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http_date.[ch] encapsulate HTTP-date parse/compare (import from one of my development branches from 2015)master
9 changed files with 159 additions and 1 deletions
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/*
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* http_date - HTTP date manipulation |
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* |
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* Copyright(c) 2015 Glenn Strauss gstrauss()gluelogic.com All rights reserved |
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* License: BSD 3-clause (same as lighttpd) |
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*/ |
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#include "http_date.h" |
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#include "sys-time.h" |
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/**
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* https://tools.ietf.org/html/rfc7231
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* [RFC7231] 7.1.1.1 Date/Time Formats |
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* Prior to 1995, there were three different formats commonly used by |
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* servers to communicate timestamps. For compatibility with old |
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* implementations, all three are defined here. The preferred format is |
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* a fixed-length and single-zone subset of the date and time |
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* specification used by the Internet Message Format [RFC5322]. |
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* HTTP-date = IMF-fixdate / obs-date |
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* An example of the preferred format is |
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* Sun, 06 Nov 1994 08:49:37 GMT ; IMF-fixdate |
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* |
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* |
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* (intended for use with strftime() and strptime()) |
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* "%a, %d %b %Y %T GMT" |
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*/ |
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#if defined(__CYGWIN__) && defined(__STRICT_ANSI__) |
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/* (prototype for strptime() from cygwin /usr/include/time.h) */ |
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char *_EXFUN(strptime, (const char *__restrict, |
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const char *__restrict, |
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struct tm *__restrict)); |
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#endif |
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static char * |
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http_date_str_to_tm (const char * const s, struct tm * const tm) |
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{ |
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/* attempt strptime() using multiple date formats
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* support RFC 822,1123; RFC 850; and ANSI C asctime() date strings, |
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* as required by [RFC7231] https://tools.ietf.org/html/rfc7231#section-7.1
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* [RFC7231] 7.1.1.1 Date/Time Formats |
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* HTTP-date = IMF-fixdate / obs-date |
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* [...] |
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* A recipient that parses a timestamp value in an HTTP header field |
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* MUST accept all three HTTP-date formats. |
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*/ |
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static const char *datefmts[] = { |
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"%a, %d %b %Y %T GMT", /* RFC 822, RFC 1123; RFC 7231 IMF-fixdate */ |
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"%A, %d-%b-%y %T GMT", /* RFC 850 */ |
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"%a %b %d %T %Y" /* ANSI C asctime() (obsolete in POSIX.1-2008) */ |
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}; |
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char *p; |
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int i = 0; |
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do { |
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p = strptime(s, datefmts[i], tm); |
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} while (__builtin_expect( (NULL == p), 0) |
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&& ++i < (int)(sizeof(datefmts)/sizeof(char *))); |
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return p; /* NULL if error; date string could not be parsed */ |
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} |
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size_t |
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http_date_time_to_str (char * const s, const size_t max, const time_t t) |
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{ |
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/*('max' is expected to be >= 30 (IMF-fixdate is 29 chars + '\0'))*/ |
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struct tm tm; |
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return (__builtin_expect( (NULL != gmtime_r(&t, &tm)), 1)) |
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? strftime(s, max, "%a, %d %b %Y %T GMT", &tm) /* IMF-fixdate format */ |
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: 0; |
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} |
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#ifdef HAVE_TIMEGM |
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#define http_date_timegm(tm) timegm(tm) |
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#else |
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#ifdef _WIN32 |
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#define http_date_timegm(tm) _mkgmtime(tm) |
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#else |
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/* If OS missing timegm(), then for best portability it is recommended to set
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* $ export LC_TIME=C TZ=UTC0 |
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* |
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* tm->tm_isdst = 0 for mktime() to indicate daylight saving time not in effect |
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* which is fine since two strings should be GMT dates, and both are converted |
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* with mktime() and then the results compared */ |
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#define http_date_timegm(tm) ((tm)->tm_isdst = 0, mktime(tm)) |
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#endif |
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#endif |
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int |
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http_date_if_modified_since (const char * const ifmod, |
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const char * const lmod, time_t lmtime) |
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{ |
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/* if caller provides non-zero lmtime, it must match Last-Modified lmod,
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* and will typically be same arg given to http_response_set_last_modified() |
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* (small opt to elide one strptime(),timegm() call) |
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* (In absense of timegm(), substitute mktime(), which works reasonably well |
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* since mktime() strings are used for comparison of If-Modified-Since) |
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* (use mktime() to convert both strings for compare) */ |
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struct tm ifmodtm; |
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if (NULL == http_date_str_to_tm(ifmod, &ifmodtm)) |
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return 1; /* date parse error */ |
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#if defined(HAVE_TIMEGM) || defined(_WIN32) |
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if (0 == lmtime) |
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#endif |
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{ |
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struct tm lmodtm; |
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if (NULL == http_date_str_to_tm(lmod, &lmodtm)) |
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return 1; /* date parse error */ |
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lmtime = http_date_timegm(&lmodtm); |
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} |
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const time_t ifmtime = http_date_timegm(&ifmodtm); |
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return (lmtime > ifmtime); |
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/* returns 0 if not modified since,
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* returns 1 if modified since or date parse error */ |
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} |
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@ -0,0 +1,29 @@
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/*
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* http_date - HTTP date manipulation |
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* |
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* Copyright(c) 2015 Glenn Strauss gstrauss()gluelogic.com All rights reserved |
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* License: BSD 3-clause (same as lighttpd) |
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*/ |
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#ifndef INCLUDED_HTTP_DATE_H |
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#define INCLUDED_HTTP_DATE_H |
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#include "first.h" |
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#ifdef __cplusplus |
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extern "C" { |
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#endif |
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#define HTTP_DATE_SZ 30 /* (IMF-fixdate is 29 chars + '\0') */ |
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size_t http_date_time_to_str (char *s, size_t max, time_t t); |
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int http_date_if_modified_since (const char *ifmod, const char *lmod, time_t lmtime); |
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#ifdef __cplusplus |
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} |
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#endif |
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#endif |
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