?? parse_metafile.c
字號:
#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; // 保存種子文件的內容
long filesize; // 種子文件的長度
int piece_length = 0; // 每個piece的長度,通常為256KB即262144字節
char *pieces = NULL; // 保存每個pieces的哈希值,每個哈希值為20字節
int pieces_length = 0; // pieces緩沖區的長度
int multi_file = 0; // 指明是單文件還是多文件
char *file_name = NULL; // 對于單文件,存放文件名;對于多文件,存放目錄名
long long file_length = 0; // 存放待下載文件的總長度
Files *files_head = NULL; // 只對多文件種子有效,存放各個文件的路徑和長度
unsigned char info_hash[20]; // 保存info_hash的值,連接tracker和peer時使用
unsigned char peer_id[20]; // 保存peer_id的值,連接peer時使用
Announce_list *announce_list_head = NULL; // 用于保存所有tracker服務器的URL
int read_metafile(char *metafile_name)
{
long i;
// 以二進制、只讀的方式打開文件
FILE *fp = fopen(metafile_name,"rb");
if(fp == NULL) {
printf("%s:%d can not open file\n",__FILE__,__LINE__);
return -1;
}
// 獲取種子文件的長度
fseek(fp,0,SEEK_END);
filesize = ftell(fp);
if(filesize == -1) {
printf("%s:%d fseek failed\n",__FILE__,__LINE__);
return -1;
}
metafile_content = (char *)malloc(filesize+1);
if(metafile_content == NULL) {
printf("%s:%d malloc failed\n",__FILE__,__LINE__);
return -1;
}
// 讀取種子文件的內容到metafile_content緩沖區中
fseek(fp,0,SEEK_SET);
for(i = 0; i < filesize; i++)
metafile_content[i] = fgetc(fp);
metafile_content[i] = '\0';
fclose(fp);
#ifdef DEBUG
printf("metafile size is: %ld\n",filesize);
#endif
return 0;
}
int find_keyword(char *keyword,long *position)
{
long i;
*position = -1;
if(keyword == NULL) return 0;
for(i = 0; i < filesize-strlen(keyword); i++) {
if( memcmp(&metafile_content[i], keyword, strlen(keyword)) == 0 ) {
*position = i;
return 1;
}
}
return 0;
}
int read_announce_list()
{
Announce_list *node = NULL;
Announce_list *p = NULL;
int len = 0;
long i;
if( find_keyword("13:announce-list",&i) == 0 ) {
if( find_keyword("8:announce",&i) == 1 ) {
i = i + strlen("8:announce");
while( isdigit(metafile_content[i]) ) {
len = len * 10 + (metafile_content[i] - '0');
i++;
}
i++; // 跳過 ':'
node = (Announce_list *)malloc(sizeof(Announce_list));
strncpy(node->announce,&metafile_content[i],len);
node->announce[len] = '\0';
node->next = NULL;
announce_list_head = node;
}
}
else { // 如果有13:announce-list關鍵詞就不用處理8:announce關鍵詞
i = i + strlen("13:announce-list");
i++; // skip 'l'
while(metafile_content[i] != 'e') {
i++; // skip 'l'
while( isdigit(metafile_content[i]) ) {
len = len * 10 + (metafile_content[i] - '0');
i++;
}
if( metafile_content[i] == ':' ) i++;
else return -1;
// 只處理以http開頭的tracker地址,不處理以udp開頭的地址
if( memcmp(&metafile_content[i],"http",4) == 0 ) {
node = (Announce_list *)malloc(sizeof(Announce_list));
strncpy(node->announce,&metafile_content[i],len);
node->announce[len] = '\0';
node->next = NULL;
if(announce_list_head == NULL)
announce_list_head = node;
else {
p = announce_list_head;
while( p->next != NULL) p = p->next; // 使p指向最后個結點
p->next = node; // node成為tracker列表的最后一個結點
}
}
i = i + len;
len = 0;
i++; // skip 'e'
if(i >= filesize) return -1;
}
}
#ifdef DEBUG
p = announce_list_head;
while(p != NULL) {
printf("%s\n",p->announce);
p = p->next;
}
#endif
return 0;
}
// 連接某些tracker時會返回一個重定向URL,需要連接該URL才能獲取peer
int add_an_announce(char *url)
{
Announce_list *p = announce_list_head, *q;
// 若參數指定的URL在tracker列表中已存在,則無需添加
while(p != NULL) {
