lib_ropes: better buffering in equalsFile, cleanups

lib/pure/ropes.nim

@@ -340,29 +340,46 @@ proc addf*(c: var Rope, frmt: string, args: openArray[Rope]) {.
   ## shortcut for ``add(c, frmt % args)``.
   add(c, frmt % args)
 
+const
+  bufSize = 1024              # 1 KB is reasonable
+
 proc equalsFile*(r: Rope, f: File): bool {.rtl, extern: "nro$1File".} =
   ## returns true if the contents of the file `f` equal `r`.
-  var bufSize = 1024 # reasonable start value
+  var 
-  var buf = alloc(bufSize)
+    buf: array[bufSize, char]
-  for s in leaves(r):
+    bpos = buf.len
-    if s.len > bufSize:
+    blen = buf.len
-      bufSize = max(bufSize * 2, s.len)
-      buf = realloc(buf, bufSize)
-    var readBytes = readBuffer(f, buf, s.len)
-    result = readBytes == s.len and equalMem(buf, cstring(s), s.len)
-    if not result: break
-  if result:
-    result = readBuffer(f, buf, 1) == 0 # really at the end of file?
-  dealloc(buf)
 
-proc equalsFile*(r: Rope, f: string): bool {.rtl, extern: "nro$1Str".} =
+  for s in leaves(r):
+    var spos = 0
+    let slen = s.len
+    while spos < slen:
+      if bpos == blen:
+        # Read more data
+        bpos = 0
+        blen = readBuffer(f, addr(buf[0]), buf.len)
+        if blen == 0:  # no more data in file
+          result = false
+          return
+      let n = min(blen - bpos, slen - spos)
+      # TODO There's gotta be a better way of comparing here...
+      if not equalMem(addr(buf[bpos]), 
+                      cast[pointer](cast[int](cstring(s))+spos), n):
+        result = false
+        return
+      spos += n
+      bpos += n
+
+  result = readBuffer(f, addr(buf[0]), 1) == 0  # check that we've read all
+
+proc equalsFile*(r: Rope, filename: string): bool {.rtl, extern: "nro$1Str".} =
   ## returns true if the contents of the file `f` equal `r`. If `f` does not
   ## exist, false is returned.
-  var bin: File
+  var f: File
-  result = open(bin, f)
+  result = open(f, filename)
   if result:
-    result = equalsFile(r, bin)
+    result = equalsFile(r, f)
-    close(bin)
+    close(f)
 
 new(N) # init dummy node for splay algorithm