proxy2ch/utils.h

#pragma once

static const char threadTimestampFmt[] = "%Y/%m/%d %H:%M:%S %Z";
static const char httpTimestampFmt[] = "%a, %d %b %Y %H:%M:%S GMT";

static void *
memmem_priv(const void *l, size_t l_len, const void *s, size_t s_len)
{
	register char *cur, *last;
	const char *cl = (const char *)l;
	const char *cs = (const char *)s;
	
	/* we need something to compare */
	if (l_len == 0 || s_len == 0)
		return NULL;
	
	/* "s" must be smaller or equal to "l" */
	if (l_len < s_len)
		return NULL;
	
	/* special case where s_len == 1 */
	if (s_len == 1)
		return (void *)memchr(l, (int)*cs, l_len);
	
	/* the last position where its possible to find "s" in "l" */
	last = (char *)cl + l_len - s_len;
	
	for (cur = (char *)cl; cur <= last; cur++)
		if (cur[0] == cs[0] && memcmp(cur, cs, s_len) == 0)
			return cur;
	
	return NULL;
}

static int decryptMail(unsigned char *decrypted, char *encrypted)
{
	char current[5]="0x";
	unsigned char *ptr = decrypted;
	current[2] = encrypted[0];
	current[3] = encrypted[1];
	unsigned int r = strtol(current,NULL,16);
	int len = strlen(encrypted);
	int n = 2;
	for(;n<len;n+=2) {
		current[2] = encrypted[n];
		current[3] = encrypted[n+1];
		unsigned int i = strtol(current,NULL,16);
		*ptr++ = i^r;
	}
	*ptr = 0;
	//fprintf(stderr,"%s->%s\n",encrypted,decrypted);
	return ptr - decrypted;
}

static size_t header_callback_proxy(char *buffer, size_t size, size_t nitems, void *userdata)
{
	BBS2chProxyConnection *conn = reinterpret_cast<BBS2chProxyConnection *>(userdata);
	if(conn->status > 0) return size*nitems;
	else if(conn->status == -1) {
		if(!memcmp(buffer,"\r\n",2)) {
			conn->status = 0;
		}
		return size*nitems;
	}
	if(!strncasecmp("HTTP/", buffer, 5) && !strchr(buffer, ':')) {
		const char *ptr = buffer + 5;
		const char *end = buffer + size*nitems;
		while(*ptr != ' ' && ptr < end) ptr++;
		while(*ptr == ' ' && ptr < end) ptr++;
		if(ptr < end) {
			int code = atoi(ptr);
			if (code == 100) {
				conn->status = -1;
				return size*nitems;
			}
		}
	}
	
	if(!strncasecmp("Connection",buffer,10)) {
		conn->socketToClient->writeString("Connection: Close\r\n");
		return size*nitems;
	}
	else if(!strncasecmp("Transfer-Encoding",buffer,17)) {
		if(allow_chunked && !conn->isClientHttp1_0 && strstr(buffer+19,"chunked")) {
			conn->isResponseChunked = true;
			//fprintf(stderr,"%s",buffer);
			size_t ret = conn->socketToClient->write(buffer, size*nitems);
			return ret;
		}
		return size*nitems;
	}
	else if(conn->force5ch && !strncasecmp("Set-Cookie:",buffer,11)) {
		char *ptr = (char *)memmem_priv(buffer,size*nitems,"domain=",7);
		if(ptr) {
			char *end = ptr;
			while(*end != ';' && *end != '\r') end++;
			ptr = (char *)memmem_priv(ptr,end-ptr,"5ch.net",7);
			if(ptr) {
				conn->socketToClient->write(buffer, ptr-buffer);
				conn->socketToClient->write("2", 1);
				conn->socketToClient->write(ptr+1, size*nitems-(ptr+1-buffer));
				return size*nitems;
			}
		}
		return conn->socketToClient->write(buffer, size*nitems);
	}
	else {
		if (conn->bbscgi) {
			if (!strncasecmp("X-Chx-Error:", buffer, 12)) {
				const char *ptr = buffer + 12;
				while (*ptr == ' ') ptr++;
				log_printf(0, "Posting to bbs.cgi has been cancelled. Reason: %s", ptr);
				if (*ptr == 'E') {
					int code = atoi(ptr+1);
					if ((code >= 3310 && code <= 3311) || /* inconsistent with User-Agent or something? */
						(code >= 3320 && code <= 3324) || /* key expiration? */
						(code >= 3390 && code <= 3392))   /* 3390: BAN, 3391-3392: key expiration? */
						conn->setMonaKey("", code);
				}
			}
			else if (!strncasecmp("X-MonaKey:", buffer, 10)) {
				const char *ptr = buffer + 10;
				while (*ptr == ' ') ptr++;
				const char *end = ptr;
				while (*end != '\n' && *end != '\r' && *end) end++;
				conn->setMonaKey(std::string(ptr, end-ptr), 0);
			}
		}
		size_t ret = conn->socketToClient->write(buffer, size*nitems);
		//fprintf(stderr,"%s",buffer);
		if(!memcmp(buffer,"\r\n",2)) {
			conn->status = 1;
		}
		return ret;
	}
}

