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sendfile.c

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+#include <unistd.h>
+#include <sys/sendfile.h>
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <sys/time.h>
+#include <sys/mman.h>
+
+/*
+./sendfile Titanik.mp4 
+Copied by sendfile, time: 30.1055s
+Copied by mmap, time: 35.6469s
+
+du Titanik.mp4 
+2.6GTitanik.mp4
+*/
+
+
+double dtime(){
+	double t;
+	struct timeval tv;
+	gettimeofday(&tv, NULL);
+	t = tv.tv_sec + ((double)tv.tv_usec)/1e6;
+	return t;
+}
+
+typedef struct{
+	char *data;
+	size_t len;
+} mmapbuf;
+
+void My_munmap(mmapbuf **b){
+	if(munmap((*b)->data, (*b)->len))
+		perror("Can't munmap");
+	free(*b);
+	*b = NULL;
+}
+
+mmapbuf *My_mmap(char *filename){
+	int fd;
+	char *ptr = NULL;
+	size_t Mlen;
+	struct stat statbuf;
+	if((fd = open(filename, O_RDONLY)) < 0){
+		perror("Can't open file for reading");
+		goto ret;
+	}
+	if(fstat (fd, &statbuf) < 0){
+		perror("Can't stat file");
+		goto ret;
+	}
+	Mlen = statbuf.st_size;
+	if((ptr = mmap (0, Mlen, PROT_READ, MAP_PRIVATE, fd, 0)) == MAP_FAILED){
+		perror("Mmap error for input");
+		goto ret;
+	}
+	mmapbuf *ret = calloc(sizeof(mmapbuf), 1);
+	if(ret){
+		ret->data = ptr;
+		ret->len = Mlen;
+	}else munmap(ptr, Mlen);
+ret:
+	if(close(fd)) perror("Can't close mmap'ed file");
+	return  ret;
+}
+
+
+int main(int argc, char **argv){
+	struct stat st;
+	double T0;
+	if(argc != 2){
+		printf("Usage: %s file\n", argv[0]);
+		return 2;
+	}
+	if (stat(argv[1], &st) == 0 && S_ISREG(st.st_mode)){
+		off_t off = 0;
+		int fd = open(argv[1], O_RDONLY);
+		int fdo = open("tmpoutput", O_WRONLY | O_CREAT,  S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
+		if (fd < 0 || fdo < 0){
+			perror("can't open");
+			return 1;
+		}
+		T0 = dtime();
+		posix_fadvise(fd, 0, 0, POSIX_FADV_SEQUENTIAL);
+		while (off < st.st_size) {
+			ssize_t bytes = sendfile(fdo, fd, &off, st.st_size - off);
+			if (bytes <= 0){
+				perror("can't sendfile");
+			}
+		}
+		close(fd);
+		close(fdo);
+		printf("Copied by sendfile, time: %gs\n", dtime()-T0);
+		T0 = dtime();
+		mmapbuf *map = My_mmap(argv[1]);
+		if(map){
+			fdo = open("tmpoutput", O_WRONLY | O_CREAT,  S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
+			if (fd < 0 || fdo < 0){
+				perror("can't open");
+				return 1;
+			}
+			size_t written = 0, towrite = map->len;
+			char *ptr = map->data;
+			do{
+				ssize_t wr = write(fdo, ptr, towrite);
+				if(wr <= 0) break;
+				written += wr;
+				towrite -= wr;
+				ptr += wr;
+			}while(towrite);
+			if(written != map->len){
+				printf("err: writed only %zd byted of %zd\n", written, map->len);
+			}
+			close(fdo);
+			My_munmap(&map);
+			printf("Copied by mmap, time: %gs\n", dtime()-T0);
+		}
+	}else
+		perror("Can't stat file");
+	return 0;
+}