER_NAME(Statement)(_count, _array);
  }

  NS_IMETHOD
  GetScriptableHelper(nsIXPCScriptable **_helper) override
  {
    static StatementJSHelper sJSHelper;
    *_helper = &sJSHelper;
    return NS_OK;
  }

  NS_IMETHOD
  GetContractID(char **_contractID) override
  {
    *_contractID = nullptr;
    return NS_OK;
  }

  NS_IMETHOD
  GetClassDescription(char **_desc) override
  {
    *_desc = nullptr;
    return NS_OK;
  }

  NS_IMETHOD
  GetClassID(nsCID **_id) override
  {
    *_id = nullptr;
    return NS_OK;
  }

  NS_IMETHOD
  GetFlags(uint32_t *_flags) override
  {
    *_flags = 0;
    return NS_OK;
  }

  NS_IMETHOD
  GetClassIDNoAlloc(nsCID *_cid) override
  {
    return NS_ERROR_NOT_AVAILABLE;
  }
};

NS_IMETHODIMP_(MozExternalRefCountType) StatementClassInfo::AddRef() { return 2; }
NS_IMETHODIMP_(MozExternalRefCountType) StatementClassInfo::Release() { return 1; }
NS_IMPL_QUERY_INTERFACE(StatementClassInfo, nsIClassInfo)

static StatementClassInfo sStatementClassInfo;

////////////////////////////////////////////////////////////////////////////////
//// Statement

Statement::Statement()
: StorageBaseStatementInternal()
, mDBStatement(nullptr)
, mColumnNames()
, mExecuting(false)
{
}

nsresult
Statement::initialize(Connection *aDBConnection,
                      sqlite3 *aNativeConnection,
                      const nsACString &aSQLStatement)
{
  MOZ_ASSERT(aDBConnection, "No database connection given!");
  MOZ_ASSERT(!aDBConnection->isClosed(), "Database connection should be valid");
  MOZ_ASSERT(!mDBStatement, "Statement already initialized!");
  MOZ_ASSERT(aNativeConnection, "No native connection given!");

  int srv = aDBConnection->prepareStatement(aNativeConnection,
                                            PromiseFlatCString(aSQLStatement),
                                            &mDBStatement);
  if (srv != SQLITE_OK) {
      MOZ_LOG(gStorageLog, LogLevel::Error,
             ("Sqlite statement prepare error: %d '%s'", srv,
              ::sqlite3_errmsg(aNativeConnection)));
      MOZ_LOG(gStorageLog, LogLevel::Error,
             ("Statement was: '%s'", PromiseFlatCString(aSQLStatement).get()));
      return NS_ERROR_FAILURE;
    }

  MOZ_LOG(gStorageLog, LogLevel::Debug, ("Initialized statement '%s' (0x%p)",
                                      PromiseFlatCString(aSQLStatement).get(),
                                      mDBStatement));

  mDBConnection = aDBConnection;
  mNativeConnection = aNativeConnection;
  mParamCount = ::sqlite3_bind_parameter_count(mDBStatement);
  mResultColumnCount = ::sqlite3_column_count(mDBStatement);
  mColumnNames.Clear();

  nsCString* columnNames = mColumnNames.AppendElements(mResultColumnCount);
  for (uint32_t i = 0; i < mResultColumnCount; i++) {
      const char *name = ::sqlite3_column_name(mDBStatement, i);
      columnNames[i].Assign(name);
  }

