fs: exfat: Import libexfat from fuse-exfat

Import most of libexfat from [1] except for log.c verbatim. The code
does not even compile and further adjustments and integration into
U-Boot filesystem code is in the next patch.

[1] https://github.com/relan/exfat
    0b41c6d3560d ("CI: bump FreeBSD to 13.1.")

Acked-by: Tom Rini <trini@konsulko.com>
Signed-off-by: Marek Vasut <marex@denx.de>
diff --git a/fs/exfat/utils.c b/fs/exfat/utils.c
new file mode 100644
index 0000000..0d97b65
--- /dev/null
+++ b/fs/exfat/utils.c
@@ -0,0 +1,192 @@
+/*
+	utils.c (04.09.09)
+	exFAT file system implementation library.
+
+	Free exFAT implementation.
+	Copyright (C) 2010-2023  Andrew Nayenko
+
+	This program is free software; you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 2 of the License, or
+	(at your option) any later version.
+
+	This program is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License along
+	with this program; if not, write to the Free Software Foundation, Inc.,
+	51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+*/
+
+#include "exfat.h"
+#include <string.h>
+#include <stdio.h>
+#include <inttypes.h>
+
+void exfat_stat(const struct exfat* ef, const struct exfat_node* node,
+		struct stat* stbuf)
+{
+	memset(stbuf, 0, sizeof(struct stat));
+	if (node->attrib & EXFAT_ATTRIB_DIR)
+		stbuf->st_mode = S_IFDIR | (0777 & ~ef->dmask);
+	else
+		stbuf->st_mode = S_IFREG | (0777 & ~ef->fmask);
+	stbuf->st_nlink = 1;
+	stbuf->st_uid = ef->uid;
+	stbuf->st_gid = ef->gid;
+	stbuf->st_size = node->size;
+	stbuf->st_blocks = ROUND_UP(node->size, CLUSTER_SIZE(*ef->sb)) / 512;
+	stbuf->st_mtime = node->mtime;
+	stbuf->st_atime = node->atime;
+	/* set ctime to mtime to ensure we don't break programs that rely on ctime
+	   (e.g. rsync) */
+	stbuf->st_ctime = node->mtime;
+}
+
+void exfat_get_name(const struct exfat_node* node,
+		char buffer[EXFAT_UTF8_NAME_BUFFER_MAX])
+{
+	if (exfat_utf16_to_utf8(buffer, node->name, EXFAT_UTF8_NAME_BUFFER_MAX,
+				EXFAT_NAME_MAX) != 0)
+		exfat_bug("failed to convert name to UTF-8");
+}
+
+static uint16_t add_checksum_byte(uint16_t sum, uint8_t byte)
+{
+	return ((sum << 15) | (sum >> 1)) + byte;
+}
+
+static uint16_t add_checksum_bytes(uint16_t sum, const void* buffer, size_t n)
+{
+	size_t i;
+
+	for (i = 0; i < n; i++)
+		sum = add_checksum_byte(sum, ((const uint8_t*) buffer)[i]);
+	return sum;
+}
+
+uint16_t exfat_start_checksum(const struct exfat_entry_meta1* entry)
+{
+	uint16_t sum = 0;
+	size_t i;
+
+	for (i = 0; i < sizeof(struct exfat_entry); i++)
+		if (i != 2 && i != 3) /* skip checksum field itself */
+			sum = add_checksum_byte(sum, ((const uint8_t*) entry)[i]);
+	return sum;
+}
+
+uint16_t exfat_add_checksum(const void* entry, uint16_t sum)
+{
+	return add_checksum_bytes(sum, entry, sizeof(struct exfat_entry));
+}
+
+le16_t exfat_calc_checksum(const struct exfat_entry* entries, int n)
+{
+	uint16_t checksum;
+	int i;
+
