1 files changed, 153 insertions, 0 deletions
diff --git a/truncater.c b/truncater.c
new file mode 100644
index 0000000..d703406
--- /dev/null
+++ b/truncater.c
@@ -0,0 +1,153 @@
+/* ponysaytruncater
+ * Output truncater used by ponysay to stop
+ * large ponies from being printed badly.
+ * 
+ * Licensed under WTFPL
+ * See COPYING for details
+ */
+#include <stdio.h>
+#define  String   char*
+#define  boolean  char
+#define  true     1
+#define  false    0
+
+/* Stdin file descriptor ID */
+#define  STDIN  0
+
+/* The number of columns on the current line */
+static int col =  0;
+
+/* Escape sequence state */
+static int esc = 0;
+
+/* Last bytes as written */
+static boolean ok = true;
+
+void write(char b, int width);
+int toInt(String string);
+
+
+/* Mane method!
+ *   The only argument, in addition to the executed file,
+ *   should be the width of the terminal which you get by
+ *   adding <code>`tput cols || echo 0`</code> as an argument.
+ *   
+ * @param  argc  The number of startup arguments
+ * @param  argv  The startup arguments, the first is the file itself
+ * 
+ * @author  Mattias Andrée, maandree@kth.se
+ */
+void main(int argc, String* argv)
+{
+  int width = 0;
+  if (argc > 1)
+    width = toInt(*(argv + 1));
+  
+  char b = 0;
+  
+  if (width > 15) /* sanity */
+    while (read(STDIN, &b, 1))
+      write(b, width);
+  else
+    while (read(STDIN, &b, 1))
+      printf("%c", b);
+}
+
+/* Writes a character to stdout, iff it fits within the terminal
+ * 
+ * @param  b      The character (byte) to write
+ * @param  width  The width of the terminal
+ */
+void write(char b, int width)
+{
+  int i;
+  char tabstop;
+  
+  if (esc == 0)
+    {
+      if (b == '\n')
+	{
+	  if (col >= width)
+	    {
+	      /* Reset background colour */
+	      write('\e', width);
+	      write('[', width);
+	      write('4', width);
+	      write('9', width);
+	      write('m', width);
+	    }
+	  col = -1;
+	}
+      else if (b == '\t')
+	{
+	  /* Tab to next pos ≡₈ 0 */
+	  tabstop = 8 - (col & 7);
+	  for (i = 0; i < tabstop; i++)
+	    write(' ', width);
+	  return; /* (!) */
+	}
+      else if (b == '\e')
+	esc = 1;
+    }
+  else if (esc == 1)
+    {
+      if      (b == '[')  esc = 2;  /* CSI: CSI ends with a letter, m is for colour */
+      else if (b == ']')  esc = 3;  /* OSI: OSI P is for palette editing in Linux VT */
+      else                esc = 10; /* Nothing to see here, move along */
+    }
+  else if (esc == 2)
+    {
+      if ((('a' <= b) && (b <= 'z')) || (('A' <= b) && (b <= 'Z')))
+	esc = 10;
+    }
+  else if ((esc == 3) && (b == 'P'))
+    {
+      esc = ~0;
+    }
+  else if (esc < 0)
+    {
+      esc--;
+      if (esc == ~7)
+	esc = 10;
+    }
+  else
+    esc = 10;
+  
+  if (
+      /* Can be printed:
+	 within bounds  ∨
+	 ∨ escape sequence  ∨
+	 ∨ last with printed ∧ not first byte in character */
+      (col < width) ||
+      (esc != 0) ||
+      (ok && ((b & 0xC0) == 0x80)))
+    {
+      printf("%c", b);
+      if ((esc == 0) && ((b & 0xC0) != 0x80))
+	/* Count up columns of not in escape sequnce and */
+	col++; /* the byte is not the first byte in the character */
+      ok = true;
+    }
+  else
+    ok = false;
+  
+  if (esc == 10)
+    esc = 0;
+}
+
+/* Converts a string to an integer
+ * 
+ * @param   string  The string to convert
+ * @return          The integer represented by the string
+ */
+int toInt(String string)
+{
+  int rc = 0;
+  String str = string;
+  char c = 0;
+  
+  while ((c = *str++) != 0)
+    rc = (rc << 1) + (rc << 3) - (c & 15);
+  
+  return -rc;
+}