#ifdef DEBUG
  // We want to try and test for LIKE and that consumers are using
  // escapeStringForLIKE instead of just trusting user input.  The idea to
  // check to see if they are binding a parameter after like instead of just
  // using a string.  We only do this in debug builds because it's expensive!
  const nsCaseInsensitiveCStringComparator c;
  nsACString::const_iterator start, end, e;
  aSQLStatement.BeginReading(start);
  aSQLStatement.EndReading(end);
  e = end;
  while (::FindInReadable(NS_LITERAL_CSTRING(" LIKE"), start, e, c)) {
    // We have a LIKE in here, so we perform our tests
    // FindInReadable moves the iterator, so we have to get a new one for
    // each test we perform.
    nsACString::const_iterator s1, s2, s3;
    s1 = s2 = s3 = start;

    if (!(::FindInReadable(NS_LITERAL_CSTRING(" LIKE ?"), s1, end, c) ||
          ::FindInReadable(NS_LITERAL_CSTRING(" LIKE :"), s2, end, c) ||
          ::FindInReadable(NS_LITERAL_CSTRING(" LIKE @"), s3, end, c))) {
      // At this point, we didn't find a LIKE statement followed by ?, :,
      // or @, all of which are valid characters for binding a parameter.
      // We will warn the consumer that they may not be safely using LIKE.
      NS_WARNING("Unsafe use of LIKE detected!  Please ensure that you "
                 "are using mozIStorageStatement::escapeStringForLIKE "
                 "and that you are binding that result to the statement "
                 "to prevent SQL injection attacks.");
    }

    // resetting start and e
    start = e;
    e = end;
  }
#endif

  return NS_OK;
}

mozIStorageBindingParams *
Statement::getParams()
{
  nsresult rv;

  // If we do not have an array object yet, make it.
  if (!mParamsArray) {
    nsCOMPtr<mozIStorageBindingParamsArray> array;
    rv = NewBindingParamsArray(getter_AddRefs(array));
    NS_ENSURE_SUCCESS(rv, nullptr);

    mParamsArray = static_cast<BindingParamsArray *>(array.get());
  }

  // If there isn't already any rows added, we'll have to add one to use.
  if (mParamsArray->length() == 0) {
    RefPtr<BindingParams> params(new BindingParams(mParamsArray, this));
    NS_ENSURE_TRUE(params, nullptr);

    rv = mParamsArray->AddParams(params);
    NS_ENSURE_SUCCESS(rv, nullptr);

    // We have to unlock our params because AddParams locks them.  This is safe
    // because no reference to the params object was, or ever will be given out.
    params->unlock(this);

    // We also want to lock our array at this point - we don't want anything to
    // be added to it.  Nothing has, or will ever get a reference to it, but we
    // will get additional safety checks via assertions by doing this.
    mParamsArray->lock();
  }

  return *mParamsArray->begin();
}

Statement::~Statement()
{
  (void)internalFinalize(true);
}

////////////////////////////////////////////////////////////////////////////////
//// nsISupports

NS_IMPL_ADDREF(Statement)
NS_IMPL_RELEASE(Statement)

NS_INTERFACE_MAP_BEGIN(Statement)
  NS_INTERFACE_MAP_ENTRY(mozIStorageStatement)
  NS_INTERFACE_MAP_ENTRY(mozIStorageBaseStatement)
  NS_INTERFACE_MAP_ENTRY(mozIStorageBindingParams)
  NS_INTERFACE_MAP_ENTRY(mozIStorageValueArray)
  NS_INTERFACE_MAP_ENTRY(mozilla::storage::StorageBaseStatementInternal)
  if (aIID.Equals(NS_GET_IID(nsIClassInfo))) {
    foundInterface = static_cast<nsIClassInfo *>(&sStatementClassInfo);
  }
  else
  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, mozIStorageStatement)
NS_INTERFACE_MAP_END


////////////////////////////////////////////////////////////////////////////////
//// StorageBaseStatementInternal

Connection *
Statement::getOwner()
{
  return mDBConnection;
}

int
Statement::getAsyncStatement(sqlite3_stmt **_stmt)
{
  // If we have no statement, we shouldn't be calling this method!
  NS_ASSERTION(mDBStatement != nullptr, "We have no statement to clone!");

  // If we do not yet have a cached async statement, clone our statement now.
  if (!mAsyncStatement) {
    nsDependentCString sql(::sqlite3_sql(mDBStatement));
    int rc = mDBConnection->prepareStatement(mNativeConnection, sql,
                                             &mAsyncStatement);
    if (rc != SQLITE_OK) {
      *_stmt = nullptr;
      return rc;
    }

