BitTorrent protocol analysis Three __bittorrent protocol

design and implementation of each module

design and implementation of 4.1 seed parsing module

Parsing seed files is done primarily in parse_metafile.h and parse_metafile.c. The contents of the Parse_metafile.h file are:

Parse_metafile.h

#ifndef Parse_metafile

#define Parse_metafile

Save the URL of the tracker retrieved from the seed file

typedef struct _ANNOUNCE_LIST {

Char announce[128];

struct _announce_list *next;

} announce_list;

Save the path and length of each file to be downloaded

typedef struct _FILES {

Char path[256];

Long length;

struct _files *next;

} Files;

int Read_metafile (char *metafile_name); Read the seed file

int Find_keyword (char *keyword,long *position); Find a keyword in a seed file

int read_announce_list (); Get the address of each tracker server

int add_an_announce (char* URL); Add a URL to the tracker list

int Get_piece_length (); Gets the length of each piece, typically 256KB

int get_pieces (); Read hash values for individual piece

int Is_multi_files (); Decide whether to download a single file or multiple files

int Get_file_name (); Gets the file name, for multiple files, gets the directory name

int Get_file_length (); Get the total length of the file to download

int Get_files_length_path (); Gets the path and length of the file, valid for multiple file seeds

int Get_info_hash (); Calculate Info_hash by the value corresponding to the Info keyword

int get_peer_id (); Generates PEER_ID, each peer has a 20-byte peer_id

void Release_memory_in_parse_metafile ()//releasing dynamically allocated memory in PARSE_METAFILE.C

int Parse_metafile (char *metafile); Call the function defined in this file to complete the parse seed file

#endif

The following is the head of the parse_metafile.c file, which contains some header files and defines some global variables, and the definitions of each function are listed later.

Parse_metafile.c

#include <stdio.h>

#include <ctype.h>

#include <malloc.h>

#include <stdlib.h>

#include <string.h>

#include <time.h>

#include "parse_metafile.h"

#include "Sha1.h"

char *metafile_content = NULL; Save the contents of a seed file

Long filesize; The length of the seed file

int piece_length = 0; Length of each piece, usually 256KB or 262144 bytes