packer-cn/common/download.go

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package common
import (
"bytes"
"crypto/md5"
"crypto/sha1"
"crypto/sha256"
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"encoding/hex"
"errors"
"fmt"
"hash"
"io"
"log"
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"net/http"
"net/url"
"os"
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"runtime"
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)
// DownloadConfig is the configuration given to instantiate a new
// download instance. Once a configuration is used to instantiate
// a download client, it must not be modified.
type DownloadConfig struct {
// The source URL in the form of a string.
Url string
// This is the path to download the file to.
TargetPath string
// DownloaderMap maps a schema to a Download.
DownloaderMap map[string]Downloader
// If true, this will copy even a local file to the target
// location. If false, then it will "download" the file by just
// returning the local path to the file.
CopyFile bool
// The hashing implementation to use to checksum the downloaded file.
Hash hash.Hash
// The checksum for the downloaded file. The hash implementation configuration
// for the downloader will be used to verify with this checksum after
// it is downloaded.
Checksum []byte
}
// A DownloadClient helps download, verify checksums, etc.
type DownloadClient struct {
config *DownloadConfig
downloader Downloader
}
// HashForType returns the Hash implementation for the given string
// type, or nil if the type is not supported.
func HashForType(t string) hash.Hash {
switch t {
case "md5":
return md5.New()
case "sha1":
return sha1.New()
case "sha256":
return sha256.New()
default:
return nil
}
}
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// NewDownloadClient returns a new DownloadClient for the given
// configuration.
func NewDownloadClient(c *DownloadConfig) *DownloadClient {
if c.DownloaderMap == nil {
c.DownloaderMap = map[string]Downloader{
"http": new(HTTPDownloader),
}
}
return &DownloadClient{config: c}
}
// A downloader is responsible for actually taking a remote URL and
// downloading it.
type Downloader interface {
Cancel()
Download(io.Writer, *url.URL) error
Progress() uint
Total() uint
}
func (d *DownloadClient) Cancel() {
// TODO(mitchellh): Implement
}
func (d *DownloadClient) Get() (string, error) {
// If we already have the file and it matches, then just return the target path.
if verify, _ := d.VerifyChecksum(d.config.TargetPath); verify {
log.Println("Initial checksum matched, no download needed.")
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return d.config.TargetPath, nil
}
url, err := url.Parse(d.config.Url)
if err != nil {
return "", err
}
log.Printf("Parsed URL: %#v", url)
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// Files when we don't copy the file are special cased.
var finalPath string
if url.Scheme == "file" && !d.config.CopyFile {
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finalPath = url.Path
// Remove forward slash on absolute Windows file URLs before processing
if runtime.GOOS == "windows" && finalPath[0] == '/' {
finalPath = finalPath[1:len(finalPath)]
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}
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} else {
finalPath = d.config.TargetPath
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var ok bool
d.downloader, ok = d.config.DownloaderMap[url.Scheme]
if !ok {
return "", fmt.Errorf("No downloader for scheme: %s", url.Scheme)
}
// Otherwise, download using the downloader.
f, err := os.Create(finalPath)
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if err != nil {
return "", err
}
defer f.Close()
log.Printf("Downloading: %s", url.String())
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err = d.downloader.Download(f, url)
if err != nil {
return "", err
}
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}
if d.config.Hash != nil {
var verify bool
verify, err = d.VerifyChecksum(finalPath)
if err == nil && !verify {
err = fmt.Errorf("checksums didn't match expected: %s", hex.EncodeToString(d.config.Checksum))
}
}
return finalPath, err
}
// PercentProgress returns the download progress as a percentage.
func (d *DownloadClient) PercentProgress() int {
if d.downloader == nil {
return -1
}
return int((float64(d.downloader.Progress()) / float64(d.downloader.Total())) * 100)
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}
// VerifyChecksum tests that the path matches the checksum for the
// download.
func (d *DownloadClient) VerifyChecksum(path string) (bool, error) {
if d.config.Checksum == nil || d.config.Hash == nil {
return false, errors.New("Checksum or Hash isn't set on download.")
}
f, err := os.Open(path)
if err != nil {
return false, err
}
defer f.Close()
log.Printf("Verifying checksum of %s", path)
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d.config.Hash.Reset()
io.Copy(d.config.Hash, f)
return bytes.Compare(d.config.Hash.Sum(nil), d.config.Checksum) == 0, nil
}
// HTTPDownloader is an implementation of Downloader that downloads
// files over HTTP.
type HTTPDownloader struct {
progress uint
total uint
}
func (*HTTPDownloader) Cancel() {
// TODO(mitchellh): Implement
}
func (d *HTTPDownloader) Download(dst io.Writer, src *url.URL) error {
log.Printf("Starting download: %s", src.String())
req, err := http.NewRequest("GET", src.String(), nil)
if err != nil {
return err
}
httpClient := &http.Client{
Transport: &http.Transport{
Proxy: http.ProxyFromEnvironment,
},
}
resp, err := httpClient.Do(req)
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if err != nil {
return err
}
if resp.StatusCode != 200 {
log.Printf(
"Non-200 status code: %d. Getting error body.", resp.StatusCode)
errorBody := new(bytes.Buffer)
io.Copy(errorBody, resp.Body)
return fmt.Errorf("HTTP error '%d'! Remote side responded:\n%s",
resp.StatusCode, errorBody.String())
}
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d.progress = 0
d.total = uint(resp.ContentLength)
var buffer [4096]byte
for {
n, err := resp.Body.Read(buffer[:])
if err != nil && err != io.EOF {
return err
}
d.progress += uint(n)
if _, werr := dst.Write(buffer[:n]); werr != nil {
return werr
}
if err == io.EOF {
break
}
}
return nil
}
func (d *HTTPDownloader) Progress() uint {
return d.progress
}
func (d *HTTPDownloader) Total() uint {
return d.total
}