mufs: add mufs_read() to read data using a file tree

source/fs/mufs/tree.c

@@ -1,7 +1,10 @@
 #include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
 
 #include <bitops.h>
 #include <flash.h>
+#include <macros.h>
 
 #include <fs/mufs.h>
 
@@ -157,3 +160,38 @@ int mufs_shrink_tree(struct mufs *fs, struct mufs_tree *tree, uint32_t max_size)
 
 	return 0;
 }
+
+static size_t mufs_do_read(struct mufs *fs, struct mufs_tree *tree,
+	void *data, uint32_t va, size_t len)
+{
+	uint32_t page, offset;
+
+	offset = va & ((UINT32_C(1) << fs->dev->log2_block_size) - 1);
+	va = align(va, fs->dev->log2_block_size);
+
+	memset(data, 0, len);
+	len = min(len, (UINT32_C(1) << fs->dev->log2_block_size) - offset);
+
+	if (mufs_lookup_page(fs, tree, &page, va) < 0)
+		return 0;
+
+	return flash_read(fs->dev, page, data, len);
+}
+
+size_t mufs_read(struct mufs *fs, struct mufs_tree *tree, void *data,
+	uint32_t va, size_t len)
+{
+	uint8_t *buf = data;
+	size_t ret, nbytes = 0;
+
+	while (len) {
+		if ((ret = mufs_do_read(fs, tree, buf, va, len)) == 0)
+			return nbytes;
+
+		buf += ret;
+		va += ret;
+		len -= ret;
+	}
+
+	return nbytes;
+}

source/fs/mufs/tree.h

@@ -7,3 +7,5 @@ int mufs_alloc_page(struct mufs *fs, struct mufs_tree *tree, uint32_t *page,
 void mufs_free_page(struct mufs *fs, struct mufs_tree *tree, uint32_t va);
 int mufs_extend_tree(struct mufs *fs, struct mufs_tree *tree, uint8_t depth);
 int mufs_shrink_tree(struct mufs *fs, struct mufs_tree *tree, uint32_t max_size);
+size_t mufs_read(struct mufs *fs, struct mufs_tree *tree, void *data,
+	uint32_t va, size_t len);