Golang : How to split or chunking a file to smaller pieces?
Problem :
You have a big file and you want to split / chunk the file into smaller pieces. How to do that in Golang?
Solution :
- Calculate the size of each chunk that you want to split the file into.
- Read the file content into a buffer(created according to the calculated chunk size).
- Write the buffer content into individual pieces.
Here you go :
package main
import (
"fmt"
"io/ioutil"
"math"
"os"
"strconv"
)
func main() {
fileToBeChunked := "./somebigfile"
file, err := os.Open(fileToBeChunked)
if err != nil {
fmt.Println(err)
os.Exit(1)
}
defer file.Close()
fileInfo, _ := file.Stat()
var fileSize int64 = fileInfo.Size()
const fileChunk = 1 * (1 << 20) // 1 MB, change this to your requirement
// calculate total number of parts the file will be chunked into
totalPartsNum := uint64(math.Ceil(float64(fileSize) / float64(fileChunk)))
fmt.Printf("Splitting to %d pieces.\n", totalPartsNum)
for i := uint64(0); i < totalPartsNum; i++ {
partSize := int(math.Min(fileChunk, float64(fileSize-int64(i*fileChunk))))
partBuffer := make([]byte, partSize)
file.Read(partBuffer)
// write to disk
fileName := "somebigfile_" + strconv.FormatUint(i, 10)
_, err := os.Create(fileName)
if err != nil {
fmt.Println(err)
os.Exit(1)
}
// write/save buffer to disk
ioutil.WriteFile(fileName, partBuffer, os.ModeAppend)
fmt.Println("Split to : ", fileName)
}
}
Sample output :
Splitting to 5 pieces.
Split to : somebigfile_1
Split to : somebigfile_2
Split to : somebigfile_3
Split to : somebigfile_4
References :
https://www.socketloop.com/tutorials/golang-convert-cast-int64-to-string
See also : Golang : Upload big file (larger than 100MB) to AWS S3 with multipart upload
By Adam Ng
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