/*
 * include/proto/spoe.h
 * Encoding/Decoding functions for the SPOE filters (and other helpers).
 *
 * Copyright (C) 2017 HAProxy Technologies, Christopher Faulet <cfaulet@haproxy.com>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation, version 2.1
 * exclusively.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 */

#ifndef _PROTO_SPOE_H
#define _PROTO_SPOE_H

#include <types/spoe.h>

#include <proto/sample.h>


/* Encode the integer <i> into a varint (variable-length integer). The encoded
 * value is copied in <*buf>. Here is the encoding format:
 *
 *        0 <= X < 240        : 1 byte  (7.875 bits)  [ XXXX XXXX ]
 *      240 <= X < 2288       : 2 bytes (11 bits)     [ 1111 XXXX ] [ 0XXX XXXX ]
 *     2288 <= X < 264432     : 3 bytes (18 bits)     [ 1111 XXXX ] [ 1XXX XXXX ]   [ 0XXX XXXX ]
 *   264432 <= X < 33818864   : 4 bytes (25 bits)     [ 1111 XXXX ] [ 1XXX XXXX ]*2 [ 0XXX XXXX ]
 * 33818864 <= X < 4328786160 : 5 bytes (32 bits)     [ 1111 XXXX ] [ 1XXX XXXX ]*3 [ 0XXX XXXX ]
 * ...
 *
 * On success, it returns the number of written bytes and <*buf> is moved after
 * the encoded value. Otherwise, it returns -1. */
int
spoe_encode_varint(uint64_t i, char **buf, char *end)
{
	unsigned char *p = (unsigned char *)*buf;
	int r;

	if (p >= (unsigned char *)end)
		return -1;

	if (i < 240) {
		*p++ = i;
		*buf = (char *)p;
		return 1;
	}

	*p++ = (unsigned char)i | 240;
	i = (i - 240) >> 4;
	while (i >= 128) {
		if (p >= (unsigned char *)end)
			return -1;
		*p++ = (unsigned char)i | 128;
		i = (i - 128) >> 7;
	}

	if (p >= (unsigned char *)end)
		return -1;
	*p++ = (unsigned char)i;

	r    = ((char *)p - *buf);
	*buf = (char *)p;
	return r;
}

/* Decode a varint from <*buf> and save the decoded value in <*i>. See
 * 'spoe_encode_varint' for details about varint.
 * On success, it returns the number of read bytes and <*buf> is moved after the
 * varint. Otherwise, it returns -1. */
int
spoe_decode_varint(char **buf, char *end, uint64_t *i)
{
	unsigned char *p = (unsigned char *)*buf;
	int r;

	if (p >= (unsigned char *)end)
		return -1;

	*i = *p++;
	if (*i < 240) {
		*buf = (char *)p;
		return 1;
	}

	r = 4;
	do {
		if (p >= (unsigned char *)end)
			return -1;
		*i += (uint64_t)*p << r;
		r  += 7;
	} while (*p++ >= 128);

	r    = ((char *)p - *buf);
	*buf = (char *)p;
	return r;
}

/* Encode a buffer. Its length <len> is encoded as a varint, followed by a copy
 * of <str>. It must have enough space in <*buf> to encode the buffer, else an
 * error is triggered.
 * On success, it returns <len> and <*buf> is moved after the encoded value. If
 * an error occurred, it returns -1. */
int
spoe_encode_buffer(const char *str, size_t len, char **buf, char *end)
{
	char *p = *buf;
	int   ret;

	if (p >= end)
		return -1;

	if (!len) {
		*p++ = 0;
		*buf = p;
		return 0;
	}

	ret = spoe_encode_varint(len, &p, end);
	if (ret == -1 || p + len > end)
		return -1;

	memcpy(p, str, len);
	*buf = p + len;
	return len;
}

/* Encode a buffer, possibly partially. It does the same thing than
 * 'spoe_encode_buffer', but if there is not enough space, it does not fail.
 * On success, it returns the number of copied bytes and <*buf> is moved after
 * the encoded value. If an error occured, it returns -1. */
int
spoe_encode_frag_buffer(const char *str, size_t len, char **buf, char *end)
{
	char *p = *buf;
	int   ret;

	if (p >= end)
		return -1;

	if (!len) {
		*p++ = 0;
		*buf = p;
		return 0;
	}

	ret = spoe_encode_varint(len, &p, end);
	if (ret == -1 || p >= end)
		return -1;

	ret = (p+len < end) ? len : (end - p);
	memcpy(p, str, ret);
	*buf = p + ret;
	return ret;
}