static size_t header_callback_bbscgi(char *buffer, size_t size, size_t nitems, void *userdata)
{
	BBS2chProxyConnection *conn = reinterpret_cast<BBS2chProxyConnection *>(userdata);
	if(conn->status > 0) return size*nitems;
	else if(conn->status == -1) {
		if(!memcmp(buffer,"\r\n",2)) {
			conn->status = 0;
		}
		return size*nitems;
	}
	if(!strncasecmp("HTTP/", buffer, 5) && !strchr(buffer, ':')) {
		const char *ptr = buffer + 5;
		const char *end = buffer + size*nitems;
		while(*ptr != ' ' && ptr < end) ptr++;
		while(*ptr == ' ' && ptr < end) ptr++;
		if(ptr < end) {
			int code = atoi(ptr);
			if (code == 100) {
				conn->status = -1;
				return size*nitems;
			}
		}
	}
	
	if(!strncasecmp("Connection",buffer,10)) {
		conn->responseHeaders.append("Connection: Close\r\n");
		return size*nitems;
	}
	else if(!strncasecmp("Transfer-Encoding",buffer,17)) {
		if(allow_chunked && !conn->isClientHttp1_0 && strstr(buffer+19,"chunked")) {
			conn->isResponseChunked = true;
			//fprintf(stderr,"%s",buffer);
			conn->responseHeaders.append(buffer, size*nitems);
		}
		return size*nitems;
	}
	else if(conn->force5ch && !strncasecmp("Set-Cookie:",buffer,11)) {
		char *ptr = (char *)memmem_priv(buffer,size*nitems,"domain=",7);
		if(ptr) {
			char *end = ptr;
			while(*end != ';' && *end != '\r') end++;
			ptr = (char *)memmem_priv(ptr,end-ptr,"5ch.net",7);
			if(ptr) {
				conn->responseHeaders.append(buffer, ptr-buffer);
				conn->responseHeaders.append(1, '2');
				conn->responseHeaders.append(ptr+1, size*nitems-(ptr+1-buffer));
				return size*nitems;
			}
		}
		conn->responseHeaders.append(buffer, size*nitems);
		return size*nitems;
	}
	else {
		if (!strncasecmp("X-Chx-Error:", buffer, 12)) {
			const char *ptr = buffer + 12;
			while (*ptr == ' ') ptr++;
			log_printf(0, "Posting to bbs.cgi has been cancelled. Reason: %s", ptr);
			if (*ptr == 'E') {
				int code = atoi(ptr+1);
				if ((code >= 3310 && code <= 3311) || /* inconsistent with User-Agent or something? */
					(code >= 3320 && code <= 3324) || /* key expiration? */
					(code >= 3390 && code <= 3392))   /* 3390: BAN, 3391-3392: key expiration? */
				{
					conn->setMonaKey("", code);
					conn->status = 2;
					return 0;
				}
			}
		}
		else if (!strncasecmp("X-MonaKey:", buffer, 10)) {
			const char *ptr = buffer + 10;
			while (*ptr == ' ') ptr++;
			const char *end = ptr;
			while (*end != '\n' && *end != '\r' && *end) end++;
			conn->setMonaKey(std::string(ptr, end-ptr), 0);
		}
		conn->responseHeaders.append(buffer, size*nitems);
		//fprintf(stderr,"%s",buffer);
		if(!memcmp(buffer,"\r\n",2)) {
			conn->socketToClient->write(conn->responseHeaders.data(), conn->responseHeaders.size());
			conn->status = 1;
		}
		return size*nitems;
	}
}

