separate the i2c over tcp from puzzle bus libraries

4 files changed, 142 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;
+}
+
diff --git a/i2ctcp/i2ctcpv1.h b/i2ctcp/i2ctcpv1.h
new file mode 100644
index 0000000..799b668
--- /dev/null
+++ b/i2ctcp/i2ctcpv1.h
@@ -0,0 +1,71 @@
+#pragma once
+
+#include <stddef.h>
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/** \brief I2C over TCP message (v1) */
+struct i2ctcp_msg {
+	uint16_t addr; //!< I^2^C address
+	char * data;   //!< message content
+	size_t length; //!< message size
+	size_t _rdata; //!< \private remaining bytes to read until message is complete
+};
+typedef struct i2ctcp_msg i2ctcp_msg_t;
+
+/**
+ * \brief Read chunk of input stream, and store resulting message in \p target
+ *
+ * This function is called for each chunk of data from an input stream, and
+ * will parse the next puzzle bus message into \p target. The input stream is
+ * assumed to only contain messages encoded by \p i2ctcp_write()
+ *
+ * \param target  pointer to struct that will contain the finished message data
+ * \param buf     pointer to input stream data chunk
+ * \param buf_sz  size of \p buf
+ *
+ * \returns Integer representing amount of bytes required to finish message, or
+ * -1 if the message header could not be read. If this function returns 0, the
+ *  message in \p target is complete.
+ *
+ * \note target->data will automatically be allocated by this function, even if
+ * the message is not fully parsed. This variable must be `free()`d by the
+ * caller after each complete message to prevent memory leaks.
+ */
+int i2ctcp_read(i2ctcp_msg_t * target, const char * buf, size_t buf_sz);
+
+/**
+ * \brief reset the remaining message data counter
+ *
+ * Calling this function has the effect of forcing \c i2ctcp_read() to parse
+ * the next buffer chunk as the start of a new message. This function may be
+ * called before reading a TCP frame's data to mitigate any synchronization
+ * issues arising from earlier corrupt or otherwise malformed messages.
+ */
+void i2ctcp_read_reset(i2ctcp_msg_t * target);
+
+/**
+ * \brief Allocate and write a msgpack-formatted message to \p buf
+ *
+ * This function allocates a buffer large enough to fit the message specified
+ * in \p target, and encodes the data in \p target in a format that can be
+ * decoded later using \p i2ctcp_read()
+ *
+ * \param target  pointer to struct that contains the message data
+ * \param buf     pointer to \c char* that will contain the formatted message
+ * \param buf_sz  pointer to \c size_t that will represent the final size of \p buf
+ *
+ * \returns boolean true if a the message could be encoded successfully, false
+ * if there was some kind of error
+ *
+ * \note the pointer stored in \p buf must be `free()`d by the caller afterwards
+ */
+bool i2ctcp_write(const i2ctcp_msg_t * target, char ** buf, size_t * buf_sz);
+
+#ifdef __cplusplus
+}
+#endif
+
diff --git a/i2ctcp/include.cmake b/i2ctcp/include.cmake
new file mode 100644
index 0000000..d755b57
--- /dev/null
+++ b/i2ctcp/include.cmake
@@ -0,0 +1,16 @@
+include_directories(${CMAKE_CURRENT_LIST_DIR})
+add_library(i2ctcp STATIC
+	${CMAKE_CURRENT_LIST_DIR}/i2ctcpv1.c
+	)
+
+# mpack
+include_directories(${CMAKE_CURRENT_LIST_DIR}/lib/mpack/src/mpack)
+add_library(mpack STATIC
+	${CMAKE_CURRENT_LIST_DIR}/lib/mpack/src/mpack/mpack-common.c
+	${CMAKE_CURRENT_LIST_DIR}/lib/mpack/src/mpack/mpack-expect.c
+	${CMAKE_CURRENT_LIST_DIR}/lib/mpack/src/mpack/mpack-node.c
+	${CMAKE_CURRENT_LIST_DIR}/lib/mpack/src/mpack/mpack-platform.c
+	${CMAKE_CURRENT_LIST_DIR}/lib/mpack/src/mpack/mpack-reader.c
+	${CMAKE_CURRENT_LIST_DIR}/lib/mpack/src/mpack/mpack-writer.c
+	)
+
diff --git a/i2ctcp/lib b/i2ctcp/lib
new file mode 120000
index 0000000..dc598c5
--- /dev/null
+++ b/i2ctcp/lib
@@ -0,0 +1 @@
+../lib
\ No newline at end of file