Thomas Klaehn
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README.md
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README.md
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# FIT File Parser for Go
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A pure Go implementation of a FIT (Flexible and Interoperable Data Transfer) file parser. FIT is a binary file format used by Garmin and other fitness device manufacturers to store activity data, workouts, courses, and more.
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## Features
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- ✅ Full FIT file decoder
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- ✅ Support for all FIT base types (integers, floats, strings, arrays)
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- ✅ **Complete CRC-16 validation** (tested on 170+ real-world FIT files)
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- ✅ Support for both little-endian and big-endian architectures
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- ✅ Header parsing (12 and 14-byte headers with proper CRC handling)
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- ✅ Message definitions and data records
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- ✅ Developer field support
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- ✅ Profile definitions for common message types
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- ✅ Timestamp conversion utilities
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- ✅ Semicircles to degrees conversion
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- ✅ Zero dependencies (uses only Go standard library)
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## Installation
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```bash
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go get git.blackfinn.de/go/fit-parser/fitparser
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```
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Or clone and use locally:
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```bash
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git clone https://git.blackfinn.de/go/fit-parser.git
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cd fitparser
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go test ./fitparser
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```
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## Quick Start
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```go
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package main
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import (
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"fmt"
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"log"
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"os"
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"git.blackfinn.de/go/fit-parser/fitparser"
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)
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func main() {
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// Read FIT file
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data, err := os.ReadFile("activity.fit")
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if err != nil {
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log.Fatal(err)
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}
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// Create decoder
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decoder, err := fitparser.NewDecoder(data)
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if err != nil {
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log.Fatal(err)
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}
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// Decode messages
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messages, err := decoder.Decode()
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if err != nil {
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log.Fatal(err)
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}
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// Process messages
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fmt.Printf("Decoded %d messages\n", len(messages))
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for _, msg := range messages {
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switch msg.Num {
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case fitparser.MesgNumFileId:
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if fileType, ok := msg.GetFieldValueUint8(fitparser.FieldFileIdType); ok {
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fmt.Printf("File Type: %s\n", fitparser.GetFileTypeName(fileType))
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}
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case fitparser.MesgNumRecord:
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// Get timestamp
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if timestamp, ok := msg.GetFieldValueUint32(fitparser.FieldRecordTimestamp); ok {
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t := fitparser.ConvertFITTimestamp(timestamp)
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fmt.Printf("Record at %s\n", t.Format("2006-01-02 15:04:05"))
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}
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// Get heart rate
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if hr, ok := msg.GetFieldValueUint8(fitparser.FieldRecordHeartRate); ok && hr != fitparser.Uint8Invalid {
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fmt.Printf(" Heart Rate: %d bpm\n", hr)
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}
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// Get position (if available)
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if lat, ok := msg.Fields[fitparser.FieldRecordPositionLat]; ok {
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if latInt, ok := lat.(int32); ok && latInt != fitparser.Sint32Invalid {
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latDeg := fitparser.ConvertSemicirclesToDegrees(latInt)
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if lon, ok := msg.Fields[fitparser.FieldRecordPositionLong]; ok {
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if lonInt, ok := lon.(int32); ok && lonInt != fitparser.Sint32Invalid {
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lonDeg := fitparser.ConvertSemicirclesToDegrees(lonInt)
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fmt.Printf(" Position: %.6f, %.6f\n", latDeg, lonDeg)
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}
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}
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}
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}
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}
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}
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}
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```
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## API Documentation
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### Creating a Decoder
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```go
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// From byte slice
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data, _ := os.ReadFile("activity.fit")
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decoder, err := fitparser.NewDecoder(data)
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// Enable/disable CRC checking (enabled by default)
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decoder.EnableCRCCheck(false)
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```
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### Decoding Files
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```go
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// Decode all messages
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messages, err := decoder.Decode()
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// Check file integrity only
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err := fitparser.CheckIntegrity(data)
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// Check if data is a FIT file
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if fitparser.IsFIT(data) {
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// Process FIT file
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}
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```
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### Working with Messages
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```go
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for _, msg := range messages {
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// Get message type name
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name := fitparser.GetMessageName(msg.Num)
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// Access fields by field number
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if value, ok := msg.GetFieldValue(fieldNum); ok {
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// Process value
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}
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// Type-safe field accessors
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uint8Val, ok := msg.GetFieldValueUint8(fieldNum)
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uint16Val, ok := msg.GetFieldValueUint16(fieldNum)
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uint32Val, ok := msg.GetFieldValueUint32(fieldNum)
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stringVal, ok := msg.GetFieldValueString(fieldNum)
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// Direct field access
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if value, ok := msg.Fields[fieldNum]; ok {
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// Type assert as needed
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switch v := value.(type) {
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case uint8:
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// Handle uint8
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case uint32:
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// Handle uint32
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case []uint8:
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// Handle byte array
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case string:
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// Handle string
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}
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}
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}
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```
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### Utility Functions
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```go
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// Convert FIT timestamp to Go time.Time
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timestamp := uint32(12345678)
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t := fitparser.ConvertFITTimestamp(timestamp)
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// Convert semicircles to degrees (for GPS coordinates)
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latSemicircles := int32(464800000)
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latDegrees := fitparser.ConvertSemicirclesToDegrees(latSemicircles) // ~19.47 degrees
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// Get human-readable names
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fileTypeName := fitparser.GetFileTypeName(fitparser.FileTypeActivity) // "Activity"
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sportName := fitparser.GetSportName(fitparser.SportRunning) // "Running"
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messageName := fitparser.GetMessageName(fitparser.MesgNumRecord) // "Record"
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```
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## Common Message Types
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The parser includes constants for common FIT message types:
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- `MesgNumFileId` - File identification
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- `MesgNumRecord` - Activity data points (GPS, heart rate, power, etc.)