    MOZ_LOG(gStorageLog, LogLevel::Debug,
           ("Cloned statement 0x%p to 0x%p", mDBStatement, mAsyncStatement));
  }

  *_stmt = mAsyncStatement;
  return SQLITE_OK;
}

nsresult
Statement::getAsynchronousStatementData(StatementData &_data)
{
  if (!mDBStatement)
    return NS_ERROR_UNEXPECTED;

  sqlite3_stmt *stmt;
  int rc = getAsyncStatement(&stmt);
  if (rc != SQLITE_OK)
    return convertResultCode(rc);

  _data = StatementData(stmt, bindingParamsArray(), this);

  return NS_OK;
}

already_AddRefed<mozIStorageBindingParams>
Statement::newBindingParams(mozIStorageBindingParamsArray *aOwner)
{
  nsCOMPtr<mozIStorageBindingParams> params = new BindingParams(aOwner, this);
  return params.forget();
}


////////////////////////////////////////////////////////////////////////////////
//// mozIStorageStatement

// proxy to StorageBaseStatementInternal using its define helper.
MIXIN_IMPL_STORAGEBASESTATEMENTINTERNAL(Statement, (void)0;)

NS_IMETHODIMP
Statement::Clone(mozIStorageStatement **_statement)
{
  RefPtr<Statement> statement(new Statement());
  NS_ENSURE_TRUE(statement, NS_ERROR_OUT_OF_MEMORY);

  nsAutoCString sql(::sqlite3_sql(mDBStatement));
  nsresult rv = statement->initialize(mDBConnection, mNativeConnection, sql);
  NS_ENSURE_SUCCESS(rv, rv);

  statement.forget(_statement);
  return NS_OK;
}

NS_IMETHODIMP
Statement::Finalize()
{
  return internalFinalize(false);
}

nsresult
Statement::internalFinalize(bool aDestructing)
{
  if (!mDBStatement)
    return NS_OK;

  int srv = SQLITE_OK;

  if (!mDBConnection->isClosed()) {
    //
    // The connection is still open. While statement finalization and
    // closing may, in some cases, take place in two distinct threads,
    // we have a guarantee that the connection will remain open until
    // this method terminates:
    //
    // a. The connection will be closed synchronously. In this case,
    // there is no race condition, as everything takes place on the
    // same thread.
    //
    // b. The connection is closed asynchronously and this code is
    // executed on the opener thread. In this case, asyncClose() has
    // not been called yet and will not be called before we return
    // from this function.
    //
    // c. The connection is closed asynchronously and this code is
    // executed on the async execution thread. In this case,
    // AsyncCloseConnection::Run() has not been called yet and will
    // not be called before we return from this function.
    //
    // In either case, the connection is still valid, hence closing
    // here is safe.
    //
    MOZ_LOG(gStorageLog, LogLevel::Debug, ("Finalizing statement '%s' during garbage-collection",
                                        ::sqlite3_sql(mDBStatement)));
    srv = ::sqlite3_finalize(mDBStatement);
  }
#ifdef DEBUG
  else {
    //
    // The database connection is either closed or closing. The sqlite
    // statement has either been finalized already by the connection
    // or is about to be finalized by the connection.
    //
    // Finalizing it here would be useless and segfaultish.
    //

    char *msg = ::PR_smprintf("SQL statement (%x) should have been finalized"
      " before garbage-collection. For more details on this statement, set"
      " NSPR_LOG_MESSAGES=mozStorage:5 .",
      mDBStatement);

    //
    // Note that we can't display the statement itself, as the data structure
    // is not valid anymore. However, the address shown here should help
    // developers correlate with the more complete debug message triggered
    // by AsyncClose().
    //

#if 0
    // Deactivate the warning until we have fixed the exising culprit
    // (see bug 914070).
    NS_WARNING(msg);
#endif // 0

