mach0data.ic

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/**********************************************************************
Utilities for converting data from the database file
to the machine format. 

(c) 1995 Innobase Oy

Created 11/28/1995 Heikki Tuuri
***********************************************************************/

/***********************************************************
The following function is used to store data in one byte. */
UNIV_INLINE
void 
mach_write_to_1(
/*============*/
	byte*   b,      /* in: pointer to byte where to store */
	ulint   n)      /* in: ulint integer to be stored, >= 0, < 256 */ 
{
	ut_ad(b);
	ut_ad(n <= 0xFFUL);

	b[0] = (byte)n;
}

/************************************************************
The following function is used to fetch data from one byte. */
UNIV_INLINE
ulint 
mach_read_from_1(
/*=============*/
			/* out: ulint integer, >= 0, < 256 */
	byte*   b)      /* in: pointer to byte */
{
	ut_ad(b);
	return((ulint)(b[0]));
}

/***********************************************************
The following function is used to store data in two consecutive
bytes. We store the most significant byte to the lowest address. */
UNIV_INLINE
void 
mach_write_to_2(
/*============*/
	byte*   b,      /* in: pointer to two bytes where to store */
	ulint	n)      /* in: ulint integer to be stored */ 
{
	ut_ad(b);
	ut_ad(n <= 0xFFFFUL);

	b[0] = (byte)(n >> 8);
	b[1] = (byte)(n);
}

/************************************************************
The following function is used to fetch data from 2 consecutive
bytes. The most significant byte is at the lowest address. */
UNIV_INLINE
ulint 
mach_read_from_2(
/*=============*/
			/* out: ulint integer */
	byte*   b)      /* in: pointer to 2 bytes */
{
	ut_ad(b);
	return( ((ulint)(b[0]) << 8)
		+ (ulint)(b[1])
	      );
}

/************************************************************
The following function is used to convert a 16-bit data item
to the canonical format, for fast bytewise equality test
against memory. */
UNIV_INLINE
uint16
mach_encode_2(
/*==========*/
			/* out: 16-bit integer in canonical format */
	ulint	n)	/* in: integer in machine-dependent format */
{
	uint16	ret;
	ut_ad(2 == sizeof ret);
	mach_write_to_2((byte*) &ret, n);
	return(ret);
}
/************************************************************
The following function is used to convert a 16-bit data item
from the canonical format, for fast bytewise equality test
against memory. */
UNIV_INLINE
ulint
mach_decode_2(
/*==========*/
			/* out: integer in machine-dependent format */
	uint16	n)	/* in: 16-bit integer in canonical format */
{
	ut_ad(2 == sizeof n);
	return(mach_read_from_2((byte*) &n));
}

/***********************************************************
The following function is used to store data in 3 consecutive
bytes. We store the most significant byte to the lowest address. */
UNIV_INLINE
void 
mach_write_to_3(
/*============*/
	byte*   b,      /* in: pointer to 3 bytes where to store */
	ulint	n)      /* in: ulint integer to be stored */ 
{
	ut_ad(b);
	ut_ad(n <= 0xFFFFFFUL);

	b[0] = (byte)(n >> 16);
	b[1] = (byte)(n >> 8);
	b[2] = (byte)(n);
}

/************************************************************
The following function is used to fetch data from 3 consecutive
bytes. The most significant byte is at the lowest address. */
UNIV_INLINE
ulint 
mach_read_from_3(
/*=============*/
			/* out: ulint integer */
	byte*   b)      /* in: pointer to 3 bytes */
{
	ut_ad(b);
	return( ((ulint)(b[0]) << 16)
		+ ((ulint)(b[1]) << 8)
		+ (ulint)(b[2])
	      );
}

/***********************************************************
The following function is used to store data in four consecutive
bytes. We store the most significant byte to the lowest address. */
UNIV_INLINE
void 
mach_write_to_4(
/*============*/
	byte*   b,      /* in: pointer to four bytes where to store */
	ulint	n)      /* in: ulint integer to be stored */ 
{
	ut_ad(b);

#if (0 == 1) && !defined(__STDC__) && defined(UNIV_INTEL) && (UNIV_WORD_SIZE == 4) && defined(UNIV_VISUALC)

	/* We do not use this even on Intel, because unaligned accesses may
	be slow */

	__asm	MOV	EAX, n
	__asm	BSWAP	EAX	/* Intel is little-endian, must swap bytes */
	__asm	MOV	n, EAX
	
	*((ulint*)b) = n;
#else
	b[0] = (byte)(n >> 24);
	b[1] = (byte)(n >> 16);
	b[2] = (byte)(n >> 8);
	b[3] = (byte)n;
#endif
}

/************************************************************
The following function is used to fetch data from 4 consecutive
bytes. The most significant byte is at the lowest address. */
UNIV_INLINE
ulint 
mach_read_from_4(
/*=============*/
			/* out: ulint integer */
	byte*   b)      /* in: pointer to four bytes */
{
#if (0 == 1) && !defined(__STDC__) && defined(UNIV_INTEL) && (UNIV_WORD_SIZE == 4) && defined(UNIV_VISUALC)
	/* We do not use this even on Intel, because unaligned accesses may
	be slow */

	ulint	res;

	ut_ad(b);

