Add two features suggested by Mike Schiraldi (mike@reddit.com);

1. "autolinks" -- expand unbracketed urls into links
      (flag MKD_AUTOLINK, -fautolink in the markdown program)
   2. "safe links" -- don't linkify footnotes where the link protocol
      isn't a well-known protocol (currently http: https:,ftp:,news:)
      (flag MKD_SAFELINK, -fsafelink in the markdown program)

VERSION

@@ -1 +1 @@
-1.4.0
+1.4.1

generate.c

@@ -17,11 +17,6 @@
 #include "markdown.h"
 #include "amalloc.h"
 
-/* prefixes for <automatic links>
- */
-static char *autoprefix[] = { "http://", "https://", "ftp://", "news://" };
-#define SZAUTOPREFIX	(sizeof autoprefix / sizeof autoprefix[0])
-
 typedef int (*stfu)(const void*,const void*);
 
 
@@ -556,6 +551,24 @@ linkykey(int image, Footnote *val, MMIOT *f)
 }
 
 
+
+/* prefixes for <automatic links>
+ */
+static char *protocol[] = { "http://", "https://", "ftp://", "news://" };
+#define NRPROTOCOLS	(sizeof protocol / sizeof protocol[0])
+
+static int
+isautoprefix(char *text)
+{
+    int i;
+
+    for (i=0; i < NRPROTOCOLS; i++)
+	if ( strncasecmp(text, protocol[i], strlen(protocol[i])) == 0 )
+	    return 1;
+    return 0;
+}
+
+
 /*
  * all the tag types that linkylinky can produce are
  * defined by this structure. 
@@ -625,8 +638,14 @@ linkylinky(int image, MMIOT *f)
 
     if ( image )
 	tag = &imaget;
-    else if ( (f->flags & NO_PSEUDO_PROTO) || (tag = extratag(link.link)) == 0 )
+    else if ( (f->flags & NO_PSEUDO_PROTO) || (tag = extratag(link.link)) == 0 ) {
 	tag = &linkt;
+	if ( (f->flags & SAFELINK) && (T(link.link)[0] != '/')
+				   && !isautoprefix(T(link.link)) ) {
+	    mmiotseek(f, start);
+	    return 0;
+	}
+    }
 
     if ( f->flags & tag-> flags ) {
 	mmiotseek(f, start);
@@ -719,17 +738,19 @@ forbidden_tag(MMIOT *f)
  * spaminess of the rendered page.
  */
 static int
-maybe_tag_or_link(MMIOT *f)
+maybe_tag_or_link(MMIOT *f, int close)
 {
     char *text;
     int c, size, i;
-    int maybetag=1, maybeaddress=0;
+    int maybetag = (close != EOF);
+    int maybeaddress=0;
     int mailto;
+    int consume;
 
     if ( f->flags & INSIDE_TAG )
 	return 0;
 
-    for ( size=0; ((c = peek(f,size+1)) != '>') && !isspace(c); size++ ) {
+    for ( size=0; ((c = peek(f,size+1)) != close) && !isspace(c); size++ ) {
 	if ( ! (c == '/' || isalnum(c) || c == '~') )
 	    maybetag=0;
 	if ( c == '@' )
@@ -740,6 +761,8 @@ maybe_tag_or_link(MMIOT *f)
 
     if ( size == 0 )
 	return 0;
+    
+    consume = ( close != EOF ) ? (size+1) : (size);
 
     if ( maybetag  || (size >= 3 && strncmp(cursor(f), "!--", 3) == 0) ) {
 	Qstring(forbidden_tag(f) ? "&lt;" : "<", f);
@@ -751,19 +774,17 @@ maybe_tag_or_link(MMIOT *f)
     if ( f->flags & DENY_A ) return 0;
 
     text = cursor(f);
-    shift(f, size+1);
+    shift(f, consume);
 
