use Response.ContentLength & clarify log messages (#49)

internal/releasesjson/checksum_downloader.go

@@ -121,12 +121,23 @@ func fileMapFromChecksums(checksums strings.Builder) (ChecksumFileMap, error) {
 	return csMap, nil
 }
 
-func compareChecksum(logger *log.Logger, r io.Reader, verifiedHashSum HashSum) error {
+func compareChecksum(logger *log.Logger, r io.Reader, verifiedHashSum HashSum, filename string, expectedSize int64) error {
 	h := sha256.New()
-	_, err := io.Copy(h, r)
+
+	// This may take a while depending on network connection as the io.Reader
+	// is expected to be http.Response.Body which streams the bytes
+	// on demand over the network.
+	logger.Printf("copying %q (%d bytes) to calculate checksum", filename, expectedSize)
+	bytesCopied, err := io.Copy(h, r)
 	if err != nil {
 		return err
 	}
+	logger.Printf("copied %d bytes of %q", bytesCopied, filename)
+
+	if expectedSize != 0 && bytesCopied != int64(expectedSize) {
+		return fmt.Errorf("unexpected size (downloaded: %d, expected: %d)",
+			bytesCopied, expectedSize)
+	}
 
 	calculatedSum := h.Sum(nil)
 	if !bytes.Equal(calculatedSum, verifiedHashSum) {

internal/releasesjson/downloader.go

@@ -12,7 +12,6 @@ import (
 	"os"
 	"path/filepath"
 	"runtime"
-	"strconv"
 
 	"github.com/hashicorp/hc-install/internal/httpclient"
 )
@@ -95,14 +94,16 @@ func (d *Downloader) DownloadAndUnpack(ctx context.Context, pv *ProductVersion,
 			contentType, zipMimeTypes)
 	}
 
+	expectedSize := resp.ContentLength
+
 	if d.VerifyChecksum {
-		d.Logger.Printf("calculating checksum of %q", pb.Filename)
+		d.Logger.Printf("verifying checksum of %q", pb.Filename)
 		// provide extra reader to calculate & compare checksum
 		var buf bytes.Buffer
 		r := io.TeeReader(resp.Body, &buf)
 		pkgReader = &buf
 
-		err := compareChecksum(d.Logger, r, verifiedChecksum)
+		err := compareChecksum(d.Logger, r, verifiedChecksum, pb.Filename, expectedSize)
 		if err != nil {
 			return err
 		}
@@ -114,21 +115,17 @@ func (d *Downloader) DownloadAndUnpack(ctx context.Context, pv *ProductVersion,
 	}
 	defer pkgFile.Close()
 
-	d.Logger.Printf("copying downloaded file to %s", pkgFile.Name())
+	d.Logger.Printf("copying %q (%d bytes) to %s", pb.Filename, expectedSize, pkgFile.Name())
+	// Unless the bytes were already downloaded above for checksum verification
+	// this may take a while depending on network connection as the io.Reader
+	// is expected to be http.Response.Body which streams the bytes
+	// on demand over the network.
 	bytesCopied, err := io.Copy(pkgFile, pkgReader)
 	if err != nil {
 		return err
 	}
 	d.Logger.Printf("copied %d bytes to %s", bytesCopied, pkgFile.Name())
 
-	expectedSize := 0
-	if length := resp.Header.Get("content-length"); length != "" {
-		var err error
-		expectedSize, err = strconv.Atoi(length)
-		if err != nil {
-			return err
-		}
-	}
 	if expectedSize != 0 && bytesCopied != int64(expectedSize) {
 		return fmt.Errorf("unexpected size (downloaded: %d, expected: %d)",
 			bytesCopied, expectedSize)