static size_t write_callback_proxy(char *buffer, size_t size, size_t nitems, void *userdata)
{
	BBS2chProxyConnection *conn = reinterpret_cast<BBS2chProxyConnection *>(userdata);
	if(conn->isResponseChunked) {
		char buf[64];
		snprintf(buf, 64, "%lx\r\n", size*nitems);
		conn->socketToClient->write(buf, strlen(buf));
	}
	size_t ret = conn->socketToClient->write(buffer, size*nitems);
	if(conn->isResponseChunked) conn->socketToClient->writeString("\r\n");
	return ret;
}

static size_t header_callback_download(char *buffer, size_t size, size_t nitems, void *userdata)
{
	DataStorage *data = reinterpret_cast<DataStorage *>(userdata);
	if(!strncasecmp("Connection",buffer,10)) {
		data->appendBytes("Connection: Close\r\n",19);
		return size*nitems;
	}
	else if(!strncasecmp("Transfer-Encoding",buffer,17)) {
		return size*nitems;
	}
	else {
		data->appendBytes(buffer,size*nitems);
		return size*nitems;
	}
}

static size_t write_callback_download(char *buffer, size_t size, size_t nitems, void *userdata)
{
	DataStorage *data = reinterpret_cast<DataStorage *>(userdata);
	size_t downloaded = size*nitems;
	data->appendBytes(buffer, downloaded);
	return downloaded;
}

static size_t read_callback_proxy(char *buffer, size_t size, size_t nitems, void *userdata)
{
	BBS2chProxyConnection *conn = reinterpret_cast<BBS2chProxyConnection *>(userdata);
	if (size*nitems < 1) return 0;
	if (conn->isClientChunked) {
		size_t chunkSize;
		char tmp[64];
		if (!conn->content_length) {
			if (!conn->socketToClient->readLine(tmp, 64)) return 0;
			chunkSize = strtol(tmp, NULL, 16);
			if (chunkSize == 0) {
				return 0;
			}
		}
		else {
			chunkSize = conn->content_length;
			conn->content_length = 0;
		}
		if (chunkSize <= size*nitems) {
			size_t ret = conn->socketToClient->read(buffer, chunkSize);
			if (ret <= 0) return 0;
			conn->socketToClient->readLine(tmp, 64);
			return ret;
		}
		else {
			size_t ret = conn->socketToClient->read(buffer, size*nitems);
			if (ret <= 0) return 0;
			conn->content_length = chunkSize - ret;
			return ret;
		}
	}
	else if (conn->content_length) {
		size_t bytesToRead = conn->content_length;
		if (size*nitems < conn->content_length) bytesToRead = size*nitems;
		size_t ret = conn->socketToClient->read(buffer, bytesToRead);
		conn->content_length -= ret;
		return ret;
	}
	return 0;
}

static void sendBasicHeaders(int respCode, const char *respMsg, IBBS2chProxySocket *socket)
{
	char date[256];
	time_t now = time(0);
	strftime(date, 256, httpTimestampFmt, gmtime(&now));
	std::ostringstream ss;
	ss << "HTTP/1.1 " << respCode << " " << respMsg << "\r\n";
	if(0 >= socket->writeString(ss.str())) return;
	if(0 >= socket->writeString("Connection: Close\r\n")) return;
	if(0 >= socket->writeString("Server: 2ch Proxy\r\n")) return;
	if(0 >= socket->writeString(std::string("Date: ") + date + "\r\n")) return;
}

