c sendfile doesn't works the 2nd time
Вопрос
This is a snippet of the LIST ftp's cmd:
count = file_list("./", &files);
if((fp_list = fopen("listfiles.txt", "w")) == NULL){
perror("Impossibile aprire il file per la scrittura LIST");
onexit(newsockd, sockd, 0, 2);
}
for(i=0; i < count; i++){
if(strcmp(files[i], "DIR ..") == 0 || strcmp(files[i], "DIR .") == 0) continue;
else{
fprintf(fp_list, "%s\n", files[i]);
}
}
fclose(fp_list);
if((fpl = open("listfiles.txt", O_RDONLY)) < 0){
perror("open file with open");
onexit(newsockd, sockd, 0, 2);
exit(1);
}
if(fstat(fpl, &fileStat) < 0){
perror("Errore fstat");
onexit(newsockd, sockd, fpl, 3);
}
fsize = fileStat.st_size;
if(send(newsockd, &fsize, sizeof(fsize), 0) < 0){
perror("Errore durante l'invio grande file list");
onexit(newsockd, sockd, fpl, 3);
}
rc_list = sendfile(newsockd, fpl, &offset_list, fileStat.st_size);
if(rc_list == -1){
perror("Invio file list non riuscito");
onexit(newsockd, sockd, fpl, 3);
}
if((uint32_t)rc_list != fsize){
fprintf(stderr, "Error: transfer incomplete: %d di %d bytes inviati\n", rc_list, (int)fileStat.st_size);
onexit(newsockd, sockd, fpl, 3);
}
printf("OK\n");
close(fpl);
if(remove( "listfiles.txt" ) == -1 ){
perror("errore cancellazione file");
onexit(newsockd, sockd, 0, 2);
}
wher &files
is declared as char **files
and the function list_files
is a function written by me that isn't relevant for my problem.
My problem: the first time LIST cmd it's called it works properly but if i call LIST another time it always give me "error, transfer incomplete" i don't understand why...
Решение
The sendfile
function may not send all data in one call, in which case it will return a number less than requested. You treat this as an error, but instead you should try again. One way is to use a loop similar to this:
// Offset into buffer, this is where sendfile starts reading the buffer
off_t offset = 0;
// Loop while there's still some data to send
for (size_t size_to_send = fsize; size_to_send > 0; )
{
ssize_t sent = sendfile(newsockd, fpl, &offset, size_to_send);
if (sent <= 0)
{
// Error or end of file
if (sent != 0)
perror("sendfile"); // Was an error, report it
break;
}
size_to_send -= sent; // Decrease the length to send by the amount actually sent
}
Другие советы
I've found my problem.
When i call sendfile
multiple times the variable off_t offset_list;
remains "dirty".
If a call sendfile the 1st time offest_list
will have a value that won't be deleted the 2nd time i call that function.
So if i have to write offset_list = 0;
before rc_list = sendfile(newsockd, fpl, &offset_list, fileStat.st_size);
and all work!