stdout.c

   1 /*
   2  * Copyright (C) 2006-2008 Andre Noll <maan@systemlinux.org>
   3  *
   4  * Licensed under the GPL v2. For licencing details see COPYING.
   5  */
   6
   7 /** \file stdout.c Functions that deal with writing to stdout. */
   8
   9 #include <dirent.h> /* readdir() */
  10 #include <assert.h>
  11
  12 #include "para.h"
  13 #include "string.h"
  14 #include "list.h"
  15 #include "sched.h"
  16 #include "fd.h"
  17 #include "error.h"
  18 #include "stdout.h"
  19
  20 /**
  21  * The pre_select function of the stdout task.
  22  *
  23  * \param s The scheduler this task was registered to.
  24  * \param t The task structure of the stdout task.
  25  *
  26  * This function is always successful. If there is data available in the input
  27  * buffer, it adds \p STDOUT_FILENO to the write fd set of \a s.
  28  */
  29 static void stdout_pre_select(struct sched *s, struct task *t)
  30 {
  31         struct stdout_task *sot = t->private_data;
  32
  33         t->ret = 1;
  34         sot->check_fd = 0;
  35         if (!*sot->loaded) {
  36                 if (*sot->input_error) {
  37                         t->ret = *sot->input_error;
  38                         s->timeout.tv_sec = 0;
  39                         s->timeout.tv_usec = 1;
  40                 }
  41                 return;
  42         }
  43         sot->check_fd = 1;
  44         para_fd_set(STDOUT_FILENO, &s->wfds, &s->max_fileno);
  45 }
  46
  47 /**
  48  * The post select function of the stdout task.
  49  *
  50  * \param s The scheduler this task was registered to.
  51  * \param t The task structure of the stdout task.
  52  *
  53  * This function checks if \p STDOUT_FILENO was included by in the write fd set
  54  * of \a s during the previous pre_select call.  If yes, and \p STDOUT_FILENO
  55  * appeears to be writable, the data loaded in the input buffer is written to
  56  * stdout.
  57  */
  58 static void stdout_post_select(struct sched *s, struct task *t)
  59 {
  60         struct stdout_task *sot = t->private_data;
  61         ssize_t ret;
  62
  63         t->ret = 1;
  64         if (!sot->check_fd) {
  65                 if (*sot->input_error)
  66                         t->ret = *sot->input_error;
  67                 return;
  68         }
  69         if (!FD_ISSET(STDOUT_FILENO, &s->wfds))
  70                 return;
  71         t->ret = -E_STDOUT_WRITE;
  72         ret = write(STDOUT_FILENO, sot->buf, *sot->loaded);
  73         if (ret <= 0)
  74                 return;
  75         *sot->loaded -= ret;
  76         if (*sot->loaded)
  77                 memmove(sot->buf, sot->buf + ret, *sot->loaded);
  78         t->ret = 1;
  79 }
  80
  81 static void stdout_default_event_handler(struct task *t)
  82 {
  83         PARA_NOTICE_LOG("%p: %s\n", t, para_strerror(-t->ret));
  84         unregister_task(t);
  85 }
  86
  87 /**
  88  * Initialize a stdout task structure with default values.
  89  *
  90  * \param sot The stdout task structure.
  91  *
  92  * This fills in the pre/post select function poinzters of the task structure
  93  * given by \a sot. It also sets up a default error handler which unregisters
  94  * the task on errors and clears the eof flag of \a sot.
  95  */
  96 void stdout_set_defaults(struct stdout_task *sot)
  97 {
  98         int ret;
  99
 100         sot->task.private_data = sot;
 101         sot->task.pre_select = stdout_pre_select;
 102         sot->task.post_select = stdout_post_select;
 103         sot->task.event_handler = stdout_default_event_handler;
 104         sot->error = 0;
 105         sprintf(sot->task.status, "stdout writer");
 106         ret = mark_fd_nonblocking(STDOUT_FILENO);
 107         if (ret >= 0)
 108                 return;
 109         PARA_EMERG_LOG("%s\n", para_strerror(-ret));
 110         exit(EXIT_FAILURE);
 111 }