從ffmpeg中抽取出來的UDP組播接收程式

前言
程式碼抽取方法:
1. 跟蹤並複製
跟蹤要抽取程式碼的主要流程, 將主流程相關的，函式層次不是很深的程式碼原樣複製到新的工程中;
函式呼叫層次很複雜的函式可以先只留下函式介面，將函式體的內容全部註釋掉。
2. 編譯
編譯新的工程，一個一個解決編譯提示的警告和出錯資訊。
3. 除錯
使用除錯工具，同步除錯原工程和新工程，將新工程註釋掉函式體的函式補全。
4. 優化完成

下面是從ffmpeg抽取出來的udp組播接收程式。
/******************************************************************************

* \File
* main.c
* \Brief
* Recording udp-multicast data to a file
* \Author
* Hank
* \Created date
* 2013-02-25
******************************************************************************
*/
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>

#include <errno.h>
#include <memory.h>
#include <fcntl.h>
#include <unistd.h>
#include <pthread.h>
#include <sys/types.h>
#include <netdb.h>
#include <sys/socket.h>
#include <arpa/inet.h>

#ifndef AI_PASSIVE
#define AI_PASSIVE 1
#endif

#ifndef NI_NUMERICSERV
#define NI_NUMERICSERV 8
#endif

#define UDP_TX_BUF_SIZE 32768
#define UDP_MAX_PKT_SIZE 65536

#ifndef IN_MULTICAST
#define IN_MULTICAST(a) ((((uint32_t)(a)) & 0xf0000000) == 0xe0000000)
#endif

#define HAVE_AVX 1
#define HAVE_PTHREADS 1
#define ALIGN (HAVE_AVX ? 32 : 16)

#define AVIO_FLAG_READ 1 /**< read-only */
#define AVERROR(e) (-(e)) ///< Returns a negative error code from a POSIX error code, to return from library functions.
#define closesocket close
#define FFMIN(a,b) ((a) > (b) ? (b) : (a))
#define ff_neterrno() AVERROR(errno)

typedef struct AVFifoBuffer {
uint8_t *buffer;
uint8_t *rptr, *wptr, *end;
uint32_t rndx, wndx;
} AVFifoBuffer;

typedef struct {
int udp_fd;
int ttl;
int buffer_size;
int is_multicast;
/*Added by Anderson, Fixed udp multicast*/
int b_localaddr_flag;
char local_addr[20];
/*end*/

int local_port;
int reuse_socket;
struct sockaddr_storage dest_addr;
int dest_addr_len;
int is_connected;

/* Circular Buffer variables for use in UDP receive code */
int circular_buffer_size;
AVFifoBuffer *fifo;
int circular_buffer_error;
#if HAVE_PTHREADS
pthread_t circular_buffer_thread;
#endif
} UDPContext;

typedef struct URLContext {
int flags;
int is_streamed; /**< true if streamed (no seek possible), default = false */
int max_packet_size; /**< if non zero, the stream is packetized with this max packet size */
void *priv_data;
int is_connected;
} URLContext;

static int default_interrupt_cb(void);
int (*url_interrupt_cb)(void) = default_interrupt_cb;

int udp_set_url(struct sockaddr_storage *addr,
const char *hostname, int port);
int ff_is_multicast_address(struct sockaddr *addr);

/**
* If no filename is given to av_open_input_file because you want to
* get the local port first, then you must call this function to set
* the remote server address.
*
* url syntax: udp://host:port[?option=val...]
* option: 'ttl=n' : set the ttl value (for multicast only)
* 'localport=n' : set the local port
* 'pkt_size=n' : set max packet size
* 'reuse=1' : enable reusing the socket
*
* @param h media file context
* @param uri of the remote server
* @return zero if no error.
*/
int ff_udp_set_remote_url(URLContext *h, const char *uri)
{
UDPContext *s = h->priv_data;
char hostname[256], buf[10];
int port;
const char *p;

//av_url_split(NULL, 0, NULL, 0, hostname, sizeof(hostname), &port, NULL, 0, uri);
strcpy(hostname, "225.1.1.31");
port = 1234;