static void sendResponse(int respCode, const char *respMsg, IBBS2chProxySocket *socket)
{
	sendBasicHeaders(respCode, respMsg, socket);
	if(0 >= socket->writeString("Content-Type: text/plain; charset=UTF-8\r\n")) return;
	if(0 >= socket->writeString("\r\n")) return;
	if(respCode >= 400) {
		if(0 >= socket->writeString("　　  ∧＿∧　　 ／￣￣￣￣￣\n")) return;
		if(0 >= socket->writeString(std::string("　　（ ´∀｀）＜　") + respMsg + "\n")) return;
		if(0 >= socket->writeString("　　（　　 　）  ＼＿＿＿＿＿\n")) return;
		if(0 >= socket->writeString("　　 │ │  │\n")) return;
		if(0 >= socket->writeString("　　（＿_）＿）\n")) return;
	}
}

static double getCurrentTime(void)
{
#ifdef _WIN32
	FILETIME ft;
	GetSystemTimeAsFileTime(&ft);
	unsigned long long now = ft.dwHighDateTime;
	now <<= 32;
	now |= ft.dwLowDateTime;
	return (double)(now * 1e-7 - 11644473600.0);
#else
	struct timeval tv;
	gettimeofday(&tv, NULL);
	return (double)(tv.tv_sec + tv.tv_usec * 1e-6);
#endif
}

static std::string decodeURIComponent(const char *input, size_t inputLength, bool decodePlus)
{
	std::string output;
	for (int i=0;i<inputLength;i++) {
		if (input[i] == '%') {
			if (i < inputLength - 2) {
				char from[3];
				char *end;
				from[0] = input[i+1];
				from[1] = input[i+2];
				from[2] = 0;
				unsigned long n = strtoul(from, &end, 16);
				if (n < 256 && end == from+2) {
					output.append(1, n);
					i += 2;
					continue;
				}
			}
		}
		else if (decodePlus && input[i] == '+') {
			output.append(" ");
			continue;
		}
		output.append(1, input[i]);
	}
	return output;
}

static std::string encodeURIComponent(const char *input, size_t inputLength, bool spaceAsPlus)
{
	std::string output;
	for (int i=0;i<inputLength;i++) {
		unsigned char c = (unsigned char)input[i];
		if ((c >= '0' && c <= '9') ||
			(c >= 'A' && c <= 'Z') ||
			(c >= 'a' && c <= 'z') ||
			(c == '*') || (c == '-') || (c == '.') || (c == '_')) {
			output.append(1, c);
		}
		else if (c == ' ' && spaceAsPlus) {
			output.append("+");
		}
		else {
			char percentEncoded[4];
			snprintf(percentEncoded, 4, "%%%02X", c);
			output.append(percentEncoded);
		}
	}
	return output;
}

static bool isValidAsUTF8(const char *input, size_t inputLength) {
	for (int i=0; i<inputLength; i++) {
		unsigned char c1 = input[i];
		if (c1 < 0x80) continue;
		else if (c1 >= 0xc2 && c1 <= 0xdf) {
			if (i >= inputLength - 1) return false;
			unsigned char c2 = input[++i];
			if (c2 < 0x80 || c2 > 0xbf) return false;
			unsigned int unicode = c2 & 0xf;
			unicode |= (((c2 >> 4) & 0x3) | ((c1 & 0x3) << 2)) << 4;
			unicode |= ((c1 >> 2) & 0x7) << 8;
			if (unicode < 0x80 || unicode > 0x7ff) return false;
		}
		else if (c1 >= 0xe0 && c1 <= 0xef) {
			if (i >= inputLength - 2) return false;
			unsigned char c2 = input[++i];
			if (c2 < 0x80 || c2 > 0xbf) return false;
			unsigned char c3 = input[++i];
			if (c3 < 0x80 || c3 > 0xbf) return false;
			unsigned int unicode = c3 & 0xf;
			unicode |= (((c3 >> 4) & 0x3) | ((c2 & 0x3) << 2)) << 4;
			unicode |= ((c2 >> 2) & 0xf) << 8;
			unicode |= (c1 & 0xf) << 12;
			if (unicode < 0x800 || unicode > 0xffff) return false;
			else if (unicode >= 0xd800 && unicode <= 0xdfff) return false; /* for surrogate pairs */
		}
		else if (c1 >= 0xf0 && c1 <= 0xf7) {
			if (i >= inputLength - 3) return false;
			unsigned char c2 = input[++i];
			if (c2 < 0x80 || c2 > 0xbf) return false;
			unsigned char c3 = input[++i];
			if (c3 < 0x80 || c3 > 0xbf) return false;
			unsigned char c4 = input[++i];
			if (c4 < 0x80 || c4 > 0xbf) return false;
			unsigned int unicode = c4 & 0xf;
			unicode |= (((c4 >> 4) & 0x3) | ((c3 & 0x3) << 2)) << 4;
			unicode |= ((c3 >> 2) & 0xf) << 8;
			unicode |= (c2 & 0xf) << 12;
			unicode |= (((c2 >> 4) & 0x3) | ((c1 & 0x3) << 2)) << 16;
			unicode |= ((c1 >> 2) & 0x1) << 20;
			if (unicode < 0x10000 || unicode > 0x10ffff) return false;
		}
	}
	return true;
}

