decode_qp.c

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

 
static const char char16table[128] = {
    -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
    -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
    -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
     0, 1, 2, 3,  4, 5, 6, 7,  8, 9,-1,-1, -1,-1,-1,-1,
    -1,10,11,12, 13,14,15,-1, -1,-1,-1,-1, -1,-1,-1,-1,
    -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
    -1,10,11,12, 13,14,15,-1, -1,-1,-1,-1, -1,-1,-1,-1,
    -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1
};
 
#define char16enc(c)  (((c) & 0x80) ? -1 : char16table[(int)(c)])
 
static void die_nomem() { logmsg(WHO,111,FATAL,ERR_NOMEM); }
 
void decode_qp(const char *cpfrom,unsigned int n,stralloc *outdata)
{
  const char *cp,*cpnext;
  char ch1, ch2;                       /* need to be signed */
  char ch;
 
  cp = cpfrom;
  cpnext = cp + n;
  if (!stralloc_readyplus(outdata,n)) die_nomem();
 
  while (cp < cpnext) {
    ch = *cp++;
    if (ch == '_') ch = ' ';                   /* '_' -> space */
    if (ch == '=') {                                 /* "=F8" -> '\xF8' */
      if (*cp == '\n') {                         /* skip soft line break */
        ++cp;
        continue;
      }
      ch1 = char16enc(*cp); ++cp;
      if (cp >= cpnext) break;
      ch2 = char16enc(*cp); ++cp;
      if (ch1 >= 0 && ch2 >= 0) {            /* ignore illegals */
        ch = (ch1 << 4 | ch2) & 0xff;
      }
    }
    if (!stralloc_append(outdata,&ch)) die_nomem();
  }
}