Linux Kernel  3.7.1
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buffers.c
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1 #include <linux/console.h>
2 #include <linux/types.h>
3 #include <linux/wait.h>
4 
5 #include "speakup.h"
6 #include "spk_priv.h"
7 
8 #define synthBufferSize 8192 /* currently 8K bytes */
9 
10 static u_char synth_buffer[synthBufferSize]; /* guess what this is for! */
11 static u_char *buff_in = synth_buffer;
12 static u_char *buff_out = synth_buffer;
13 static u_char *buffer_end = synth_buffer+synthBufferSize-1;
14 
15 /* These try to throttle applications by stopping the TTYs
16  * Note: we need to make sure that we will restart them eventually, which is
17  * usually not possible to do from the notifiers. TODO: it should be possible
18  * starting from linux 2.6.26.
19  *
20  * So we only stop when we know alive == 1 (else we discard the data anyway),
21  * and the alive synth will eventually call start_ttys from the thread context.
22  */
24 {
25  int i;
26 
27  for (i = 0; i < MAX_NR_CONSOLES; i++) {
28  if (speakup_console[i] && speakup_console[i]->tty_stopped)
29  continue;
30  if ((vc_cons[i].d != NULL) && (vc_cons[i].d->port.tty != NULL))
31  start_tty(vc_cons[i].d->port.tty);
32  }
33 }
35 
36 static void speakup_stop_ttys(void)
37 {
38  int i;
39 
40  for (i = 0; i < MAX_NR_CONSOLES; i++)
41  if ((vc_cons[i].d != NULL) && (vc_cons[i].d->port.tty != NULL))
42  stop_tty(vc_cons[i].d->port.tty);
43 }
44 
45 static int synth_buffer_free(void)
46 {
47  int bytesFree;
48 
49  if (buff_in >= buff_out)
50  bytesFree = synthBufferSize - (buff_in - buff_out);
51  else
52  bytesFree = buff_out - buff_in;
53  return bytesFree;
54 }
55 
57 {
58  return (buff_in == buff_out);
59 }
61 
62 void synth_buffer_add(char ch)
63 {
64  if (!synth->alive) {
65  /* This makes sure that we won't stop TTYs if there is no synth
66  * to restart them */
67  return;
68  }
69  if (synth_buffer_free() <= 100) {
70  synth_start();
71  speakup_stop_ttys();
72  }
73  if (synth_buffer_free() <= 1)
74  return;
75  *buff_in++ = ch;
76  if (buff_in > buffer_end)
77  buff_in = synth_buffer;
78 }
79 
81 {
82  char ch;
83 
84  if (buff_out == buff_in)
85  return 0;
86  ch = *buff_out++;
87  if (buff_out > buffer_end)
88  buff_out = synth_buffer;
89  return ch;
90 }
92 
94 {
95  if (buff_out == buff_in)
96  return 0;
97  return *buff_out;
98 }
100 
102 {
103  buff_in = buff_out = synth_buffer;
104  return;
105 }