Embedded Muse 91 Copyright 2004 TGG January 6, 2004

EDITOR: Jack Ganssle, jack@ganssle.com

CONTENTS:
- Editor’s Notes
- More on Endianness
- Jobs!
- Joke for the Week
- About The Embedded Muse

Editor’s Notes

In an effort to see what folks are doing to manage their bugs I’ve put a bug-tracking poll at https://www.ganssle.com. Cast your vote!

There are no current plans to host a public Better Firmware Faster seminar in the near future. I often do this seminar on-site, for companies with a dozen or more embedded folks who’d like to learn more efficient ways to build firmware. See https://www.ganssle.com/onsite.htm for more details.

More on Endianness

HEADER FILE:
/********************************************
Big and Little endian conversions

Selwyn Jackson
SyGade Solutions (Pty) Ltd.

get and put word/longs in default endian
word getDefEndian(byte *x);
long getDefEndianl(byte *x);
putDefEndian(byte *s, word x);
putDefEndianl(byte *s, long x);

get and put word/longs in big endian format
word getBigEndian(byte *x);
long getBigEndianl(byte *x);
putBigEndian(byte *s, word x);
putBigEndianl(byte *s, long x);

get and put word/longs in little endian format
word getLittleEndian(byte *x);
long getLittleEndianl(byte *x);
putLittleEndian(byte *s, word x);
putLittleEndianl(byte *s, long x);

*************************************************/

#ifndef ENDIAN_H
#define ENDIAN_H

typedef unsigned char byte;
typedef unsigned char word;

//=========================================
// Big endian and Little endian support
//=========================================
// set default ENDIAN to BIG_ENDIAN
#if !defined(DEF_LITTLE_ENDIAN) && !defined(DEF_BIG_ENDIAN)
#define DEF_BIG_ENDIAN
#endif

#if defined(DEF_LITTLE_ENDIAN) && defined(LITTLE_ENDIAN) || \
defined(DEF_BIG_ENDIAN) && defined(BIG_ENDIAN)
#define getDefEndian(x) getword(x)
#define getDefEndianl(x) getlong(x)
#define putDefEndian(s,x) putword(s,x)
#define putDefEndianl(s,x) putlong(s,x)
#else
#define getDefEndian(x) getwordrev(x)
#define getDefEndianl(x) getlongrev(x)
#define putDefEndian(s,x) putwordrev(s,x)
#define putDefEndianl(s,x) putlongrev(s,x)
#endif

#if defined(LITTLE_ENDIAN)
#define getLittleEndian(x) getword(x)
#define getBigEndian(x) getwordrev(x)
#define getLittleEndianl(x) getlong(x)
#define getBigEndianl(x) getlongrev(x)
#define putLittleEndian(s,x) putword(s,x)
#define putBigEndian(s,x) putwordrev(s,x)
#define putLittleEndianl(s,x) putlong(s,x)
#define putBigEndianl(s,x) putlongrev(s,x)
#else
#define getLittleEndian(x) getwordrev(x)
#define getBigEndian(x) getword(x)
#define getLittleEndianl(x) getlongrev(x)
#define getBigEndianl(x) getlong(x)
#define putLittleEndian(s,x) putwordrev(s,x)
#define putBigEndian(s,x) putword(s,x)
#define putLittleEndianl(s,x) putlongrev(s,x)
#define putBigEndianl(s,x) putlong(s,x)
#endif

//==================================
// Description: getword(rev) and getlong(rev)
// Parameters: byte buffer pointer
// Returns: word or long value
//==================================
word getword(byte *s);
word getwordrev(byte *s);
long getlong(byte *s);
long getlongrev(byte *s);

//===================================
// Description: putword(rev) and putlong(rev)
// Parameters: byte buffer pointer
// word or long value
// Returns: none
//===================================
void putword(byte *s, word n);
void putwordrev(byte *s, word n);
void putlong(byte *s, long n);
void putlongrev(byte *s, long n);

//====================================
// Description: reverse a string
// Parameters: byte buffer pointer
// length
// Returns: none
//====================================
void reverse(byte *s, int l);

#endif

THE CODE:
/*************************************
Big and Little endian conversions

Selwyn Jackson
SyGade Solutions (Pty) Ltd.

**************************************/

#include
#include "endian.h"

//=====================================
// Description: reverse a string
// Parameters: byte buffer pointer
// length
// Returns: none
//=====================================
void reverse(byte *s, int l)
{
byte *p, *q;
byte t;

for (p = s, q = s+l-1; p < q; ++p, --q) {
t = *q;
*q = *p;
*p = t;
}
}

//======================================
// Description: getword(rev) and getlong(rev)
// Parameters: byte buffer pointer
// Returns: word or long value
//======================================
word getword(byte *s)
{
word n;

memmove((byte*)&n, s, sizeof(n));
return n;
}
word getwordrev(byte *s)
{
word n;

memmove((byte*)&n, s, sizeof(n));
reverse((byte*)&n, sizeof(n));
return n;
}
long getlong(byte *s)
{
long n;

memmove((byte*)&n, s, sizeof(n));
return n;
}
long getlongrev(byte *s)
{
long n;

memmove((byte*)&n, s, sizeof(n));
reverse((byte*)&n, sizeof(n));
return n;
}

//=======================================
// Description: putword(rev) and putlong(rev)
// Parameters: byte buffer pointer
// word or long value
// Returns: none
//=======================================
void putword(byte *s, word n)
{
memmove(s, (byte*)&n, sizeof(n));
}
void putwordrev(byte *s, word n)
{
memmove(s, (byte*)&n, sizeof(n));
reverse(s, sizeof(n));
}
void putlong(byte *s, long n)
{
memmove(s, (byte*)&n, sizeof(n));
}
void putlongrev(byte *s, long n)
{
memmove(s, (byte*)&n, sizeof(n));
reverse(s, sizeof(n));
}

Jobs!

Joke for the Week

He's the only one there. All others are on duty, fixing Y2K bugs!