tp2
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tp/tp2/README.md
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151
tp/tp2/README.md
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# TP2 : Fichiers
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#### Ex1
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Écrire deux versions d'un programme qui copie "octet par octet" un fichier source dans un fichier destination :
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```
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./copy infile outfile
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```
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en utilisant :
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1. les appels systèmes linux : `open`, `read`, `write`, `close`.
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2. les fonctions E/S standards (sdtio) : `fopen`, `fread`, `fwrite`, `fclose`.
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Testez vos deux programmes sur un fichier volumineux (utilisez la commande `dd` le pseudo fichier `dev/urandom` pour
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générer un contenu aléatoire) et expliquez pourquoi le deuxième programme est beaucoup plus rapide que le
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premier.
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Remarques :
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- pour être dans les mêmes conditions, il faut être sur que le fichier à copier n'est pas en cache en mémoire. Générez un nouveau fichier de même taille, ou utilisez le programme [fadvise.c](./src/fadvise.c) qui permet de vider les blocs du cache pour un fichier quelconque.
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- utilisez `strace` pour tracer les appels systèmes de vos deux programmes.
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#### Ex2
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Écrire un programme qui copie un fichier en utilisant `mmap`.
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#### Ex3
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Compilez et exécutez Le programme [coherence.c](./src/coherence.c). Qu'est ce que cela montre ?
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#### Ex4
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Le but est d'écrire en C un programme qui efface un fichier du disque de telle manière que le contenu effacé ne soit pas
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récupérable. Pour des raisons physiques, on procédera de la manière suivante :
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- Si l'inode correspondant au fichier à effacer a plusieurs références, on efface juste l'entrée du répertoire correspondant.
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- Sinon, on réécrit les blocs de données :
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- une première passe avec `0xff` pour tous les octets.
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- une deuxième passe avec des valeurs aléatoires (on utilisera le pseudo-fichier `/dev/urandom`)
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- enfin, avant d'effacer le fichier, on le renomera de manière aléatoire.
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Toutes les E/S devront utilisées un cache.
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Fonctions utiles :
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```c
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#include <sys/stat.h>
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int stat(const char *restrict pathname,
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struct stat *restrict statbuf);
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#include <fcntl.h>
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int open(const char *pathname, int flags, ...
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/* mode_t mode */ );
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#include <unistd.h>
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ssize_t read(int fd, void buf[.count], size_t count);
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ssize_t write(int fd, const void buf[.count], size_t count);
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int unlink(const char *pathname);
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int close(int fd);
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#include <stdio.h>
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int rename(const char *oldpath, const char *newpath);
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```
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#### Ex5
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Le but est d'écrire une version simplifiée de la commande `ls -al`.
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```bash
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$./myls /
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drwxr-xr-x 18 root root 4096 07 sept. 12:48 ..
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drwxr-xr-x 6 root root 4096 03 nov. 09:40 srv
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drwxr-xr-x 10 root root 4096 24 sept. 21:07 usr
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dr-xr-xr-x 301 root root 0 18 sept. 07:10 proc
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drwxr-xr-x 312 root root 258048 12 sept. 09:46 lib
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drwxrwxrwt 25 root root 2140 27 sept. 13:02 tmp
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drwxr-xr-x 18 root root 4096 07 sept. 12:48 .
