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substr.go
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substr.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 functions
import (
"fmt"
"github.com/dolthub/doltgresql/server/functions/framework"
pgtypes "github.com/dolthub/doltgresql/server/types"
)
// initSubstr registers the functions to the catalog.
func initSubstr() {
framework.RegisterFunction(substr_varchar_int32)
framework.RegisterFunction(substr_varchar_int32_int32)
}
// substr_varchar_int32 represents the PostgreSQL function of the same name, taking the same parameters.
var substr_varchar_int32 = framework.Function2{
Name: "substr",
Return: pgtypes.VarChar,
Parameters: []pgtypes.DoltgresType{pgtypes.VarChar, pgtypes.Int32},
Callable: func(ctx framework.Context, str any, start any) (any, error) {
if str == nil || start == nil {
return nil, nil
}
runes := []rune(str.(string))
if start.(int32) < 1 {
start = int32(1)
}
// start is 1-indexed
start = start.(int32) - int32(1)
if int(start.(int32)) >= len(runes) {
return "", nil
}
return string(runes[start.(int32):]), nil
},
}
// substr_varchar_int32_int32 represents the PostgreSQL function of the same name, taking the same parameters.
var substr_varchar_int32_int32 = framework.Function3{
Name: "substr",
Return: pgtypes.VarChar,
Parameters: []pgtypes.DoltgresType{pgtypes.VarChar, pgtypes.Int32, pgtypes.Int32},
Callable: func(ctx framework.Context, str any, startInt any, countInt any) (any, error) {
if str == nil || startInt == nil || countInt == nil {
return nil, nil
}
start := startInt.(int32)
count := countInt.(int32)
runes := []rune(str.(string))
if count < 0 {
return nil, fmt.Errorf("negative substring length not allowed")
}
// start is 1-indexed
start--
if start < 0 {
count += start
start = 0
}
if count <= 0 {
return "", nil
}
if int(start) >= len(runes) {
return "", nil
} else if int64(start)+int64(count) > int64(len(runes)) {
return string(runes[start:]), nil
}
return string(runes[start : start+count]), nil
},
}