package main

import (
	"encoding/binary"
	"fmt"
)

// Helpers for converting straight from modbus data to floats.

func u16(data []byte) (float64, error) {
	n := binary.BigEndian.Uint16(data)
	if n == 0xFFFF {
		// probably a misread
		return 0, fmt.Errorf("likely misread: u16 read %v", n)
	}
	return float64(n), nil
}

func s16(data []byte) (float64, error) {
	return float64(int16(binary.BigEndian.Uint16(data))), nil
}

func u32(data []byte) (float64, error) {
	// Little-endian big-endian :#
	n := uint32(binary.BigEndian.Uint16(data)) + uint32(binary.BigEndian.Uint16(data[2:]))<<16
	if n == 0xFFFFFFFF {
		// probably a misread
		return 0, fmt.Errorf("likely misread: u32 read %v", n)
	}
	return float64(n), nil
}

func s32(data []byte) (float64, error) {
	// Little-endian big-endian :#
	return float64(int32(binary.BigEndian.Uint16(data)) + int32(binary.BigEndian.Uint16(data[2:]))<<16), nil
}