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drwxr-xr-x 5 root root 1024 07 sept. 12:57 boot
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drwxr-xr-x 32 root root 760 27 sept. 09:57 run
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drwxr-xr-x 11 root root 4096 25 juil. 18:14 opt
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drwxr-x--- 32 root root 4096 25 sept. 13:49 root
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drwxr-xr-x 122 root root 12288 27 sept. 09:57 etc
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drwxr-xr-x 4 root root 4096 10 déc. 08:27 home
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drwxr-xr-x 6 root root 151552 24 sept. 21:07 bin
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drwxr-xr-x 6 root root 151552 24 sept. 21:07 sbin
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drwxr-xr-x 23 root root 3580 27 sept. 09:57 dev
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drwxr-xr-x 10 root root 4096 13 sept. 13:33 media
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drwxr-xr-x 15 root root 4096 18 sept. 07:10 var
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drwxr-xr-x 312 root root 258048 12 sept. 09:46 lib64
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dr-xr-xr-x 13 root root 0 18 sept. 07:10 sys
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drwx------ 2 root root 16384 02 sept. 11:30 lost+found
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-rw-r--r-- 1 root root 2333 28 juin 20:49 fonts.conf
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drwxr-xr-x 2 root root 4096 02 sept. 11:40 mnt
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```
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- pour parcourir les entrées du repertoire passé en argument :
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```c
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#include <sys/types.h>
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#include <dirent.h>
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DIR *opendir(const char *name);
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```
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```c
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#include <dirent.h>
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struct dirent *readdir(DIR *dirp);
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struct dirent {
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ino_t d_ino; /* Inode number */
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off_t d_off; /* Not an offset; see below */
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unsigned short d_reclen; /* Length of this record */
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unsigned char d_type; /* Type of file; not supported
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by all filesystem types */
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char d_name[256]; /* Null-terminated filename */
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};
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```
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- les autres informations sont accessibles grâce à la fonction :
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```c
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <unistd.h>
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int stat(const char *pathname, struct stat *statbuf);
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struct stat {
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dev_t st_dev; /* ID of device containing file */
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ino_t st_ino; /* Inode number */
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mode_t st_mode; /* File type and mode */
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nlink_t st_nlink; /* Number of hard links */
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uid_t st_uid; /* User ID of owner */
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gid_t st_gid; /* Group ID of owner */
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dev_t st_rdev; /* Device ID (if special file) */
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off_t st_size; /* Total size, in bytes */
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blksize_t st_blksize; /* Block size for filesystem I/O */
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blkcnt_t st_blocks; /* Number of 512B blocks allocated */
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/* Since Linux 2.6, the kernel supports nanosecond
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precision for the following timestamp fields.
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For the details before Linux 2.6, see NOTES. */
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struct timespec st_atim; /* Time of last access */
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struct timespec st_mtim; /* Time of last modification */
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struct timespec st_ctim; /* Time of last status change */
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#define st_atime st_atim.tv_sec /* Backward compatibility */
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#define st_mtime st_mtim.tv_sec
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#define st_ctime st_ctim.tv_sec
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};
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```
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Faire `man 7 inode`.
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BIN
tp/tp2/src.tar.gz
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BIN
tp/tp2/src.tar.gz
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Binary file not shown.
96
tp/tp2/src/coherence.c
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96
tp/tp2/src/coherence.c
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <assert.h>
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#include <sys/fcntl.h>
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#define TESTFILE "coherence-test.txt"
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void write_asr_c_pas_bien()
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{
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FILE* f = fopen(TESTFILE, "w");
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fprintf(f, "L'asr, c'est pas bien!\n");
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fclose(f);
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}
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void write_asr_c_bien()
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{
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FILE* f = fopen(TESTFILE, "w");
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fprintf(f, "L'asr, c'est bien!!\n");
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fclose(f);
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}
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void read_using_syscalls()
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{
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write_asr_c_pas_bien();
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// open file descriptor
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int fd = open(TESTFILE, O_RDONLY);
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// read first 12 bytes
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char buf[BUFSIZ];
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ssize_t nr1 = read(fd, buf, 12);
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assert(nr1 >= 0);
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write_asr_c_bien();
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// read rest of file, print to stdout
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ssize_t nr2 = read(fd, buf + nr1, BUFSIZ - nr1);
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close(fd);
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fwrite(buf, 1, nr1 + nr2, stdout);
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}
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void read_using_stdio()
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{
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write_asr_c_pas_bien();
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// open stdio file
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FILE* f = fopen(TESTFILE, "r");