static void appendPostSignature(const char *body, const std::string &userAgent, const std::string &monaKey, BBS2chProxyHttpHeaders *headers)
{
	std::map<std::string, std::string> fields;
	const char *ptr = body;
	while (1) {
		const char *tmp = ptr;
		while (*tmp != '=' && *tmp != 0) tmp++;
		if (*tmp == 0) break;
		std::string key(ptr, tmp-ptr);
		tmp++;
		ptr = tmp;
		while (*tmp != '&' && *tmp != 0) tmp++;
		std::string deocdedValue = decodeURIComponent(ptr, tmp-ptr, true);
		fields.insert(std::make_pair(key, deocdedValue));
		if (*tmp == 0) break;
		ptr = tmp + 1;
	}
	char nonce[32];
	snprintf(nonce, 32, "%.3f", getCurrentTime());
	std::string message;
	message.append(fields["bbs"]);
	message.append("<>");
	message.append(fields["key"]);
	message.append("<>");
	message.append(fields["time"]);
	message.append("<>");
	message.append(fields["FROM"]);
	message.append("<>");
	message.append(fields["mail"]);
	message.append("<>");
	message.append(fields["MESSAGE"]);
	message.append("<>");
	message.append(fields["subject"]);
	message.append("<>");
	message.append(userAgent);
	message.append("<>");
	message.append(monaKey);
	message.append("<>");
	message.append("<>");
	message.append(nonce);
	unsigned char digest[32];
	char digestStr[65];
	static const char *table = "0123456789abcdef";
	proxy2ch_HMAC_SHA256(hmacKey, strlen(hmacKey), message.data(), message.length(), digest);
	for (int i=0; i<32; i++) {
		unsigned char c = digest[i];
		unsigned char upper = (c >> 4) & 0xf;
		unsigned char lower = c & 0xf;
		digestStr[i*2] = table[upper];
		digestStr[i*2+1] = table[lower];
	}
	digestStr[64] = 0;
	headers->set("X-APIKey", appKey);
	log_printf(1, "Appended header \"X-APIKey: %s\"\n", appKey);
	headers->set("X-PostSig", digestStr);
	log_printf(1, "Appended header \"X-PostSig: %s\"\n", digestStr);
	headers->set("X-PostNonce", nonce);
	log_printf(1, "Appended header \"X-PostNonce: %s\"\n", nonce);
	headers->set("X-MonaKey", monaKey);
	log_printf(1, "Appended header \"X-MonaKey: %s\"\n", monaKey.c_str());
}

