Add a copy file routine

Add io_file_cp() which can be used to copy an existing source file to
another location. We will need this for our new hash-based note file
names.

Signed-off-by: Lukas Fleischer <calcurse@cryptocrack.de>

src/calcurse.h

@@ -693,6 +693,7 @@ void             io_set_lock (void);
 unsigned         io_dump_pid (char *);
 unsigned         io_get_pid (char *);
 int              io_file_is_empty (char *);
+int              io_file_cp (const char *, const char *);
 
 /* keys.c */
 void      keys_init (void);

src/io.c

@@ -3050,3 +3050,36 @@ io_file_is_empty (char *file)
 
   return -1;
 }
+
+/*
+ * Copy an existing file to a new location.
+ */
+int
+io_file_cp (const char *src, const char *dst)
+{
+  FILE *fp_src, *fp_dst;
+  char *buffer[BUFSIZ];
+  unsigned int bytes_read;
+
+  if (!(fp_src = fopen (src, "rb")))
+    return 0;
+  if (!(fp_dst = fopen (dst, "wb")))
+    return 0;
+
+  while (!feof (fp_src))
+    {
+      bytes_read = fread (buffer, 1, BUFSIZ, fp_src);
+      if (bytes_read > 0)
+        {
+          if (fwrite (buffer, 1, bytes_read, fp_dst) != bytes_read)
+            return 0;
+        }
+      else
+        return 0;
+    }
+
+  fclose (fp_dst);
+  fclose (fp_src);
+
+  return 1;
+}