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// read first 12 bytes
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char buf[BUFSIZ];
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size_t nr1 = fread(buf, 1, 12, f);
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write_asr_c_bien();
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// read rest of file, print to stdout
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size_t nr2 = fread(buf + nr1, 1, BUFSIZ - nr1, f);
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fclose(f);
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fwrite(buf, 1, nr1 + nr2, stdout);
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}
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static void usage()
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{
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fprintf(stderr, "Usage: ./coherence -l (linux syscalls) or ./coherence -s (stdio)\n");
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exit(1);
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}
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int main(int argc, char** argv)
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{
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int which = 0;
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int opt;
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while ((opt = getopt(argc, argv, "ls")) != -1) {
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switch (opt) {
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case 's':
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which = 's';
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break;
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case 'l':
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which = 'l';
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break;
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default:
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usage();
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}
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}
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if (which == 's') {
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read_using_stdio();
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} else if (which == 'l') {
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read_using_syscalls();
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} else {
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usage();
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}
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}
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35
tp/tp2/src/copy.c
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35
tp/tp2/src/copy.c
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#include <fcntl.h>
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#include <unistd.h>
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#include <assert.h>
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#define BLOCK_SIZE 1
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int main(int argc, char *argv[])
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{
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int fin,
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fout;
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char buf[BLOCK_SIZE];
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assert( argc == 3 );
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fin = open(argv[1],O_RDONLY);
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assert( fin >= 0 );
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fout = open(argv[2],O_CREAT|O_WRONLY|O_TRUNC,0600);
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assert( fout >= 0 );
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while(1){
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ssize_t nb_read;
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nb_read = read(fin,buf,BLOCK_SIZE);
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if (nb_read <= 0)
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break;
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write(fout,buf,nb_read);
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}
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close(fin);
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close(fout);
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return 0;
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}
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155
tp/tp2/src/fadvise.c
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155
tp/tp2/src/fadvise.c
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#include <linux/falloc.h>
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#include <linux/fadvise.h>
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#include <stdio.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <unistd.h>
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#include <sys/syscall.h>
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#include <asm/unistd_64.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <stdlib.h>
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#include <string.h>
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//#include <linux-ftools.h>
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#define LINUX_FTOOLS_VERSION "1.0.0"
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/**
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SYNTAX: filename mode [offset] [,length]
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Where mode can be:
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POSIX_FADV_NORMAL No further special treatment.
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POSIX_FADV_RANDOM Expect random page references.
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POSIX_FADV_SEQUENTIAL Expect sequential page references.
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POSIX_FADV_WILLNEED Will need these pages.
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POSIX_FADV_DONTNEED Don't need these pages.
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POSIX_FADV_NOREUSE Data will be accessed once.
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Allows an application to to tell the kernel how it expects to use a file handle,
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so that the kernel can choose appropriate read-ahead and caching techniques for
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access to the corresponding file. This is similar to the POSIX version of the
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madvise system call, but for file access instead of memory access. The
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sys_fadvise64() function is obsolete and corresponds to a broken glibc API,
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sys_fadvise64_64() is the fixed version. The following are the values for the
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advice parameter:
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FADV_NORMAL
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No special treatment.
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FADV_RANDOM
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Expect page references in random order.
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FADV_SEQUENTIAL
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Expect page references in sequential order.
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FADV_WILLNEED
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Expect access in the near future.
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FADV_DONTNEED
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Do not expect access in the near future. Subsequent access of pages in this
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range will succeed, but will result either in reloading of the memory contents
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from the underlying mapped file or zero-fill-in-demand pages for mappings
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without an underlying file.
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FADV_NOREUSE
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Access data only once.
