do not crash on invalid utf-8

grcat

@@ -4,6 +4,34 @@ from __future__ import print_function
 
 import sys, os, string, re, signal, errno
 
+
+# redefine readline to pass invalidly encoded characters unchanged, if possible
+if hasattr(sys.stdin, 'reconfigure') and hasattr(sys.stdout, 'reconfigure'):
+    # at least python3.7
+    sys.stdin.reconfigure(errors='surrogateescape')
+    sys.stdout.reconfigure(errors='surrogateescape')
+    myreadline = sys.stdin.readline
+    myprint = print
+else:
+    if hasattr(sys.stdin, 'buffer'):
+        # python3
+        buffer_reader = sys.stdin.buffer
+    else:
+        buffer_reader = sys.stdin
+    def myreadline():
+        for line in buffer_reader:
+            try:
+                decoded = line.decode('utf-8', errors='surrogateescape')
+            except (UnicodeDecodeError, LookupError):
+                decoded = line.decode('utf-8', errors='ignore')
+            return decoded
+        return ''
+    def myprint(x):
+        try:
+            print(x)
+        except UnicodeEncodeError:
+            print(x.encode('utf-8', errors='replace').decode('utf-8'))
+
 #some default definitions
 colours = {
             'none'       :    "",
@@ -175,9 +203,9 @@ while not is_last:
 prevcolour = colours['default']
 prevcount = "more"
 blockflag = 0
-freadline = sys.stdin.readline
+
 while 1:
-    line = freadline()
+    line = myreadline()
     if line == "" :
         break
     if line[-1] in '\r\n':
@@ -275,7 +303,7 @@ while 1:
                 clineprev = cline[i]
         nline = nline + colours['default']
         try:
-            print(nline)
+            myprint(nline)
         except IOError as e:
             if e.errno == errno.EPIPE:
                 break