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#include <DataTypes/DataTypeString.h>
#include <Columns/ColumnString.h>
#include <Columns/ColumnFixedString.h>
#include <Columns/ColumnArray.h>
#include <Functions/FunctionFactory.h>
#include <Functions/FunctionHelpers.h>
#include <base/map.h>
namespace DB
{
namespace ErrorCodes
{
extern const int ILLEGAL_COLUMN;
extern const int ILLEGAL_TYPE_OF_ARGUMENT;
}
namespace
{
/** Reverse the string as a sequence of bytes.
*/
struct ReverseImpl
{
static void vector(const ColumnString::Chars & data,
const ColumnString::Offsets & offsets,
ColumnString::Chars & res_data,
ColumnString::Offsets & res_offsets)
{
res_data.resize(data.size());
res_offsets.assign(offsets);
size_t size = offsets.size();
ColumnString::Offset prev_offset = 0;
for (size_t i = 0; i < size; ++i)
{
for (size_t j = prev_offset; j < offsets[i] - 1; ++j)
res_data[j] = data[offsets[i] + prev_offset - 2 - j];
res_data[offsets[i] - 1] = 0;
prev_offset = offsets[i];
}
}
static void vectorFixed(const ColumnString::Chars & data, size_t n, ColumnString::Chars & res_data)
{
res_data.resize(data.size());
size_t size = data.size() / n;
for (size_t i = 0; i < size; ++i)
for (size_t j = i * n; j < (i + 1) * n; ++j)
res_data[j] = data[(i * 2 + 1) * n - j - 1];
}
};
class FunctionReverse : public IFunction
{
public:
static constexpr auto name = "reverse";
static FunctionPtr create(ContextPtr)
{
return std::make_shared<FunctionReverse>();
}
String getName() const override
{
return name;
}
size_t getNumberOfArguments() const override
{
return 1;
}
bool isInjective(const ColumnsWithTypeAndName &) const override
{
return true;
}
bool isSuitableForShortCircuitArgumentsExecution(const DataTypesWithConstInfo & /*arguments*/) const override { return true; }
DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
{
if (!isStringOrFixedString(arguments[0])
&& !isArray(arguments[0]))
throw Exception(ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT, "Illegal type {} of argument of function {}",
arguments[0]->getName(), getName());
return arguments[0];
}
bool useDefaultImplementationForConstants() const override { return true; }
ColumnPtr executeImpl(const ColumnsWithTypeAndName & arguments, const DataTypePtr &, size_t) const override
{
const ColumnPtr column = arguments[0].column;
if (const ColumnString * col = checkAndGetColumn<ColumnString>(column.get()))
{
auto col_res = ColumnString::create();
ReverseImpl::vector(col->getChars(), col->getOffsets(), col_res->getChars(), col_res->getOffsets());
return col_res;
}
else if (const ColumnFixedString * col_fixed = checkAndGetColumn<ColumnFixedString>(column.get()))
{
auto col_res = ColumnFixedString::create(col_fixed->getN());
ReverseImpl::vectorFixed(col_fixed->getChars(), col_fixed->getN(), col_res->getChars());
return col_res;
}
else
throw Exception(ErrorCodes::ILLEGAL_COLUMN, "Illegal column {} of argument of function {}",
arguments[0].column->getName(), getName());
}
};
/// Also works with arrays.
class ReverseOverloadResolver : public IFunctionOverloadResolver
{
public:
static constexpr auto name = "reverse";
static FunctionOverloadResolverPtr create(ContextPtr context) { return std::make_unique<ReverseOverloadResolver>(context); }
explicit ReverseOverloadResolver(ContextPtr context_) : context(context_) {}
String getName() const override { return name; }
size_t getNumberOfArguments() const override { return 1; }
FunctionBasePtr buildImpl(const ColumnsWithTypeAndName & arguments, const DataTypePtr & return_type) const override
{
if (isArray(arguments.at(0).type))
return FunctionFactory::instance().getImpl("arrayReverse", context)->build(arguments);
else
return std::make_unique<FunctionToFunctionBaseAdaptor>(
FunctionReverse::create(context),
collections::map<DataTypes>(arguments, [](const auto & elem) { return elem.type; }),
return_type);
}
DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
{
return arguments.at(0);
}
private:
ContextPtr context;
};
}
REGISTER_FUNCTION(Reverse)
{
factory.registerFunction<ReverseOverloadResolver>({}, FunctionFactory::CaseInsensitive);
}
}
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