if(strcmp(p->announce,url) == 0) break;
p = p->next;
}
if(p != NULL) return 0;
q = (Announce_list *)malloc(sizeof(Announce_list));
strcpy(q->announce,url);
q->next = NULL;
p = announce_list_head;
if(p == NULL) { announce_list_head = q; return 1; }
while(p->next != NULL) p = p->next;
p->next = q;
return 1;
}
int is_multi_files()
{
long i;
if( find_keyword("5:files",&i) == 1 ) {
multi_file = 1;
return 1;
}
#ifdef DEBUG
// printf("is_multi_files:%d\n",multi_file);
#endif
return 0;
}
int get_piece_length()
{
long i;
if( find_keyword("12:piece length",&i) == 1 ) {
i = i + strlen("12:piece length"); // skip "12:piece length"
i++; // skip 'i'
while(metafile_content[i] != 'e') {
piece_length = piece_length * 10 + (metafile_content[i] - '0');
i++;
}
} else {
return -1;
}
#ifdef DEBUG
printf("piece length:%d\n",piece_length);
#endif
return 0;
}
int get_pieces()
{
long i;
if( find_keyword("6:pieces", &i) == 1 ) {
i = i + 8; // skip "6:pieces"
while(metafile_content[i] != ':') {
pieces_length = pieces_length * 10 + (metafile_content[i] - '0');
i++;
}
i++; // skip ':'
pieces = (char *)malloc(pieces_length+1);
memcpy(pieces,&metafile_content[i],pieces_length);
pieces[pieces_length] = '\0';
} else {
return -1;
}
#ifdef DEBUG
printf("get_pieces ok\n");
#endif
return 0;
}
int get_file_name()
{
long i;
int count = 0;
if( find_keyword("4:name", &i) == 1 ) {
i = i + 6; // skip "4:name"
while(metafile_content[i] != ':') {
count = count * 10 + (metafile_content[i] - '0');
i++;
}
i++; // skip ':'
file_name = (char *)malloc(count+1);
memcpy(file_name,&metafile_content[i],count);
file_name[count] = '\0';
} else {
return -1;
}
#ifdef DEBUG
// 由于可能含有中文字符,因此可能打印出亂碼
// printf("file_name:%s\n",file_name);
#endif
return 0;
}
int get_file_length()
{
long i;
if(is_multi_files() == 1) {
if(files_head == NULL) get_files_length_path();
Files *p = files_head;
while(p != NULL) { file_length += p->length; p = p->next; }
} else {
if( find_keyword("6:length",&i) == 1 ) {
i = i + 8; // skip "6:length"
i++; // skip 'i'
while(metafile_content[i] != 'e') {
file_length = file_length * 10 + (metafile_content[i] - '0');
i++;
}
}
}
#ifdef DEBUG
printf("file_length:%lld\n",file_length);
#endif
return 0;
}
int get_files_length_path()
{
long i;
int length;
int count;
Files *node = NULL;
Files *p = NULL;
if(is_multi_files() != 1) {
return 0;
}
for(i = 0; i < filesize-8; i++) {
if( memcmp(&metafile_content[i],"6:length",8) == 0 )
{
i = i + 8; // skip "6:length"
i++; // skip 'i'
length = 0;
while(metafile_content[i] != 'e') {
length = length * 10 + (metafile_content[i] - '0');
i++;
}
node = (Files *)malloc(sizeof(Files));
node->length = length;
node->next = NULL;
if(files_head == NULL)
files_head = node;
else {
p = files_head;
while(p->next != NULL) p = p->next;
p->next = node;
}
}
if( memcmp(&metafile_content[i],"4:path",6) == 0 )
{
i = i + 6; // skip "4:path"
i++; // skip 'l'
count = 0;
while(metafile_content[i] != ':') {
count = count * 10 + (metafile_content[i] - '0');
i++;
}
i++; // skip ':'
p = files_head;
while(p->next != NULL) p = p->next;
memcpy(p->path,&metafile_content[i],count);
*(p->path + count) = '\0';
}
}
#ifdef DEBUG
// 由于可能含有中文字符,因此可能打印出亂碼
// p = files_head;
