// SPDX-License-Identifier: GPL-2.0

  /*

   *  linux/fs/ext4/hash.c

   *
   * Copyright (C) 2002 by Theodore Ts'o

   */
  
  #include <linux/fs.h>

  #include <linux/compiler.h>
  #include <linux/bitops.h>

  #include "ext4.h"

  
  #define DELTA 0x9E3779B9
  
  static void TEA_transform(__u32 buf[4], __u32 const in[])
  {
  	__u32	sum = 0;
  	__u32	b0 = buf[0], b1 = buf[1];
  	__u32	a = in[0], b = in[1], c = in[2], d = in[3];
  	int	n = 16;
  
  	do {
  		sum += DELTA;
  		b0 += ((b1 << 4)+a) ^ (b1+sum) ^ ((b1 >> 5)+b);
  		b1 += ((b0 << 4)+c) ^ (b0+sum) ^ ((b0 >> 5)+d);

  	} while (--n);

  
  	buf[0] += b0;
  	buf[1] += b1;
  }

  /* F, G and H are basic MD4 functions: selection, majority, parity */
  #define F(x, y, z) ((z) ^ ((x) & ((y) ^ (z))))
  #define G(x, y, z) (((x) & (y)) + (((x) ^ (y)) & (z)))
  #define H(x, y, z) ((x) ^ (y) ^ (z))
  
  /*
   * The generic round function.  The application is so specific that
   * we don't bother protecting all the arguments with parens, as is generally
   * good macro practice, in favor of extra legibility.
   * Rotation is separate from addition to prevent recomputation
   */
  #define ROUND(f, a, b, c, d, x, s)	\
  	(a += f(b, c, d) + x, a = rol32(a, s))
  #define K1 0
  #define K2 013240474631UL
  #define K3 015666365641UL
  
  /*
   * Basic cut-down MD4 transform.  Returns only 32 bits of result.
   */
  static __u32 half_md4_transform(__u32 buf[4], __u32 const in[8])
  {
  	__u32 a = buf[0], b = buf[1], c = buf[2], d = buf[3];
  
  	/* Round 1 */
  	ROUND(F, a, b, c, d, in[0] + K1,  3);
  	ROUND(F, d, a, b, c, in[1] + K1,  7);
  	ROUND(F, c, d, a, b, in[2] + K1, 11);
  	ROUND(F, b, c, d, a, in[3] + K1, 19);
  	ROUND(F, a, b, c, d, in[4] + K1,  3);
  	ROUND(F, d, a, b, c, in[5] + K1,  7);
  	ROUND(F, c, d, a, b, in[6] + K1, 11);
  	ROUND(F, b, c, d, a, in[7] + K1, 19);
  
  	/* Round 2 */
  	ROUND(G, a, b, c, d, in[1] + K2,  3);
  	ROUND(G, d, a, b, c, in[3] + K2,  5);
  	ROUND(G, c, d, a, b, in[5] + K2,  9);
  	ROUND(G, b, c, d, a, in[7] + K2, 13);
  	ROUND(G, a, b, c, d, in[0] + K2,  3);
  	ROUND(G, d, a, b, c, in[2] + K2,  5);
  	ROUND(G, c, d, a, b, in[4] + K2,  9);
  	ROUND(G, b, c, d, a, in[6] + K2, 13);
  
  	/* Round 3 */
  	ROUND(H, a, b, c, d, in[3] + K3,  3);
  	ROUND(H, d, a, b, c, in[7] + K3,  9);
  	ROUND(H, c, d, a, b, in[2] + K3, 11);
  	ROUND(H, b, c, d, a, in[6] + K3, 15);
  	ROUND(H, a, b, c, d, in[1] + K3,  3);
  	ROUND(H, d, a, b, c, in[5] + K3,  9);
  	ROUND(H, c, d, a, b, in[0] + K3, 11);
  	ROUND(H, b, c, d, a, in[4] + K3, 15);
  
  	buf[0] += a;
  	buf[1] += b;
  	buf[2] += c;
  	buf[3] += d;
  
  	return buf[1]; /* "most hashed" word */
  }
  #undef ROUND
  #undef K1
  #undef K2
  #undef K3
  #undef F
  #undef G
  #undef H

  
  /* The old legacy hash */

  static __u32 dx_hack_hash_unsigned(const char *name, int len)

