finish puzzle bus writer/reader functions

2 files changed, 66 insertions, 14 deletions

diff --git a/proto/puzbusv1.c b/proto/puzbusv1.c
index 3ff7c63..d6cd597 100644
--- a/proto/puzbusv1.c
+++ b/proto/puzbusv1.c
@@ -1,25 +1,44 @@
 #include <mpack.h>
 #include <stdio.h>
 
+// MIN() macro
+#include <sys/param.h>
+// TODO: check if this works on pico as well
+
 #include "puzbusv1.h"
 
-int pb_read(struct pb_msg* target, char* buf, size_t buf_sz) {
-	mpack_reader_t reader;
-	printf("read %lu bytes...\n", buf_sz);
+bool pb_read(struct pb_msg* target, char* buf, size_t buf_sz) {
+	// remaining bytes to be read to target->data; this is the only variable that
+	// needs to persist between buffer blocks, and is therefore static
+	static size_t rdata = 0;
 
+	// a new reader is used per buffer block passed to this function
+	mpack_reader_t reader;
 	mpack_reader_init_data(&reader, buf, buf_sz);
 
-	uint16_t address = mpack_expect_u16(&reader);
-	char data_buf[80];
-	size_t data_size = mpack_expect_bin_buf(&reader, data_buf, sizeof(data_buf));
-
-	printf("0x%02x\n", address);
-	printf("\"%.*s\"\n", data_size, data_buf);
-
-	return 0;
+	// at start of message
+	if (rdata == 0) {
+		// NOTE: This approach will crash and burn when target->addr can be read
+		// and target->length is past the end of the current buffer block. This is
+		// a highly unlikely scenario, as pb_read is called for each chunk of a TCP
+		// frame, and frames (should) include only one puzzle bus message.
+		target->addr = mpack_expect_u16(&reader);
+		target->length = 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
+	mpack_read_bytes(&reader, data, to_read);
+	rdata -= to_read;
+
+	// if rdata = 0, the message was completely read
+	return rdata == 0;
 }
 
-int pb_write(struct pb_msg* target, char** buf, size_t* buf_sz) {
+bool pb_write(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 116dbf9..814bc93 100644
--- a/proto/puzbusv1.h
+++ b/proto/puzbusv1.h
@@ -13,8 +13,41 @@ struct pb_msg {
 	size_t length;
 };
 
-int pb_read(struct pb_msg* target, char* buf, size_t buf_sz);
-int pb_write(struct pb_msg* target, char** buf, size_t* buf_sz);
+/**
+ * \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 pb_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 boolean true if a message was completely read, false if more data
+ * is required
+ *
+ * \note target->data will automatically be allocated by this function, and
+ * must be `free()`d by the caller when finished
+ */
+bool pb_read(struct pb_msg* target, char* buf, size_t buf_sz);
+/**
+ * \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 pb_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 pb_write(struct pb_msg* target, char** buf, size_t* buf_sz);
 
 #ifdef __cplusplus
 }