2 files changed, 19 insertions, 28 deletions

diff --git a/proto/puzbusv1.c b/proto/puzbusv1.c
index 3be4939..73deda5 100644
--- a/proto/puzbusv1.c
+++ b/proto/puzbusv1.c
@@ -7,24 +7,13 @@
 
 #include "puzbusv1.h"
 
-/**
- * \brief Remaining bytes to be read to target->data
- *
- * This is the only variable that needs to persist between buffer blocks. It is
- * declared in the global scope to allow resetting using the \c pb_read_reset()
- * function.
- *
- * \note \p rdata may be reset by calling \c pb_read_reset()
- */
-static size_t rdata = 0;
-
-int pb_read(struct pb_msg* target, char* buf, size_t buf_sz) {
+int pb_read(struct pb_msg * 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 (rdata == 0) {
+	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.
@@ -34,26 +23,26 @@ int pb_read(struct pb_msg* target, char* buf, size_t buf_sz) {
 		if (buf_sz < 4) return -1;
 
 		target->addr = mpack_expect_u16(&reader);
-		target->length = rdata = mpack_expect_bin(&reader);
-		target->data = (char*) malloc(target->length);
+		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), rdata);
-	char* data = target->data + target->length - rdata; // 'ol pointer arithmetic
+	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);
-	rdata -= to_read;
+	target->_rdata -= to_read;
 
 	// if rdata = 0, the message was completely read
-	return rdata;
+	return target->_rdata;
 }
 
-void pb_read_reset() {
-	rdata = 0;
+void pb_read_reset(struct pb_msg * target) {
+	target->_rdata = 0;
 }
 
-bool pb_write(struct pb_msg* target, char** buf, size_t* buf_sz) {
+bool pb_write(const struct pb_msg * target, char ** buf, size_t * buf_sz) {
 	mpack_writer_t writer;
 	mpack_writer_init_growable(&writer, buf, buf_sz);
 
diff --git a/proto/puzbusv1.h b/proto/puzbusv1.h
index 95130c9..0985b2b 100644
--- a/proto/puzbusv1.h
+++ b/proto/puzbusv1.h
@@ -7,10 +7,12 @@
 extern "C" {
 #endif
 
+/** \brief Puzzle bus message (v1) */
 struct pb_msg {
-	uint16_t addr;
-	char* data;
-	size_t length;
+	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
 };
 
 /**
@@ -32,7 +34,7 @@ struct pb_msg {
  * the message is not fully parsed. This variable must be `free()`d by the
  * caller after each complete message to prevent memory leaks.
  */
-int pb_read(struct pb_msg* target, char* buf, size_t buf_sz);
+int pb_read(struct pb_msg * target, const char * buf, size_t buf_sz);
 
 /**
  * \brief reset the remaining message data counter
@@ -42,7 +44,7 @@ int pb_read(struct pb_msg* target, char* buf, size_t buf_sz);
  * before reading a TCP frame's data to mitigate any synchronization issues
  * arising from earlier corrupt or otherwise malformed messages.
  */
-void pb_read_reset();
+void pb_read_reset(struct pb_msg * target);
 
 /**
  * \brief Allocate and write a msgpack-formatted message to \p buf
@@ -60,7 +62,7 @@ void pb_read_reset();
  *
  * \note the pointer stored in \p buf must be `free()`d by the caller afterwards
  */
-bool pb_write(struct pb_msg* target, char** buf, size_t* buf_sz);
+bool pb_write(const struct pb_msg * target, char ** buf, size_t * buf_sz);
 
 #ifdef __cplusplus
 }