Modify _io's fd_buf_reader to do something slightly more useful: produce multiple buffers on demand.

src/lib/_io.rs

@@ -1,26 +1,46 @@
-type buf_reader = obj {
-  fn read(vec[u8] buf) -> uint;
+type buf_reader = unsafe obj {
+  fn read() -> vec[u8];
 };
 
-type buf_writer = obj {
-  fn write(vec[u8] buf) -> uint;
-};
+fn default_bufsz() -> uint {
+  ret uint(4096);
+}
 
-fn mk_buf_reader(str s) -> buf_reader {
+fn new_buf() -> vec[u8] {
+  let vec[u8] v = vec();
+  let uint i = default_bufsz();
+  while (i > uint(0)) {
+    i -= uint(1);
+    v += vec(u8(0));
+  }
+  // FIXME (issue #93): should be:
+  // ret _vec.alloc[u8](default_bufsz());
+}
+
+fn new_buf_reader(str s) -> buf_reader {
+
+  unsafe obj fd_buf_reader(int fd, mutable vec[u8] buf) {
+
+    fn read() -> vec[u8] {
+
+      // Ensure our buf is singly-referenced.
+      if (_vec.rustrt.refcount[u8](buf) != uint(1)) {
+        buf = new_buf();
+      }
+
+      auto len = _vec.len[u8](buf);
+      auto vbuf = _vec.buf[u8](buf);
+      auto count = os.libc.read(fd, vbuf, len);
 
-  obj fd_reader(int fd) {
-    fn read(vec[u8] v) -> uint {
-      auto len = _vec.len[u8](v);
-      auto buf = _vec.buf[u8](v);
-      auto count = os.libc.read(fd, buf, len);
       if (count < 0) {
         log "error filling buffer";
         log sys.rustrt.last_os_error();
         fail;
       } else {
-        ret uint(count);
+        ret buf;
       }
     }
+
     drop {
       os.libc.close(fd);
     }
@@ -32,5 +52,5 @@ fn mk_buf_reader(str s) -> buf_reader {
     log sys.rustrt.last_os_error();
     fail;
   }
-  ret fd_reader(fd);
+  ret fd_buf_reader(fd, new_buf());
 }