reiserfslib: add basic extended attribute helpers

Signed-off-by: Jeff Mahoney <jeffm@suse.com>

reiserfscore/xattr.c

@@ -0,0 +1,116 @@
+#include <sys/types.h>
+#include <stdio.h>
+#include <errno.h>
+#include <sys/acl.h>
+#include "reiserfs_lib.h"
+
+static inline unsigned short from32to16(unsigned int x)
+{
+	/* add up 16-bit and 16-bit for 16+c bit */
+	x = (x & 0xffff) + (x >> 16);
+	/* add up carry.. */
+	x = (x & 0xffff) + (x >> 16);
+	return x;
+}
+
+static unsigned int do_csum(const unsigned char *buff, int len)
+{
+	int odd;
+	unsigned int result = 0;
+
+	if (len <= 0)
+		goto out;
+	odd = 1 & (unsigned long) buff;
+	if (odd) {
+#ifdef __LITTLE_ENDIAN
+		result += (*buff << 8);
+#else
+		result = *buff;
+#endif
+		len--;
+		buff++;
+	}
+	if (len >= 2) {
+		if (2 & (unsigned long) buff) {
+			result += *(unsigned short *) buff;
+			len -= 2;
+			buff += 2;
+		}
+		if (len >= 4) {
+			const unsigned char *end = buff + ((unsigned)len & ~3);
+			unsigned int carry = 0;
+			do {
+				unsigned int w = *(unsigned int *) buff;
+				buff += 4;
+				result += carry;
+				result += w;
+				carry = (w > result);
+			} while (buff < end);
+			result += carry;
+			result = (result & 0xffff) + (result >> 16);
+		}
+		if (len & 2) {
+			result += *(unsigned short *) buff;
+			buff += 2;
+		}
+	}
+	if (len & 1)
+#ifdef __LITTLE_ENDIAN
+		result += *buff;
+#else
+		result += (*buff << 8);
+#endif
+	result = from32to16(result);
+	if (odd)
+		result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
+out:
+	return result;
+}
+
+__wsum csum_partial(const void *buff, int len, __wsum wsum)
+{
+	unsigned int sum = (__force unsigned int)wsum;
+	unsigned int result = do_csum(buff, len);
+
+	/* add in old sum, and carry.. */
+	result += sum;
+	if (sum > result)
+		result += 1;
+	return (__force __wsum)result;
+}
+
+inline __u32 reiserfs_xattr_hash(const char *msg, int len)
+{
+	return csum_partial(msg, len, 0);
+}
+
+
+int reiserfs_check_xattr(const void *body, int len)
+{
+	const struct reiserfs_xattr_header *xah = body;
+	int hdrsz = sizeof(struct reiserfs_xattr_header);
+	__u32 hash;
+
+	if (len < hdrsz)
+		return -EINVAL;
+
+	hash = reiserfs_xattr_hash(body + hdrsz, len - hdrsz);
+	return xah->h_magic == cpu_to_le32(REISERFS_XATTR_MAGIC) &&
+	       le32_to_cpu(xah->h_hash) == hash;
+}
+
+int reiserfs_acl_count(size_t size)
+{
+	ssize_t s;
+	size -= sizeof(struct reiserfs_acl_header);
+	s = size - 4 * sizeof(struct reiserfs_acl_entry_short);
+	if (s < 0) {
+		if (size % sizeof(struct reiserfs_acl_entry_short))
+			return -1;
+		return size / sizeof(struct reiserfs_acl_entry_short);
+	} else {
+		if (s % sizeof(struct reiserfs_acl_entry))
+			return -1;
+		return s / sizeof(struct reiserfs_acl_entry) + 4;
+	}
+}