static std::string convertBodyToUTF8(const char *body)
{
	std::string newBody;
	bool shouldConvertToUTF8 = true;
	bool shouldCheckWholeBody = true;
	const char *ptr = strstr(body, "submit=");
	if (ptr && (ptr == body || *(ptr-1) == '&')) {
		ptr += 7;
		const char *start = ptr;
		while (*ptr != '&' && *ptr != 0) ptr++;
		std::string decoded = decodeURIComponent(start, ptr-start, true);
		if (decoded.length() != (ptr-start)) {
			if (isValidAsUTF8(decoded.data(), decoded.length())) {
				shouldConvertToUTF8 = false;
			}
			shouldCheckWholeBody = false;
		}
	}
	if (shouldCheckWholeBody) {
		std::string decoded = decodeURIComponent(body, strlen(body), true);
		if (isValidAsUTF8(decoded.data(), decoded.length())) {
			shouldConvertToUTF8 = false;
		}
	}
	if (shouldConvertToUTF8) {
		ptr = body;
		while (1) {
			const char *tmp = ptr;
			while (*tmp != '=' && *tmp != 0) tmp++;
			if (*tmp == 0) break;
			std::string key(ptr, tmp-ptr);
			tmp++;
			ptr = tmp;
			while (*tmp != '&' && *tmp != 0) tmp++;
			std::string deocdedValue = decodeURIComponent(ptr, tmp-ptr, true);
			if (!deocdedValue.empty()) {
				char *converted = convertShiftJISToUTF8(deocdedValue.data(), deocdedValue.length());
				if (converted) {
					deocdedValue = std::string(converted);
					free(converted);
				}
			}
			if (!newBody.empty()) newBody.append("&");
			newBody.append(key);
			newBody.append("=");
			newBody.append(encodeURIComponent(deocdedValue.data(), deocdedValue.length(), true));
			if (*tmp == 0) break;
			ptr = tmp + 1;
		}
	}
	return newBody;
}

