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Annotation of src/usr.bin/sndiod/abuf.c, Revision 1.1

1.1     ! ratchov     1: /*     $OpenBSD$       */
        !             2: /*
        !             3:  * Copyright (c) 2008-2012 Alexandre Ratchov <alex@caoua.org>
        !             4:  *
        !             5:  * Permission to use, copy, modify, and distribute this software for any
        !             6:  * purpose with or without fee is hereby granted, provided that the above
        !             7:  * copyright notice and this permission notice appear in all copies.
        !             8:  *
        !             9:  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
        !            10:  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
        !            11:  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
        !            12:  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
        !            13:  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
        !            14:  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
        !            15:  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
        !            16:  */
        !            17: /*
        !            18:  * Simple byte fifo.
        !            19:  *
        !            20:  * The abuf data is split in two parts: (1) valid data available to the reader
        !            21:  * (2) space available to the writer, which is not necessarily unused. It works
        !            22:  * as follows: the write starts filling at offset (start + used), once the data
        !            23:  * is ready, the writer adds to used the count of bytes available.
        !            24:  */
        !            25: #include <stdio.h>
        !            26: #include <stdlib.h>
        !            27: #include <string.h>
        !            28:
        !            29: #include "abuf.h"
        !            30: #include "defs.h"
        !            31: #include "utils.h"
        !            32:
        !            33: #ifdef DEBUG
        !            34: void
        !            35: abuf_log(struct abuf *buf)
        !            36: {
        !            37:        log_putu(buf->start);
        !            38:        log_puts("+");
        !            39:        log_putu(buf->used);
        !            40:        log_puts("/");
        !            41:        log_putu(buf->len);
        !            42: }
        !            43: #endif
        !            44:
        !            45: void
        !            46: abuf_init(struct abuf *buf, unsigned int len)
        !            47: {
        !            48:        buf->data = xmalloc(len);
        !            49:        buf->len = len;
        !            50:        buf->used = 0;
        !            51:        buf->start = 0;
        !            52: }
        !            53:
        !            54: void
        !            55: abuf_done(struct abuf *buf)
        !            56: {
        !            57: #ifdef DEBUG
        !            58:        if (buf->used > 0) {
        !            59:                if (log_level >= 3) {
        !            60:                        log_puts("deleting non-empty buffer, used = ");
        !            61:                        log_putu(buf->used);
        !            62:                        log_puts("\n");
        !            63:                }
        !            64:        }
        !            65: #endif
        !            66:        xfree(buf->data);
        !            67:        buf->data = (void *)0xdeadbeef;
        !            68: }
        !            69:
        !            70: /*
        !            71:  * return the reader pointer and the number of bytes available
        !            72:  */
        !            73: unsigned char *
        !            74: abuf_rgetblk(struct abuf *buf, int *rsize)
        !            75: {
        !            76:        unsigned int count;
        !            77:
        !            78:        count = buf->len - buf->start;
        !            79:        if (count > buf->used)
        !            80:                count = buf->used;
        !            81:        *rsize = count;
        !            82:        return buf->data + buf->start;
        !            83: }
        !            84:
        !            85: /*
        !            86:  * discard "count" bytes at the start postion.
        !            87:  */
        !            88: void
        !            89: abuf_rdiscard(struct abuf *buf, int count)
        !            90: {
        !            91: #ifdef DEBUG
        !            92:        if (count < 0 || count > buf->used) {
        !            93:                log_puts("abuf_rdiscard: bad count = ");
        !            94:                log_putu(count);
        !            95:                log_puts("\n");
        !            96:                panic();
        !            97:        }
        !            98: #endif
        !            99:        buf->used -= count;
        !           100:        buf->start += count;
        !           101:        if (buf->start >= buf->len)
        !           102:                buf->start -= buf->len;
        !           103: }
        !           104:
        !           105: /*
        !           106:  * advance the writer pointer by "count" bytes
        !           107:  */
        !           108: void
        !           109: abuf_wcommit(struct abuf *buf, int count)
        !           110: {
        !           111: #ifdef DEBUG
        !           112:        if (count < 0 || count > (buf->len - buf->used)) {
        !           113:                log_puts("abuf_wcommit: bad count = ");
        !           114:                log_putu(count);
        !           115:                log_puts("\n");
        !           116:                panic();
        !           117:        }
        !           118: #endif
        !           119:        buf->used += count;
        !           120: }
        !           121:
        !           122: /*
        !           123:  * get writer pointer and the number of bytes writable
        !           124:  */
        !           125: unsigned char *
        !           126: abuf_wgetblk(struct abuf *buf, int *rsize)
        !           127: {
        !           128:        int end, avail, count;
        !           129:
        !           130:        end = buf->start + buf->used;
        !           131:        if (end >= buf->len)
        !           132:                end -= buf->len;
        !           133:        avail = buf->len - buf->used;
        !           134:        count = buf->len - end;
        !           135:        if (count > avail)
        !           136:                count = avail;
        !           137:        *rsize = count;
        !           138:        return buf->data + end;
        !           139: }