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isbinary.go
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isbinary.go
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// Copyright 2020-2021 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 (
"bytes"
"fmt"
"github.com/Rock-liyi/p2pdb-store/sql"
"github.com/Rock-liyi/p2pdb-store/sql/expression"
)
// IsBinary is a function that returns whether a blob is binary or not.
type IsBinary struct {
expression.UnaryExpression
}
var _ sql.FunctionExpression = (*IsBinary)(nil)
// NewIsBinary creates a new IsBinary expression.
func NewIsBinary(e sql.Expression) sql.Expression {
return &IsBinary{expression.UnaryExpression{Child: e}}
}
// FunctionName implements sql.FunctionExpression
func (ib *IsBinary) FunctionName() string {
return "is_binary"
}
// Description implements sql.FunctionExpression
func (ib *IsBinary) Description() string {
return "returns whether a blob is a binary file or not."
}
// Eval implements the Expression interface.
func (ib *IsBinary) Eval(
ctx *sql.Context,
row sql.Row,
) (interface{}, error) {
v, err := ib.Child.Eval(ctx, row)
if err != nil {
return nil, err
}
if v == nil {
return false, nil
}
blob, err := sql.LongBlob.Convert(v)
if err != nil {
return nil, err
}
blobBytes := blob.(string)
return isBinary(blobBytes), nil
}
func (ib *IsBinary) String() string {
return fmt.Sprintf("IS_BINARY(%s)", ib.Child)
}
// WithChildren implements the Expression interface.
func (ib *IsBinary) WithChildren(children ...sql.Expression) (sql.Expression, error) {
if len(children) != 1 {
return nil, sql.ErrInvalidChildrenNumber.New(ib, len(children), 1)
}
return NewIsBinary(children[0]), nil
}
// Type implements the Expression interface.
func (ib *IsBinary) Type() sql.Type {
return sql.Boolean
}
const sniffLen = 8000
// isBinary detects if data is a binary value based on:
// http://git.kernel.org/cgit/git/git.git/tree/xdiff-interface.c?id=HEAD#n198
func isBinary(data string) bool {
binData := []byte(data)
if len(binData) > sniffLen {
binData = binData[:sniffLen]
}
if bytes.IndexByte(binData, byte(0)) == -1 {
return false
}
return true
}