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* Copyright (c) 2004, Jeroen Asselman
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*----------------------------------------------------------------------
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* This file is part of gtk-gnutella.
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* gtk-gnutella is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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* gtk-gnutella is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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* You should have received a copy of the GNU General Public License
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* along with gtk-gnutella; if not, write to the Free Software
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* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*----------------------------------------------------------------------
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* G2 packet parser / constructor.
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* @author Jeroen Asselman
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char *g2_packet_pack(g2packet_t *packet, int *length);
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int g2_packet_calc_new_length(g2packet_t *packet);
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void g2_packet2buf(g2packet_t *packet, char *destination);
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* Creates a new G2 packet.
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return (g2packet_t *) malloc(sizeof(g2packet_t));
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* Frees a g2 packet and any associated memory. This will also
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* free a payload assigned.
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g2_free_packet(g2packet_t *packet)
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if (packet->name != NULL)
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if (packet->orig_payload != NULL)
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free(packet->orig_payload);
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*** Parse packet functions
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* Parse the packet header to extract length information.
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g2_parse_header(char **buffer, g2packet_t *packet)
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char *source = *buffer;
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char len_length = ( *source & 0xC0 ) >> 6;
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char flags = ( *source & 0x07 );
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packet->name_length = (( *source & 0x38 ) >> 3) + 1;
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packet->big_endian = ( flags & 0x02 ) > 0;
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packet->compound = ( flags & 0x04 ) > 0;
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if (packet->big_endian)
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for (i = 0; i < len_length; i++)
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packet->payload_length *= 0xFF;
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packet->payload_length += *source++;
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for (i = len_length; i > 0; i--)
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packet->payload_length += 0xFF;
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packet->payload_length += *source++;
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if (packet->payload_length > 0)
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packet->has_children = packet->compound;
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* Parse the g2 packet to retreive the start of the payload/children
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g2_parse_packet(char **buffer, g2packet_t *packet)
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char *source = *buffer;
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g2_parse_header(buffer, packet);
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packet->name = (char *) malloc(packet->name_length + 1);
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memcpy(packet->name, source, packet->name_length);
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*(packet->name + packet->name_length) = '\0';
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printf("[G2] '%s' %s children, payload length %d\n", packet->name,
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packet->has_children ? "has" : "doesn't", packet->payload_length);
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packet->payload = (char *) malloc(packet->payload_length);
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packet->orig_payload = packet->payload;
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memcpy(packet->payload, source, packet->payload_length);
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source += packet->payload_length;
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* Get the packet name.
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* Retreives the name of the packet.
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* @return a name string.
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g2_packet_get_name(g2packet_t *packet)
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* Get the next child from the current packet.
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* Retreives the next child packet from the current packet and moves to the
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* next child packet. Next time this function is called the next child packet
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* @return the child packet or NULL if no (more) child packets are available.
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g2_packet_get_next_child(g2packet_t *basepacket)
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g2packet_t *packet = NULL;
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char *before = basepacket->payload;
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if (!basepacket->compound)
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g2_parse_packet(&basepacket->payload, packet);
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basepacket->payload_length -= basepacket->payload - before;
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if (basepacket->payload_length == 0 ||
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(*basepacket->payload == '0' && packet->payload_length != 0))
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basepacket->compound = FALSE;
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* After this it isn't possible anymore to retreive any children. As it will
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g2_packet_get_payload(g2packet_t *packet, int *length)
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g2packet_t *packet_parser = g2_new_packet();
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/* Skip any children */
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while (packet->compound)
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char *before = packet->payload;
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g2_parse_header(&packet->payload, packet_parser); // This advances after the header
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packet->payload += packet_parser->payload_length; // This advances after the payload
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packet->payload_length -= (int) (packet->payload - before);
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if (packet->payload_length < 0)
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printf("[G2] Invalid packet\n");
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g2_free_packet(packet_parser);
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if (*packet->payload == '\0' || packet->payload_length == 0)
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packet->compound = FALSE;
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g2_free_packet(packet_parser);
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if (packet->payload_length == 0)
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*length = packet->payload_length;
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return packet->payload;
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*** Create packet functions
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* Add child to packet.
