remove getsxts for better function readb

Decoding input is read faster now.
With this, all options have been tuned to a reasonable degree.

input.c

@@ -1,19 +1,29 @@
 #include "input.h"
 
 #define PADDING  '='
-#define SXTETBUF  4
 
 int
-getsxts(FILE *fp, unsigned char *s)
+readb(FILE *fp, unsigned char *s, int slen)
 {
-    int c, n, pad;
+    int read, tread;
+    unsigned char *send, *sbeg;
+    unsigned char *l, *r;
+    
+    read = tread = 0;
+    sbeg = l = r = s;
+    while (tread < slen && (read = fread(l, sizeof(*l), slen-tread, fp))) {
+        tread += read;
+        send = s + tread;
+        for (r = l; r < send; ++r)
+            if (*r != '\n')
+                *l++ = *r;
+        tread -= r - l;
+        if (l > sbeg) {
+            for (--l; *l == PADDING; --l)
+                ;
+            ++l;
+        }
+    }
 
-    n = pad = 0;
-    while (n < SXTETBUF && (c = fgetc(fp)) != EOF && c != PADDING)
-        if (c != '\n')
-            s[n++] = c;
-    while (n+pad < SXTETBUF)
-        s[n+pad++] = PADDING;
-
-    return n;
+    return l-sbeg;
 }