mufs: implement block allocation

Makefile

@@ -23,6 +23,7 @@ obj-y += source/main.o
 
 obj-y += source/core/flash.o
 
+obj-y += source/fs/mufs/block.o
 obj-y += source/fs/mufs/super.o
 
 obj-y += source/ftl/dev.o

source/fs/mufs/block.c

@@ -0,0 +1,68 @@
+#include <bitops.h>
+#include <flash.h>
+#include <macros.h>
+
+#include <fs/mufs.h>
+
+#include "block.h"
+
+static int mufs_mark_block(struct mufs *fs, uint32_t block, int status)
+{
+	char data[1 << fs->dev->log2_block_size];
+	uint8_t log2_bits_per_block = fs->dev->log2_block_size + ilog2(8);
+	size_t index;
+
+	index = block & ((UINT32_C(1) << log2_bits_per_block) - 1);
+	block >>= log2_bits_per_block;
+
+	if (flash_read(fs->dev, (1 + block) << fs->dev->log2_block_size, data,
+		sizeof data) == 0)
+		return -1;
+
+	if (status) {
+		set_bit(data, index);
+	} else {
+		clear_bit(data, index);
+	}
+
+	if (flash_write(fs->dev, (1 + block) << fs->dev->log2_block_size, data,
+		sizeof data) == 0)
+		return -1;
+
+	return 0;
+}
+
+int mufs_alloc_block(struct mufs *fs, uint32_t *found)
+{
+	char data[1 << fs->dev->log2_block_size];
+	uint32_t nblocks = fs->nblocks;
+	uint32_t nbits;
+	uint32_t block = 0;
+	size_t index;
+	uint8_t log2_bits_per_block = fs->dev->log2_block_size + ilog2(8);
+
+	while (nblocks) {
+		if (flash_read(fs->dev, (1 + block) << fs->dev->log2_block_size, data,
+			sizeof data) == 0)
+			return -1;
+
+		nbits = min(nblocks, UINT32_C(1) << log2_bits_per_block);
+
+		if ((index = next_clear_bit(data, nbits)) == SIZE_MAX) {
+			++block;
+			nblocks -= nbits;
+			continue;
+		}
+
+		*found = (block << log2_bits_per_block) + index;
+
+		return mufs_mark_block(fs, *found, 1);
+	}
+
+	return -1;
+}
+
+int mufs_free_block(struct mufs *fs, uint32_t block)
+{
+	return mufs_mark_block(fs, block, 0);
+}

source/fs/mufs/block.h

@@ -0,0 +1,4 @@
+#pragma once
+
+int mufs_alloc_block(struct mufs *fs, uint32_t *block);
+int mufs_free_block(struct mufs *fs, uint32_t block);