/
bit_count.go
111 lines (92 loc) · 2.79 KB
/
bit_count.go
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// Copyright 2024 Dolthub, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package function
import (
"fmt"
"github.com/dolthub/go-mysql-server/sql"
"github.com/dolthub/go-mysql-server/sql/types"
)
// BitCount returns the smallest integer value not less than X.
type BitCount struct {
*UnaryFunc
}
var _ sql.FunctionExpression = (*BitCount)(nil)
var _ sql.CollationCoercible = (*BitCount)(nil)
// NewBitCount creates a new Ceil expression.
func NewBitCount(arg sql.Expression) sql.Expression {
return &BitCount{NewUnaryFunc(arg, "BIT_COUNT", types.Int32)}
}
// FunctionName implements sql.FunctionExpression
func (b *BitCount) FunctionName() string {
return "bit_count"
}
// Description implements sql.FunctionExpression
func (b *BitCount) Description() string {
return "returns the number of bits that are set."
}
// Type implements the Expression interface.
func (b *BitCount) Type() sql.Type {
return types.Int32
}
// CollationCoercibility implements the interface sql.CollationCoercible.
func (b *BitCount) CollationCoercibility(ctx *sql.Context) (collation sql.CollationID, coercibility byte) {
return sql.Collation_binary, 5
}
func (b *BitCount) String() string {
return fmt.Sprintf("%s(%s)", b.FunctionName(), b.Child)
}
// WithChildren implements the Expression interface.
func (b *BitCount) WithChildren(children ...sql.Expression) (sql.Expression, error) {
if len(children) != 1 {
return nil, sql.ErrInvalidChildrenNumber.New(b, len(children), 1)
}
return NewBitCount(children[0]), nil
}
func countBits(n uint64) int32 {
var res int32
for n != 0 {
res++
n &= n - 1
}
return res
}
// Eval implements the Expression interface.
func (b *BitCount) Eval(ctx *sql.Context, row sql.Row) (interface{}, error) {
if b.Child == nil {
return nil, nil
}
child, err := b.Child.Eval(ctx, row)
if err != nil {
return nil, err
}
if child == nil {
return nil, nil
}
var res int32
switch val := child.(type) {
case []byte:
for _, v := range val {
res += countBits(uint64(v))
}
default:
num, _, err := types.Int64.Convert(child)
if err != nil {
ctx.Warn(1292, "Truncated incorrect INTEGER value: '%v'", child)
num = int64(0)
}
// Must convert to unsigned because shifting a negative signed value fills with 1s
res = countBits(uint64(num.(int64)))
}
return res, nil
}