/* Decode a buffer. The buffer length is decoded and saved in <*len>. <*str>
 * points on the first byte of the buffer.
 * On success, it returns the buffer length and <*buf> is moved after the
 * encoded buffer. Otherwise, it returns -1. */
int
spoe_decode_buffer(char **buf, char *end, char **str, size_t *len)
{
	char    *p = *buf;
	uint64_t sz;
	int      ret;

	*str = NULL;
	*len = 0;

	ret = spoe_decode_varint(&p, end, &sz);
	if (ret == -1 || p + sz > end)
		return -1;

	*str = p;
	*len = sz;
	*buf = p + sz;
	return sz;
}

/* Encode a typed data using value in <smp>. On success, it returns the number
 * of copied bytes and <*buf> is moved after the encoded value. If an error
 * occured, it returns -1.
 *
 * If the value is too big to be encoded, depending on its type, then encoding
 * failed or the value is partially encoded. Only strings and binaries can be
 * partially encoded. In this case, the offset <*off> is updated to known how
 * many bytes has been encoded. If <*off> is zero at the end, it means that all
 * data has been encoded. */
int
spoe_encode_data(struct sample *smp, unsigned int *off, char **buf, char *end)
{
	char *p = *buf;
	int   ret;

	if (p >= end)
		return -1;

	if (smp == NULL) {
		*p++ = SPOE_DATA_T_NULL;
		goto end;
	}

	switch (smp->data.type) {
		case SMP_T_BOOL:
			*p    = SPOE_DATA_T_BOOL;
			*p++ |= ((!smp->data.u.sint) ? SPOE_DATA_FL_FALSE : SPOE_DATA_FL_TRUE);
			break;

		case SMP_T_SINT:
			*p++ = SPOE_DATA_T_INT64;
			if (spoe_encode_varint(smp->data.u.sint, &p, end) == -1)
				return -1;
			break;

		case SMP_T_IPV4:
			if (p + 5 > end)
				return -1;
			*p++ = SPOE_DATA_T_IPV4;
			memcpy(p, &smp->data.u.ipv4, 4);
			p += 4;
			break;

		case SMP_T_IPV6:
			if (p + 17 > end)
				return -1;
			*p++ = SPOE_DATA_T_IPV6;
			memcpy(p, &smp->data.u.ipv6, 16);
			p += 16;
			break;

		case SMP_T_STR:
		case SMP_T_BIN: {
			struct chunk *chk = &smp->data.u.str;

			/* Here, we need to know if the sample has already been
			 * partially encoded. If yes, we only need to encode the
			 * remaining, <*off> reprensenting the number of bytes
			 * already encoded. */
			if (!*off) {
				/* First evaluation of the sample : encode the
				 * type (string or binary), the buffer length
				 * (as a varint) and at least 1 byte of the
				 * buffer. */
				struct chunk *chk = &smp->data.u.str;

				*p++ = (smp->data.type == SMP_T_STR)
					? SPOE_DATA_T_STR
					: SPOE_DATA_T_BIN;
				ret = spoe_encode_frag_buffer(chk->str, chk->len, &p, end);
				if (ret == -1)
					return -1;
			}
			else {
				/* The sample has been fragmented, encode remaining data */
				ret = MIN(chk->len - *off, end - p);
				memcpy(p, chk->str + *off, ret);
				p += ret;
			}
			/* Now update <*off> */
			if (ret + *off != chk->len)
				*off += ret;
			else
				*off = 0;
			break;
		}

		case SMP_T_METH: {
			char   *m;
			size_t  len;