  {

  	__u32 hash, hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9;
  	const unsigned char *ucp = (const unsigned char *) name;
  
  	while (len--) {
  		hash = hash1 + (hash0 ^ (((int) *ucp++) * 7152373));
  
  		if (hash & 0x80000000)
  			hash -= 0x7fffffff;
  		hash1 = hash0;
  		hash0 = hash;
  	}
  	return hash0 << 1;
  }
  
  static __u32 dx_hack_hash_signed(const char *name, int len)
  {
  	__u32 hash, hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9;
  	const signed char *scp = (const signed char *) name;

  	while (len--) {

  		hash = hash1 + (hash0 ^ (((int) *scp++) * 7152373));

  		if (hash & 0x80000000)
  			hash -= 0x7fffffff;

  		hash1 = hash0;
  		hash0 = hash;
  	}

  	return hash0 << 1;
  }
  
  static void str2hashbuf_signed(const char *msg, int len, __u32 *buf, int num)
  {
  	__u32	pad, val;
  	int	i;
  	const signed char *scp = (const signed char *) msg;
  
  	pad = (__u32)len | ((__u32)len << 8);
  	pad |= pad << 16;
  
  	val = pad;
  	if (len > num*4)
  		len = num * 4;
  	for (i = 0; i < len; i++) {

  		val = ((int) scp[i]) + (val << 8);
  		if ((i % 4) == 3) {
  			*buf++ = val;
  			val = pad;
  			num--;
  		}
  	}
  	if (--num >= 0)
  		*buf++ = val;
  	while (--num >= 0)
  		*buf++ = pad;

  }

  static void str2hashbuf_unsigned(const char *msg, int len, __u32 *buf, int num)

  {
  	__u32	pad, val;
  	int	i;

  	const unsigned char *ucp = (const unsigned char *) msg;

  
  	pad = (__u32)len | ((__u32)len << 8);
  	pad |= pad << 16;
  
  	val = pad;
  	if (len > num*4)
  		len = num * 4;

  	for (i = 0; i < len; i++) {

  		val = ((int) ucp[i]) + (val << 8);

  		if ((i % 4) == 3) {
  			*buf++ = val;
  			val = pad;
  			num--;
  		}
  	}
  	if (--num >= 0)
  		*buf++ = val;
  	while (--num >= 0)
  		*buf++ = pad;
  }
  
  /*
   * Returns the hash of a filename.  If len is 0 and name is NULL, then
   * this function can be used to test whether or not a hash version is
   * supported.
   *
   * The seed is an 4 longword (32 bits) "secret" which can be used to
   * uniquify a hash.  If the seed is all zero's, then some default seed
   * may be used.
   *
   * A particular hash version specifies whether or not the seed is
   * represented, and whether or not the returned hash is 32 bits or 64
   * bits.  32 bit hashes will return 0 for the minor hash.
   */

  int ext4fs_dirhash(const char *name, int len, struct dx_hash_info *hinfo)

  {
  	__u32	hash;
  	__u32	minor_hash = 0;
  	const char	*p;
  	int		i;
  	__u32		in[8], buf[4];

  	void		(*str2hashbuf)(const char *, int, __u32 *, int) =
  				str2hashbuf_signed;

  
  	/* Initialize the default seed for the hash checksum functions */
  	buf[0] = 0x67452301;
  	buf[1] = 0xefcdab89;
  	buf[2] = 0x98badcfe;
  	buf[3] = 0x10325476;
  
  	/* Check to see if the seed is all zero's */
  	if (hinfo->seed) {

  		for (i = 0; i < 4; i++) {

  			if (hinfo->seed[i]) {
  				memcpy(buf, hinfo->seed, sizeof(buf));

  				break;

  			}

  		}

  	}
  
  	switch (hinfo->hash_version) {

  	case DX_HASH_LEGACY_UNSIGNED:
  		hash = dx_hack_hash_unsigned(name, len);
  		break;

  	case DX_HASH_LEGACY:

  		hash = dx_hack_hash_signed(name, len);

  		break;

  	case DX_HASH_HALF_MD4_UNSIGNED:
  		str2hashbuf = str2hashbuf_unsigned;

  	case DX_HASH_HALF_MD4:
  		p = name;
  		while (len > 0) {

  			(*str2hashbuf)(p, len, in, 8);

  			half_md4_transform(buf, in);
  			len -= 32;
  			p += 32;
  		}
  		minor_hash = buf[2];
  		hash = buf[1];
  		break;

  	case DX_HASH_TEA_UNSIGNED:
  		str2hashbuf = str2hashbuf_unsigned;

  	case DX_HASH_TEA:
  		p = name;
  		while (len > 0) {

  			(*str2hashbuf)(p, len, in, 4);

  			TEA_transform(buf, in);
  			len -= 16;
  			p += 16;
  		}
  		hash = buf[0];
  		minor_hash = buf[1];
  		break;
  	default:
  		hinfo->hash = 0;
  		return -1;
  	}
  	hash = hash & ~1;

  	if (hash == (EXT4_HTREE_EOF_32BIT << 1))
  		hash = (EXT4_HTREE_EOF_32BIT - 1) << 1;

  	hinfo->hash = hash;
  	hinfo->minor_hash = minor_hash;
  	return 0;
  }