Refactor file entry checksum calculation.

[android-x86/external-exfat.git] / libexfat / utils.c

diff --git a/libexfat/utils.c b/libexfat/utils.c
index 3fd718a..e0523e0 100644 (file)
--- a/libexfat/utils.c
+++ b/libexfat/utils.c
@@ -3,7 +3,7 @@
        exFAT file system implementation library.
 
        Free exFAT implementation.
-       Copyright (C) 2010-2013  Andrew Nayenko
+       Copyright (C) 2010-2016  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
@@ -52,6 +52,20 @@ void exfat_get_name(const struct exfat_node* node, char* buffer, size_t n)
                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)
+{
+       int 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;
@@ -59,34 +73,30 @@ uint16_t exfat_start_checksum(const struct exfat_entry_meta1* entry)
 
        for (i = 0; i < sizeof(struct exfat_entry); i++)
                if (i != 2 && i != 3) /* skip checksum field itself */
-                       sum = ((sum << 15) | (sum >> 1)) + ((const uint8_t*) entry)[i];
+                       sum = add_checksum_byte(sum, ((const uint8_t*) entry)[i]);
        return sum;
 }
 
 uint16_t exfat_add_checksum(const void* entry, uint16_t sum)
 {
-       int i;
-
-       for (i = 0; i < sizeof(struct exfat_entry); i++)
-               sum = ((sum << 15) | (sum >> 1)) + ((const uint8_t*) entry)[i];
-       return sum;
+       return add_checksum_bytes(sum, entry, sizeof(struct exfat_entry));
 }
 
 le16_t exfat_calc_checksum(const struct exfat_entry_meta1* meta1,
                const struct exfat_entry_meta2* meta2, const le16_t* name)
 {
        uint16_t checksum;
-       const int name_entries = DIV_ROUND_UP(utf16_length(name), EXFAT_ENAME_MAX);
+       const int name_entries = DIV_ROUND_UP(meta2->name_length, EXFAT_ENAME_MAX);
        int i;
 
        checksum = exfat_start_checksum(meta1);
        checksum = exfat_add_checksum(meta2, checksum);
        for (i = 0; i < name_entries; i++)
        {
-               struct exfat_entry_name name_entry = {EXFAT_ENTRY_FILE_NAME, 0};
-               memcpy(name_entry.name, name + i * EXFAT_ENAME_MAX,
+               checksum = add_checksum_byte(checksum, EXFAT_ENTRY_FILE_NAME);
+               checksum = add_checksum_byte(checksum, 0);
+               checksum = add_checksum_bytes(checksum, name + i * EXFAT_ENAME_MAX,
                                EXFAT_ENAME_MAX * sizeof(le16_t));
-               checksum = exfat_add_checksum(&name_entry, checksum);
        }
        return cpu_to_le16(checksum);
 }
@@ -123,8 +133,7 @@ le16_t exfat_calc_name_hash(const struct exfat* ef, const le16_t* name)
                uint16_t c = le16_to_cpu(name[i]);
 
                /* convert to upper case */
-               if (c < ef->upcase_chars)
-                       c = le16_to_cpu(ef->upcase[c]);
+               c = ef->upcase[c];
 
                hash = ((hash << 15) | (hash >> 1)) + (c & 0xff);
                hash = ((hash << 15) | (hash >> 1)) + (c >> 8);