From 35a576d2832982a6860ff15f7e6f04ad7427e140 Mon Sep 17 00:00:00 2001
From: batt <batt@38d2e660-2303-0410-9eaa-f027e97ec537>
Date: Thu, 25 Sep 2008 16:11:55 +0000
Subject: [PATCH] Refactor to fill sparse bytes with a known value (0).

git-svn-id: https://src.develer.com/svnoss/bertos/trunk@1846 38d2e660-2303-0410-9eaa-f027e97ec537
---
 bertos/fs/battfs.c      | 64 ++++++++++++++++++++++++-----------------
 bertos/fs/battfs_test.c |  6 ++--
 2 files changed, 40 insertions(+), 30 deletions(-)

diff --git a/bertos/fs/battfs.c b/bertos/fs/battfs.c
index 87b54019..2f4eee43 100644
--- a/bertos/fs/battfs.c
+++ b/bertos/fs/battfs.c
@@ -589,51 +589,61 @@ static size_t battfs_write(struct KFile *fd, const void *_buf, size_t size)
 	if (fd->seek_pos < 0)
 		return total_write;
 
-	if ((fd->seek_pos / fdb->disk->data_size) > fdb->max_off)
+	if (fd->seek_pos > fd->size)
 	{
-		/*
-		 * Handle writing when seek pos if far over EOF,
-		 * We need to allocate the missing pages first.
-		 */
-		pgoff_t missing_pages = fd->seek_pos / fdb->disk->data_size - fdb->max_off;
-
-		LOG_INFO("missing pages: %d\n", missing_pages);
+		/* Handle writing when seek pos if far over EOF */
 		if (!loadPage(fdb->disk, fdb->start[fdb->max_off], &curr_hdr))
 		{
 				#warning TODO set error?
 				return total_write;
 		}
 
-		uint8_t dummy = 0xff;
-		/* Add missing pages to reach current seek_pos */
-		while (missing_pages--)
+		/* Fill unused space of first page with 0s */
+		uint8_t dummy = 0;
+		pgaddr_t zero_bytes = MIN(fd->seek_pos - fd->size, fdb->disk->data_size - curr_hdr.fill);
+		while (zero_bytes--)
 		{
-			/* Update size and free space left */
-			fd->size += fdb->disk->data_size - curr_hdr.fill;
-			fdb->disk->free_bytes -= fdb->disk->data_size - curr_hdr.fill;
+			if (fdb->disk->bufferWrite(fdb->disk, curr_hdr.fill, &dummy, 1) != 1)
+			{
+				#warning TODO set error?
+			}
+			curr_hdr.fill++;
+			fd->size++;
+			fdb->disk->free_bytes--;
+			fdb->disk->cache_dirty = true;
+		}
+		setBufferHdr(fdb->disk, &curr_hdr);
+		flushBuffer(fdb->disk);
 
-			/* Fill empty space with 0xFF */
-			for (addr_offset = curr_hdr.fill; addr_offset < fdb->disk->data_size; addr_offset++)
+		/* Fill page buffer with 0 to avoid filling unused pages with garbage */
+		for (pgaddr_t off = 0; off < fdb->disk->data_size; off++)
+		{
+			if (fdb->disk->bufferWrite(fdb->disk, off, &dummy, 1) != 1)
 			{
-				if (fdb->disk->bufferWrite(fdb->disk, addr_offset, &dummy, 1) != 1)
-				{
-					#warning TODO set error?
-				}
+				#warning TODO set error?
 			}
-			curr_hdr.fill = fdb->disk->data_size;
-			setBufferHdr(fdb->disk, &curr_hdr);
+		}
 
+		/* Allocate the missing pages first. */
+		pgoff_t missing_pages = fd->seek_pos / fdb->disk->data_size - fdb->max_off;
+		LOG_INFO("missing pages: %d\n", missing_pages);
+
+		while (missing_pages--)
+		{
+			zero_bytes = MIN((kfile_off_t)fdb->disk->data_size, fd->seek_pos - fd->size);
 			/* Get the new page needed */
 			if (!getNewPage(fdb->disk, (fdb->start - fdb->disk->page_array) + fdb->max_off + 1, fdb->inode, fdb->max_off + 1, &curr_hdr))
 				return total_write;
 
+			/* Update size and free space left */
+			fd->size += zero_bytes;
+			fdb->disk->free_bytes -= zero_bytes;
+
+			curr_hdr.fill = zero_bytes;
+			setBufferHdr(fdb->disk, &curr_hdr);
+
 			fdb->max_off++;
 		}
-		/* Fix sizes for the last new page (could be only partially full) */
-		curr_hdr.fill = fd->seek_pos % fdb->disk->data_size;
-		setBufferHdr(fdb->disk, &curr_hdr);
-		fd->size += curr_hdr.fill;
-		fdb->disk->free_bytes -= curr_hdr.fill;
 	}
 	else if (!getBufferHdr(fdb->disk, &curr_hdr))
 		return total_write;
diff --git a/bertos/fs/battfs_test.c b/bertos/fs/battfs_test.c
index 0df504cd..ca0ded69 100644
--- a/bertos/fs/battfs_test.c
+++ b/bertos/fs/battfs_test.c
@@ -817,7 +817,7 @@ static void writeEOF(BattFsSuper *disk)
 	memset(buf, 0, 2);
 	ASSERT(kfile_read(&fd1.fd, buf, 2) == 2);
 	for (int i = 0; i < 2; i++)
-		ASSERT(buf[i] == 0xff);
+		ASSERT(buf[i] == 0);
 
 	memset(buf, 0, 2);
 	ASSERT(kfile_read(&fd1.fd, buf, 2) == 2);
@@ -838,7 +838,7 @@ static void writeEOF(BattFsSuper *disk)
 	ASSERT(kfile_read(&fd1.fd, buf, 2) == 2);
 	ASSERT(fd1.fd.seek_pos == 2);
 	for (int i = 0; i < 2; i++)
-		ASSERT(buf[i] == 0xff);
+		ASSERT(buf[i] == 0);
 
 	memset(buf, 0, 2);
 	ASSERT(kfile_read(&fd1.fd, buf, 2) == 2);
@@ -850,7 +850,7 @@ static void writeEOF(BattFsSuper *disk)
 	ASSERT(kfile_read(&fd1.fd, buf, sizeof(buf)) == sizeof(buf));
 	ASSERT(fd1.fd.seek_pos == sizeof(buf) + 4);
 	for (int i = 0; i < sizeof(buf); i++)
-		ASSERT(buf[i] == 0xff);
+		ASSERT(buf[i] == 0);
 
 	memset(buf, 0, sizeof(buf));
 	ASSERT(kfile_read(&fd1.fd, buf, sizeof(buf)) == sizeof(buf));
-- 
2.25.1