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/*
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 * Copyright (C) 2006 Josef Cejka
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 * All rights reserved.
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 *
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 * Redistribution and use in source and binary forms, with or without
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 * modification, are permitted provided that the following conditions
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 * are met:
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 *
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 * - Redistributions of source code must retain the above copyright
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 *   notice, this list of conditions and the following disclaimer.
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 * - Redistributions in binary form must reproduce the above copyright
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 *   notice, this list of conditions and the following disclaimer in the
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 *   documentation and/or other materials provided with the distribution.
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 * - The name of the author may not be used to endorse or promote products
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 *   derived from this software without specific prior written permission.
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 *
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 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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 */
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#include <key_buffer.h>
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#include <futex.h>
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atomic_t keybuffer_futex = FUTEX_INITIALIZER;
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/** Clear key buffer.
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 */
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void keybuffer_free(keybuffer_t *keybuffer)
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{
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    futex_down(&keybuffer_futex);
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    keybuffer->head = 0;
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    keybuffer->tail = 0;
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    keybuffer->items = 0;
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    futex_up(&keybuffer_futex);
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}
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/** Key buffer initialization.
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 *
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 */
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void keybuffer_init(keybuffer_t *keybuffer)
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{
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    keybuffer_free(keybuffer);
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}
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/** Get free space in buffer.
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 * This function is useful for processing some scancodes that are translated
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 * to more than one character.
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 * @return empty buffer space
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 */
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int keybuffer_available(keybuffer_t *keybuffer)
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{
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    return KEYBUFFER_SIZE - keybuffer->items;
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}
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/**
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 * @return nonzero, if buffer is not empty.
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 */
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int keybuffer_empty(keybuffer_t *keybuffer)
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{
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    return (keybuffer->items == 0);
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}
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/** Push key to key buffer.
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 * If buffer is full, character is ignored.
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 * @param key code of stored key
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 */
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void keybuffer_push(keybuffer_t *keybuffer, char key)
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{
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    futex_down(&keybuffer_futex);
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    if (keybuffer->items < KEYBUFFER_SIZE) {
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        keybuffer->fifo[keybuffer->tail] = key;
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        keybuffer->tail = (keybuffer->tail + 1) % KEYBUFFER_SIZE;
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        keybuffer->items++;
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    }
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    futex_up(&keybuffer_futex);
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}
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/** Pop character from buffer.
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 * @param c pointer to space where to store character from buffer.
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 * @return zero on empty buffer, nonzero else
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 */
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int keybuffer_pop(keybuffer_t *keybuffer, char *c)
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{
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    futex_down(&keybuffer_futex);
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    if (keybuffer->items > 0) {
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        keybuffer->items--;
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        *c = keybuffer->fifo[keybuffer->head];
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        keybuffer->head = (keybuffer->head + 1) % KEYBUFFER_SIZE;
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        futex_up(&keybuffer_futex);
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        return 1;
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    }
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    futex_up(&keybuffer_futex);
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    return 0;
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}
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