os-k/kaleid/libbuf/bgetc.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 <libbuf.h>

#ifdef _KALEID_KERNEL
#include <ke/time.h>
#endif

error_t BGetFromBuf(Buffer_t *buf, uchar *ch)
{
    error_t rc;

    if (!buf) return EINVAL;
    if (buf->flags & BF_TERM) return EBADF;
    if (buf->state != BS_RDWR && buf->state != BS_RDONLY) {
        return EBADF;
    }

    ExAcquireLock(&buf->lock);
    rc = bgetc(buf, ch);
    ExReleaseLock(&buf->lock);
    return rc;
}

// Note: any change to this must be done while
// keeping in mind vbscanf()'s workaround for ungetc()
error_t bgetc(Buffer_t *buf, uchar *ch)
{
    error_t rc = EOK;

    if (buf->flags & (BF_EOF|BF_ERR)) return EENDF;
    
    assert(!(buf->rp > buf->wp)); // Shouldn't be possible right now
    
    if (buf->rp == buf->buf + buf->size) {
        buf->flags |= BF_EOF;
        return EENDF;
    }

    // Are there things to read at all?
    if (buf->rp < buf->wp) {
        *ch = *buf->rp++;
        return EOK;
    }
    
    // We need to fill the buffer
    else {
        // We need a BFiller_t
        // For now we wait until something is in there
        // (so that BStdIn works; don't make anything else)
        while (buf->rp >= buf->wp) {
#ifdef _KALEID_KERNEL
            KeSleep(1);     // XXX synchronization with keyboard driver
#else
            buf->flags |= BF_EOF;
            return EENDF;   // Currently empty
#endif
        }
        
        *ch = *buf->rp++;
    }
    
    if (rc != EOK) {
        // buf->flags |= BF_ERR;
    }
    
    return rc;
}