add vibecoded artnet lib

draw_parra/artnet_receiver.c

@@ -0,0 +1,135 @@
+/* --------------------------------------------------------------------
+ *  artnet_receiver.c  – tiny Art‑Net DMX receiver
+ * -------------------------------------------------------------------- */
+#define _POSIX_C_SOURCE 200112L
+#include "artnet_receiver.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <arpa/inet.h>
+#include <sys/socket.h>
+#include <pthread.h>
+#include <errno.h>
+
+#define ARTNET_PORT          6454
+#define ARTNET_HEADER_SIZE   18        /* "Art-Net\0" + OpCode + … */
+#define OP_DMX               0x5000    /* low‑byte first (little‑endian) */
+
+/* --------------------------------------------------------------- */
+static int                 artnet_sock = -1;
+static pthread_t           receiver_thread;
+static volatile bool       run_thread = false;
+
+/* -----------------------------------------------------------------
+ *  Helper: map a DMX byte (0‑255) to a signed or unsigned integer
+ * ----------------------------------------------------------------- */
+static inline int map_range_uint8(uint8_t v, int dst_min, int dst_max)
+{
+    return dst_min + (int)((v * (dst_max - dst_min)) / 255.0);
+}
+
+/* -----------------------------------------------------------------
+ *  The thread that receives Art‑Net packets
+ * ----------------------------------------------------------------- */
+static void *receiver_func(void *arg)
+{
+    (void)arg;   /* unused */
+
+    struct sockaddr_in from;
+    socklen_t fromlen = sizeof(from);
+    uint8_t buf[1500];               /* big enough for a full packet */
+
+    while (run_thread) {
+        ssize_t n = recvfrom(artnet_sock, buf, sizeof(buf), 0,
+                             (struct sockaddr *)&from, &fromlen);
+        if (n < 0) {
+            if (errno == EINTR) continue;
+            perror("recvfrom");
+            continue;
+        }
+
+        /* ------------------ quick sanity checks ------------------- */
+        if (n < ARTNET_HEADER_SIZE) continue;               /* too short   */
+        if (memcmp(buf, "Art-Net\0", 8) != 0) continue;     /* not Art‑Net */
+
+        uint16_t opcode = buf[8] | (buf[9] << 8);            /* little‑endian */
+        if (opcode != OP_DMX) continue;                     /* not ArtDMX */
+
+        /* --------------------- DMX payload ----------------------- */
+        uint16_t universe = buf[14] | (buf[15] << 8);        /* not used */
+        uint16_t length   = buf[16] << 8 | buf[17];         /* big‑endian */
+        if (length + ARTNET_HEADER_SIZE != (size_t)n) continue;   /* malformed */
+
+        uint8_t *dmx = buf + ARTNET_HEADER_SIZE;            /* first DMX slot */
+
+        /* --------------------- update shared variables ------------ */
+        /* 0 … 11  → rotation angles (0‑180°) */
+        for (int i = 0; i < 12 && i < length; ++i) {
+            rotAnglesDeg[i] = map_range_uint8(dmx[i], 0, 180);
+        }
+        ///* channel 12 → line thickness (1‑10) */
+        //if (length > 12) {
+        //    LINE_THICKNESS = map_range_uint8(dmx[12], 1, 10);
+        //}
+        ///* channel 13 → top margin (0‑200 px) */
+        //if (length > 13) {
+        //    MARGIN_TOP = map_range_uint8(dmx[13], 0, 200);
+        //}
+        ///* channel 14 → bottom margin (0‑200 px) */
+        //if (length > 14) {
+        //    MARGIN_BOTTOM = map_range_uint8(dmx[14], 0, 200);
+        //}
+
+        /* (Add more channels here if you need them) */
+    }
+    return NULL;
+}
+
+/* -----------------------------------------------------------------
+ *  Public API
+ * ----------------------------------------------------------------- */
+bool artnet_init(void)
+{
+    struct sockaddr_in sa;
+
+    artnet_sock = socket(AF_INET, SOCK_DGRAM, 0);
+    if (artnet_sock < 0) {
+        perror("socket");
+        return false;
+    }
+
+    memset(&sa, 0, sizeof(sa));
+    sa.sin_family = AF_INET;
+    sa.sin_addr.s_addr = htonl(INADDR_ANY);
+    sa.sin_port = htons(ARTNET_PORT);
+
+    if (bind(artnet_sock, (struct sockaddr *)&sa, sizeof(sa)) < 0) {
+        perror("bind");
+        close(artnet_sock);
+        artnet_sock = -1;
+        return false;
+    }
+
+    run_thread = true;
+    if (pthread_create(&receiver_thread, NULL, receiver_func, NULL) != 0) {
+        perror("pthread_create");
+        close(artnet_sock);
+        artnet_sock = -1;
+        run_thread = false;
+        return false;
+    }
+    return true;
+}
+
+void artnet_stop(void)
+{
+    if (!run_thread) return;
+    run_thread = false;
+    /* Wake the thread if it is blocked in recvfrom */
+    shutdown(artnet_sock, SHUT_RDWR);
+    pthread_join(receiver_thread, NULL);
+    close(artnet_sock);
+    artnet_sock = -1;
+}