byteswap.c

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// no byteswap.h on Apple
#ifdef APPLE
#include <libkern/OSByteOrder.h>
#define bswap_16(x) OSSwapInt16(x)
#define bswap_32(x) OSSwapInt32(x)
#define bswap_64(x) OSSwapInt64(x)
#else
#include <byteswap.h>
#endif
#include <stdint.h>
#include <stdlib.h>
#include <stdio.h>
 
static int send_errors = 1; 
void
fast_byteswap_errors(int flag)
{
    send_errors=flag;
}
 
static int
simple_swap_32(void *data,size_t len)
{
    size_t i;
    uint32_t *udata;
    if ((size_t)data & 0x3)
    {
        if (send_errors)
            fprintf(stderr,"ERROR: pointer to 32-bit integer is not 32-bit aligned (pointer is 0x%llx)\n",(long long)data);
        return 0;
    }
    udata=data;
    for(i=0;i<len;i++)
        udata[i]=
            ( (udata[i]>>24)&0xff ) |
            ( (udata[i]>>8)&0xff00 ) |
            ( (udata[i]<<8)&0xff0000 ) |
            ( (udata[i]<<24)&0xff000000 );
    return 1;
}
 
static int
simple_swap_16(void *data,size_t len)
{
    size_t i;
    uint16_t *udata;
    if ((size_t)data & 0x1)
    {
        if (send_errors)
            fprintf(stderr,"ERROR: pointer to 16-bit integer is not 16-bit aligned (pointer is 0x%llx)\n",(long long)data);
        return 0;
    }
    udata=data;
    for(i=0;i<len;i++)
        udata[i]=
            ( (udata[i]>>8)&0xff ) |
            ( (udata[i]<<8)&0xff00 );
    return 1;
}
 
static int
macro_swap_64(void *data,size_t len)
{
    size_t i;
    uint64_t *udata;
    if ((size_t)data & 0x5)
    {
        if (send_errors)
            fprintf(stderr,"ERROR: pointer to 64-bit integer is not 64-bit aligned (pointer is 0x%llx)\n",(long long)data);
        return 0;
    }
    udata=data;
    for(i=0;i<len;i++)
        udata[i]=bswap_64(udata[i]);
    return 1;
}
 
int
fast_byteswap(void *data,int bytes,size_t count)
{
    switch(bytes) {
    case 1: return 1;
    case 2: return simple_swap_16(data,count);
    case 4: return simple_swap_32(data,count);
    case 8: return macro_swap_64(data,count);
    default: return 0;
    }
}
 
/* Include the C library file for definition/control */
#include "clib.h"
#include "stdio.h"
#include "fast-byteswap.h"
 
void
byteswap_(char *data, int *nbyte, int *nnum)
{
    int i, j;
    char swap[256];
    int nb = *nbyte;
    int nn = *nnum;
    size_t count = *nnum;
    
    if (!fast_byteswap(data, nb, count))
    {
        fprintf(stderr,"ERROR NOT ALIGNED SLOW CODE USED (nb and count %9d %9lu )\n",nb, count);
        /* It failed.  No data was byteswapped because it is not aligned */
        for (j = 0; j < nn; j++)
        {
            for (i = 0; i < nb; i++)
                swap[i] = data[j * nb + i];
            for (i = 0; i < nb; i++)
                data[j * nb + i] = swap[nb - i - 1];
        }
    }
}