/* set the destination address */
s->dest_addr_len = udp_set_url(&s->dest_addr, hostname, port);
if (s->dest_addr_len < 0) {
return AVERROR(EIO);
}
s->is_multicast = ff_is_multicast_address((struct sockaddr*) &s->dest_addr);

return 0;
}

struct addrinfo* udp_resolve_host(const char *hostname, int port,
int type, int family, int flags)
{
struct addrinfo hints, *res = 0;
int error;
char sport[16];
const char *node = 0, *service = "0";

if (port > 0)
{
snprintf(sport, sizeof(sport), "%d", port);
service = sport;
}
if ((hostname) && (hostname[0] != '\0') && (hostname[0] != '?'))
{
node = hostname;
}

memset(&hints, 0, sizeof(hints));
hints.ai_socktype = type;
hints.ai_family = family;
hints.ai_flags = flags;
if ((error = getaddrinfo(node, service, &hints, &res)))
{
res = NULL;
//av_log(NULL, AV_LOG_ERROR, "udp_resolve_host: %s\n", gai_strerror(error));
fprintf(stderr, "udp_resolve_host: %s\n", strerror(error));
}

return res;
}

int udp_set_url(struct sockaddr_storage *addr,
const char *hostname, int port)
{
struct addrinfo *res0;
int addr_len;

res0 = udp_resolve_host(hostname, port, SOCK_DGRAM, AF_UNSPEC, 0);
if (res0 == 0)
return AVERROR(EIO);

memcpy(addr, res0->ai_addr, res0->ai_addrlen);
addr_len = res0->ai_addrlen;
freeaddrinfo(res0);

return addr_len;
}

int ff_is_multicast_address(struct sockaddr *addr)
{
if (addr->sa_family == AF_INET) {
return IN_MULTICAST(ntohl(((struct sockaddr_in *)addr)->sin_addr.s_addr));
}
return 0;
}

int udp_socket_create(UDPContext *s,
struct sockaddr_storage *addr, int *addr_len)
{
int udp_fd = -1;
struct addrinfo *res0 = NULL, *res = NULL;
int family = AF_UNSPEC;

if (((struct sockaddr *) &s->dest_addr)->sa_family)
family = ((struct sockaddr *) &s->dest_addr)->sa_family;

res0 = udp_resolve_host(0, s->local_port, SOCK_DGRAM, family, AI_PASSIVE);
if (res0 == 0)
goto fail;

for (res = res0; res; res=res->ai_next)
{
udp_fd = socket(res->ai_family, SOCK_DGRAM, 0);
if (udp_fd > 0)
break;
//av_log(NULL, AV_LOG_ERROR, "socket: %s\n", strerror(errno));
fprintf(stderr, "socket: %s\n", strerror(errno));
}

if (udp_fd < 0)
goto fail;

memcpy(addr, res->ai_addr, res->ai_addrlen);
*addr_len = res->ai_addrlen;
freeaddrinfo(res0);

return udp_fd;

fail:
if (udp_fd >= 0)
closesocket(udp_fd);
if(res0)
freeaddrinfo(res0);
return -1;
}

int udp_port(struct sockaddr_storage *addr, int addr_len)
{
char sbuf[sizeof(int)*3+1];

if (getnameinfo((struct sockaddr *)addr, addr_len, NULL, 0, sbuf, sizeof(sbuf), NI_NUMERICSERV) != 0) {
//av_log(NULL, AV_LOG_ERROR, "getnameinfo: %s\n", strerror(errno));
fprintf(stderr, "getnameinfo: %s\n", strerror(errno));
return -1;
}

return strtol(sbuf, NULL, 10);
}

int udp_join_multicast_group(int sockfd, struct sockaddr *addr, int b_localaddr, char *pc_local_addr)
{
#ifdef IP_ADD_MEMBERSHIP
if (addr->sa_family == AF_INET) {
struct ip_mreq mreq;

mreq.imr_multiaddr.s_addr = ((struct sockaddr_in *)addr)->sin_addr.s_addr;
if ( 0 == b_localaddr )
{
mreq.imr_interface.s_addr= INADDR_ANY;
}
else
{
mreq.imr_interface.s_addr= inet_addr(pc_local_addr);
}

if (setsockopt(sockfd, IPPROTO_IP, IP_ADD_MEMBERSHIP, (const void *)&mreq, sizeof(mreq)) < 0) {
//av_log(NULL, AV_LOG_ERROR, "setsockopt(IP_ADD_MEMBERSHIP): %s\n", strerror(errno));
fprintf(stderr, "setsockopt(IP_ADD_MEMBERSHIP): %s\n", strerror(errno));
return -1;
}

從ffmpeg中抽取出來的UDP組播接收程式

從ffmpeg中抽取出來的UDP組播接收程式

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