init

packet.c

@@ -0,0 +1,136 @@
+//
+// Created by bruno on 13. 7. 2026.
+//
+
+#include "packet.h"
+#include "crc32.h"
+
+#include <stdlib.h>
+#include <string.h>
+
+
+#define MAGIC 0xCA55
+
+
+#define PACKET_SIZE 223
+
+
+uint8_t *build_stream(
+    uint8_t *file,
+    uint32_t size,
+    uint32_t *outSize) {
+    uint32_t packets =
+            (size + PACKET_SIZE - 1)
+            /
+            PACKET_SIZE;
+
+
+    /*
+        estimate:
+
+        preamble 256 bytes
+        sync 16 bytes
+        packets:
+          header 4
+          payload 223
+          crc 4
+    */
+
+
+    uint32_t capacity =
+            256 +
+            16 +
+            packets * (4 + 2 + 2 + 223 + 4);
+
+
+    uint8_t *out =
+            malloc(capacity);
+
+
+    uint32_t pos = 0;
+
+
+    /*
+        preamble
+    */
+
+    for (int i = 0; i < 256; i++)
+        out[pos++] = 0x55;
+
+
+    /*
+        sync
+    */
+
+    uint8_t sync[] =
+    {
+        0xD3,
+        0x91,
+        0xAC,
+        0x55,
+        0x77,
+        0x22,
+        0xF0,
+        0x0F
+    };
+
+
+    memcpy(
+        out + pos,
+        sync,
+        sizeof(sync));
+
+    pos += sizeof(sync);
+
+
+    uint32_t offset = 0;
+
+
+    for (uint32_t p = 0; p < packets; p++) {
+        uint16_t magic = MAGIC;
+
+        uint16_t packet = p;
+
+
+        uint16_t len =
+                size - offset > PACKET_SIZE ? PACKET_SIZE : size - offset;
+
+
+        memcpy(out + pos, &magic, 2);
+        pos += 2;
+
+
+        memcpy(out + pos, &packet, 2);
+        pos += 2;
+
+
+        memcpy(out + pos, &len, 2);
+        pos += 2;
+
+
+        memcpy(out + pos,
+               file + offset,
+               len);
+
+        pos += len;
+
+
+        uint32_t crc =
+                calcCRC32(
+                    file + offset,
+                    len);
+
+
+        memcpy(out + pos, &crc, 4);
+
+        pos += 4;
+
+
+        offset += len;
+    }
+
+
+    *outSize = pos;
+
+    return out;
+}