-    for ( i=0; i < SZAUTOPREFIX; i++ )
-	if ( strncasecmp(text, autoprefix[i], strlen(autoprefix[i])) == 0 ) {
-	    Qstring("<a href=\"", f);
-	    puturl(text,size,f);
-	    Qstring("\">", f);
-	    puturl(text,size,f);
-	    Qstring("</a>", f);
-	    return 1;
-	}
+    if ( isautoprefix(text) ) {
+	Qstring("<a href=\"", f);
+	puturl(text,size,f);
+	Qstring("\">", f);
+	puturl(text,size,f);
+	Qstring("</a>", f);
+	return 1;
+    }
     if ( maybeaddress ) {
-
 	Qstring("<a href=\"", f);
 	if ( (size > 7) && strncasecmp(text, "mailto:", 7) == 0 )
 	    mailto = 7;
@@ -780,7 +801,8 @@ maybe_tag_or_link(MMIOT *f)
 	return 1;
     }
 
-    shift(f, -(size+1));
+    shift(f, -consume);
+
     return 0;
 } /* maybe_tag_or_link */
 
@@ -922,7 +944,15 @@ text(MMIOT *f)
     int rep;
     int smartyflags = 0;
 
-    while ( (c = pull(f)) != EOF ) {
+    while (1) {
+        if (f->flags & AUTOLINK)
+	    maybe_tag_or_link(f, EOF);
+
+        c = pull(f);
+
+        if (c == EOF)
+          break;
+
 	if ( smartypants(c, &smartyflags, f) )
 	    continue;
 	switch (c) {
@@ -1022,7 +1052,7 @@ text(MMIOT *f)
 		    }
 		    break;
 
-	case '<':   if ( !maybe_tag_or_link(f) )
+	case '<':   if ( !maybe_tag_or_link(f, '>') )
 			Qstring("&lt;", f);
 		    break;
 

main.c

@@ -52,6 +52,8 @@ static struct {
     { "pants",   1, MKD_NOPANTS  },
     { "smarty",  1, MKD_NOPANTS  },
     { "toc",     0, MKD_TOC      },
+    { "autolink",0, MKD_AUTOLINK },
+    { "safelink",0, MKD_SAFELINK },
     { "1.0",     0, MKD_1_COMPAT },
 } ;
 

markdown.h

@@ -75,6 +75,8 @@ typedef struct mmiot {
 #define CDATA_OUTPUT	0x0080
 #define TOC		0x1000
 #define MKD_1_COMPAT	0x2000
+#define AUTOLINK	0x4000
+#define SAFELINK	0x8000
 #define USER_FLAGS	0xF0FF
 #define EMBEDDED	DENY_A|DENY_IMG|NO_PSEUDO_PROTO|CDATA_OUTPUT
     char *base;

mkdio.h

@@ -65,6 +65,8 @@ extern char markdown_version[];
 #define MKD_CDATA	0x0080	/* generate code for xml ![CDATA[...]] */
 #define MKD_TOC		0x1000	/* do table-of-contents processing */
 #define MKD_1_COMPAT	0x2000	/* compatability with MarkdownTest_1.0 */
+#define MKD_AUTOLINK	0x4000	/* make http://foo.com link even without <>s */
+#define MKD_SAFELINK	0x8000	/* paranoid check for link protocol */
 #define MKD_EMBED	MKD_NOLINKS|MKD_NOIMAGE|MKD_TAGTEXT
 
 /* special flags for mkd_in() and mkd_string()

tests/linkylinky.t

@@ -144,6 +144,16 @@ else
     rc=1
 fi
 
+./echo -n '  Reddit-style embedded links ...... '
+V="http://www.pell.portland.or.us/~orc/Code/discount"
 
+Q=`echo "$V" | ./markdown -fautolink | grep -i '<a href=' | wc -l`
+
+if [ ${Q:-0} -eq 1 ]; then
+    ./echo "ok"
+else
+    ./echo "FAILED"
+    rc=1
+fi
 
 exit $rc