ringbuffer, guid, iovec stuff, and mmio

include/zinnia/iovec.h

@@ -8,31 +8,42 @@
 
 typedef struct __iovec iovec_t;
 
-struct iovec_iter {
+typedef struct {
     iovec_t* iovecs;
     size_t iovecs_len;
     size_t total_len;
     size_t total_offset;
     size_t current_idx;
     size_t current_offset;
-};
+    // Whether the iovecs point to user memory.
+    bool user;
+} iovec_iter_t;
 
-static inline size_t iovec_iter_len(struct iovec_iter* iter) {
+static inline size_t iovec_iter_len(iovec_iter_t* iter) {
     return iter->total_len - iter->total_offset;
 }
 
 // Creates an iovec iterator over kernel memory.
-static inline struct iovec_iter iovec_iter_kernel(iovec_t* iovecs, size_t count) {
+static inline iovec_iter_t iovec_iter_kernel(iovec_t* iovecs, size_t count) {
     size_t total = 0;
     for (size_t i = 0; i < count; i++)
         total += iovecs[i].len;
 
-    return (struct iovec_iter){
+    return (iovec_iter_t){
         .iovecs = iovecs,
         .iovecs_len = count,
         .total_len = total,
         .total_offset = 0,
         .current_idx = 0,
         .current_offset = 0,
+        .user = false,
     };
 }
+
+// Copies up to `len` bytes from `src` into the iterator and advances it.
+// Returns the amount of bytes actually copied in `out_copied`.
+errno_t iovec_iter_copy_to(iovec_iter_t* iter, const void* src, size_t len, size_t* out_copied);
+
+// Copies up to `len` bytes out of the iterator into `dst` and advances it.
+// Returns the amount of bytes actually copied in `out_copied`.
+errno_t iovec_iter_copy_from(iovec_iter_t* iter, void* dst, size_t len, size_t* out_copied);