44 lines
1.2 KiB
Go
44 lines
1.2 KiB
Go
package fitparser
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// CRC lookup table for FIT files
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var crcTable = [16]uint16{
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0x0000, 0xCC01, 0xD801, 0x1400, 0xF001, 0x3C00, 0x2800, 0xE401,
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0xA001, 0x6C00, 0x7800, 0xB401, 0x5000, 0x9C01, 0x8801, 0x4400,
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}
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// CalculateCRC calculates the CRC-16 checksum for FIT files
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// This uses the CRC-16-ANSI algorithm with polynomial 0x8005
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func CalculateCRC(data []byte) uint16 {
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crc := uint16(0)
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for _, b := range data {
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// Compute CRC for lower nibble (bits 0-3)
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tmp := crcTable[crc&0xF]
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crc = (crc >> 4) & 0x0FFF
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crc = crc ^ tmp ^ crcTable[b&0xF]
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// Compute CRC for upper nibble (bits 4-7)
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tmp = crcTable[crc&0xF]
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crc = (crc >> 4) & 0x0FFF
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crc = crc ^ tmp ^ crcTable[(b>>4)&0xF]
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}
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return crc
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}
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// UpdateCRC updates an existing CRC with new data
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func UpdateCRC(crc uint16, data []byte) uint16 {
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for _, b := range data {
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// Compute CRC for lower nibble (bits 0-3)
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tmp := crcTable[crc&0xF]
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crc = (crc >> 4) & 0x0FFF
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crc = crc ^ tmp ^ crcTable[b&0xF]
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// Compute CRC for upper nibble (bits 4-7)
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tmp = crcTable[crc&0xF]
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crc = (crc >> 4) & 0x0FFF
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crc = crc ^ tmp ^ crcTable[(b>>4)&0xF]
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}
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return crc
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}
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