initial commit

1 files changed, 35 insertions, 0 deletions

diff --git a/mavlink-library/src/main/scala/com/github/jodersky/mavlink/Crc.scala b/mavlink-library/src/main/scala/com/github/jodersky/mavlink/Crc.scala
new file mode 100644
index 0000000..6150e48
--- /dev/null
+++ b/mavlink-library/src/main/scala/com/github/jodersky/mavlink/Crc.scala
@@ -0,0 +1,35 @@
+package com.github.jodersky.mavlink
+
+/**
+ * X.25 CRC calculation for MAVlink messages. The checksum must be initialized,
+ * updated with each field of a message, and then finished with the message
+ * id.
+ */
+case class Crc(val crc: Int = 0xffff) extends AnyVal {
+
+  /**
+   * Accumulates data into a new checksum.
+   */
+  def accumulate(datum: Byte): Crc = {
+    val d = datum & 0xff
+    var tmp = d ^ (crc & 0xff)
+    tmp ^= (tmp << 4) & 0xff;
+    Crc(
+      ((crc >> 8) & 0xff) ^ (tmp << 8) ^ (tmp << 3) ^ ((tmp >> 4) & 0xff))
+  }
+
+  def accumulate(data: Seq[Byte]): Crc = {
+    var next = this
+    for (d <- data) {
+      next = next.accumulate(d)
+    }
+    next
+  }
+
+  /** Least significant byte of checksum. */
+  def lsb: Byte = crc.toByte
+
+  /** Most significant byte of checksum. */
+  def msb: Byte = (crc >> 8).toByte
+
+}
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