    MOZ_LOG(gStorageLog, LogLevel::Warning, (msg));

    ::PR_smprintf_free(msg);
  }

#endif

  mDBStatement = nullptr;

  if (mAsyncStatement) {
    // If the destructor called us, there are no pending async statements (they
    // hold a reference to us) and we can/must just kill the statement directly.
    if (aDestructing)
      destructorAsyncFinalize();
    else
      asyncFinalize();
  }

  // Release the holders, so they can release the reference to us.
  mStatementParamsHolder = nullptr;
  mStatementRowHolder = nullptr;

  return convertResultCode(srv);
}

NS_IMETHODIMP
Statement::GetParameterCount(uint32_t *_parameterCount)
{
  if (!mDBStatement)
    return NS_ERROR_NOT_INITIALIZED;

  *_parameterCount = mParamCount;
  return NS_OK;
}

NS_IMETHODIMP
Statement::GetParameterName(uint32_t aParamIndex,
                            nsACString &_name)
{
  if (!mDBStatement)
    return NS_ERROR_NOT_INITIALIZED;
  ENSURE_INDEX_VALUE(aParamIndex, mParamCount);

  const char *name = ::sqlite3_bind_parameter_name(mDBStatement,
                                                   aParamIndex + 1);
  if (name == nullptr) {
    // this thing had no name, so fake one
    nsAutoCString fakeName(":");
    fakeName.AppendInt(aParamIndex);
    _name.Assign(fakeName);
  }
  else {
    _name.Assign(nsDependentCString(name));
  }

  return NS_OK;
}

NS_IMETHODIMP
Statement::GetParameterIndex(const nsACString &aName,
                             uint32_t *_index)
{
  if (!mDBStatement)
    return NS_ERROR_NOT_INITIALIZED;

  // We do not accept any forms of names other than ":name", but we need to add
  // the colon for SQLite.
  nsAutoCString name(":");
  name.Append(aName);
  int ind = ::sqlite3_bind_parameter_index(mDBStatement, name.get());
  if (ind  == 0) // Named parameter not found.
    return NS_ERROR_INVALID_ARG;

  *_index = ind - 1; // SQLite indexes are 1-based, we are 0-based.

  return NS_OK;
}

NS_IMETHODIMP
Statement::GetColumnCount(uint32_t *_columnCount)
{
  if (!mDBStatement)
    return NS_ERROR_NOT_INITIALIZED;

  *_columnCount = mResultColumnCount;
  return NS_OK;
}

NS_IMETHODIMP
Statement::GetColumnName(uint32_t aColumnIndex,
                         nsACString &_name)
{
  if (!mDBStatement)
    return NS_ERROR_NOT_INITIALIZED;
  ENSURE_INDEX_VALUE(aColumnIndex, mResultColumnCount);

  const char *cname = ::sqlite3_column_name(mDBStatement, aColumnIndex);
  _name.Assign(nsDependentCString(cname));

  return NS_OK;
}

NS_IMETHODIMP
Statement::GetColumnIndex(const nsACString &aName,
                          uint32_t *_index)
{
  if (!mDBStatement)
      return NS_ERROR_NOT_INITIALIZED;

  // Surprisingly enough, SQLite doesn't provide an API for this.  We have to
  // determine it ourselves sadly.
  for (uint32_t i = 0; i < mResultColumnCount; i++) {
    if (mColumnNames[i].Equals(aName)) {
      *_index = i;
      return NS_OK;
    }
  }

  return NS_ERROR_INVALID_ARG;
}

NS_IMETHODIMP
Statement::Reset()
{
  if (!mDBStatement)
    return NS_ERROR_NOT_INITIALIZED;