+	checksum = exfat_start_checksum((const struct exfat_entry_meta1*) entries);
+	for (i = 1; i < n; i++)
+		checksum = exfat_add_checksum(entries + i, checksum);
+	return cpu_to_le16(checksum);
+}
+
+uint32_t exfat_vbr_start_checksum(const void* sector, size_t size)
+{
+	size_t i;
+	uint32_t sum = 0;
+
+	for (i = 0; i < size; i++)
+		/* skip volume_state and allocated_percent fields */
+		if (i != 0x6a && i != 0x6b && i != 0x70)
+			sum = ((sum << 31) | (sum >> 1)) + ((const uint8_t*) sector)[i];
+	return sum;
+}
+
+uint32_t exfat_vbr_add_checksum(const void* sector, size_t size, uint32_t sum)
+{
+	size_t i;
+
+	for (i = 0; i < size; i++)
+		sum = ((sum << 31) | (sum >> 1)) + ((const uint8_t*) sector)[i];
+	return sum;
+}
+
+le16_t exfat_calc_name_hash(const struct exfat* ef, const le16_t* name,
+		size_t length)
+{
+	size_t i;
+	uint16_t hash = 0;
+
+	for (i = 0; i < length; i++)
+	{
+		uint16_t c = le16_to_cpu(name[i]);
+
+		/* convert to upper case */
+		c = ef->upcase[c];
+
+		hash = ((hash << 15) | (hash >> 1)) + (c & 0xff);
+		hash = ((hash << 15) | (hash >> 1)) + (c >> 8);
+	}
+	return cpu_to_le16(hash);
+}
+
+void exfat_humanize_bytes(uint64_t value, struct exfat_human_bytes* hb)
+{
+	size_t i;
+	/* 16 EB (minus 1 byte) is the largest size that can be represented by
+	   uint64_t */
+	const char* units[] = {"bytes", "KB", "MB", "GB", "TB", "PB", "EB"};
+	uint64_t divisor = 1;
+	uint64_t temp = 0;
+
+	for (i = 0; ; i++, divisor *= 1024)
+	{
+		temp = (value + divisor / 2) / divisor;
+
+		if (temp == 0)
+			break;
+		if (temp / 1024 * 1024 == temp)
+			continue;
+		if (temp < 10240)
+			break;
+	}
+	hb->value = temp;
+	hb->unit = units[i];
+}
+
+void exfat_print_info(const struct exfat_super_block* sb,
+		uint32_t free_clusters)
+{
+	struct exfat_human_bytes hb;
+	off_t total_space = le64_to_cpu(sb->sector_count) * SECTOR_SIZE(*sb);
+	off_t avail_space = (off_t) free_clusters * CLUSTER_SIZE(*sb);
+
+	printf("File system version           %hhu.%hhu\n",
+			sb->version.major, sb->version.minor);
+	exfat_humanize_bytes(SECTOR_SIZE(*sb), &hb);
+	printf("Sector size          %10"PRIu64" %s\n", hb.value, hb.unit);
+	exfat_humanize_bytes(CLUSTER_SIZE(*sb), &hb);
+	printf("Cluster size         %10"PRIu64" %s\n", hb.value, hb.unit);
+	exfat_humanize_bytes(total_space, &hb);
+	printf("Volume size          %10"PRIu64" %s\n", hb.value, hb.unit);
+	exfat_humanize_bytes(total_space - avail_space, &hb);
+	printf("Used space           %10"PRIu64" %s\n", hb.value, hb.unit);
+	exfat_humanize_bytes(avail_space, &hb);
+	printf("Available space      %10"PRIu64" %s\n", hb.value, hb.unit);
+}
+
+bool exfat_match_option(const char* options, const char* option_name)
+{
+	const char* p;
+	size_t length = strlen(option_name);
+
+	for (p = strstr(options, option_name); p; p = strstr(p + 1, option_name))
+		if ((p == options || p[-1] == ',') &&
+				(p[length] == ',' || p[length] == '\0'))
+			return true;
+	return false;
+}