1 files changed, 144 insertions, 0 deletions
diff --git a/slipenc/slipenc.c b/slipenc/slipenc.c
new file mode 100644
index 0000000..fc2747b
--- /dev/null
+++ b/slipenc/slipenc.c
@@ -0,0 +1,144 @@
+/* slipenc.c 20070711 Martin Peach */
+/**encode a list of bytes as SLIP /
+/*
+/*
+From RFC 1055:
+PROTOCOL
+
+   The SLIP protocol defines two special characters: SLIP_END and SLIP_ESC. SLIP_END is
+   octal 300 (decimal 192) and SLIP_ESC is octal 333 (decimal 219) not to be
+   confused with the ASCII ESCape character; for the purposes of this
+   discussion, SLIP_ESC will indicate the SLIP SLIP_ESC character.  To send a
+   packet, a SLIP host simply starts sending the data in the packet.  If
+   a data byte is the same code as SLIP_END character, a two byte sequence of
+   SLIP_ESC and octal 334 (decimal 220) is sent instead.  If it the same as
+   an SLIP_ESC character, an two byte sequence of SLIP_ESC and octal 335 (decimal
+   221) is sent instead.  When the last byte in the packet has been
+   sent, an SLIP_END character is then transmitted.
+
+   Phil Karn suggests a simple change to the algorithm, which is to
+   begin as well as end packets with an SLIP_END character.  This will flush
+   any erroneous bytes which have been caused by line noise.  In the
+   normal case, the receiver will simply see two back-to-back SLIP_END
+   characters, which will generate a bad IP packet.  If the SLIP
+   implementation does not throw away the zero-length IP packet, the IP
+   implementation certainly will.  If there was line noise, the data
+   received due to it will be discarded without affecting the following
+   packet.
+
+   Because there is no 'standard' SLIP specification, there is no real
+   defined maximum packet size for SLIP.  It is probably best to accept
+   the maximum packet size used by the Berkeley UNIX SLIP drivers: 1006
+   bytes including the IP and transport protocol headers (not including
+   the framing characters).  Therefore any new SLIP implementations
+   should be prepared to accept 1006 byte datagrams and should not send
+   more than 1006 bytes in a datagram.
+*/
+
+#include "m_pd.h" 
+
+/* -------------------------- slipenc -------------------------- */
+#ifndef _SLIPCODES
+/* SLIP special character codes */
+#define SLIP_END     0300 /* indicates end of packet */
+#define SLIP_ESC     0333 /* indicates byte stuffing */
+#define SLIP_ESC_END 0334 /* SLIP_ESC SLIP_ESC_END means SLIP_END data byte */
+#define SLIP_ESC_ESC 0335 /* SLIP_ESC SLIP_ESC_ESC means SLIP_ESC data byte */
+#define MAX_SLIP 1006 /* maximum SLIP packet size */
+#define _SLIPCODES
+#endif // _SLIPCODES
+
+static t_class *slipenc_class;
+
+typedef struct _slipenc
+{
+    t_object    x_obj;
+    t_outlet    *x_slipenc_out;
+    t_atom      *x_slip_buf;
+    t_int       x_slip_length;
+} t_slipenc;
+
+static void *slipenc_new(t_symbol *s, int argc, t_atom *argv);
+static void slipenc_list(t_slipenc *x, t_symbol *s, int ac, t_atom *av);
+static void slipenc_free(t_slipenc *x);
+void slipenc_setup(void);
+
+static void *slipenc_new(t_symbol *s, int argc, t_atom *argv)
+{
+    int i;
+    t_slipenc  *x = (t_slipenc *)pd_new(slipenc_class);
+
+    x->x_slip_buf = (t_atom *)getbytes(sizeof(t_atom)*MAX_SLIP);
+    if(x->x_slip_buf == NULL)
+    {
+        error("slipenc: unable to allocate %lu bytes for x_slip_buf", (long)sizeof(t_atom)*MAX_SLIP);
+        return NULL;
+    }
+    /* Initialize all the slip buf atoms to float type */
+    for (i = 0; i < MAX_SLIP; ++i) x->x_slip_buf[i].a_type = A_FLOAT;
+    x->x_slipenc_out = outlet_new(&x->x_obj, &s_list);
+    return (x);
+}
+
+static void slipenc_list(t_slipenc *x, t_symbol *s, int ac, t_atom *av)
+{
+    /* SLIP encode a list of bytes */
+    float   f;
+    int     i, c;
+
+    i = x->x_slip_length = 0;
+    /* send an initial SLIP_END character to flush out any data that may */
+    /* have accumulated in the receiver due to line noise */
+    x->x_slip_buf[x->x_slip_length++].a_w.w_float = SLIP_END;
+
+    /* for each byte in the packet, send the appropriate character sequence */
+    while((i < ac) && (x->x_slip_length < (MAX_SLIP-1)))
+    {
+        /* check each atom for byteness */
+        f = atom_getfloat(&av[i++]);
+        c = (((int)f) & 0x0FF);
+        if (c != f)
+        {
+            /* abort, bad input character */
+            pd_error (x, "slipenc: input %d out of range [0..255]", f);
+            return;
+        }
+        if(SLIP_END == c)
+        {
+            /* If it's the same code as a SLIP_END character, replace it with a */
+            /* special two-character code so as not to make the receiver think we sent SLIP_END */
+            x->x_slip_buf[x->x_slip_length++].a_w.w_float = SLIP_ESC;
+            x->x_slip_buf[x->x_slip_length++].a_w.w_float = SLIP_ESC_END;
+        }
+        else if (SLIP_ESC == c)
+        {
+            /* If it's the same code as a SLIP_ESC character, replace it with a special two-character code */
+            /* so as not to make the receiver think we sent SLIP_ESC */
+            x->x_slip_buf[x->x_slip_length++].a_w.w_float = SLIP_ESC;
+            x->x_slip_buf[x->x_slip_length++].a_w.w_float = SLIP_ESC_ESC;
+        }
+        else
+        {
+            /* Otherwise, pass the character */
+            x->x_slip_buf[x->x_slip_length++].a_w.w_float = c;
+        }
+    }
+    /* Add the SLIP_END code to tell the receiver that the packet is complete */
+    x->x_slip_buf[x->x_slip_length++].a_w.w_float = SLIP_END;
+    outlet_list(x->x_slipenc_out, &s_list, x->x_slip_length, x->x_slip_buf);
+}
+
+static void slipenc_free(t_slipenc *x)
+{
+    if (x->x_slip_buf != NULL) freebytes((void *)x->x_slip_buf, sizeof(t_atom)*MAX_SLIP);
+}
+
+void slipenc_setup(void)
+{
+    slipenc_class = class_new(gensym("slipenc"), 
+        (t_newmethod)slipenc_new, (t_method)slipenc_free,
+        sizeof(t_slipenc), 0, A_GIMME, 0);
+    class_addlist(slipenc_class, slipenc_list);
+}
+
+/* fin slipenc.c*/