stdin.c

   1 /*
   2  * Copyright (C) 2006-2013 Andre Noll <maan@systemlinux.org>
   3  *
   4  * Licensed under the GPL v2. For licencing details see COPYING.
   5  */
   6
   7 /** \file stdin.c Functions that deal with reading from stdin. */
   8
   9 #include <assert.h>
  10 #include <regex.h>
  11
  12 #include "para.h"
  13 #include "list.h"
  14 #include "sched.h"
  15 #include "fd.h"
  16 #include "error.h"
  17 #include "stdin.h"
  18 #include "buffer_tree.h"
  19 #include "string.h"
  20
  21 /**
  22  * The pre_select function of the stdin task.
  23  *
  24  * \param s The scheduler this task was registered to.
  25  * \param t The task structure of the stdin task.
  26  *
  27  * This function is always successful. If there is space left in the
  28  * buffer of the stdin task, it adds \p STDIN_FILENO to the read fd set
  29  * of \a s.
  30  */
  31 static void stdin_pre_select(struct sched *s, struct task *t)
  32 {
  33         struct stdin_task *sit = container_of(t, struct stdin_task, task);
  34         int ret;
  35
  36         ret = btr_node_status(sit->btrn, 0, BTR_NT_ROOT);
  37         if (ret < 0)
  38                 sched_min_delay(s);
  39         if (ret <= 0)
  40                 return;
  41         if (btr_pool_unused(sit->btrp) > 0)
  42                 return para_fd_set(STDIN_FILENO, &s->rfds, &s->max_fileno);
  43         sched_request_timeout_ms(100, s);
  44 }
  45
  46 /**
  47  * The post select function of the stdin task.
  48  *
  49  * \param s The scheduler this task was registered to.
  50  * \param t The task structure of the stdin task.
  51  *
  52  * This function checks if \p STDIN_FILENO was included by in the read fd set
  53  * of \a s during the previous pre_select call.  If yes, and \p STDIN_FILENO
  54  * appears to be readable, data is read from stdin and fed into the buffer
  55  * tree.
  56  */
  57 static int stdin_post_select(struct sched *s, struct task *t)
  58 {
  59         struct stdin_task *sit = container_of(t, struct stdin_task, task);
  60         ssize_t ret;
  61         size_t sz, n;
  62         char *buf = NULL;
  63
  64         ret = btr_node_status(sit->btrn, 0, BTR_NT_ROOT);
  65         if (ret < 0)
  66                 goto err;
  67         if (ret == 0)
  68                 return 0;
  69         sz = btr_pool_get_buffer(sit->btrp, &buf);
  70         if (sz == 0)
  71                 return 0;
  72         if (sit->must_set_nonblock_flag) {
  73                 ret = mark_fd_nonblocking(STDIN_FILENO);
  74                 if (ret < 0)
  75                         goto err;
  76                 sit->must_set_nonblock_flag = false;
  77         }
  78         /*
  79          * Do not use the maximal size to avoid having only a single buffer
  80          * reference for the whole pool. This is bad because if that single
  81          * reference can not be freed, we're stuck.
  82          */
  83         sz = PARA_MIN(sz, btr_pool_size(sit->btrp) / 2);
  84         ret = read_nonblock(STDIN_FILENO, buf, sz, &s->rfds, &n);
  85         if (n > 0)
  86                 btr_add_output_pool(sit->btrp, n, sit->btrn);
  87         if (ret >= 0)
  88                 return 0;
  89 err:
  90         btr_remove_node(&sit->btrn);
  91         /* Revert to blocking mode if necessary. */
  92         fcntl(STDIN_FILENO, F_SETFL, sit->fd_flags);
  93         //btr_pool_free(sit->btrp);
  94         return ret;
  95 }
  96
  97 /**
  98  * Initialize a stdin task structure with default values.
  99  *
 100  * \param sit The stdin task structure.
 101  *
 102  * This fills in the pre/post select function pointers of the task structure
 103  * given by \a sit and creates a buffer tree for I/O.
 104  */
 105 void stdin_set_defaults(struct stdin_task *sit)
 106 {
 107         int ret;
 108
 109         sit->task.pre_select = stdin_pre_select;
 110         sit->task.post_select = stdin_post_select;
 111         sit->btrp = btr_pool_new("stdin", 128 * 1024);
 112         sprintf(sit->task.status, "stdin reader");
 113         /*
 114          * Both STDIN_FILENO and STDOUT_FILENO may refer to the same open file
 115          * description (the terminal), and thus share the same file status
 116          * flags. In order to not interfere with the stdout task, we only get
 117          * the file status flags for STDIN here and save a copy. The nonblock
 118          * flag is set later on the first read.
 119          */
 120         ret = fcntl(STDIN_FILENO, F_GETFL);
 121         if (ret < 0) {
 122                 PARA_EMERG_LOG("F_GETFL: %s\n", strerror(errno));
 123                 exit(EXIT_FAILURE);
 124         }
 125         sit->fd_flags = ret;
 126         sit->must_set_nonblock_flag = (sit->fd_flags & O_NONBLOCK) == 0;
 127 }