Bound FTP range transfers to requested size

CMakeLists.txt

@@ -1,6 +1,6 @@
 cmake_minimum_required(VERSION 3.20)
 
-project(libprozilla VERSION 1.2.0 LANGUAGES C)
+project(libprozilla VERSION 1.2.1 LANGUAGES C)
 
 include(CTest)
 

src/curl-retr.c

@@ -12,7 +12,9 @@ typedef struct {
   CURL *curl;
   int write_failed;
   int require_partial_response;
+  int range_complete;
   size_t bytes_written;
+  off_t expected_bytes;
 } curl_write_context;
 
 static CURLcode configure_curl(CURL *curl, connection_t *connection)
@@ -122,6 +124,20 @@ static size_t curl_write(void *data, size_t size, size_t count, void *opaque)
   if (size != 0 && count > SIZE_MAX / size)
     return 0;
   bytes = size * count;
+  if (ctx->expected_bytes > 0)
+    {
+      off_t remaining = ctx->expected_bytes - (off_t) ctx->bytes_written;
+      if (remaining <= 0)
+        {
+          ctx->range_complete = 1;
+          return 0;
+        }
+      if ((uintmax_t) bytes > (uintmax_t) remaining)
+        {
+          bytes = (size_t) remaining;
+          ctx->range_complete = 1;
+        }
+    }
   if (ctx->require_partial_response)
     {
       curl_easy_getinfo(ctx->curl, CURLINFO_RESPONSE_CODE, &response);
@@ -139,6 +155,8 @@ static size_t curl_write(void *data, size_t size, size_t count, void *opaque)
   ctx->bytes_written += bytes;
   connection_calc_ratebps(ctx->connection);
   connection_throttle_bps(ctx->connection);
+  if (ctx->range_complete)
+    return 0;
   return bytes;
 }
 
@@ -146,7 +164,7 @@ static uerr_t curl_get_file(connection_t *connection)
 {
   CURL *curl = curl_easy_init();
   CURLcode result;
-  curl_write_context ctx = { connection, curl, 0, 0, 0 };
+  curl_write_context ctx = { connection, curl, 0, 0, 0, 0, 0 };
   char range[96];
   long response = 0;
 
@@ -161,6 +179,8 @@ static uerr_t curl_get_file(connection_t *connection)
                    (intmax_t) connection->remote_startpos,
                    (intmax_t) (connection->remote_endpos - 1));
           curl_easy_setopt(curl, CURLOPT_RANGE, range);
+          ctx.expected_bytes =
+            connection->remote_endpos - connection->remote_startpos;
           if (connection->u.proto == URLHTTP
               || connection->u.proto == URLHTTPS)
             ctx.require_partial_response = 1;
@@ -181,7 +201,9 @@ static uerr_t curl_get_file(connection_t *connection)
       && (off_t) ctx.bytes_written
          != connection->remote_endpos - connection->remote_startpos)
     return READERR;
-  if (result == CURLE_OK && response < 400)
+  if ((ctx.expected_bytes > 0
+       && (off_t) ctx.bytes_written == ctx.expected_bytes)
+      || ((result == CURLE_OK || ctx.range_complete) && response < 400))
     {
       connection_change_status(connection, COMPLETED);
       return HOK;