Source of endianness.go - Zabbix

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/*
** Copyright (C) 2001-2025 Zabbix SIA
**
** This program is free software: you can redistribute it and/or modify it under the terms of
** the GNU Affero General Public License as published by the Free Software Foundation, version 3.
**
** This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
** without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
** See the GNU Affero General Public License for more details.
**
** You should have received a copy of the GNU Affero General Public License along with this program.
** If not, see <https://www.gnu.org/licenses/>.
**/
​
package modbus
​
import (
    "bytes"
    "encoding/binary"
    "encoding/json"
    "fmt"
)
​
// main data transformation
func pack2Json(val []byte, p *mbParams) (jdata interface{}, err error) {
​
    if p.RetType == Bit {
        ar := getArr16(p.RetType, uint(p.Count), val)
        if p.RetCount == 1 {
            return getFirst(ar), nil
        }
​
        if len(ar) < int(p.Offset) {
            return nil, fmt.Errorf("Wrong length of received data: %d", len(ar))
        }
​
        if p.Offset > 0 {
            ar = ar[p.Offset:]
        }
​
        jd, jerr := json.Marshal(ar)
        if jerr != nil {
            return nil, fmt.Errorf("Unable to create json: %s", jerr)
        }
        return string(jd), nil
    }
​
    if len(val) < int(p.Offset*2) {
        return nil, fmt.Errorf("Wrong length of received data: %d", len(val))
    }
​
    if p.Offset > 0 {
        val = val[p.Offset*2:]
    }
​
    var typeSize int
    switch p.RetType {
    case Uint64, Double:
        typeSize = 8
    case Int32, Uint32, Float:
        typeSize = 4
    case Int16, Uint16:
        typeSize = 2
    default:
        typeSize = 1
    }
​
    var arr interface{}
    if typeSize == 1 && p.Endianness.order == binary.LittleEndian {
        arr = swapPairByte(val, p.RetType, p.RetCount)
    } else {
        arr = makeRetArray(p.RetType, p.RetCount)
        r := bytes.NewReader(val)
        if err = binary.Read(r, p.Endianness.order, arr); err != nil {
            return nil, fmt.Errorf("Unable to convert returned data: %w", err)
        }
    }
​
    if typeSize > 2 && 0 != p.Endianness.middle {
        arr = middlePack(arr, p.RetType)
    }
​
    if p.RetCount == 1 {
        return getFirst(arr), nil
    }
​
    if p.RetType == Uint8 {
        arr = getArr16(p.RetType, p.RetCount, arr.([]byte))
    }
​
    jd, jerr := json.Marshal(arr)