Simplify Download to single-threaded flow

util.go

@@ -9,18 +9,17 @@ import (
 	"path/filepath"
 	"slices"
 	"strings"
-	"sync"
 
 	"golang.org/x/net/proxy"
 )
 
 var Debug = false
 var Tor = false
-var DownThreads = 8
+var Socks5Address = "127.0.0.1:9050"
 
 func getHttpClient() (*http.Client, error) {
 	if Tor {
-		dialer, err := proxy.SOCKS5("tcp", "127.0.0.1:9050", nil, proxy.Direct)
+		dialer, err := proxy.SOCKS5("tcp", Socks5Address, nil, proxy.Direct)
 		if err != nil {
 			return nil, err
 		}
@@ -120,8 +119,8 @@ func Download(manifest Manifest, downloadDir string, filen string) ([]byte, erro
 		if err != nil {
 			return nil, err
 		}
-		remContent = content
-		downloaded += len(content)
+		remContent = *content
+		downloaded += len(*content)
 
 		if Debug {
 			// save remainder to file in the fragments/ directory, prefix with gap
@@ -137,60 +136,21 @@ func Download(manifest Manifest, downloadDir string, filen string) ([]byte, erro
 	ret := make([]byte, manifest.Size)
 	totalMB := float32(manifest.Size) / 1024.0 / 1024.0
 
-	// A channel to signal the main goroutine to check for errors
-	doneChan := make(chan bool)
-
-	var wg sync.WaitGroup
-	wg.Add(DownThreads)
-	var mu sync.Mutex
-
-	fragChan := make(chan Fragment, DownThreads)
-	errChan := make(chan error, DownThreads)
-
-	// Start worker threads
-	for i := 0; i < DownThreads; i++ {
-		go func() {
-			defer wg.Done()
-			for fragment := range fragChan {
+	// Download all fragments serially to keep execution simple and deterministic.
+	for _, fragment := range manifest.Fragments {
 		url := transformShaToURL(fragment.Sha512, fragment.Size)
 		content, err := getContent(url)
 		if err != nil {
-					errChan <- err
-					return
+			return nil, err
 		}
-				mu.Lock()
-				downloaded += len(content) * len(fragment.Offsets)
+		downloaded += len(*content) * len(fragment.Offsets)
 		for _, offset := range fragment.Offsets {
-					trackFrag = append(trackFrag, Frag{Offset: offset, Size: len(content)})
-					copy(ret[offset:offset+len(content)], content)
+			trackFrag = append(trackFrag, Frag{Offset: offset, Size: len(*content)})
+			copy(ret[offset:offset+len(*content)], *content)
 		}
 		percent := float32(downloaded) / float32(manifest.Size) * 100.0
 		downedMB := float32(downloaded) / 1024.0 / 1024.0
 		fmt.Printf("\r\033[32mDownloaded\033[0m %fMB/%fMB (\033[36m%.2f%%\033[0m) of \033[33m%s\033[0m", downedMB, totalMB, percent, filen)
-				mu.Unlock()
-			}
-		}()
-	}
-
-	// A separate goroutine to wait for all workers to finish and then close the error channel
-	go func() {
-		wg.Wait()
-		close(doneChan)
-	}()
-
-	// Send fragments to workers
-	for _, fragment := range manifest.Fragments {
-		fragChan <- fragment
-	}
-	close(fragChan)
-
-	// Wait for workers to finish or an error to occur
-	select {
-	case <-doneChan:
-		// All workers finished successfully
-	case err := <-errChan:
-		// An error occurred
-		return nil, err
 	}
 
 	// sort trackFrag by Offset
@@ -221,7 +181,7 @@ func Download(manifest Manifest, downloadDir string, filen string) ([]byte, erro
 	return ret, nil
 }
 
-func getContent(url string) ([]byte, error) {
+func getContent(url string) (*[]byte, error) {
 	client, err := getHttpClient()
 	if err != nil {
 		return nil, err
@@ -241,7 +201,7 @@ func getContent(url string) ([]byte, error) {
 		return nil, err
 	}
 
-	return body, nil
+	return &body, nil
 }
 
 func transformShaToURL(sha512s string, size int) string {