Reduce the number of HTTP HEAD requests

- Removed redundant http head requests that were used to query
  filesizes, even after the filesize was known already.

src/download.rs

@@ -74,20 +74,22 @@ pub fn url_to_filename(url: &str) -> String {
     file_name.split("?").next().unwrap().to_string()
 }
 
-pub async fn download_feedback(url: &str, into_file: &str, rep: DlReporter) -> ResBE<()> {
+pub async fn download_feedback(url: &str, into_file: &str, rep: DlReporter, content_length: Option<u64>) -> ResBE<()> {
 
-    download_feedback_chunks(url, into_file, rep, None, false).await
+    download_feedback_chunks(url, into_file, rep, None, false, content_length).await
 
 }
 
-pub async fn download_feedback_chunks(url: &str, into_file: &str, rep: DlReporter, from_to: Option<(u64, u64)>, seek_from: bool) -> ResBE<()> {
+pub async fn download_feedback_chunks(url: &str, into_file: &str, rep: DlReporter, from_to: Option<(u64, u64)>, seek_from: bool, content_length: Option<u64>) -> ResBE<()> {
     let into_file = Path::new(into_file);
     
-    let (mut content_length, range_supported) = http_get_filesize_and_range_support(url).await?;
+    let mut content_length = match content_length {
-
+        Some(it) => it,
-    if from_to != None && !range_supported{
+        None => {
-        return Err(DlError::Other("Server doesn't support range header".to_string()).into());
+            let (content_length, _) = http_get_filesize_and_range_support(url).await?;
+            content_length
         }
+    };
 
     // Send the HTTP request to download the given link
     let mut req = reqwest::Client::new()
@@ -223,9 +225,15 @@ pub async fn download_feedback_chunks(url: &str, into_file: &str, rep: DlReporte
 
 // This will spin up multiple tasks that and manage the status updates for them.
 // The combined status will be reported back to the caller
-pub async fn download_feedback_multi(url: &str, into_file: &str, rep: DlReporter, conn_count: i32) -> ResBE<()> {
+pub async fn download_feedback_multi(url: &str, into_file: &str, rep: DlReporter, conn_count: i32, content_length: Option<u64>) -> ResBE<()> {
 
+    let content_length = match content_length {
+        Some(it) => it,
+        None => {
             let (content_length, _) = http_get_filesize_and_range_support(url).await?;
+            content_length
+        }
+    };
     
     // Create zeroed file with 1 byte too much. This will be truncated on download
     // completion and can indicate that the file is not suitable for continuation
@@ -260,7 +268,9 @@ pub async fn download_feedback_multi(url: &str, into_file: &str, rep: DlReporter
                 from_to.1 += rest;
             }
 
-            download_feedback_chunks(&url, &into_file, rep, Some(from_to), true).await.map_err(|e| e.to_string())
+            let specific_content_length = from_to.1 - from_to.0 + 1;
+
+            download_feedback_chunks(&url, &into_file, rep, Some(from_to), true, Some(specific_content_length)).await.map_err(|e| e.to_string())
 
         }))
     }

src/errors.rs

@@ -4,6 +4,7 @@ use std::fmt::{ self, Display, Formatter };
 /// Result Boxed Error
 pub type ResBE<T> = Result<T, Box<dyn Error>>;
 
+#[allow(unused)]
 #[derive(Clone, Debug)]
 pub enum DlError {
     BadHttpStatus,

src/main.rs

@@ -240,10 +240,8 @@ async fn download_multiple(urls: Vec<String>, outdir: &str, file_count: i32, con
                     .to_str().unwrap().to_string();
                 let path_into_file = Path::new(&into_file);
 
-                // If file with same name is present locally, check filesize
+                let (filesize, range_supported) = match download::http_get_filesize_and_range_support(&url).await {
-                if path_into_file.exists() {
+                    Ok((filesize, range_supported)) => (filesize, range_supported),
-                    let filesize = match download::http_get_filesize_and_range_support(&url).await {
-                        Ok((filesize, _)) => filesize,
                     Err(_e) => {
                         rep.send(
                             DlStatus::Message(format!("Error while querying metadata: {}", url))
@@ -252,6 +250,9 @@ async fn download_multiple(urls: Vec<String>, outdir: &str, file_count: i32, con
                     }
                 };
             
+                // If file with same name is present locally, check filesize
+                if path_into_file.exists() {
+
                     let local_filesize = std::fs::metadata(path_into_file).unwrap().len();
             
                     if filesize == local_filesize {
@@ -263,13 +264,21 @@ async fn download_multiple(urls: Vec<String>, outdir: &str, file_count: i32, con
                 }
 
                 if conn_count == 1 {
-                    if let Err(_e) = download::download_feedback(&url, &into_file, rep.clone()).await {
+                    if let Err(_e) = download::download_feedback(&url, &into_file, rep.clone(), Some(filesize)).await {
                         rep.send(DlStatus::DoneErr {
                             filename: into_file.to_string()
                         });
                     }
                 } else {
-                    if let Err(_e) = download::download_feedback_multi(&url, &into_file, rep.clone(), conn_count).await {
+                    
+                    if !range_supported {
+                        rep.send(
+                            DlStatus::Message(format!("Error Server does not support range header: {}", url))
+                        );
+                        continue;
+                    }
+
+                    if let Err(_e) = download::download_feedback_multi(&url, &into_file, rep.clone(), conn_count, Some(filesize)).await {
                         rep.send(DlStatus::DoneErr {
                             filename: into_file.to_string()
                         });