Quoted-Printable
Quoted-Printable is referred to as qp, which is generally used in the Email system. It is usually used for the 8-bit character of a small amount of text, such as foxmail, uses it to do coding for the subject and the alias. This coding should be well identified: it has a lot of "=". Here is an example of it:
MIME-VERSION: 1.0
Content-Transfer-Encoding: Quoted-Printable
= A1 = b6 = C2 = D2 = C2 = EB = CB = E3 = b7 = a8 = b4 = f3 = c8 = AB = a1 = b7
= D7 = f7 = D5 = DF: MOGAO = A3 = AC = B0 = D7 = D4 = C6 = bb = c6 = ba = D7 = D5 = be = a3 = a8TELNET: //202.112.20.132: 23 = A3 = A9 = B3 = C9 = D4 = b1 = a1 = a3
= C4 = aa = b8 = DF = C8 = ED = BC = Fe = b9 = a4 = D7 = f7 = ca = d2 = a3 = bahttp: //mogao.bentiun.net
Emailto: Mogao@371.net
***************************************************
* = B3 = fd = C1 = CB = BC = C7 = D2 = E4 = Ca = B2 = C3 = B4 = B6 = BC = B2 = bb = b4 = f8 = D7 = DF = A3 = AC = B3 = fd = C1 = CB = D7 = E3 = BC = a3 = ca = b2 = c3 = b4 = b6 = bc = b2 = bb = c1 = f4 = cf = c2 *
***************************************************
You can separate it into a file, named: mogao.eml, double-click to open it with Outlook (the original information of the first two behaviors, starting from the fourth line as coding content).
QP's algorithm can be said to be the easiest to say that the coded efficiency is the lowest (its coding rate is 1: 3), which is specifically to handle 8-bit characters. Its algorithm is: read a character, if the ASCII code is greater than 127, that is, the character's top 8 is 1, the encoding is performed, otherwise it is ignored (sometimes 7-bit character encoding). The encoding is simple, look at the C language description below:
/ * QP code * /
Void QP (Unsigned Char Sour, Unsigned Char first, unsigned char second)
/ *
SOUR: Character to be encoded
First: The first character after encoding
Second: The second character encoded
First and second are return values
* /
{
IF (Sour> 127)
{first = SOUR >> 4;
SECOND = SOUR & 15;
IF (first> 9) first = 55;
Else First = 48;
IF (Second> 9) Second = 55; Else Second = 48;
Printf ("% C% C% C", '=', first, second);
}
}
/ * QP decoding * /
Void UQP (Unsigned Char Sour, Unsigned Char SECOND)
/ *
Sour: Decoded characters
First: QP code first character
Second: The second character of QP code
SOUR is the return value
* /
{
IF (first> = 65) first- = 55;
Else first- = 48;
IF (Second> = 65) second- = 55;
Else Second- = 48;
Sour = NULL;
SOUR = first << 4;
Sour | = second;
}
See RFC2045 for detailed descriptions and accurate definitions of QP.
