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/**
* \file rfc822.c
* Code for slicing and dicing RFC822 mail headers.
*
* How to parse RFC822 headers in C. This is not a fully conformant
* implementation of RFC822 or RFC2822, but it has been in production use in a
* widely-deployed MTA (fetcmail) since 1996 without complaints. Really
* perverse combinations of quoting and commenting could break it.
*
* \author Eric S. Raymond <esr@thyrsus.com>, 1997. This source code example
* is part of fetchmail and the Unix Cookbook, and are released under the MIT
* license.
*/
#include <stdio.h>
#include <ctype.h>
#include <string.h>
#include <stdlib.h>
#define HEADER_END(p) ((p)[0] == '\n' && ((p)[1] != ' ' && (p)[1] != '\t'))
#define START_HDR 0 /**< before header colon */
#define SKIP_JUNK 1 /**< skip whitespace, \n, and junk */
#define BARE_ADDRESS 2 /**< collecting address without delimiters */
#define INSIDE_DQUOTE 3 /**< inside double quotes */
#define INSIDE_PARENS 4 /**< inside parentheses */
#define INSIDE_BRACKETS 5 /**< inside bracketed address */
#define ENDIT_ALL 6 /**< after last address */
/**
* Parse addresses in succession out of a specified RFC822 header.
*
* \param hdr header to be parsed, NUL to continue previous \p hdr.
*/
char *next_address(const char *hdr)
{
static char address[BUFSIZ];
static int tp;
static const char *hp;
static int state, oldstate;
int parendepth = 0;
#define NEXTTP() ((tp < sizeof(address)-1) ? tp++ : tp)
if (hdr)
{
hp = hdr;
state = START_HDR;
tp = 0;
}
for (; *hp; hp++)
{
if (state == ENDIT_ALL) /* after last address */
return(NULL);
else if (HEADER_END(hp))
{
state = ENDIT_ALL;
if (tp)
{
while (isspace(address[--tp]))
continue;
address[++tp] = '\0';
tp = 0;
return (address);
}
return(NULL);
}
else if (*hp == '\\') /* handle RFC822 escaping */
{
if (state != INSIDE_PARENS)
{
address[NEXTTP()] = *hp++; /* take the escape */
address[NEXTTP()] = *hp; /* take following char */
}
}
else switch (state)
{
case START_HDR: /* before header colon */
if (*hp == ':')
state = SKIP_JUNK;
break;
case SKIP_JUNK: /* looking for address start */
if (*hp == '"') /* quoted string */
{
oldstate = SKIP_JUNK;
state = INSIDE_DQUOTE;
address[NEXTTP()] = *hp;
}
else if (*hp == '(') /* address comment -- ignore */
{
parendepth = 1;
oldstate = SKIP_JUNK;
state = INSIDE_PARENS;
}
else if (*hp == '<') /* begin <address> */
{
state = INSIDE_BRACKETS;
tp = 0;
}
else if (*hp != ',' && !isspace(*hp))
{
--hp;
state = BARE_ADDRESS;
}
break;
case BARE_ADDRESS: /* collecting address without delimiters */
if (*hp == ',') /* end of address */
{
if (tp)
{
address[NEXTTP()] = '\0';
state = SKIP_JUNK;
tp = 0;
return(address);
}
}
else if (*hp == '(') /* beginning of comment */
{
parendepth = 1;
oldstate = BARE_ADDRESS;
state = INSIDE_PARENS;
}
else if (*hp == '<') /* beginning of real address */
{
state = INSIDE_BRACKETS;
tp = 0;
}
else if (*hp == '"') /* quoted word, copy verbatim */
{
oldstate = state;
state = INSIDE_DQUOTE;
address[NEXTTP()] = *hp;
}
else if (!isspace(*hp)) /* just take it, ignoring whitespace */
address[NEXTTP()] = *hp;
break;
case INSIDE_DQUOTE: /* we're in a quoted string, copy verbatim */
if (*hp != '"')
address[NEXTTP()] = *hp;
else
{
address[NEXTTP()] = *hp;
state = oldstate;
}
break;
case INSIDE_PARENS: /* we're in a parenthesized comment, ignore */
if (*hp == '(')
++parendepth;
else if (*hp == ')')
--parendepth;
if (parendepth == 0)
state = oldstate;
break;
case INSIDE_BRACKETS: /* possible <>-enclosed address */
if (*hp == '>') /* end of address */
{
address[NEXTTP()] = '\0';
state = SKIP_JUNK;
++hp;
tp = 0;
return(address);
}
else if (*hp == '<') /* nested <> */
tp = 0;
else if (*hp == '"') /* quoted address */
{
address[NEXTTP()] = *hp;
oldstate = INSIDE_BRACKETS;
state = INSIDE_DQUOTE;
}
else /* just copy address */
address[NEXTTP()] = *hp;
break;
}
}
return(NULL);
}
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