made some char * into const char * and I removed the check for size > 0

in the add_buffer function.

lib/http.c

@@ -104,7 +104,7 @@
  * be sent in one go.
  */
 static CURLcode
- add_buffer(send_buffer *in, void *inptr, size_t size);
+ add_buffer(send_buffer *in, const void *inptr, size_t size);
 
 /*
  * add_buffer_init() returns a fine buffer struct
@@ -148,7 +148,7 @@ size_t add_buffer_send(int sockfd, struct connectdata *conn, send_buffer *in)
  * add_bufferf() builds a buffer from the formatted input
  */
 static
-CURLcode add_bufferf(send_buffer *in, char *fmt, ...)
+CURLcode add_bufferf(send_buffer *in, const char *fmt, ...)
 {
   CURLcode result = CURLE_OUT_OF_MEMORY;
   char *s;
@@ -168,32 +168,30 @@ CURLcode add_bufferf(send_buffer *in, char *fmt, ...)
  * add_buffer() appends a memory chunk to the existing one
  */
 static
-CURLcode add_buffer(send_buffer *in, void *inptr, size_t size)
+CURLcode add_buffer(send_buffer *in, const void *inptr, size_t size)
 {
   char *new_rb;
   int new_size;
 
-  if(size > 0) {
-    if(!in->buffer ||
-       ((in->size_used + size) > (in->size_max - 1))) {
-      new_size = (in->size_used+size)*2;
-      if(in->buffer)
-        /* we have a buffer, enlarge the existing one */
-        new_rb = (char *)realloc(in->buffer, new_size);
-      else
-        /* create a new buffer */
-        new_rb = (char *)malloc(new_size);
+  if(!in->buffer ||
+     ((in->size_used + size) > (in->size_max - 1))) {
+    new_size = (in->size_used+size)*2;
+    if(in->buffer)
+      /* we have a buffer, enlarge the existing one */
+      new_rb = (char *)realloc(in->buffer, new_size);
+    else
+      /* create a new buffer */
+      new_rb = (char *)malloc(new_size);
 
-      if(!new_rb)
-        return CURLE_OUT_OF_MEMORY;
+    if(!new_rb)
+      return CURLE_OUT_OF_MEMORY;
 
-      in->buffer = new_rb;
-      in->size_max = new_size;
-    }
-    memcpy(&in->buffer[in->size_used], inptr, size);
-      
-    in->size_used += size;
+    in->buffer = new_rb;
+    in->size_max = new_size;
   }
+  memcpy(&in->buffer[in->size_used], inptr, size);
+      
+  in->size_used += size;
 
   return CURLE_OK;
 }
@@ -240,7 +238,7 @@ int GetLine(int sockfd, char *buf, struct connectdata *conn)
  * This function checks the linked list of custom HTTP headers for a particular
  * header (prefix).
  */
-bool static checkheaders(struct UrlData *data, char *thisheader)
+static bool checkheaders(struct UrlData *data, const char *thisheader)
 {
   struct curl_slist *head;
   size_t thislen = strlen(thisheader);