separate the i2c over tcp from puzzle bus libraries

1 files changed, 54 insertions, 0 deletions

diff --git a/i2ctcp/i2ctcpv1.c b/i2ctcp/i2ctcpv1.c
new file mode 100644
index 0000000..36a5dbd
--- /dev/null
+++ b/i2ctcp/i2ctcpv1.c
@@ -0,0 +1,54 @@
+#include <mpack.h>
+#include <stdio.h>
+
+// MIN() macro
+#include <sys/param.h>
+
+#include "i2ctcpv1.h"
+
+int i2ctcp_read(i2ctcp_msg_t * target, const char * buf, size_t buf_sz) {
+	// a new reader is used per buffer block passed to this function
+	mpack_reader_t reader;
+	mpack_reader_init_data(&reader, buf, buf_sz);
+
+	// at start of message
+	if (target->_rdata == 0) {
+		// NOTE: The entire start of a message needs to be readable from the buffer
+		// at this point. When target->addr can be read and target->length is past
+		// the end of the current buffer block, this function will crash and burn.
+		// This is a highly unlikely scenario, as i2ctcp_read is called for each
+		// chunk of a TCP frame, and frames (should) include only one puzzle bus
+		// message. The check here is kind of optional.
+		if (buf_sz < 4) return -1;
+
+		target->addr = mpack_expect_u16(&reader);
+		target->length = target->_rdata = mpack_expect_bin(&reader);
+		target->data = (char *) malloc(target->length);
+	}
+
+	// continue reading chunks of target->data until the amount of bytes
+	// specified in target->length
+	size_t to_read = MIN(mpack_reader_remaining(&reader, NULL), target->_rdata);
+	char * data = target->data + target->length - target->_rdata;
+	mpack_read_bytes(&reader, data, to_read);
+	target->_rdata -= to_read;
+
+	// if rdata = 0, the message was completely read
+	return target->_rdata;
+}
+
+void i2ctcp_read_reset(i2ctcp_msg_t * target) {
+	target->_rdata = 0;
+}
+
+bool i2ctcp_write(const i2ctcp_msg_t * target, char ** buf, size_t * buf_sz) {
+	mpack_writer_t writer;
+	mpack_writer_init_growable(&writer, buf, buf_sz);
+
+	mpack_write_u16(&writer, target->addr);
+	mpack_write_bin(&writer, target->data, target->length);
+
+	// finish writing
+	return mpack_writer_destroy(&writer) == mpack_ok;
+}
+