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* Adds a child packet to the packet. Do _not_ add child packets after adding
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* @param packet is a pointer to the packet to which the child should be added.
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* @param child is a pointer to the packet to add.
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g2_packet_add_child(g2packet_t *packet, g2packet_t *child)
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buffer = g2_packet_pack(child, &length);
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if (packet->payload == NULL) {
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packet->orig_payload = (char *) malloc(length);
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packet->payload = packet->orig_payload;
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int diff = packet->payload - packet->orig_payload;
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packet->orig_payload = (char *) realloc(packet->orig_payload,
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packet->payload_length + length);
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/* Set payload to the new not used memory space */
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packet->payload = packet->orig_payload + diff + length;
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memcpy(packet->payload, buffer, length);
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packet->has_children = TRUE;
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packet->payload_length += length;
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/* Payload points again to the newly added child */
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* G2 Packet add payload.
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* Adds a payload to the current packet. After this do _NOT_ add children
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* @param packet is a pointer to the packet to which the payload should be
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* @param payload is a pointer to the payload which will be added to the packet.
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* @param length is the length of the payload to add.
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g2_packet_add_payload(g2packet_t *packet, char *payload, int length)
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if (packet->orig_payload != NULL) {
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int diff = packet->payload - packet->orig_payload;
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int extra = length + packet->has_children ? 1 : 0;
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packet->orig_payload = (char *) realloc(packet->orig_payload,
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packet->payload_length + extra);
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packet->payload = packet->orig_payload + diff;
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if (packet->has_children)
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*packet->payload = '0';
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packet->payload_length++;
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memcpy(packet->payload, payload, length);
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packet->payload_length += length;
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/* Payload now points to the newly added payload */
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g_assert(packet->orig_payload - packet->payload ==
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packet->payload_length - length);
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* Construct a buffer from a G2Packet and return the newly allocated
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* @return a pointer to the buffer containing the packed G2Packet.
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g2_packet_pack(g2packet_t *packet, int *length)
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*length = g2_packet_calc_new_length(packet);
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char *buffer = (char *) malloc(*length);
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g2_packet2buf(packet, buffer);
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* Calculate the lenlength field from a given length.
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g2_packet_calc_lenlength(int length)
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if (length > 0xFFFFFF)
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* G2 Packet calculate length/
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* Calculates the size that will be used by this G2Packet when transformed
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* to a buffer / char pointer.
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* @return the length of the G2Packet when transformed to a buffer.
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g2_packet_calc_new_length(g2packet_t *packet)
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length += packet->name_length;
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length += g2_packet_calc_lenlength(packet->payload_length);
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length += packet->payload_length;
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* In the destination pointer a g2 packet is constructed from the given
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* The destination should be at least the size retreived with
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* g2_packet_calc_new_length(packet).
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g2_packet2buf(g2packet_t *packet, char *destination)
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len_length = g2_packet_calc_lenlength(packet->payload_length);
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if (packet->payload_length > 0)
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packet->has_children = packet->compound;
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packet->compound = packet->has_children;
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packet->compound = TRUE;
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*destination |= (len_length << 6);
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*destination |= ((packet->name_length - 1) << 3);
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if (packet->compound)
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*destination |= 0x04;
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if (packet->big_endian)
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*destination |= 0x02;
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/* Advance to next byte, control byte is now finished. */
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for (i = 0; i < packet->name_length; i++)
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*destination = packet->name[i];
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/* Insert payload length */
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*destination = packet->payload_length;
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if (!packet->big_endian)
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memmove(destination, destination + sizeof(int) - len_length, len_length);
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destination += len_length;
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memcpy(destination, packet->orig_payload, packet->payload_length);
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/* vi: set ts=4 sw=4 cindent: */
added
removed
src/g2/packet.c
