Quoted-Printable is also one of the commonly used coding methods in MIME messages. Like BASE64, it also intenss the input string or data encoding a printable string of the ASCII code.
The basic method of the quoted-printable encoding is: input data within 33-60, 62-126, direct output; other need to be encoded as "=" plus two bytes of HEX code (uppercase). To ensure that the output line does not exceed the specified length, the "= / r / n" sequence can be added as a soft back bus at the end of the line.
Int Encodequoted (const unsigned char * psrc, char * pdst, int nsrclen, int nmaxlinelen)
{
INT ndstlen; // output character count
INT NLINELEN; / / Output Director count
Ndstlen = 0;
NLINELEN = 0;
For (int i = 0; i { // ASCII 33-60, 62-126 is originally output, the rest needs to be encoded IF ((* psrc> = '!') && (* psrc <= '~') && (* psrc! = '='))) { * PDST = (char) * psrc; NDSTLEN ; NLINELEN ; } Else { Sprintf (PDST, "=% 02x", * psrc); PDST = 3; NDSTLEN = 3; NLINELEN = 3; } / / Output wrap? IF (nLinelen> = nmaxlinelen - 3) { Sprintf (PDST, "= / R / N"); PDST = 3; NDSTLEN = 3; NLINELEN = 0; } } // Output add a end value * PDST = '/ 0'; Return ndstlen; } Quoted-printable decoding is very simple, it will be in turn of the encoding process. INT decodequoted (const char * psrc, unsigned char * pdst, int nsrclen) { INT ndstlen; // output character count INT I; i = 0; Ndstlen = 0; While (i { IF (strncmp (psrc, "= / r / n", 3) == 0) // soft back to the bus, skip { PSRC = 3; I = 3; } Else { IF (* psrc == '=') // is the encoded byte { SSCANF (PSRC, "=% 02x", PDST); PDST ; PSRC = 3; I = 3; } ELSE // Non-coded bytes { * PDST = (unsigned char) * psrc ; i ; } NDSTLEN ; } } // Output add a end value * PDST = '/ 0'; Return ndstlen; } [related resources] RFC / STD document: Internet FAQ Archives BHW98 column: http://www.9cbs.net/develop/author/netauthor/bhw98/ First release: 2003-06-23 Last revision: 2003-06-23
