SP. A recipient MAY replace any linear white space with a single SP
before interpreting the field value or forwarding the message
downstream.
LWS = [CRLF] 1*( SP | HT )
The TEXT rule is only used for descriptive field contents and values
that are not intended to be interpreted by the message parser. Words
of *TEXT MAY contain characters from character sets other than
ISO-8859-1 [ISO 8859] only when encoded according to the rules of RFC
2047 [RFC2047].
TEXT = <any OCTET except CTLs,
but including LWS>
A CRLF is allowed in the definition of TEXT only as part of a header
field continuation. It is expected that the folding LWS will be
replaced with a single SP before interpretation of the TEXT value.
Hexadecimal numeric characters are used in several protocol elements.
HEX = "A" | "B" | "C" | "D" | "E" | "F"
| "a" | "b" | "c" | "d" | "e" | "f" | DIGIT
Many HTTP/1.1 header field values consist of words separated by LWS
or special characters. These special characters MUST be in a quoted
string to be used within a parameter value.
token = 1*<any CHAR except CTLs or separators>
separators = "(" | ")" | "<" | ">" | "@"
| "," | ";" | ":" | "\" | <">
| "/" | "[" | "]" | "?" | "="
| "{" | "}" | SP | HT
A string of text is parsed as a single word if it is quoted using
double-quote marks.
quoted-string = ( <"> qdstr-val <"> )
qdstr-val = *( qdtext | quoted-pair )
qdtext = <any TEXT except <">>
Note that LWS is NOT implicit between the double-quote marks (<">)
surrounding a qdstr-val and the qdstr-val; any LWS will be considered
part of the qdstr-val. This is also the case for quotation marks
surrounding any other construct.
The backslash character ("\") MAY be used as a single-character
quoting mechanism only within qdstr-val and comment constructs.
quoted-pair = "\" CHAR
The value of this construct is CHAR. Note that an effect of this rule
is that backslash must be quoted.
8 Sample Code
The sample implementation in [Digest] also applies to DIGEST-MD5.
The following code implements the conversion from UTF-8 to 8859-1 if
necessary.
/* if the string is entirely in the 8859-1 subset of UTF-8, then
* translate to 8859-1 prior to MD5
*/
void MD5_UTF8_8859_1(MD5_CTX *ctx, const unsigned char *base,
int len)
{
const unsigned char *scan, *end;
unsigned char cbuf;
end = base + len;
for (scan = base; scan < end; ++scan) {
if (*scan > 0xC3) break; /* abort if outside 8859-1 */
if (*scan >= 0xC0 && *scan <= 0xC3) {
if (++scan == end || *scan < 0x80 || *scan > 0xBF)
break;
}
}
/* if we found a character outside 8859-1, don't alter string
*/
if (scan < end) {
MD5Update(ctx, base, len);
return;
}
/* convert to 8859-1 prior to applying hash
*/
do {
for (scan = base; scan < end && *scan < 0xC0; ++scan)
;
if (scan != base) MD5Update(ctx, base, scan - base);
if (scan + 1 >= end) break;
cbuf = ((scan[0] & 0x3) << 6) | (scan[1] & 0x3f);
MD5Update(ctx, &cbuf, 1);
base = scan + 2;
} while (base < end);
}
9 Full Copyright Statement
Copyright (C) The Internet Society (2000). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Acknowledgement
Funding for the RFCEditor function is currently provided by the
Internet Society.