	__asm	MOV	EDX, b
	__asm	MOV	ECX, DWORD PTR [EDX]
	__asm	BSWAP	ECX	/* Intel is little-endian, must swap bytes */
	__asm	MOV	res, ECX

	return(res);
#else
	ut_ad(b);
	return( ((ulint)(b[0]) << 24)
		+ ((ulint)(b[1]) << 16)
		+ ((ulint)(b[2]) << 8)
		+ (ulint)(b[3])
	      );
#endif
}

/*************************************************************
Writes a ulint in a compressed form where the first byte codes the
length of the stored ulint. We look at the most significant bits of
the byte. If the most significant bit is zero, it means 1-byte storage,
else if the 2nd bit is 0, it means 2-byte storage, else if 3rd is 0,
it means 3-byte storage, else if 4th is 0, it means 4-byte storage, 
else the storage is 5-byte. */
UNIV_INLINE
ulint
mach_write_compressed(
/*==================*/
			/* out: compressed size in bytes */
	byte*   b,      /* in: pointer to memory where to store */
	ulint   n)      /* in: ulint integer (< 2^32) to be stored */ 
{
	ut_ad(b);

	if (n < 0x80UL) {
		mach_write_to_1(b, n);
		return(1);
	} else if (n < 0x4000UL) {
		mach_write_to_2(b, n | 0x8000UL);
		return(2);
	} else if (n < 0x200000UL) {
		mach_write_to_3(b, n | 0xC00000UL);
		return(3);
	} else if (n < 0x10000000UL) {
		mach_write_to_4(b, n | 0xE0000000UL);
		return(4);
	} else {
		mach_write_to_1(b, 0xF0UL);
		mach_write_to_4(b + 1, n);
		return(5);
	}
}

/*************************************************************
Returns the size of a ulint when written in the compressed form. */
UNIV_INLINE
ulint
mach_get_compressed_size(
/*=====================*/
			/* out: compressed size in bytes */
	ulint   n)      /* in: ulint integer (< 2^32) to be stored */ 
{
	if (n < 0x80UL) {
		return(1);
	} else if (n < 0x4000UL) {
		return(2);
	} else if (n < 0x200000UL) {
		return(3);
	} else if (n < 0x10000000UL) {
		return(4);
	} else {
		return(5);
	}
}

/*************************************************************
Reads a ulint in a compressed form. */
UNIV_INLINE
ulint
mach_read_compressed(
/*=================*/
			/* out: read integer (< 2^32) */
	byte*   b)      /* in: pointer to memory from where to read */
{
	ulint	flag;

	ut_ad(b);

	flag = mach_read_from_1(b);

	if (flag < 0x80UL) {
		return(flag);
	} else if (flag < 0xC0UL) {
		return(mach_read_from_2(b) & 0x7FFFUL);
	} else if (flag < 0xE0UL) {
		return(mach_read_from_3(b) & 0x3FFFFFUL);
	} else if (flag < 0xF0UL) {
		return(mach_read_from_4(b) & 0x1FFFFFFFUL);
	} else {
		ut_ad(flag == 0xF0UL);
		return(mach_read_from_4(b + 1));
	}
}

/***********************************************************
The following function is used to store data in 8 consecutive
bytes. We store the most significant byte to the lowest address. */
UNIV_INLINE
void 
mach_write_to_8(
/*============*/
	byte*   b,      /* in: pointer to 8 bytes where to store */
	dulint	n)      /* in: dulint integer to be stored */ 
{
	ut_ad(b);

	mach_write_to_4(b, ut_dulint_get_high(n));
	mach_write_to_4(b + 4, ut_dulint_get_low(n));
}

/************************************************************
The following function is used to fetch data from 8 consecutive
bytes. The most significant byte is at the lowest address. */
UNIV_INLINE
dulint 
mach_read_from_8(
/*=============*/
			/* out: dulint integer */
	byte*   b)      /* in: pointer to 8 bytes */
{
	ulint	high;
	ulint	low;

	ut_ad(b);

	high = mach_read_from_4(b);
	low = mach_read_from_4(b + 4);

	return(ut_dulint_create(high, low)); 
}

/***********************************************************
The following function is used to store data in 7 consecutive
bytes. We store the most significant byte to the lowest address. */
UNIV_INLINE
void 
mach_write_to_7(
/*============*/
	byte*   b,      /* in: pointer to 7 bytes where to store */
	dulint	n)      /* in: dulint integer to be stored */ 
{
	ut_ad(b);

	mach_write_to_3(b, ut_dulint_get_high(n));
	mach_write_to_4(b + 3, ut_dulint_get_low(n));
}

/************************************************************
The following function is used to fetch data from 7 consecutive
bytes. The most significant byte is at the lowest address. */
UNIV_INLINE
dulint 
mach_read_from_7(
/*=============*/
			/* out: dulint integer */
	byte*   b)      /* in: pointer to 7 bytes */
{
	ulint	high;
	ulint	low;

	ut_ad(b);

	high = mach_read_from_3(b);
	low = mach_read_from_4(b + 3);

	return(ut_dulint_create(high, low)); 
}