core: Add blob + data stream abstraction

A blob is a piece of data of variable length that belongs in a blob list
while a data stream is a buffer used to move data between blobs among
other things.

Signed-off-by: Chloe M. <chloe@mirocom.org>

inc/blobchain/blob.h

@@ -0,0 +1,63 @@
+/*
+ * Copyright (c) 2026, Chloe M.
+ * Provided under the BSD-3 clause
+ */
+
+#ifndef BLOBCHAIN_BLOB_H
+#define BLOBCHAIN_BLOB_H 1
+
+#include <stdint.h>
+#include <stddef.h>
+#include "blobchain/stream.h"
+
+/*
+ * Represents a single blob of data
+ *
+ * @data:   Buffer containing blob data
+ * @length: Length of blob
+ * @next:   Next blob
+ */
+struct blob {
+    void *data;
+    size_t length;
+    struct blob *next;
+};
+
+/*
+ * Represents a list of data blobs
+ *
+ * @head:  List head
+ * @tail:  List tail
+ * @count: Number of blobs present
+ */
+struct blob_list {
+    struct blob *head;
+    struct blob *tail;
+    size_t count;
+};
+
+/*
+ * Allocate memory for a new blob descriptor
+ *
+ * @stmp:  Stream pointer to copy data from [NULLable]
+ */
+struct blob *blob_allocate(struct data_stream *stmp);
+
+/*
+ * Add a blob to a list
+ *
+ * @lp:   Blob list pointer
+ * @blob: Blob to add
+ *
+ * Returns zero on success
+ */
+int blob_list_append(struct blob_list *lp, struct blob *blob);
+
+/*
+ * Initialize a list of blobs
+ *
+ * @lp:  Bloblist pointer
+ */
+int blob_list_init(struct blob_list *lp);
+
+#endif  /* !BLOBCHAIN_BLOB_H */

inc/blobchain/stream.h

@@ -0,0 +1,22 @@
+/*
+ * Copyright (c) 2026, Chloe M.
+ * Provided under the BSD-3 clause
+ */
+
+#ifndef BLOBCHAIN_STREAM_H
+#define BLOBCHAIN_STREAM_H 1
+
+#include <stddef.h>
+
+/*
+ * Represents a data stream
+ *
+ * @data:   Data buffer
+ * @length: Number of bytes in data buffer
+ */
+struct data_stream {
+    void *data;
+    size_t length;
+};
+
+#endif  /* !BLOBCHAIN_STREAM_H */