http://technica-blog.jp/1159 の下にあるコードをC言語で高速に？ 読み込んだファイルは頭出し後、STDOUTに出力

tshead.c

#define _LARGEFILE_SOURCE
#define _FILE_OFFSET_BITS 64

#include <stdio.h>
#include <stdlib.h>
#ifdef _WIN32
  #include <io.h>
  #include <fcntl.h>
#endif

int main(int argc, char *argv[0]){
#ifdef _WIN32
  setmode(fileno(stdout),O_BINARY);
  setmode(fileno(stdin),O_BINARY);
#endif
	FILE *fp;
	unsigned char buf[188];
	int pid,pmt,fore_pid;
	pmt = -1;
	fore_pid = 0;
	if((fp = fopen(argv[1], "rb")) == NULL) {
		fprintf(stderr,"file open error");
		exit(EXIT_FAILURE);
	}
	//printf("%d,%d\n",(int)sizeof(buf[0]),(int)(sizeof(buf)/sizeof(buf[0])));
	while(fread(buf, sizeof(buf[0]),sizeof(buf)/sizeof(buf[0]),fp)){
		if(buf[0] != 0x47){
			fprintf(stderr,"not sync\n");
			fclose(fp);
			exit(EXIT_FAILURE);
		}
		pid = (((buf[1] & 0x1f) << 8) | buf[2]);
		
		if(pid == 0x00 && pmt == -1){
			pmt = (((buf[19] & 0x1f) << 8) | buf[20]);
		}
 

		if(pmt != 0 && pid == pmt && ((buf[1]&0x40) == 0x40)){
			int plen = ((buf[15]&0xf) * 16 * 16) + buf[16];
			int index = 17 + plen;
			int currentpid;
			if(index+19 > 188){
				fprintf(stderr,"index err\n");
				fclose(fp);
				exit(EXIT_FAILURE);
			}
			if(buf[index] == 0x02){
				currentpid = (buf[index+1]<<8) | buf[index+2];
			}
			if(fore_pid != 0 && fore_pid != currentpid){
				fprintf(stderr,"pid changed%d,%d\n",fore_pid,currentpid);
				size_t rcount;
				//unsigned char largebuf[1024*1024*1];
				int largebufsize = 1024*1024*1;
				unsigned char *largebuf = (unsigned char *)malloc(largebufsize);
				while((rcount = fread(largebuf, 1,largebufsize,fp))){
					fwrite(largebuf, 1, rcount,stdout);
				}
				fclose(fp);
				exit(EXIT_SUCCESS);
			}
			fore_pid = currentpid;
		}
		
	}

printf("hoge\n");
fclose(fp);
}