void
write_buffer_queue_init(
write_buffer_queue_t* queue,
request_context_t* request_context,
write_callback_t write_callback,
void* write_context,
bool_t reuse_buffers)
{
queue->request_context = request_context;
queue->write_callback = write_callback;
queue->write_context = write_context;
queue->reuse_buffers = reuse_buffers;
initialize_list_head(&queue->buffers);
queue->cur_write_buffer = NULL;
queue->cur_offset = 0;
}
int main(int argc, char **argv)
{
buffer_t* new_buffer;
FILE *source;
long buffer_start_offset;
long cur_line_count;
long initial_offset;
long bytes_to_read;
long offset;
long requested_line_count = DEFAULT_N_LINES;
int inotify_fd = -1;
// parse the command line
parse_options(argc, argv, &requested_line_count);
requested_line_count++;
if (optind + 1 != argc)
{
usage(EXIT_FAILURE);
}
// open the file
source = fopen(argv[optind], "rb");
if (source == NULL)
{
printf("fopen %s failed %d\n", argv[optind], errno);
goto error;
}
if (forever)
{
// set an inotify watch
inotify_fd = inotify_init();
if (inotify_fd == -1)
{
printf("inotify_init failed %d", errno);
goto error;
}
if (inotify_add_watch(inotify_fd, argv[optind], IN_MODIFY) == -1)
{
printf("inotify_add_watch failed %d", errno);
goto error;
}
}
// seek to the end
if (fseek(source, 0, SEEK_END) == -1)
{
printf("fseek failed (1) %d\n", errno);
goto error;
}
initial_offset = ftell(source);
if (initial_offset == -1)
{
printf("ftell failed %d\n", errno);
goto error;
}
offset = initial_offset;
initialize_list_head(&buffer_queue);
for (;;)
{
if (offset > CHUNK_SIZE_READ)
{
bytes_to_read = CHUNK_SIZE_READ;
}
else
{
bytes_to_read = offset;
}
offset -= bytes_to_read;
if (offset + MEMORY_LIMIT < initial_offset)
{
printf("memory limit exceeded\n");
goto error;
}
// allocate a buffer
new_buffer = (buffer_t*)malloc(sizeof(buffer_t));
if (new_buffer == NULL)
{
printf("malloc failed (1)\n");
goto error;
}
new_buffer->data = malloc(bytes_to_read);
if (new_buffer->data == NULL)
{
printf("malloc failed (2)\n");
goto error;
}
insert_head_list(&buffer_queue, &new_buffer->node);
new_buffer->offset = offset;
new_buffer->size = bytes_to_read;
// read from the file
if (fseek(source, offset, SEEK_SET) == -1)
{
printf("fseek failed (2) %d\n", errno);
goto error;
}
if (fread(new_buffer->data, 1, bytes_to_read, source) != bytes_to_read)
{
printf("fread failed %d\n", errno);
goto error;
}
cur_line_count = get_line_count(new_buffer, &buffer_start_offset);
if (cur_line_count >= requested_line_count)
{
// read enough data, seek to the initial offset and print the result
if (fseek(source, initial_offset, SEEK_SET) == -1)
{
printf("fseek failed (3) %d\n", errno);
goto error;
}
return print_lines(source, inotify_fd, new_buffer, buffer_start_offset, cur_line_count - requested_line_count + 1);
}
if (offset > 0)
{
continue;
}
if (cur_line_count <= 0)
{
goto error;
}
// reached the beginning of the file, seek to the initial offset and print the result
if (fseek(source, initial_offset, SEEK_SET) == -1)
{
printf("fseek failed (4) %d\n", errno);
goto error;
}
return print_lines(source, inotify_fd, new_buffer, buffer_start_offset, 0);
}
return 0;
error:
// not bothering to clean up anything since the process quits
return 1;
}