// while(p != NULL) {
// printf("%ld:%s\n",p->length,p->path);
// p = p->next;
// }
#endif
return 0;
}
int get_info_hash()
{
int push_pop = 0;
long i, begin, end;
if(metafile_content == NULL) return -1;
if( find_keyword("4:info",&i) == 1 ) {
begin = i+6; // begin是關鍵字"4:info"對應值的起始下標
} else {
return -1;
}
i = i + 6; // skip "4:info"
for(; i < filesize; )
if(metafile_content[i] == 'd') {
push_pop++;
i++;
} else if(metafile_content[i] == 'l') {
push_pop++;
i++;
} else if(metafile_content[i] == 'i') {
i++; // skip i
if(i == filesize) return -1;
while(metafile_content[i] != 'e') {
if((i+1) == filesize) return -1;
else i++;
}
i++; // skip e
} else if((metafile_content[i] >= '0') && (metafile_content[i] <= '9')) {
int number = 0;
while((metafile_content[i] >= '0') && (metafile_content[i] <= '9')) {
number = number * 10 + metafile_content[i] - '0';
i++;
}
i++; // skip :
i = i + number;
} else if(metafile_content[i] == 'e') {
push_pop--;
if(push_pop == 0) { end = i; break; }
else i++;
} else {
return -1;
}
if(i == filesize) return -1;
SHA1_CTX context;
SHA1Init(&context);
SHA1Update(&context, &metafile_content[begin], end-begin+1);
SHA1Final(info_hash, &context);
#ifdef DEBUG
printf("info_hash:");
for(i = 0; i < 20; i++)
printf("%.2x ",info_hash[i]);
printf("\n");
#endif
return 0;
}
int get_peer_id()
{
// 設置產生隨機數的種子
srand(time(NULL));
// 生成隨機數,并把其中12位賦給peer_id,peer_id前8位固定為-TT1000-
sprintf(peer_id,"-TT1000-%12d",rand());
#ifdef DEBUG
int i;
printf("peer_id:");
for(i = 0; i < 20; i++) printf("%c",peer_id[i]);
printf("\n");
#endif
return 0;
}
void release_memory_in_parse_metafile()
{
Announce_list *p;
Files *q;
if(metafile_content != NULL) free(metafile_content);
if(file_name != NULL) free(file_name);
if(pieces != NULL) free(pieces);
while(announce_list_head != NULL) {
p = announce_list_head;
announce_list_head = announce_list_head->next;
free(p);
}
while(files_head != NULL) {
q = files_head;
files_head = files_head->next;
free(q);
}
}
int parse_metafile(char *metafile)
{
int ret;
// 讀取種子文件
ret = read_metafile(metafile);
if(ret < 0) { printf("%s:%d wrong",__FILE__,__LINE__); return -1; }
// 從種子文件中獲取tracker服務器的地址
ret = read_announce_list();
if(ret < 0) { printf("%s:%d wrong",__FILE__,__LINE__); return -1; }
// 判斷是否為多文件
ret = is_multi_files();
if(ret < 0) { printf("%s:%d wrong",__FILE__,__LINE__); return -1; }
// 獲取每個piece的長度,一般為256KB
ret = get_piece_length();
if(ret < 0) { printf("%s:%d wrong",__FILE__,__LINE__); return -1; }
// 讀取各個piece的哈希值
ret = get_pieces();
if(ret < 0) { printf("%s:%d wrong",__FILE__,__LINE__); return -1; }
// 獲取要下載的文件名，對于多文件的種子，獲取的是目錄名
ret = get_file_name();
if(ret < 0) { printf("%s:%d wrong",__FILE__,__LINE__); return -1; }
// 對于多文件的種子，獲取各個待下載的文件路徑和文件長度
ret = get_files_length_path();
if(ret < 0) { printf("%s:%d wrong",__FILE__,__LINE__); return -1; }
// 獲取待下載的文件的總長度
ret = get_file_length();
if(ret < 0) { printf("%s:%d wrong",__FILE__,__LINE__); return -1; }
// 獲得info_hash，生成peer_id
ret = get_info_hash();
if(ret < 0) { printf("%s:%d wrong",__FILE__,__LINE__); return -1; }
ret = get_peer_id();
if(ret < 0) { printf("%s:%d wrong",__FILE__,__LINE__); return -1; }
return 0;
}
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