accessibility/speakup/buffers.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 #include <linux/console.h>
0003 #include <linux/types.h>
0004 #include <linux/wait.h>
0005
0006 #include "speakup.h"
0007 #include "spk_priv.h"
0008
0009 #define SYNTH_BUF_SIZE 8192 /* currently 8K bytes */
0010
0011 static u16 synth_buffer[SYNTH_BUF_SIZE];    /* guess what this is for! */
0012 static u16 *buff_in = synth_buffer;
0013 static u16 *buff_out = synth_buffer;
0014 static u16 *buffer_end = synth_buffer + SYNTH_BUF_SIZE - 1;
0015
0016 /* These try to throttle applications by stopping the TTYs
0017  * Note: we need to make sure that we will restart them eventually, which is
0018  * usually not possible to do from the notifiers. TODO: it should be possible
0019  * starting from linux 2.6.26.
0020  *
0021  * So we only stop when we know alive == 1 (else we discard the data anyway),
0022  * and the alive synth will eventually call start_ttys from the thread context.
0023  */
0024 void speakup_start_ttys(void)
0025 {
0026     int i;
0027
0028     for (i = 0; i < MAX_NR_CONSOLES; i++) {
0029         if (speakup_console[i] && speakup_console[i]->tty_stopped)
0030             continue;
0031         if (vc_cons[i].d && vc_cons[i].d->port.tty)
0032             start_tty(vc_cons[i].d->port.tty);
0033     }
0034 }
0035 EXPORT_SYMBOL_GPL(speakup_start_ttys);
0036
0037 static void speakup_stop_ttys(void)
0038 {
0039     int i;
0040
0041     for (i = 0; i < MAX_NR_CONSOLES; i++)
0042         if (vc_cons[i].d && vc_cons[i].d->port.tty)
0043             stop_tty(vc_cons[i].d->port.tty);
0044 }
0045
0046 static int synth_buffer_free(void)
0047 {
0048     int chars_free;
0049
0050     if (buff_in >= buff_out)
0051         chars_free = SYNTH_BUF_SIZE - (buff_in - buff_out);
0052     else
0053         chars_free = buff_out - buff_in;
0054     return chars_free;
0055 }
0056
0057 int synth_buffer_empty(void)
0058 {
0059     return (buff_in == buff_out);
0060 }
0061 EXPORT_SYMBOL_GPL(synth_buffer_empty);
0062
0063 void synth_buffer_add(u16 ch)
0064 {
0065     if (!synth->alive) {
0066         /* This makes sure that we won't stop TTYs if there is no synth
0067          * to restart them
0068          */
0069         return;
0070     }
0071     if (synth_buffer_free() <= 100) {
0072         synth_start();
0073         speakup_stop_ttys();
0074     }
0075     if (synth_buffer_free() <= 1)
0076         return;
0077     *buff_in++ = ch;
0078     if (buff_in > buffer_end)
0079         buff_in = synth_buffer;
0080     /* We have written something to the speech synthesis, so we are not
0081      * paused any more.
0082      */
0083     spk_paused = false;
0084 }
0085
0086 u16 synth_buffer_getc(void)
0087 {
0088     u16 ch;
0089
0090     if (buff_out == buff_in)
0091         return 0;
0092     ch = *buff_out++;
0093     if (buff_out > buffer_end)
0094         buff_out = synth_buffer;
0095     return ch;
0096 }
0097 EXPORT_SYMBOL_GPL(synth_buffer_getc);
0098
0099 u16 synth_buffer_peek(void)
0100 {
0101     if (buff_out == buff_in)
0102         return 0;
0103     return *buff_out;
0104 }
0105 EXPORT_SYMBOL_GPL(synth_buffer_peek);
0106
0107 void synth_buffer_skip_nonlatin1(void)
0108 {
0109     while (buff_out != buff_in) {
0110         if (*buff_out < 0x100)
0111             return;
0112         buff_out++;
0113         if (buff_out > buffer_end)
0114             buff_out = synth_buffer;
0115     }
0116 }
0117 EXPORT_SYMBOL_GPL(synth_buffer_skip_nonlatin1);
0118
0119 void synth_buffer_clear(void)
0120 {
0121     buff_in = synth_buffer;
0122     buff_out = synth_buffer;
0123 }
0124 EXPORT_SYMBOL_GPL(synth_buffer_clear);