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- `MesgNumLap` - Lap summaries
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- `MesgNumSession` - Session summaries
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- `MesgNumActivity` - Activity summaries
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- `MesgNumEvent` - Events (start, stop, lap button, etc.)
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- `MesgNumDeviceInfo` - Device information
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- `MesgNumUserProfile` - User profile data
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## Field Numbers
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Common field numbers are defined as constants:
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### FileId Message
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- `FieldFileIdType` - File type
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- `FieldFileIdManufacturer` - Manufacturer ID
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- `FieldFileIdProduct` - Product ID
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- `FieldFileIdSerialNumber` - Device serial number
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- `FieldFileIdTimeCreated` - File creation timestamp
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### Record Message
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- `FieldRecordTimestamp` - Record timestamp
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- `FieldRecordPositionLat` - Latitude (semicircles)
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- `FieldRecordPositionLong` - Longitude (semicircles)
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- `FieldRecordAltitude` - Altitude
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- `FieldRecordHeartRate` - Heart rate (bpm)
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- `FieldRecordCadence` - Cadence (rpm)
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- `FieldRecordDistance` - Distance (meters)
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- `FieldRecordSpeed` - Speed (m/s)
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- `FieldRecordPower` - Power (watts)
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- `FieldRecordTemperature` - Temperature (°C)
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## Example: Processing an Activity File
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```go
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package main
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import (
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"fmt"
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"log"
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"os"
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"git.blackfinn.de/go/fit-parser/fitparser"
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)
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func main() {
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data, err := os.ReadFile("activity.fit")
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if err != nil {
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log.Fatal(err)
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}
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decoder, err := fitparser.NewDecoder(data)
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if err != nil {
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log.Fatal(err)
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}
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messages, err := decoder.Decode()
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if err != nil {
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log.Fatal(err)
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}
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// Count message types
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msgCounts := make(map[uint16]int)
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for _, msg := range messages {
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msgCounts[msg.Num]++
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}
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fmt.Println("Message Statistics:")
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for mesgNum, count := range msgCounts {
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fmt.Printf(" %s: %d\n", fitparser.GetMessageName(mesgNum), count)
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}
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// Process session data
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for _, msg := range messages {
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if msg.Num == fitparser.MesgNumSession {
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if sport, ok := msg.GetFieldValueUint8(fitparser.FieldSessionSport); ok {
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fmt.Printf("\nSport: %s\n", fitparser.GetSportName(sport))
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}
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if totalTime, ok := msg.GetFieldValueUint32(fitparser.FieldSessionTotalTimerTime); ok {
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fmt.Printf("Total Time: %.2f minutes\n", float64(totalTime)/1000.0/60.0)
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}
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if totalDist, ok := msg.GetFieldValueUint32(fitparser.FieldSessionTotalDistance); ok {
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fmt.Printf("Total Distance: %.2f km\n", float64(totalDist)/100000.0)
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}
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if avgHR, ok := msg.GetFieldValueUint8(fitparser.FieldSessionAvgHeartRate); ok {
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fmt.Printf("Average Heart Rate: %d bpm\n", avgHR)
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}
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if maxHR, ok := msg.GetFieldValueUint8(fitparser.FieldSessionMaxHeartRate); ok {
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fmt.Printf("Max Heart Rate: %d bpm\n", maxHR)
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}
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}
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}
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}
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```
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## Performance
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The parser is designed for efficiency:
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- Decodes activity files with thousands of records in milliseconds
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- Zero-allocation field decoding where possible
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- Optional CRC checking can be disabled for faster parsing
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- Memory-efficient streaming approach
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## Testing
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Run the test suite:
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```bash
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cd fitparser
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go test -v
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```
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Run benchmarks:
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```bash
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cd fitparser
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go test -bench=.
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```
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## Limitations
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- Write/encode functionality not yet implemented (decode only)
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- Some advanced features like subfields and components are not fully implemented
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- Developer fields are decoded but not interpreted
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## Contributing
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Contributions are welcome! Please feel free to submit issues or pull requests.
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## License
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This implementation is based on the official Garmin FIT SDK. Please refer to the FIT Protocol License for usage terms.
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## References
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- [Official FIT SDK](https://developer.garmin.com/fit/)
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- [FIT Protocol Documentation](https://developer.garmin.com/fit/protocol/)
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- [FIT File Format Specification](https://developer.garmin.com/fit/file-types/)
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## Acknowledgments
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This Go implementation was created by studying the C, C++, and Python implementations from the official Garmin FIT SDK.
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Reference in New Issue
Block a user