os-k/kaleid/libbuf/bscroll.c

//----------------------------------------------------------------------------//
//                           GNU GPL OS/K                                     //
//                                                                            //
//  Desc:       Buffer library                                                //
//                                                                            //
//                                                                            //
//  Copyright © 2018-2020 The OS/K Team                                       //
//                                                                            //
//  This file is part of OS/K.                                                //
//                                                                            //
//  OS/K is free software: you can redistribute it and/or modify              //
//  it under the terms of the GNU General Public License as published by      //
//  the Free Software Foundation, either version 3 of the License, or         //
//  any later version.                                                        //
//                                                                            //
//  OS/K is distributed in the hope that it will be useful,                   //
//  but WITHOUT ANY WARRANTY//without even the implied warranty of            //
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the             //
//  GNU General Public License for more details.                              //
//                                                                            //
//  You should have received a copy of the GNU General Public License         //
//  along with OS/K.  If not, see <https://www.gnu.org/licenses/>.            //
//----------------------------------------------------------------------------//

#include <lib/buf.h>

void BEnableAutoScroll(Buffer_t *buf) { buf->flags |= BF_AUTOSCROLL; }
void BDisableAutoScroll(Buffer_t *buf) { buf->flags &= ~BF_AUTOSCROLL; }

error_t BScrollDownBuf(Buffer_t *buf)
{
    error_t rc;

    if (!buf) return EINVAL;
    if (!(buf->flags & BF_TERM)) return EBADF;
    if (buf->flags & (BF_EOF|BF_ERR)) return EENDF;
    if (buf->state != BS_RDWR && buf->state != BS_WRONLY) {
        return EBADF;
    }

    ExAcquireLock(&buf->lock);
    rc = bscrolldown(buf);
    ExReleaseLock(&buf->lock);
    return rc;
}

error_t bscrolldown(Buffer_t *buf)
{
    size_t bufSize, pbCount;

    assert(buf->wp == buf->buf + buf->size);

    // We give up a whole playback buffer worth
    // of lines so we don't have to do this too often
    // (we make the current buffer a pb one)
    bufSize = buf->nLines * buf->lineLen;
    pbCount = (buf->size / bufSize) - 1;

    // Paranoia check
    assert(buf->size >= (size_t)(buf->nLines * buf->lineLen));

    // If we only have one playback buffer we just give up a line
    if (pbCount == 0) {
        // Use of memcpy() is safe because the source occur
        // after the destination
        memmove(buf->buf, buf->buf + buf->lineLen,
            buf->size - buf->lineLen);
        buf->wp -= buf->lineLen;
    }

    // We do have a playback buffer worth of lines to give up
    else {
        memmove(buf->buf, buf->buf + bufSize,
            buf->size - bufSize);
        buf->wp -= bufSize;
    }
    
    return EOK;
}