#ifdef DEBUG
  MOZ_LOG(gStorageLog, LogLevel::Debug, ("Resetting statement: '%s'",
                                     ::sqlite3_sql(mDBStatement)));

  checkAndLogStatementPerformance(mDBStatement);
#endif

  mParamsArray = nullptr;
  (void)sqlite3_reset(mDBStatement);
  (void)sqlite3_clear_bindings(mDBStatement);

  mExecuting = false;

  return NS_OK;
}

NS_IMETHODIMP
Statement::BindParameters(mozIStorageBindingParamsArray *aParameters)
{
  NS_ENSURE_ARG_POINTER(aParameters);

  if (!mDBStatement)
    return NS_ERROR_NOT_INITIALIZED;

  BindingParamsArray *array = static_cast<BindingParamsArray *>(aParameters);
  if (array->getOwner() != this)
    return NS_ERROR_UNEXPECTED;

  if (array->length() == 0)
    return NS_ERROR_UNEXPECTED;

  mParamsArray = array;
  mParamsArray->lock();

  return NS_OK;
}

NS_IMETHODIMP
Statement::Execute()
{
  if (!mDBStatement)
    return NS_ERROR_NOT_INITIALIZED;

  bool ret;
  nsresult rv = ExecuteStep(&ret);
  nsresult rv2 = Reset();

  return NS_FAILED(rv) ? rv : rv2;
}

NS_IMETHODIMP
Statement::ExecuteStep(bool *_moreResults)
{
  PROFILER_LABEL("Statement", "ExecuteStep",
    js::ProfileEntry::Category::STORAGE);

  if (!mDBStatement)
    return NS_ERROR_NOT_INITIALIZED;

  // Bind any parameters first before executing.
  if (mParamsArray) {
    // If we have more than one row of parameters to bind, they shouldn't be
    // calling this method (and instead use executeAsync).
    if (mParamsArray->length() != 1)
      return NS_ERROR_UNEXPECTED;

    BindingParamsArray::iterator row = mParamsArray->begin();
    nsCOMPtr<IStorageBindingParamsInternal> bindingInternal = 
      do_QueryInterface(*row);
    nsCOMPtr<mozIStorageError> error = bindingInternal->bind(mDBStatement);
    if (error) {
      int32_t srv;
      (void)error->GetResult(&srv);
      return convertResultCode(srv);
    }

    // We have bound, so now we can clear our array.
    mParamsArray = nullptr;
  }
  int srv = mDBConnection->stepStatement(mNativeConnection, mDBStatement);

  if (srv != SQLITE_ROW && srv != SQLITE_DONE && MOZ_LOG_TEST(gStorageLog, LogLevel::Debug)) {
      nsAutoCString errStr;
      (void)mDBConnection->GetLastErrorString(errStr);
      MOZ_LOG(gStorageLog, LogLevel::Debug,
             ("Statement::ExecuteStep error: %s", errStr.get()));
  }

  // SQLITE_ROW and SQLITE_DONE are non-errors
  if (srv == SQLITE_ROW) {
    // we got a row back
    mExecuting = true;
    *_moreResults = true;
    return NS_OK;
  }
  else if (srv == SQLITE_DONE) {
    // statement is done (no row returned)
    mExecuting = false;
    *_moreResults = false;
    return NS_OK;
  }
  else if (srv == SQLITE_BUSY || srv == SQLITE_MISUSE) {
    mExecuting = false;
  }
  else if (mExecuting) {
    MOZ_LOG(gStorageLog, LogLevel::Error,
           ("SQLite error after mExecuting was true!"));
    mExecuting = false;
  }

  return convertResultCode(srv);
}

NS_IMETHODIMP
Statement::GetState(int32_t *_state)
{
  if (!mDBStatement)
    *_state = MOZ_STORAGE_STATEMENT_INVALID;
  else if (mExecuting)
    *_state = MOZ_STORAGE_STATEMENT_EXECUTING;
  else
    *_state = MOZ_STORAGE_STATEMENT_READY;

  return NS_OK;
}

NS_IMETHODIMP
Statement::GetColumnDecltype(uint32_t aParamIndex,
                             nsACString &_declType)
{
  if (!mDBStatement)
    return NS_ERROR_NOT_INITIALIZED;

