mvm: Add initial mvm groundwork

Signed-off-by: Ian Moffett <ian@mirocom.org>

mvm/core/balloon_subr.c

@@ -0,0 +1,75 @@
+/*
+ * Copyright (c) 2026 Mirocom Laboratories and MSP engineers.
+ * All Rights Reserved.
+ */
+
+#include <stdint.h>
+#include <stddef.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <string.h>
+#include <assert.h>
+#include "mvm/balloon.h"
+
+int
+balloon_init(struct mvm_balloon *bp, size_t cap)
+{
+    if (bp == NULL || cap == 0) {
+        errno = EINVAL;
+        return -1;
+    }
+
+    assert(cap > BALLOON_INIT_SIZE && "cap must be bigger than minimum");
+    bp->cap = cap;
+    bp->size = BALLOON_INIT_SIZE;
+    bp->data = calloc(bp->size, sizeof(char));
+
+    if (bp->data == NULL) {
+        errno = ENOMEM;
+        return -1;
+    }
+
+    return 0;
+}
+
+int
+balloon_memcpy(struct mvm_balloon *dest, off_t off, void *source, size_t count)
+{
+    size_t overflow, newsize;
+    size_t delta;
+    void *p;
+
+    if (dest == NULL || source == NULL) {
+        errno = EINVAL;
+        return -1;
+    }
+
+    if (count == 0) {
+        errno = EINVAL;
+        return -1;
+    }
+
+    /* Compute how far off this will push us */
+    overflow = off + count;
+
+    /* If we are overflowing size and have room to expand, do it */
+    if (overflow >= dest->size && dest->size < dest->cap) {
+        delta = overflow - dest->size;
+        newsize = dest->size + delta;
+
+        /* Attempt to resize the pool */
+        if ((p = realloc(dest->data, newsize)) == NULL) {
+            errno = -ENOMEM;
+            return -1;
+        }
+
+        dest->size = newsize;
+        dest->data = p;
+    } else if (overflow >= dest->cap) {
+        errno = -ENOSPC;
+        return -1;
+    }
+
+    memcpy((char *)dest->data + off, source, count);
+    return 0;
+}