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*/
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int main(int argc, char *argv[]) {
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if ( argc < 3 ) {
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fprintf( stderr, "%s version %s\n", argv[0], LINUX_FTOOLS_VERSION );
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printf( "SYNTAX: fadvise filename mode [offset] [,length]\n" );
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printf( "Where mode can be:\n\n" );
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printf( " POSIX_FADV_NORMAL No further special treatment. \n" );
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printf( " POSIX_FADV_RANDOM Expect random page references. \n" );
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printf( " POSIX_FADV_SEQUENTIAL Expect sequential page references. \n" );
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printf( " POSIX_FADV_WILLNEED Will need these pages. \n" );
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printf( " POSIX_FADV_DONTNEED Don't need these pages. \n" );
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printf( " POSIX_FADV_NOREUSE Data will be accessed once. \n" );
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exit( 1 );
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}
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char* path = argv[1];
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char* param_mode = argv[2];
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printf( "Going to fadvise %s\n", path );
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int flags = O_RDWR;
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int fd = open( path, flags );
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if ( fd == -1 ) {
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perror( NULL );
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return 1;
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}
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struct stat fd_stat ;
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if ( fstat( fd, &fd_stat ) < 0 ) {
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perror( "Could not stat file: " );
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return 1;
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}
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loff_t offset = 0;
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loff_t length = fd_stat.st_size;
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if ( argc >= 4 ) {
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offset = strtol( argv[3], NULL, 10 );
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}
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if ( argc >= 5 ) {
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length = strtol( argv[4], NULL, 10 );
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}
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printf( "offset: %ld\n", offset );
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printf( "length: %ld\n", length );
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int mode = -1;
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if ( strcmp( param_mode , "POSIX_FADV_NORMAL" ) == 0 ) {
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mode = POSIX_FADV_NORMAL;
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} else if ( strcmp( param_mode , "POSIX_FADV_RANDOM" ) == 0 ) {
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mode = POSIX_FADV_RANDOM;
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} else if ( strcmp( param_mode , "POSIX_FADV_SEQUENTIAL" ) == 0 ) {
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mode = POSIX_FADV_SEQUENTIAL;
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} else if ( strcmp( param_mode , "POSIX_FADV_WILLNEED" ) == 0 ) {
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mode = POSIX_FADV_DONTNEED;
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} else if ( strcmp( param_mode , "POSIX_FADV_DONTNEED" ) == 0 ) {
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mode = POSIX_FADV_DONTNEED;
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} else if ( strcmp( param_mode , "POSIX_FADV_NOREUSE" ) == 0 ) {
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mode = POSIX_FADV_NOREUSE;
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} else {
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printf( "Invalid mode %s\n", param_mode );
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exit( 1 );
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}
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printf( "mode: %s\n", param_mode );
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long result = syscall( SYS_fadvise64, fd, offset, length , mode );
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if ( result != 0 ) {
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if ( result != -1 ) {
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errno=result;
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perror( "Unable to fadvise" );
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} else {
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printf( "Unable to fadvise: %ld\n" , result );
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}
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return 1;
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}
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printf( "WIN\n" );
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close( fd );
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return 0;
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}
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70
tp/tp2/src/my_cp_map.c
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70
tp/tp2/src/my_cp_map.c
Normal file
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#include <stdio.h>
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#include <string.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <fcntl.h>
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#include <assert.h>
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#include <time.h>
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#include <sys/mman.h>
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#define BUFSIZE 1024
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static inline double tstamp(void)
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{
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struct timespec tv;
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clock_gettime(CLOCK_REALTIME, &tv);
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return tv.tv_sec + tv.tv_nsec * 1.0e-9;
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}
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int main(int argc, char *argv[])
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{
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//char buf[BUFSIZE];
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char * bufin = NULL,
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* bufout = NULL;
|
||||
|
||||
|
||||
int fin,
|
||||
fout;
|
||||
|
||||
double start,
|
||||
end;
|
||||
|
||||
size_t filesize = 0;
|
||||
|
||||
assert(argc == 3);
|
||||
|
||||
start = tstamp();
|
||||
|
||||
fin = open(argv[1],O_RDONLY);
|
||||
assert(fin >=0);
|
||||
|
||||
fout = open(argv[2],O_RDWR|O_CREAT|O_TRUNC,0600);
|
||||
assert(fout >=0);
|
||||
|
||||
filesize = lseek(fin,0,SEEK_END);
|
||||
ftruncate (fout,filesize);
|
||||
|
||||
bufin = mmap(NULL,filesize,PROT_READ,MAP_PRIVATE,fin,0);
|
||||
assert(bufin != (void*)-1);
|
||||
|
||||
bufout = mmap(NULL,filesize,PROT_WRITE,MAP_SHARED,fout,0);
|
||||
|
||||
assert(bufout != (void*)-1);
|
||||
|
||||
|
||||
memcpy(bufout,bufin,filesize);
|
||||
|
||||
//munmap(bufin,filesize);
|
||||
//munmap(bufout,filesize);
|
||||
|
||||
//ssize_t nb_read = read(fin,buf,sizeof(buf));
|
||||
close(fin);
|
||||
close(fout);
|
||||
|
||||
end = tstamp();
|
||||
|
||||
printf("time = %.3lf\n",end - start);
|
||||
return 0;
|
||||
}
|
||||
Loading…
Reference in New Issue
Block a user