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Add documentation to our uri scanner

master
Dirk Engling 14 years ago
parent
commit
5be5e46f2a
  1. 32
      scan_urlencoded_query.c
  2. 6
      scan_urlencoded_query.h

32
scan_urlencoded_query.c

@ -14,6 +14,16 @@
relax = "+" | "," | "/" | ";" | "<" | ">" | ":"
*/
/* This matrix holds for each ascii character the information,
whether it is a non-terminating character for on of the three
scan states we are in, that is 'path', 'param' and 'value' from
/path?param=value&param=value, it is encoded in bit 0, 1 and 2
respectively
The top bit of lower nibble indicates, whether this character is
a hard terminator, ie. \0, \n or \s, where the whole scanning
process should terminate
*/
static const unsigned char is_unreserved[256] = {
8,0,0,0,0,0,0,0,0,0,8,0,0,8,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
0,7,8,8,8,7,0,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,4,7,6,
@ -25,6 +35,7 @@ static const unsigned char is_unreserved[256] = {
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
};
/* Do a fast nibble to hex representation conversion */
static unsigned char fromhex(unsigned char x) {
x-='0'; if( x<=9) return x;
x&=~0x20; x-='A'-'0';
@ -32,12 +43,19 @@ static unsigned char fromhex(unsigned char x) {
return 0xff;
}
/* Skip the value of a param=value pair */
void scan_urlencoded_skipvalue( char **string ) {
const unsigned char* s=*(const unsigned char**) string;
unsigned char f;
/* Since we are asked to skip the 'value', we assume to stop at
terminators for a 'value' string position */
while( ( f = is_unreserved[ *s++ ] ) & SCAN_SEARCHPATH_VALUE );
/* If we stopped at a hard terminator like \0 or \n, make the
next scan_urlencoded_query encounter it again */
if( f & SCAN_SEARCHPATH_TERMINATOR ) --s;
*string = (char*)s;
}
@ -46,21 +64,35 @@ ssize_t scan_urlencoded_query(char **string, char *deststring, SCAN_SEARCHPATH_F
unsigned char *d = (unsigned char*)deststring;
unsigned char b, c, f;
/* This is the main decoding loop.
'flag' determines, which characters are non-terminating in current context
(ie. stop at '=' and '&' if scanning for a 'param'; stop at '?' if scanning for the path )
*/
while( ( f = is_unreserved[ c = *s++ ] ) & flags ) {
/* When encountering an url escaped character, try to decode */
if( c=='%') {
if( ( b = fromhex(*s++) ) == 0xff ) return -1;
if( ( c = fromhex(*s++) ) == 0xff ) return -1;
c|=(b<<4);
}
/* Write (possibly decoded) character to output */
*d++ = c;
}
switch( c ) {
case 0: case '\r': case '\n': case ' ':
/* If we started scanning on a hard terminator, indicate we've finished */
if( d == (unsigned char*)deststring ) return -2;
/* Else make the next call to scan_urlencoded_param encounter it again */
--s;
break;
case '?':
/* XXX to help us parse path?param=value?param=value?... sent by µTorrent 1600
do not return an error but silently terminate
if( flags != SCAN_PATH ) return -1; */
break;
case '=':
if( flags != SCAN_SEARCHPATH_PARAM ) return -1;

6
scan_urlencoded_query.h

@ -11,7 +11,8 @@ typedef enum {
SCAN_SEARCHPATH_TERMINATOR = 8
} SCAN_SEARCHPATH_FLAG;
/* string pointer to source, pointer to next scan position on return
/* string in: pointer to source
out: pointer to next scan position
deststring pointer to destination
flags determines, what to parse
returns number of valid converted characters in deststring
@ -19,7 +20,8 @@ typedef enum {
*/
ssize_t scan_urlencoded_query(char **string, char *deststring, SCAN_SEARCHPATH_FLAG flags);
/* string pointer to source, pointer to next scan position on return
/* string in: pointer to value of a param=value pair to skip
out: pointer to next scan position on return
*/
void scan_urlencoded_skipvalue( char **string );

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