flipbit filter

concieggs/compiled/flipbit.c

@@ -1,22 +1,39 @@
+#define _POSIX_C_SOURCE 200809L
 #include <stdio.h>
 #include <stdlib.h>
 #include <assert.h>
 #include <unistd.h>
 
+void flipline(void) {
+  char* line = NULL;
+  size_t n;
+  ssize_t m;
+  while ((m = getline(&line, &n, stdin)) > 0) {
+    int i = rand() % m;
+    int j = rand() % 8;
+    line[i] ^= i<<j;
+    fputs(line, stdout);
+  }
+}
+
 int main(int argc, char* argv[]) {
-  assert(argc==2);
-  FILE* f = fopen(argv[1], "r+");
   srand(getpid());
-  assert(f != NULL);
-  assert(fseek(f, 0, SEEK_END) == 0);
-  int size = ftell(f);
-  if (size == 0) return 0;
-  int i = rand() % size;
-  int j = rand() % 8;
-  assert(fseek(f, i, SEEK_SET) == 0);
-  unsigned char c;
-  assert(fread(&c, 1, 1, f) == 1);
-  c ^= (1<<j);
-  assert(fseek(f, i, SEEK_SET) == 0);
-  assert(fwrite(&c, 1, 1, f) == 1);
+  if (argc == 1) {
+    flipline();
+  } else {
+    assert(argc==2);
+    FILE* f = fopen(argv[1], "r+");
+    assert(f != NULL);
+    assert(fseek(f, 0, SEEK_END) == 0);
+    int size = ftell(f);
+    if (size == 0) return 0;
+    int i = rand() % size;
+    int j = rand() % 8;
+    assert(fseek(f, i, SEEK_SET) == 0);
+    unsigned char c;
+    assert(fread(&c, 1, 1, f) == 1);
+    c ^= 1<<j;
+    assert(fseek(f, i, SEEK_SET) == 0);
+    assert(fwrite(&c, 1, 1, f) == 1);
+  }
 }

concieggs/filters/flipbit

@@ -0,0 +1,3 @@
+#!/bin/sh
+
+exec flipbit