- Matt Witherspoon fixed the flaw which made libcurl 7.16.0 always store

downloaded data in two buffers, just to be able to deal with a special HTTP
  pipelining case. That is now only activated for pipelined transfers. In
  Matt's case, it showed as a considerable performance difference,

CHANGES

@@ -6,6 +6,12 @@
 
                                   Changelog
 
+Daniel (3 January 2007)
+- Matt Witherspoon fixed the flaw which made libcurl 7.16.0 always store
+  downloaded data in two buffers, just to be able to deal with a special HTTP
+  pipelining case. That is now only activated for pipelined transfers. In
+  Matt's case, it showed as a considerable performance difference,
+
 Daniel (2 January 2007)
 - Victor Snezhko helped us fix bug report #1603712
   (http://curl.haxx.se/bug/view.cgi?id=1603712) (known bug #36) --limit-rate

RELEASE-NOTES

@@ -45,6 +45,7 @@ This release includes the following bugfixes:
  o libcurl.pc now uses Libs.private for "private" libs
  o --limit-rate (CURLOPT_MAX_SEND_SPEED_LARGE and CURLOPT_MAX_RECV_SPEED_LARGE)
    now work on windows again
+ o improved download performance by avoiding the unconditional "double copying"
 
 Other curl-related news:
 

lib/sendf.c

@@ -5,7 +5,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2006, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1998 - 2007, Daniel Stenberg, <daniel@haxx.se>, et al.
  *
  * This software is licensed as described in the file COPYING, which
  * you should have received as part of this distribution. The terms
@@ -46,6 +46,7 @@
 #include "connect.h" /* for the Curl_sockerrno() proto */
 #include "sslgen.h"
 #include "ssh.h"
+#include "multiif.h"
 
 #define _MPRINTF_REPLACE /* use the internal *printf() functions */
 #include <curl/mprintf.h>
@@ -453,7 +454,7 @@ CURLcode Curl_client_write(struct connectdata *conn,
   return CURLE_OK;
 }
 
-#define MIN(a,b) (a < b ? a : b)
+#define MIN(a,b) ((a) < (b) ? (a) : (b))
 
 /*
  * Internal read-from-socket function. This is meant to deal with plain
@@ -469,8 +470,10 @@ int Curl_read(struct connectdata *conn, /* connection data */
               ssize_t *n)               /* amount bytes read */
 {
   ssize_t nread;
-  size_t bytestocopy = MIN(conn->buf_len - conn->read_pos, sizerequested);
   size_t bytesfromsocket = 0;
+  char *buffertofill = NULL;
+  bool pipelining = (conn->data->multi &&
+                     Curl_multi_canPipeline(conn->data->multi));
 
   /* Set 'num' to 0 or 1, depending on which socket that has been sent here.
      If it is the second socket, we set num to 1. Otherwise to 0. This lets
@@ -479,6 +482,10 @@ int Curl_read(struct connectdata *conn, /* connection data */
 
   *n=0; /* reset amount to zero */
 
+  /* If session can pipeline, check connection buffer  */
+  if(pipelining) {
+    size_t bytestocopy = MIN(conn->buf_len - conn->read_pos, sizerequested);
+
     /* Copy from our master buffer first if we have some unread data there*/
     if (bytestocopy > 0) {
       memcpy(buf, conn->master_buffer + conn->read_pos, bytestocopy);
@@ -488,13 +495,19 @@ int Curl_read(struct connectdata *conn, /* connection data */
       *n = (ssize_t)bytestocopy;
       return CURLE_OK;
     }
-
     /* If we come here, it means that there is no data to read from the buffer,
      * so we read from the socket */
     bytesfromsocket = MIN(sizerequested, sizeof(conn->master_buffer));
+    buffertofill = conn->master_buffer;
+  }
+  else {
+    bytesfromsocket = MIN((long)sizerequested, conn->data->set.buffer_size ?
+                          conn->data->set.buffer_size : BUFSIZE);
+    buffertofill = buf;
+  }
 
   if(conn->ssl[num].use) {
-    nread = Curl_ssl_recv(conn, num, conn->master_buffer, bytesfromsocket);
+    nread = Curl_ssl_recv(conn, num, buffertofill, bytesfromsocket);
 
     if(nread == -1) {
       return -1; /* -1 from Curl_ssl_recv() means EWOULDBLOCK */
@@ -502,20 +515,20 @@ int Curl_read(struct connectdata *conn, /* connection data */
   }
 #ifdef USE_LIBSSH2
   else if (conn->protocol & PROT_SCP) {
-    nread = Curl_scp_recv(conn, num, conn->master_buffer, bytesfromsocket);
+    nread = Curl_scp_recv(conn, num, buffertofill, bytesfromsocket);
     /* TODO: return CURLE_OK also for nread <= 0
              read failures and timeouts ? */
   }
   else if (conn->protocol & PROT_SFTP) {
-    nread = Curl_sftp_recv(conn, num, conn->master_buffer, bytesfromsocket);
+    nread = Curl_sftp_recv(conn, num, buffertofill, bytesfromsocket);
   }
 #endif /* !USE_LIBSSH2 */
   else {
     if(conn->sec_complete)
-      nread = Curl_sec_read(conn, sockfd, conn->master_buffer,
+      nread = Curl_sec_read(conn, sockfd, buffertofill,
                             bytesfromsocket);
     else
-      nread = sread(sockfd, conn->master_buffer, bytesfromsocket);
+      nread = sread(sockfd, buffertofill, bytesfromsocket);
 
     if(-1 == nread) {
       int err = Curl_sockerrno();
@@ -529,10 +542,12 @@ int Curl_read(struct connectdata *conn, /* connection data */
   }
 
   if (nread >= 0) {
+    if(pipelining) {
       memcpy(buf, conn->master_buffer, nread);
-
       conn->buf_len = nread;
       conn->read_pos = nread;
+    }
+
     *n = nread;
   }