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Rewrote the implementation of the SwapEndian_16() and SwapEndian_32() functions so that they compile down in most instances to minimal loads and stores rather than complicated shifts.

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Fixed SCSI.c implementations of all the demos/projects casting the block count to a 32-bit temporary before calling SwapEndian_16().
This commit is contained in:
Dean Camera 2010-07-09 07:24:34 +00:00
parent 2b0e86243f
commit c326fe9605
8 changed files with 60 additions and 37 deletions
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39
LUFA/Common/Common.h
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@ -174,7 +174,21 @@
static inline uint16_t SwapEndian_16(uint16_t Word) ATTR_WARN_UNUSED_RESULT ATTR_CONST;
static inline uint16_t SwapEndian_16(uint16_t Word)
{
return ((Word >> 8) | (Word << 8));
uint8_t Temp;
union
{
uint16_t Word;
uint8_t Bytes[2];
} Data;
Data.Word = Word;
Temp = Data.Bytes[0];
Data.Bytes[0] = Data.Bytes[1];
Data.Bytes[1] = Temp;
return Data.Word;
}
/** Function to reverse the byte ordering of the individual bytes in a 32 bit number.
@ -186,10 +200,25 @@
static inline uint32_t SwapEndian_32(uint32_t DWord) ATTR_WARN_UNUSED_RESULT ATTR_CONST;
static inline uint32_t SwapEndian_32(uint32_t DWord)
{
return (((DWord & 0xFF000000) >> 24) |
((DWord & 0x00FF0000) >> 8) |
((DWord & 0x0000FF00) << 8) |
((DWord & 0x000000FF) << 24));
uint8_t Temp;
union
{
uint32_t DWord;
uint8_t Bytes[4];
} Data;
Data.DWord = DWord;
Temp = Data.Bytes[0];
Data.Bytes[0] = Data.Bytes[3];
Data.Bytes[3] = Temp;
Temp = Data.Bytes[1];
Data.Bytes[1] = Data.Bytes[2];
Data.Bytes[2] = Temp;
return Data.DWord;
}
/** Function to reverse the byte ordering of the individual bytes in a n byte number.