  ENSURE_INDEX_VALUE(aParamIndex, mResultColumnCount);

  _declType.Assign(::sqlite3_column_decltype(mDBStatement, aParamIndex));
  return NS_OK;
}

////////////////////////////////////////////////////////////////////////////////
//// mozIStorageValueArray (now part of mozIStorageStatement too)

NS_IMETHODIMP
Statement::GetNumEntries(uint32_t *_length)
{
  *_length = mResultColumnCount;
  return NS_OK;
}

NS_IMETHODIMP
Statement::GetTypeOfIndex(uint32_t aIndex,
                          int32_t *_type)
{
  if (!mDBStatement)
    return NS_ERROR_NOT_INITIALIZED;

  ENSURE_INDEX_VALUE(aIndex, mResultColumnCount);

  if (!mExecuting)
    return NS_ERROR_UNEXPECTED;

  int t = ::sqlite3_column_type(mDBStatement, aIndex);
  switch (t) {
    case SQLITE_INTEGER:
      *_type = mozIStorageStatement::VALUE_TYPE_INTEGER;
      break;
    case SQLITE_FLOAT:
      *_type = mozIStorageStatement::VALUE_TYPE_FLOAT;
      break;
    case SQLITE_TEXT:
      *_type = mozIStorageStatement::VALUE_TYPE_TEXT;
      break;
    case SQLITE_BLOB:
      *_type = mozIStorageStatement::VALUE_TYPE_BLOB;
      break;
    case SQLITE_NULL:
      *_type = mozIStorageStatement::VALUE_TYPE_NULL;
      break;
    default:
      return NS_ERROR_FAILURE;
  }

  return NS_OK;
}

NS_IMETHODIMP
Statement::GetInt32(uint32_t aIndex,
                    int32_t *_value)
{
  if (!mDBStatement)
    return NS_ERROR_NOT_INITIALIZED;

  ENSURE_INDEX_VALUE(aIndex, mResultColumnCount);

  if (!mExecuting)
    return NS_ERROR_UNEXPECTED;

  *_value = ::sqlite3_column_int(mDBStatement, aIndex);
  return NS_OK;
}

NS_IMETHODIMP
Statement::GetInt64(uint32_t aIndex,
                    int64_t *_value)
{
  if (!mDBStatement)
    return NS_ERROR_NOT_INITIALIZED;

  ENSURE_INDEX_VALUE(aIndex, mResultColumnCount);

  if (!mExecuting)
    return NS_ERROR_UNEXPECTED;

  *_value = ::sqlite3_column_int64(mDBStatement, aIndex);

  return NS_OK;
}

NS_IMETHODIMP
Statement::GetDouble(uint32_t aIndex,
                     double *_value)
{
  if (!mDBStatement)
    return NS_ERROR_NOT_INITIALIZED;

  ENSURE_INDEX_VALUE(aIndex, mResultColumnCount);

  if (!mExecuting)
    return NS_ERROR_UNEXPECTED;

  *_value = ::sqlite3_column_double(mDBStatement, aIndex);

  return NS_OK;
}

NS_IMETHODIMP
Statement::GetUTF8String(uint32_t aIndex,
                         nsACString &_value)
{
  // Get type of Index will check aIndex for us, so we don't have to.
  int32_t type;
  nsresult rv = GetTypeOfIndex(aIndex, &type);
  NS_ENSURE_SUCCESS(rv, rv);
  if (type == mozIStorageStatement::VALUE_TYPE_NULL) {
    // NULL columns should have IsVoid set to distinguish them from the empty
    // string.
    _value.SetIsVoid(true);
  }
  else {
    const char *value =
      reinterpret_cast<const char *>(::sqlite3_column_text(mDBStatement,
                                                           aIndex));
    _value.Assign(value, ::sqlite3_column_bytes(mDBStatement, aIndex));
  }
  return NS_OK;
}

