added repocli

pkg/repocli/getman.go

@@ -0,0 +1,90 @@
+package repocli
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"fmt"
+	"net/http"
+	"strconv"
+	"strings"
+)
+
+func (cli *Client) GetManifest(ctx context.Context, rawrepo, tag string) (bool, string, []byte, error) {
+	var err error
+	var exist bool
+	var mime string
+	var man []byte
+
+	ref, err := NewRepository(rawrepo)
+	if err != nil {
+		return exist, mime, man, err
+	}
+	uri := ref.Manifest(tag)
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, uri, nil)
+	if err != nil {
+		return exist, mime, man, err
+	}
+	req.Header.Set("User-Agent", cli.userAgent)
+	req.Header.Set("Accept", "*/*")
+	resp, err := cli.httpClient.Do(req)
+	if err != nil {
+		return exist, mime, man, err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode == http.StatusNotFound {
+		return exist, mime, man, err
+	}
+	if resp.StatusCode != http.StatusOK {
+		err := fmt.Errorf("Unxected response code %s", resp.Status)
+		return exist, mime, man, err
+	}
+	contentLength := resp.Header.Get("Content-Length")
+	if contentLength == "" {
+		err = errors.New("Empty Content-Length header")
+		return exist, mime, man, err
+	}
+	manSize, err := strconv.ParseInt(contentLength, 10, 64)
+	if err != nil {
+		return exist, mime, man, err
+	}
+	mime = resp.Header.Get("Content-Type")
+	if mime == "" {
+		err := fmt.Errorf("Empty MIME type declaration")
+		return exist, mime, man, err
+	}
+	buffer := bytes.NewBuffer(nil)
+	recSize, err := Copy(ctx, buffer, resp.Body)
+	if manSize != recSize {
+		err := fmt.Errorf("Mismatch declared and actual body size, %d and %d", manSize, recSize)
+		return exist, mime, man, err
+	}
+	man = buffer.Bytes()
+
+	csum := resp.Header.Get("Docker-Content-Digest")
+	if csum == "" {
+		err := fmt.Errorf("Empty digest declaration")
+		return exist, mime, man, err
+	}
+	csum = strings.ToLower(csum)
+	switch DigestType(csum) {
+	case SHA256:
+		if csum != SHA256Digest(man) {
+			err := fmt.Errorf("Mismatch digest and actual declaration")
+			return exist, mime, man, err
+		}
+	case SHA512:
+		if csum != SHA256Digest(man) {
+			err := fmt.Errorf("Mismatch digest and actual declaration")
+			return exist, mime, man, err
+		}
+	default:
+		err := fmt.Errorf("Unknown digest type: %s", csum)
+		return exist, mime, man, err
+	}
+
+	exist = true
+	return exist, mime, man, err
+}