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SQL/ODBC: optimize toSQLTCHAR() - avoid an unneeded copy 

Avoid an unneeded copy in toSQLTCHAR() when sizeof(SQLTCHAR) == 1 or 4
by directly writing the encoded data into the QVarLengthArray.

Change-Id: Ic4180343764fa1ca175a9cdd444c5359d664c754
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
bb10
Christian Ehrlicher 2023-02-03 23:04:36 +01:00
parent 18c73ad47d
commit 694a92ab24
1 changed files with 16 additions and 27 deletions
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43
src/plugins/sqldrivers/odbc/qsql_odbc.cpp
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@ -14,6 +14,7 @@
#include <qsqlerror.h>
#include <qsqlfield.h>
#include <qsqlindex.h>
#include <qstringconverter.h>
#include <qstringlist.h>
#include <qvariant.h>
#include <qvarlengtharray.h>
@ -58,39 +59,27 @@ inline static QString fromSQLTCHAR(const QVarLengthArray<SQLTCHAR>& input, qsize
return result;
}
template <size_t SizeOfChar = sizeof(SQLTCHAR)>
void toSQLTCHARImpl(QVarLengthArray<SQLTCHAR> &result, const QString &input); // primary template undefined
template <typename Container>
void do_append(QVarLengthArray<SQLTCHAR> &result, const Container &c)
template<int SIZE = sizeof(SQLTCHAR)>
QStringConverter::Encoding encodingForSqlTChar()
{
result.append(reinterpret_cast<const SQLTCHAR *>(c.data()), c.size());
}
template <>
void toSQLTCHARImpl<1>(QVarLengthArray<SQLTCHAR> &result, const QString &input)
{
const auto u8 = input.toUtf8();
do_append(result, u8);
}
template <>
void toSQLTCHARImpl<2>(QVarLengthArray<SQLTCHAR> &result, const QString &input)
{
do_append(result, input);
}
template <>
void toSQLTCHARImpl<4>(QVarLengthArray<SQLTCHAR> &result, const QString &input)
{
const auto u32 = input.toUcs4();
do_append(result, u32);
if constexpr (SIZE == 1)
return QStringConverter::Utf8;
else if constexpr (SIZE == 2)
return QStringConverter::Utf16;
else if constexpr (SIZE == 4)
return QStringConverter::Utf32;
else
static_assert(QtPrivate::value_dependent_false<SIZE>(),
"Don't know how to handle sizeof(SQLTCHAR) != 1/2/4");
}
inline static QVarLengthArray<SQLTCHAR> toSQLTCHAR(const QString &input)
{
QVarLengthArray<SQLTCHAR> result;
toSQLTCHARImpl(result, input);
QStringEncoder enc(encodingForSqlTChar());
result.resize(enc.requiredSpace(input.size()));
const auto end = enc.appendToBuffer(reinterpret_cast<char *>(result.data()), input);
result.resize((end - reinterpret_cast<char *>(result.data())) / sizeof(SQLTCHAR));
result.append(0); // make sure it's null terminated, doesn't matter if it already is, it does if it isn't.
return result;
}