Implement incoming NVT EOL translation in process()

The translation is enabled by a new bit in telnet_init() flags
parameter.

Remove telnet_translate_eol() since that function is subsumed.

README

@@ -123,6 +123,11 @@ IIa. Initialization
       Operate in proxy mode.  This disables the RFC1143 support and
       enables automatic detection of COMPRESS2 streams.
 
+    TELNET_FLAG_NVT_EOL
+      Receive data with translation of the TELNET NVT CR NUL and CR LF
+      sequences specified in RFC854 to C carriage return (\r) and C
+      newline (\n), respectively.
+
    If telnet_init() fails to allocate the required memory, the
    returned pointer will be zero.
 
@@ -145,15 +150,6 @@ IIb. Receiving Data
    triggered for any regular data such as user input or server
    process output.
 
- size_t telnet_translate_eol(telnet_t *telnet,
-     char *buffer, size_t size, int *eol_was_split);
-   Scans a buffer received in a TELNET_EV_DATA event to translate the
-   TELNET NVT CR NUL and CR LF sequences specified in RFC854 to C
-   carriage return (\r) and C newline (\n), respectively.  Sequences
-   split across a buffer boundary are handled using the eol_was_split
-   flag that should be initialized to 0 before the first call.  The
-   possibly shorter length of the text after translation is returned.
-
 IIc. Sending Data
 
  All of the output functions will invoke the TELNET_EV_SEND event.

libtelnet.c

@@ -64,6 +64,7 @@
 /* telnet state codes */
 enum telnet_state_t {
 	TELNET_STATE_DATA = 0,
+	TELNET_STATE_EOL,
 	TELNET_STATE_IAC,
 	TELNET_STATE_WILL,
 	TELNET_STATE_WONT,
@@ -105,10 +106,6 @@ struct telnet_t {
 	unsigned char q_size;
 };
 
-/* Internal-only bits in option flags */
-#define TELNET_FLAG_TRANSMIT_BINARY (1<<1)
-#define TELNET_FLAG_RECEIVE_BINARY (1<<2)
-
 /* RFC1143 option negotiation state */
 typedef struct telnet_rfc1143_t {
 	unsigned char telopt;
@@ -978,9 +975,38 @@ static void _process(telnet_t *telnet, const char *buffer, size_t size) {
 					telnet->eh(telnet, &ev, telnet->ud);
 				}
 				telnet->state = TELNET_STATE_IAC;
+			} else if (byte == '\r' &&
+					   (telnet->flags & TELNET_FLAG_NVT_EOL) &&
+					   !(telnet->flags & TELNET_FLAG_RECEIVE_BINARY)) {
+				if (i != start) {
+					ev.type = TELNET_EV_DATA;
+					ev.data.buffer = buffer + start;
+					ev.data.size = i - start;
+					telnet->eh(telnet, &ev, telnet->ud);
+				}
+				telnet->state = TELNET_STATE_EOL;
 			}
 			break;
 
+		/* NVT EOL to be translated */
+		case TELNET_STATE_EOL:
+			if (byte != '\n') {
+				byte = '\r';
+				ev.type = TELNET_EV_DATA;
+				ev.data.buffer = (char*)&byte;
+				ev.data.size = 1;
+				telnet->eh(telnet, &ev, telnet->ud);
+				byte = buffer[i];
+			}
+			// any byte following '\r' other than '\n' or '\0' is invalid,
+			// so pass both \r and the byte
+			start = i;
+			if (byte == '\0')
+				++start;
+			/* state update */
+			telnet->state = TELNET_STATE_DATA;
+			break;
+
 		/* IAC command */
 		case TELNET_STATE_IAC:
 			switch (byte) {
@@ -1137,49 +1163,6 @@ static void _process(telnet_t *telnet, const char *buffer, size_t size) {
 	}
 }
 
-/* perform NVT end-of-line translation for received text */
-size_t telnet_translate_eol(telnet_t *telnet, char *buffer, size_t size,
-		int *eol_was_split) {
-	size_t i = 0, l = 0;
-	if (size == 0)
-		return size;
-
-	/* no translation if in BINARY mode */
-	if (telnet->flags & TELNET_FLAG_RECEIVE_BINARY)
-		return size;
-
-	/* fix up translation if split across buffer boundary */
-	if (*eol_was_split) {
-		/* CR-NUL translates to \r which was skipped at end of previous */
-		/* buffer, while CR-LF translates to \n, so just leave it */
-		if (buffer[i] == '\0') {
-			buffer[i] = '\r';
-		}
-		++i;
-	}
-
-	for ( ; i < size-1; ++i, ++l) {
-		buffer[l] = buffer[i];
-		if (buffer[i] == '\r') {
-			if (buffer[i+1] == '\n') {
-				/* CR-LF translates to \n */
-				buffer[l] = '\n';
-				++i;
-			} else if (buffer[i+1] == '\0') {
-				/* CR-NUL translates to \r */
-				++i;
-			}
-		}
-	}
-	if (buffer[i] == '\r') {
-		--l;
-		*eol_was_split = 1;
-	} else {
-		*eol_was_split = 0;
-	}
-	return l + 1;
-}
-
 /* push a bytes into the state tracker */
 void telnet_recv(telnet_t *telnet, const char *buffer,
 		size_t size) {

libtelnet.h

@@ -175,7 +175,11 @@ typedef struct telnet_telopt_t telnet_telopt_t;
 /*@{*/
 /*! Control behavior of telnet state tracker. */
 #define TELNET_FLAG_PROXY (1<<0)
+#define TELNET_FLAG_NVT_EOL (1<<1)
 
+/* Internal-only bits in option flags */
+#define TELNET_FLAG_TRANSMIT_BINARY (1<<5)
+#define TELNET_FLAG_RECEIVE_BINARY (1<<6)
 #define TELNET_PFLAG_DEFLATE (1<<7)
 /*@}*/
 
@@ -445,19 +449,6 @@ extern void telnet_send(telnet_t *telnet,
 extern void telnet_send_text(telnet_t *telnet,
 		const char *buffer, size_t size);
 
-/*!
- * Translate NVT EOL byte sequences into local characters
- * (CR-NUL -> \\r and CR-LF -> \\n) unless in BINARY mode.
- *
- * \param telnet Telnet state tracker object.
- * \param buffer Buffer of bytes to translate.
- * \param size   Number of bytes to translate.
- * \param split  1 if in the middle of EOL byte pair at start/end.
- * \return Number of bytes after translation.
- */
-extern size_t telnet_translate_eol(telnet_t *telnet,
-		char *buffer, size_t size, int *split);
-
 /*!
  * \brief Begin a sub-negotiation command.
  *