Save file update (incomplete)

src/duskdolphin/save/savestreamdolphin.h

@@ -0,0 +1,91 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ *
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#pragma once
+#include "error/error.h"
+#include "save/savedolphin.h"
+#include <gccore.h>
+#include <stddef.h>
+
+typedef struct {
+  /** libogc memory card file handle. */
+  card_file cardFile;
+  /** In-memory sector buffer; all reads and writes operate on this. */
+  uint8_t buffer[SAVE_DOLPHIN_SECTOR_SIZE] __attribute__((aligned(32)));
+  /** Current read/write position within buffer. */
+  size_t position;
+  /** True when opened for writing; flushes buffer to card on close. */
+  bool_t writing;
+  /** Slot index stored at open time so Close can derive the filename. */
+  uint8_t slot;
+} savestreamdolphin_t;
+
+/**
+ * Opens a memory card slot for reading by loading its sector into buffer.
+ *
+ * @param p     Stream to initialize.
+ * @param found Set to true if the file exists, false if it does not.
+ * @param slot  Save slot index.
+ * @return An error if reading the card fails for a reason other than
+ *         missing file.
+ */
+errorret_t saveStreamOpenReadDolphin(
+  savestreamdolphin_t *p, bool_t *found, const uint8_t slot
+);
+
+/**
+ * Opens a memory card slot for writing by zeroing the sector buffer.
+ * The buffer is flushed to the card when savestreamCloseDolphin is called.
+ *
+ * @param p    Stream to initialize.
+ * @param slot Save slot index.
+ * @return An error if initialization fails.
+ */
+errorret_t saveStreamOpenWriteDolphin(
+  savestreamdolphin_t *p, const uint8_t slot
+);
+
+/**
+ * Flushes the sector buffer to the memory card (write mode only) and
+ * releases the card file handle.
+ *
+ * @param p Stream to close.
+ */
+void saveStreamCloseDolphin(savestreamdolphin_t *p);
+
+/**
+ * Copies len bytes from the sector buffer at the current position into buf.
+ *
+ * @param p   Active stream.
+ * @param buf Destination buffer.
+ * @param len Number of bytes to read.
+ * @return An error if the read would exceed the sector size.
+ */
+errorret_t saveStreamReadBytesDolphin(
+  savestreamdolphin_t *p, void *buf, const size_t len
+);
+
+/**
+ * Copies len bytes from buf into the sector buffer at the current position.
+ *
+ * @param p   Active stream.
+ * @param buf Source buffer.
+ * @param len Number of bytes to write.
+ * @return An error if the write would exceed the sector size.
+ */
+errorret_t saveStreamWriteBytesDolphin(
+  savestreamdolphin_t *p, const void *buf, const size_t len
+);
+
+/**
+ * Sets the current read/write position within the sector buffer.
+ *
+ * @param p   Active stream.
+ * @param pos Target byte offset from the start of the sector.
+ * @return An error if pos is out of range.
+ */
+errorret_t saveStreamSeekDolphin(savestreamdolphin_t *p, const size_t pos);