Solve challenge 4

ex04/main.c

@@ -0,0 +1,63 @@
+#include "utils.h"
+#include <ctype.h>
+#include <stdio.h>
+
+int main(int argc, char *argv[]) {
+  if (argc < 2) {
+    printf("Usage: %s <filename>\n", argv[0]);
+    return EXIT_FAILURE;
+  }
+
+  FILE *fp = fopen(argv[1], "r");
+  if (fp == NULL) {
+    printf("Error opening file %s\n", argv[1]);
+    return EXIT_FAILURE;
+  }
+
+  printf("line | key | score | cleartext\n");
+  printf("-----+-----+-------+-------------------------------\n");
+
+  unsigned int line_count = 0;
+  char *line = NULL;
+  size_t line_length = 0;
+  ssize_t nread = 0;
+  size_t len;
+
+  while ((nread = getline(&line, &line_length, fp)) != -1) {
+    line_count++;
+
+    line[60] = '\0';
+    // printf("%3u: %s\n", line_count, line);
+    unsigned char buf[512] = {0};
+    len = hex_to_bytes(buf, line);
+
+    unsigned char cur[512] = {'\0'};
+    for (char c = 32; c < 127; ++c) {
+      for (size_t i = 0; i < len; ++i) {
+        cur[i] = buf[i] ^ c;
+      }
+      double score = frequency_score(cur, len);
+      if (score < 40.0) {
+        printf("%4u | %c   | %5.1f | ", line_count, c,
+               score);
+        for (size_t i = 0; i < len; ++i) {
+	  if (isprint(cur[i])) {
+	    putchar(cur[i]);
+	  } else if (cur[i] == '\n') {
+	    printf("\\n");
+	  }
+        }
+	printf("\n");
+      }
+    }
+  }
+
+  free(line);
+
+  if (fclose(fp)) {
+    printf("Error closing file %s\n", argv[1]);
+    return EXIT_FAILURE;
+  }
+
+  return EXIT_SUCCESS;
+}