gswap.c

C编写的格式转换程序

/***************************************************************************
 * gswap.c:
 *
 * Functions for generalized, in-pace byte swapping between LSBF and
 * MSBF byte orders.
 *
 * Some standard integer types are needed, namely uint8_t and
 * uint32_t, (these are normally declared by including inttypes.h or
 * stdint.h).  Each function expects it's input to be a void pointer
 * to a quantity of the appropriate size.
 *
 * There are two versions of most routines, one that works on
 * quantities regardless of alignment (gswapX) and one that works on
 * memory aligned quantities (gswapXa).  The memory aligned versions
 * (gswapXa) are much faster than the other versions (gswapX), but the
 * memory *must* be aligned.
 *
 * Written by Chad Trabant,
 *   IRIS Data Management Center
 *
 * Version: 2006.344
 ***************************************************************************/

#include "lmplatform.h"

/* Swap routines that work on any (aligned or not) quantities */

void
ms_gswap2 ( void *data2 )
{
  uint8_t temp;
  
  union
  {
    uint8_t  c[2];
  } dat;
  
  memcpy( &dat, data2, sizeof(dat) );
  temp     = dat.c[0];
  dat.c[0] = dat.c[1];
  dat.c[1] = temp;
  memcpy( data2, &dat, sizeof(dat) );
}


void
ms_gswap3 ( void *data3 )
{
  uint8_t temp;
  
  union
  {
    uint8_t  c[3];
  } dat;
  
  memcpy( &dat, data3, sizeof(dat) );
  temp     = dat.c[0];
  dat.c[0] = dat.c[2];
  dat.c[2] = temp;
  memcpy( data3, &dat, sizeof(dat) );
}


void
ms_gswap4 ( void *data4 )
{
  uint8_t temp;

  union {
    uint8_t c[4];
  } dat;
  
  memcpy( &dat, data4, sizeof(dat) );
  temp     = dat.c[0];
  dat.c[0] = dat.c[3];
  dat.c[3] = temp;
  temp     = dat.c[1];
  dat.c[1] = dat.c[2];
  dat.c[2] = temp;
  memcpy( data4, &dat, sizeof(dat) );
}


void
ms_gswap8 ( void *data8 )
{
  uint8_t temp;
  
  union
  {
    uint8_t   c[8];
  } dat;
  
  memcpy( &dat, data8, sizeof(dat) );
  temp     = dat.c[0];
  dat.c[0] = dat.c[7];
  dat.c[7] = temp;
  
  temp     = dat.c[1];
  dat.c[1] = dat.c[6];
  dat.c[6] = temp;
  
  temp     = dat.c[2];
  dat.c[2] = dat.c[5];
  dat.c[5] = temp;
  
  temp     = dat.c[3];
  dat.c[3] = dat.c[4];
  dat.c[4] = temp;
  memcpy( data8, &dat, sizeof(dat) );
}

/* Swap routines that work on memory aligned quantities */

void
ms_gswap2a ( void *data2 )
{
  uint16_t *data = data2;
  
  *data=(((*data>>8)&0xff) | ((*data&0xff)<<8));
}


void
ms_gswap4a ( void *data4 )
{
  uint32_t *data = data4;
  
  *data=(((*data>>24)&0xff) | ((*data&0xff)<<24) |
	 ((*data>>8)&0xff00) | ((*data&0xff00)<<8));
}


void
ms_gswap8a ( void *data8 )
{
  uint32_t *data4 = data8;
  uint32_t h0, h1;
  
  h0 = data4[0];
  h0 = (((h0>>24)&0xff) | ((h0&0xff)<<24) |
	((h0>>8)&0xff00) | ((h0&0xff00)<<8));
  
  h1 = data4[1];
  h1 = (((h1>>24)&0xff) | ((h1&0xff)<<24) |
	((h1>>8)&0xff00) | ((h1&0xff00)<<8));
  
  data4[0] = h1;
  data4[1] = h0;
}