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download and read db file in memory using only go functions #4

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download and read db file in memory using only go functions #4

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82 changes: 43 additions & 39 deletions generate/main.go
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Original file line number Diff line number Diff line change
@@ -1,10 +1,13 @@
package main

import (
"archive/zip"
"bytes"
"encoding/csv"
"fmt"
"io"
"log"
"net/http"
"os"
"os/exec"
"sort"
Expand All @@ -15,7 +18,6 @@ import (
)

const (
workDir = "tzdb"
dbFilename = "timezonedb.csv.zip"
dbURL = "https://timezonedb.com/files/" + dbFilename
countryFile = "country.csv"
Expand Down Expand Up @@ -53,7 +55,6 @@ func (a byZoneName) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
func (a byZoneName) Less(i, j int) bool { return a[i].Name < a[j].Name }

func main() {

tmpl, err := template.New("gen").Parse(output)
if err != nil {
log.Fatal("ERROR parsing template:", err)
Expand All @@ -64,32 +65,54 @@ func main() {
log.Fatal("ERROR determining current working DIR:", err)
}

cmd := exec.Command("mkdir", "-p", workDir)
err = cmd.Run()
resp, err := http.DefaultClient.Get(dbURL)
if err != nil {
log.Fatal("ERROR creating working DIR:", err)
log.Fatal("ERROR download database file", err)
}
defer resp.Body.Close()
if resp.StatusCode != http.StatusOK {
log.Fatal("ERROR download database file: response status is:", resp.Status)
}

err = os.Chdir(workDir)
buff := bytes.NewBuffer([]byte{})
size, err := io.Copy(buff, resp.Body)
if err != nil {
log.Fatal("ERROR switching to working DIR:", err)
log.Fatal(err)
}

cmd = exec.Command("curl", "-O", dbURL)

err = cmd.Run()
ar, err := zip.NewReader(bytes.NewReader(buff.Bytes()), size)
if err != nil {
log.Fatal("ERROR downloading file:", err)
log.Fatal("ERROR read zip:", err)
}

cmd = exec.Command("unzip", dbFilename)

err = cmd.Run()
if err != nil {
log.Fatal("ERROR Unzipping file:", err)
var cf, zf io.ReadCloser
for _, f := range ar.File {
switch f.Name {
case countryFile:
cf, err = f.Open()
if err != nil {
log.Fatal("ERROR open archive file:", err)
}
case zoneFile:
zf, err = f.Open()
if err != nil {
log.Fatal("ERROR open archive file:", err)
}
default:
continue
}
}
if cf == nil {
log.Fatal("ERROR country file not found in archive")
}
if zf == nil {
log.Fatal("ERROR zones file not found in archive")
}
defer func() {
cf.Close()
zf.Close()
}()

countries, err := process()
countries, err := process(cf, zf)
if err != nil {
log.Fatal("ERROR processing files:", err)
}
Expand All @@ -113,31 +136,18 @@ func main() {
f.Close()

// after file written run gofmt on file
cmd = exec.Command("gofmt", "-s", "-w", outputFile)
cmd := exec.Command("gofmt", "-s", "-w", outputFile)
if err = cmd.Run(); err != nil {
log.Fatal("ERROR running gofmt:", err)
}

err = os.RemoveAll(workDir)
if err != nil {
log.Fatal("ERROR removing working DIR:", err)
}

}

func process() ([]tz.Country, error) {

var err error
func process(cf, zf io.ReadCloser) ([]tz.Country, error) {

cmap := make(map[string]int)
countries := make([]tz.Country, 0, 10)

// process countries
cf, err := os.Open(countryFile)
if err != nil {
return nil, err
}
defer cf.Close()

r := csv.NewReader(cf)

Expand All @@ -162,12 +172,6 @@ func process() ([]tz.Country, error) {

// process zones

zf, err := os.Open(zoneFile)
if err != nil {
return nil, err
}
defer zf.Close()

r = csv.NewReader(zf)

for {
Expand Down