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44 lines
716 B
Go
44 lines
716 B
Go
package modbus
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import "sync"
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var crcTable []uint16
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var mu sync.Mutex
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// crcModbus 计算modbus的crc
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func crcModbus(data []byte) (crc uint16) {
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if crcTable == nil {
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mu.Lock()
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if crcTable == nil {
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initCrcTable()
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}
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mu.Unlock()
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}
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crc = 0xffff
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for _, v := range data {
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crc = (crc >> 8) ^ crcTable[(crc^uint16(v))&0x00FF]
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}
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return crc
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}
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// initCrcTable 初始化crcTable
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func initCrcTable() {
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crc16IBM := uint16(0xA001)
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crcTable = make([]uint16, 256)
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for i := uint16(0); i < 256; i++ {
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crc := uint16(0)
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c := i
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for j := uint16(0); j < 8; j++ {
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if ((crc ^ c) & 0x0001) > 0 {
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crc = (crc >> 1) ^ crc16IBM
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} else {
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crc = crc >> 1
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}
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c = c >> 1
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}
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crcTable[i] = crc
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}
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}
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