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ICU-6011 Change LESwaps.h to always swap through a pointer, so that it works even if the input data is mis-aligned.

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X-SVN-Rev: 23597
This commit is contained in:
Eric Mader 2008-03-15 00:30:39 +00:00
parent 1453934baa
commit 692287bab4
1 changed files with 12 additions and 46 deletions
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58
icu4c/source/layout/LESwaps.h
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@ -1,7 +1,7 @@
/*
*
* (C) Copyright IBM Corp. 1998-2005 - All Rights Reserved
* (C) Copyright IBM Corp. 1998-2008 - All Rights Reserved
*
*/
@ -23,15 +23,7 @@ U_NAMESPACE_BEGIN
*
* @stable ICU 2.8
*/
#if defined(U_IS_BIG_ENDIAN)
#if U_IS_BIG_ENDIAN
#define SWAPW(value) (value)
#else
#define SWAPW(value) LESwaps::swapWord(value)
#endif
#else
#define SWAPW(value) (LESwaps::isBigEndian() ? (value) : LESwaps::swapWord(value))
#endif
#define SWAPW(value) LESwaps::swapWord((const le_uint16 &) (value))
/**
* A convenience macro which invokes the swapLong member function
@ -39,21 +31,11 @@ U_NAMESPACE_BEGIN
*
* @stable ICU 2.8
*/
#if defined(U_IS_BIG_ENDIAN)
#if U_IS_BIG_ENDIAN
#define SWAPL(value) (value)
#else
#define SWAPL(value) LESwaps::swapLong(value)
#endif
#else
#define SWAPL(value) (LESwaps::isBigEndian() ? (value) : LESwaps::swapLong(value))
#endif
#define SWAPL(value) LESwaps::swapLong((const le_uint32 &) (value))
/**
* This class is used to access data which stored in big endian order
* regardless of the conventions of the platform. It has been designed
* to automatically detect the endian-ness of the platform, so that a
* compilation flag is not needed.
* regardless of the conventions of the platform.
*
* All methods are static and inline in an attempt to induce the compiler
* to do most of the calculations at compile time.
@ -63,26 +45,6 @@ U_NAMESPACE_BEGIN
class U_LAYOUT_API LESwaps /* not : public UObject because all methods are static */ {
public:
#if !defined(U_IS_BIG_ENDIAN)
/**
* This method detects the endian-ness of the platform by
* casting a pointer to a word to a pointer to a byte. On
* big endian platforms the FF will be in the byte with the
* lowest address. On little endian platforms, the FF will
* be in the byte with the highest address.
*
* @return TRUE if the platform is big endian
*
* @stable ICU 2.8
*/
static le_uint8 isBigEndian()
{
const le_uint16 word = 0xFF00;
return *((le_uint8 *) &word);
};
#endif
/**
* This method does the byte swap required on little endian platforms
* to correctly access a (16-bit) word.
@ -93,9 +55,11 @@ public:
*
* @stable ICU 2.8
*/
static le_uint16 swapWord(le_uint16 value)
static le_uint16 swapWord(const le_uint16 &value)
{
return (((le_uint8) (value >> 8)) | (value << 8));
const le_uint8 *p = (const le_uint8 *) &value;
return ((p[0] << 8) + p[1]);
};
/**
@ -108,9 +72,11 @@ public:
*
* @stable ICU 2.8
*/
static le_uint32 swapLong(le_uint32 value)
static le_uint32 swapLong(const le_uint32 &value)
{
return swapWord((le_uint16) (value >> 16)) | (swapWord((le_uint16) value) << 16);
const le_uint8 *p = (const le_uint8 *) &value;
return ((p[0] << 24) + (p[1] << 16) + (p[2] << 8) + p[3]);
};
private: