encode_b64.c

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#include "stralloc.h"
#include "uint_t.h"
#include "mime.h"
#include "errtxt.h"
#include "idx.h"
#include "logmsg.h"
 
#define WHO "encode_b64"

 
 
static const unsigned char base64char[64] =
   "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 
static unsigned int pos = 0;
static unsigned int i = 0;
static uint32 hold32;
static unsigned char *cpout;
 
static void die_nomem() { logmsg(WHO,111,FATAL,ERR_NOMEM); }
 
static void addone(unsigned char ch)
{
 if (!(pos++))
    hold32 = (uint32) ch;
  else
    hold32 = (hold32 << 8) | ch;
  if (pos == 3) {
    *cpout++ = base64char[(hold32 >> 18) & 0x3f];
    *cpout++ = base64char[(hold32 >> 12) & 0x3f];
    *cpout++ = base64char[(hold32 >>  6) & 0x3f];
    *cpout++ = base64char[hold32 & 0x3f];
    if (++i == 18) {
      *cpout++ = '\n';
      i = 0;
    }
    pos = 0;
  }
}
 
static void dorest(void)
{
  switch (pos) {
    case 2:
      hold32 = hold32 << 2;
      *cpout++ = base64char[(hold32 >> 12) & 0x3f];
      *cpout++ = base64char[(hold32 >> 06) & 0x3f];
      *cpout++ = base64char[hold32 & 0x3f];
      *cpout++ = '=';
      break;
    case 1:
      hold32 = hold32 << 4;
      *cpout++ = base64char[(hold32 >> 06) & 0x3f];
      *cpout++ = base64char[hold32 & 0x3f];
      *cpout++ = '=';
      *cpout++ = '=';
      break;
    default:
      break;
  }
  *cpout++ = '\n';
}   
 
void encode_b64(const unsigned char *indata,unsigned int n,stralloc *outdata,int control)      
{
  unsigned char ch;
 
  if (control == 1) {
    pos = 0;
    i = 0;
  }
  if (!stralloc_copys(outdata,"")) die_nomem();
  if (!stralloc_ready(outdata,n*8/3 + n/72 + 5)) die_nomem();
  cpout = (unsigned char *) outdata->s;
  while (n--) {
    ch = *indata++;
    if (ch == '\n')
      addone('\r');
    addone(ch);
  }
  if (control == 2)
    dorest();
  outdata->len = (unsigned int) (cpout - (unsigned char *) outdata->s);
}