add `mpack_read_remaining_bytes` function to mpack

4 files changed, 32 insertions, 10 deletions

diff --git a/lib/i2ctcp/i2ctcpv1.c b/lib/i2ctcp/i2ctcpv1.c
index 944df3a..f70cbb1 100644
--- a/lib/i2ctcp/i2ctcpv1.c
+++ b/lib/i2ctcp/i2ctcpv1.c
@@ -15,21 +15,12 @@ int i2ctcp_read(i2ctcp_msg_t * target, const char * buf, size_t buf_sz) {
 		target->length = target->_rdata = mpack_expect_bin(&reader);
 		if (mpack_reader_error(&reader) != mpack_ok) return -1;
 		target->data = (char *) malloc(target->length);
-
-		// seek forward in buf to where binary data begins (to avoid having to read
-		// from private member reader.data in the memcpy below)
-		buf += buf_sz - mpack_reader_remaining(&reader, NULL);
 	}
 
 	// 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;
-	memcpy(data, buf, to_read);
-	target->_rdata -= to_read;
-	// NOTE: memcpy is used here because mpack_read_bytes requires that a tag was
-	// opened, which is not the case for the chunks following the initial mpack
-	// header
+	target->_rdata -= mpack_read_remaining_bytes(&reader, data, target->_rdata);
 
 	// if rdata = 0, the message was completely read
 	return target->_rdata;
diff --git a/lib/mpack/CMakeLists.txt b/lib/mpack/CMakeLists.txt
index 0a904b0..0e4359d 100644
--- a/lib/mpack/CMakeLists.txt
+++ b/lib/mpack/CMakeLists.txt
@@ -16,8 +16,10 @@ add_library(mpack STATIC
 	src/src/mpack/mpack-platform.c
 	src/src/mpack/mpack-reader.c
 	src/src/mpack/mpack-writer.c
+	read-remaining.c
 	)
 target_include_directories(mpack SYSTEM INTERFACE
+	.
 	src/src/mpack
 	)
 
diff --git a/lib/mpack/mpack.h b/lib/mpack/mpack.h
new file mode 100644
index 0000000..7c0c089
--- /dev/null
+++ b/lib/mpack/mpack.h
@@ -0,0 +1,19 @@
+#pragma once
+
+#include "src/src/mpack/mpack.h"
+
+/**
+ * \brief read remaining bytes in reader without opening a tag first
+ *
+ * \param reader  pointer to mpack reader object
+ * \param p  pointer to write data to
+ * \param count  maximum number of bytes to read
+ *
+ * This function reads *up to* the amount of bytes specified in \p count, or
+ * less if there is less remaining data in the buffer. If \p count is equal to
+ * 0, all remaining data in the buffer is read.
+ *
+ * \return amount of bytes read
+ */
+size_t mpack_read_remaining_bytes(mpack_reader_t * reader, char * p, size_t count);
+
diff --git a/lib/mpack/read-remaining.c b/lib/mpack/read-remaining.c
new file mode 100644
index 0000000..ebc9b56
--- /dev/null
+++ b/lib/mpack/read-remaining.c
@@ -0,0 +1,10 @@
+#include "mpack.h"
+
+size_t mpack_read_remaining_bytes(mpack_reader_t * reader, char * p, size_t count) {
+	size_t limit =mpack_reader_remaining(reader, NULL);
+	if (0 < count && count < limit)
+		limit = count;
+	memcpy(p, reader->data, limit);
+	return limit;
+}
+