			*p++ = SPOE_DATA_T_STR;
			switch (smp->data.u.meth.meth) {
				case HTTP_METH_OPTIONS: m = "OPTIONS"; len = 7; break;
				case HTTP_METH_GET    : m = "GET";     len = 3; break;
				case HTTP_METH_HEAD   : m = "HEAD";    len = 4; break;
				case HTTP_METH_POST   : m = "POST";    len = 4; break;
				case HTTP_METH_PUT    : m = "PUT";     len = 3; break;
				case HTTP_METH_DELETE : m = "DELETE";  len = 6; break;
				case HTTP_METH_TRACE  : m = "TRACE";   len = 5; break;
				case HTTP_METH_CONNECT: m = "CONNECT"; len = 7; break;

				default :
					m   = smp->data.u.meth.str.str;
					len = smp->data.u.meth.str.len;
			}
			if (spoe_encode_buffer(m, len, &p, end) == -1)
				return -1;
			break;
		}

		default:
			*p++ = SPOE_DATA_T_NULL;
			break;
	}

  end:
	ret  = (p - *buf);
	*buf = p;
	return ret;
}

/* Skip a typed data. If an error occurred, -1 is returned, otherwise the number
 * of skipped bytes is returned and the <*buf> is moved after skipped data.
 *
 * A types data is composed of a type (1 byte) and corresponding data:
 *  - boolean: non additional data (0 bytes)
 *  - integers: a variable-length integer (see spoe_decode_varint)
 *  - ipv4: 4 bytes
 *  - ipv6: 16 bytes
 *  - binary and string: a buffer prefixed by its size, a variable-length
 *    integer (see spoe_decode_buffer) */
int
spoe_skip_data(char **buf, char *end)
{
	char    *str, *p = *buf;
	int      type, ret;
	size_t   sz;
	uint64_t v;

	if (p >= end)
		return -1;

	type = *p++;
	switch (type & SPOE_DATA_T_MASK) {
		case SPOE_DATA_T_BOOL:
			break;
		case SPOE_DATA_T_INT32:
		case SPOE_DATA_T_INT64:
		case SPOE_DATA_T_UINT32:
		case SPOE_DATA_T_UINT64:
			if (spoe_decode_varint(&p, end, &v) == -1)
				return -1;
			break;
		case SPOE_DATA_T_IPV4:
			if (p+4 > end)
				return -1;
			p += 4;
			break;
		case SPOE_DATA_T_IPV6:
			if (p+16 > end)
				return -1;
			p += 16;
			break;
		case SPOE_DATA_T_STR:
		case SPOE_DATA_T_BIN:
			/* All the buffer must be skipped */
			if (spoe_decode_buffer(&p, end, &str, &sz) == -1)
				return -1;
			break;
	}

	ret  = (p - *buf);
	*buf = p;
	return ret;
}

/* Decode a typed data and fill <smp>. If an error occurred, -1 is returned,
 * otherwise the number of read bytes is returned and <*buf> is moved after the
 * decoded data. See spoe_skip_data for details. */
int
spoe_decode_data(char **buf, char *end, struct sample *smp)
{
	char  *str, *p = *buf;
	int    type, r = 0;
	size_t sz;

	if (p >= end)
		return -1;

	type = *p++;
	switch (type & SPOE_DATA_T_MASK) {
		case SPOE_DATA_T_BOOL:
			smp->data.u.sint = ((type & SPOE_DATA_FL_MASK) == SPOE_DATA_FL_TRUE);
			smp->data.type = SMP_T_BOOL;
			break;
		case SPOE_DATA_T_INT32:
		case SPOE_DATA_T_INT64:
		case SPOE_DATA_T_UINT32:
		case SPOE_DATA_T_UINT64:
			if (spoe_decode_varint(&p, end, (uint64_t *)&smp->data.u.sint) == -1)
				return -1;
			smp->data.type = SMP_T_SINT;
			break;
		case SPOE_DATA_T_IPV4:
			if (p+4 > end)
				return -1;
			smp->data.type = SMP_T_IPV4;
			memcpy(&smp->data.u.ipv4, p, 4);
			p += 4;
			break;
		case SPOE_DATA_T_IPV6:
			if (p+16 > end)
				return -1;
			memcpy(&smp->data.u.ipv6, p, 16);
			smp->data.type = SMP_T_IPV6;
			p += 16;
			break;
		case SPOE_DATA_T_STR:
		case SPOE_DATA_T_BIN:
			/* All the buffer must be decoded */
			if (spoe_decode_buffer(&p, end, &str, &sz) == -1)
				return -1;
			smp->data.u.str.str = str;
			smp->data.u.str.len = sz;
			smp->data.type = (type == SPOE_DATA_T_STR) ? SMP_T_STR : SMP_T_BIN;
			break;
	}

	r    = (p - *buf);
	*buf = p;
	return r;
}

#endif /* _PROTO_SPOE_H */