NS_IMETHODIMP
Statement::GetString(uint32_t aIndex,
                     nsAString &_value)
{
  // Get type of Index will check aIndex for us, so we don't have to.
  int32_t type;
  nsresult rv = GetTypeOfIndex(aIndex, &type);
  NS_ENSURE_SUCCESS(rv, rv);
  if (type == mozIStorageStatement::VALUE_TYPE_NULL) {
    // NULL columns should have IsVoid set to distinguish them from the empty
    // string.
    _value.SetIsVoid(true);
  } else {
    const char16_t *value =
      static_cast<const char16_t *>(::sqlite3_column_text16(mDBStatement,
                                                             aIndex));
    _value.Assign(value, ::sqlite3_column_bytes16(mDBStatement, aIndex) / 2);
  }
  return NS_OK;
}

NS_IMETHODIMP
Statement::GetBlob(uint32_t aIndex,
                   uint32_t *_size,
                   uint8_t **_blob)
{
  if (!mDBStatement)
    return NS_ERROR_NOT_INITIALIZED;

  ENSURE_INDEX_VALUE(aIndex, mResultColumnCount);

  if (!mExecuting)
     return NS_ERROR_UNEXPECTED;

  int size = ::sqlite3_column_bytes(mDBStatement, aIndex);
  void *blob = nullptr;
  if (size) {
    blob = nsMemory::Clone(::sqlite3_column_blob(mDBStatement, aIndex), size);
    NS_ENSURE_TRUE(blob, NS_ERROR_OUT_OF_MEMORY);
  }

  *_blob = static_cast<uint8_t *>(blob);
  *_size = size;
  return NS_OK;
}

NS_IMETHODIMP
Statement::GetBlobAsString(uint32_t aIndex, nsAString& aValue)
{
  return DoGetBlobAsString(this, aIndex, aValue);
}

NS_IMETHODIMP
Statement::GetBlobAsUTF8String(uint32_t aIndex, nsACString& aValue)
{
  return DoGetBlobAsString(this, aIndex, aValue);
}

NS_IMETHODIMP
Statement::GetSharedUTF8String(uint32_t aIndex,
                               uint32_t *_length,
                               const char **_value)
{
  if (_length)
    *_length = ::sqlite3_column_bytes(mDBStatement, aIndex);

  *_value = reinterpret_cast<const char *>(::sqlite3_column_text(mDBStatement,
                                                                 aIndex));
  return NS_OK;
}

NS_IMETHODIMP
Statement::GetSharedString(uint32_t aIndex,
                           uint32_t *_length,
                           const char16_t **_value)
{
  if (_length)
    *_length = ::sqlite3_column_bytes16(mDBStatement, aIndex);

  *_value = static_cast<const char16_t *>(::sqlite3_column_text16(mDBStatement,
                                                                   aIndex));
  return NS_OK;
}

NS_IMETHODIMP
Statement::GetSharedBlob(uint32_t aIndex,
                         uint32_t *_size,
                         const uint8_t **_blob)
{
  *_size = ::sqlite3_column_bytes(mDBStatement, aIndex);
  *_blob = static_cast<const uint8_t *>(::sqlite3_column_blob(mDBStatement,
                                                              aIndex));
  return NS_OK;
}

NS_IMETHODIMP
Statement::GetIsNull(uint32_t aIndex,
                     bool *_isNull)
{
  // Get type of Index will check aIndex for us, so we don't have to.
  int32_t type;
  nsresult rv = GetTypeOfIndex(aIndex, &type);
  NS_ENSURE_SUCCESS(rv, rv);
  *_isNull = (type == mozIStorageStatement::VALUE_TYPE_NULL);
  return NS_OK;
}

////////////////////////////////////////////////////////////////////////////////
//// mozIStorageBindingParams

BOILERPLATE_BIND_PROXIES(
  Statement, 
  if (!mDBStatement) return NS_ERROR_NOT_INITIALIZED;
)

} // namespace storage
} // namespace mozilla