[Flex-help] multipart form lexer sample

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Here is something that extracts the file from stdin where stdin is
sent from a web client.  So stdin has all of the protocol headers and
such and a sample is appended at the bottom:

Its a lexer that parses that and extracts an embedded file.  Maybe you
guys could improve it.  I don't like it much.  I don't like the fact
that line ending characters may be either \n or \r\n.  I don't like
the possible memory consumption when scanning for the end of the
FILE_DATA.

%{
#include <stdio.h>
#include <string.h>

char boundary[1024];
%}

%s HEADERS
%s BODY
%s BOUNDARY
%s PARM_NAME
%s PARM_VALUE
%s FILE_TYPE
%s FILE_DATA

EOL     \r?\n
DOT     [^\r\n]

%%

<INITIAL>^(POST|GET|HEAD)" "{DOT}*"HTTP/1."[12]{DOT}*{EOL}      BEGIN(HEADERS);

<HEADERS>^"Content-Length: "[0-9]+{EOL}                         ;
<HEADERS>^"Content-Type: multipart/form-data; boundary="        BEGIN(BOUNDARY);
<HEADERS>^{EOL}                                                 BEGIN(BODY);
<HEADERS>{DOT}                                                  ;

<PARM_NAME>{DOT}+"filename="{DOT}*{EOL}
BEGIN(FILE_TYPE);
<PARM_NAME>{DOT}+{EOL}                                          ;
<PARM_NAME>^{EOL}
BEGIN(PARM_VALUE);

<PARM_VALUE>{DOT}+{EOL}                                         BEGIN(BODY);

<BOUNDARY>{DOT}*{EOL}
strncpy(boundary,yytext,yyleng - 1);  BEGIN(HEADERS);

<FILE_TYPE>{DOT}+{EOL}                                          ;
<FILE_TYPE>^{EOL}
BEGIN(FILE_DATA);
<FILE_DATA>{DOT}                                                ECHO;
<FILE_DATA>^--{DOT}*{EOL}                                       {

    if (strncmp(yytext + 2, boundary, strlen(boundary)) == 0) {
        BEGIN(PARM_NAME);
    } else {
        REJECT;
    }

                                                                }

<BODY>^--{DOT}*{EOL}                                            {

    if (strncmp(yytext + 2, boundary, strlen(boundary)) == 0) {
        BEGIN(PARM_NAME);
    } else {
        REJECT;
    }

                                                                }
<BODY>{DOT}                                                     ;

<<EOF>>                                                         yyterminate();

%%
int main(void) {

    yylex();

    exit(0);

}

Sample STDIN from a web client:

POST /form1?some_stuff HTTP/1.1
Host: whatever
Content-Length: 98398
Content-Type: ...
Other Headers: ...

--boundary
..
EOF

[Flex-help] multipart form lexer sample

flex is a tool for generating scanners

[Flex-help] multipart form lexer sample