#ifdef _WIN32
const char * strp_weekdays[] = 
    { "sunday", "monday", "tuesday", "wednesday", "thursday", "friday", "saturday"};
const char * strp_monthnames[] = 
    { "january", "february", "march", "april", "may", "june", "july", "august", "september", "october", "november", "december"};
bool strp_atoi(const char * & s, int & result, int low, int high, int offset)
    {
    bool worked = false;
    char * end;
    unsigned long num = strtoul(s, & end, 10);
    if (num >= (unsigned long)low && num <= (unsigned long)high)
        {
        result = (int)(num + offset);
        s = end;
        worked = true;
        }
    return worked;
    }
char * strptime(const char *s, const char *format, struct tm *tm)
    {
    bool working = true;
    while (working && *format && *s)
        {
        switch (*format)
            {
        case '%':
            {
            ++format;
            switch (*format)
                {
            case 'a':
            case 'A': // weekday name
                tm->tm_wday = -1;
                working = false;
                for (size_t i = 0; i < 7; ++ i)
                    {
                    size_t len = strlen(strp_weekdays[i]);
                    if (!strnicmp(strp_weekdays[i], s, len))
                        {
                        tm->tm_wday = i;
                        s += len;
                        working = true;
                        break;
                        }
                    else if (!strnicmp(strp_weekdays[i], s, 3))
                        {
                        tm->tm_wday = i;
                        s += 3;
                        working = true;
                        break;
                        }
                    }
                break;
            case 'b':
            case 'B':
            case 'h': // month name
                tm->tm_mon = -1;
                working = false;
                for (size_t i = 0; i < 12; ++ i)
                    {
                    size_t len = strlen(strp_monthnames[i]);
                    if (!strnicmp(strp_monthnames[i], s, len))
                        {
                        tm->tm_mon = i;
                        s += len;
                        working = true;
                        break;
                        }
                    else if (!strnicmp(strp_monthnames[i], s, 3))
                        {
                        tm->tm_mon = i;
                        s += 3;
                        working = true;
                        break;
                        }
                    }
                break;
            case 'd':
            case 'e': // day of month number
                working = strp_atoi(s, tm->tm_mday, 1, 31, 0);
                break;
            case 'D': // %m/%d/%y
                {
                const char * s_save = s;
                working = strp_atoi(s, tm->tm_mon, 1, 12, -1);
                if (working && *s == '/')
                    {
                    ++ s;
                    working = strp_atoi(s, tm->tm_mday, 1, 31, 0);
                    if (working && *s == '/')
                        {
                        ++ s;
                        working = strp_atoi(s, tm->tm_year, 0, 99, 0);
                        if (working && tm->tm_year < 69)
                            tm->tm_year += 100;
                        }
                    }
                if (!working)
                    s = s_save;
                }
                break;
            case 'H': // hour
                working = strp_atoi(s, tm->tm_hour, 0, 23, 0);
                break;
            case 'I': // hour 12-hour clock
                working = strp_atoi(s, tm->tm_hour, 1, 12, 0);
                break;
            case 'j': // day number of year
                working = strp_atoi(s, tm->tm_yday, 1, 366, -1);
                break;
            case 'm': // month number
                working = strp_atoi(s, tm->tm_mon, 1, 12, -1);
                break;
            case 'M': // minute
                working = strp_atoi(s, tm->tm_min, 0, 59, 0);
                break;
            case 'n': // arbitrary whitespace
            case 't':
                while (isspace((int)*s)) 
                    ++s;
                break;
            case 'p': // am / pm
                if (!strnicmp(s, "am", 2))
                    { // the hour will be 1 -> 12 maps to 12 am, 1 am .. 11 am, 12 noon 12 pm .. 11 pm
                    if (tm->tm_hour == 12) // 12 am == 00 hours
                        tm->tm_hour = 0;
                    }
                else if (!strnicmp(s, "pm", 2))
                    {
                    if (tm->tm_hour < 12) // 12 pm == 12 hours
                        tm->tm_hour += 12; // 1 pm -> 13 hours, 11 pm -> 23 hours
                    }
                else
                    working = false;
                break;
            case 'r': // 12 hour clock %I:%M:%S %p
                {
                const char * s_save = s;
                working = strp_atoi(s, tm->tm_hour, 1, 12, 0);
                if (working && *s == ':')
                    {
                    ++ s;
                    working = strp_atoi(s, tm->tm_min, 0, 59, 0);
                    if (working && *s == ':')
                        {
                        ++ s;
                        working = strp_atoi(s, tm->tm_sec, 0, 60, 0);
                        if (working && isspace((int)*s))
                            {
                            ++ s;
                            while (isspace((int)*s)) 
                                ++s;
                            if (!strnicmp(s, "am", 2))
                                { // the hour will be 1 -> 12 maps to 12 am, 1 am .. 11 am, 12 noon 12 pm .. 11 pm
                                if (tm->tm_hour == 12) // 12 am == 00 hours
                                    tm->tm_hour = 0;
                                }
                            else if (!strnicmp(s, "pm", 2))
                                {
                                if (tm->tm_hour < 12) // 12 pm == 12 hours
                                    tm->tm_hour += 12; // 1 pm -> 13 hours, 11 pm -> 23 hours
                                }
                            else
                                working = false;
                            }
                        }
                    }
                if (!working)
                    s = s_save;
                }
                break;
            case 'R': // %H:%M
                {
                const char * s_save = s;
                working = strp_atoi(s, tm->tm_hour, 0, 23, 0);
                if (working && *s == ':')
                    {
                    ++ s;
                    working = strp_atoi(s, tm->tm_min, 0, 59, 0);
                    }
                if (!working)
                    s = s_save;
                }
                break;
            case 'S': // seconds
                working = strp_atoi(s, tm->tm_sec, 0, 60, 0);
                break;
            case 'T': // %H:%M:%S
                {
                const char * s_save = s;
                working = strp_atoi(s, tm->tm_hour, 0, 23, 0);
                if (working && *s == ':')
                    {
                    ++ s;
                    working = strp_atoi(s, tm->tm_min, 0, 59, 0);
                    if (working && *s == ':')
                        {
                        ++ s;
                        working = strp_atoi(s, tm->tm_sec, 0, 60, 0);
                        }
                    }
                if (!working)
                    s = s_save;
                }
                break;
            case 'w': // weekday number 0->6 sunday->saturday
                working = strp_atoi(s, tm->tm_wday, 0, 6, 0);
                break;
            case 'Y': // year
                working = strp_atoi(s, tm->tm_year, 1900, 65535, -1900);
                break;
            case 'y': // 2-digit year
                working = strp_atoi(s, tm->tm_year, 0, 99, 0);
                if (working && tm->tm_year < 69)
                    tm->tm_year += 100;
                break;
            case '%': // escaped
                if (*s != '%')
                    working = false;
                ++s;
                break;
            default:
                working = false;
                }
            }
            break;
        case ' ':
        case '\t':
        case '\r':
        case '\n':
        case '\f':
        case '\v':
            // zero or more whitespaces:
            while (isspace((int)*s))
                ++ s;
            break;
        default:
            // match character
            if (*s != *format)
                working = false;
            else
                ++s;
            break;
            }
        ++format;
        }
    return (working?(char *)s:0);
}
#endif