source: rtems/cpukit/httpd/ringq.c @ 9b05600

/*
 * ringq.c -- Ring queue buffering module
 *
 * Copyright (c) GoAhead Software Inc., 1995-1999. All Rights Reserved.
 *
 * See the file "license.txt" for usage and redistribution license requirements
 */

/******************************** Description *********************************/

/*
 *      A ring queue allows maximum utilization of memory for data storage and is
 *      ideal for input/output buffering.  This module provides a highly effecient
 *      implementation and a vehicle for dynamic strings.
 *
 *      WARNING:  This is a public implementation and callers have full access to
 *      the queue structure and pointers.  Change this module very carefully.
 *
 *      This module follows the open/close model.
 *
 *      Operation of a ringq where rq is a pointer to a ringq :
 *
 *              rq->buflen contains the size of the buffer.
 *              rq->buf will point to the start of the buffer.
 *              rq->servp will point to the first (un-consumed) data byte.
 *              rq->endp will point to the next free location to which new data is added
 *              rq->endbuf will point to one past the end of the buffer.
 *
 *      Eg. If the ringq contains the data "abcdef", it might look like :
 *
 *      +-------------------------------------------------------------------+
 *  |   |   |   |   |   |   |   | a | b | c | d | e | f |   |   |   |   |
 *      +-------------------------------------------------------------------+
 *    ^                           ^                       ^               ^
 *    |                           |                       |               |
 *  rq->buf                    rq->servp               rq->endp      rq->enduf
 *     
 *      The queue is empty when servp == endp.  This means that the queue will hold
 *      at most rq->buflen -1 bytes.  It is the fillers responsibility to ensure
 *      the ringq is never filled such that servp == endp.
 *
 *      It is the fillers responsibility to "wrap" the endp back to point to
 *      rq->buf when the pointer steps past the end.  Correspondingly it is the
 *      consumers responsibility to "wrap" the servp when it steps to rq->endbuf.
 *      The ringqPutc and ringqGetc routines will do this automatically.
 */

/********************************* Includes ***********************************/

#if UEMF
        #include        "uemf.h"
#else
        #include        "basic/basicInternal.h"
#endif

/*********************************** Defines **********************************/
/*
 *      Faster than a function call
 */

#define RINGQ_LEN(rq) \
        ((rq->servp > rq->endp) ? \
                (rq->buflen + (rq->endp - rq->servp)) : \
                (rq->endp - rq->servp))

/***************************** Forward Declarations ***************************/

static int ringq_grow(ringq_t *rq);

/*********************************** Code *************************************/
/*
 *      Create a new ringq. "increment" is the amount to increase the size of the
 *      ringq should it need to grow to accomodate data being added. "maxsize" is
 *      an upper limit (sanity level) beyond which the q must not grow. Set maxsize
 *      to -1 to imply no upper limit. The buffer for the ringq is always 
 *      dynamically allocated. Set maxsize
 */

int ringqOpen(ringq_t *rq, int increment, int maxsize)
{
        a_assert(rq);
        a_assert(increment >= 0);

        if ((rq->buf = balloc(B_L, increment)) == NULL) {
                return -1;
        }
        rq->maxsize = maxsize;
        rq->buflen = increment;
        rq->increment = increment;
        rq->endbuf = &rq->buf[rq->buflen];
        rq->servp = rq->buf;
        rq->endp = rq->buf;
        *rq->servp = '\0';
        return 0;
}

/******************************************************************************/
/*
 *      Delete a ringq and free the ringq buffer.
 */

void ringqClose(ringq_t *rq)
{
        a_assert(rq);
        a_assert(rq->buflen == (rq->endbuf - rq->buf));

        if (rq == NULL) {
                return;
        }

        ringqFlush(rq);
        bfree(B_L, (char*) rq->buf);
        rq->buf = NULL;
}

/******************************************************************************/
/*
 *      Return the length of the ringq. Users must fill the queue to a high 
 *      water mark of at most one less than the queue size.
 */

int ringqLen(ringq_t *rq)
{
        a_assert(rq);
        a_assert(rq->buflen == (rq->endbuf - rq->buf));

        if (rq->servp > rq->endp) {
                return rq->buflen + rq->endp - rq->servp;
        }
        else {
                return rq->endp - rq->servp;
        }
}

/******************************************************************************/
/*
 *      Get a byte from the queue
 */

int ringqGetc(ringq_t *rq)
{
        char_t  c;
        char_t* cp;

        a_assert(rq);
        a_assert(rq->buflen == (rq->endbuf - rq->buf));

        if (rq->servp == rq->endp) {
                return -1;
        }

        cp = (char_t*) rq->servp;
        c = *cp++;
        rq->servp = (unsigned char *) cp;
        if (rq->servp >= rq->endbuf) {
                rq->servp = rq->buf;
        }
        return c;
}

/******************************************************************************/
/*
 *      Add a char to the queue. Note if being used to store wide strings 
 *      this does not add a trailing '\0'. Grow the q as required.
 */

int ringqPutc(ringq_t *rq, char_t c)
{
        char_t* cp;

        a_assert(rq);
        a_assert(rq->buflen == (rq->endbuf - rq->buf));

        if (ringqPutBlkMax(rq) < (int) sizeof(char_t) && !ringq_grow(rq)) {
                return -1;
        }

        cp = (char_t*) rq->endp;
        *cp++ = (char_t) c;
        rq->endp = (unsigned char *) cp;
        if (rq->endp >= rq->endbuf) {
                rq->endp = rq->buf;
        }
        return 0;
}

/******************************************************************************/
/*
 *      Insert a wide character at the front of the queue
 */

int ringqInsertc(ringq_t *rq, char_t c)
{
        char_t* cp;

        a_assert(rq);
        a_assert(rq->buflen == (rq->endbuf - rq->buf));

        if (ringqPutBlkMax(rq) < (int) sizeof(char_t) && !ringq_grow(rq)) {
                return -1;
        }
        if (rq->servp <= rq->buf) {
                rq->servp = rq->endbuf;
        }
        cp = (char_t*) rq->servp;
        *--cp = (char_t) c;
        rq->servp = (unsigned char *) cp;
        return 0;
}

/******************************************************************************/
/*
 *      Add a string to the queue. Add a trailing wide null (two nulls)
 */

int ringqPutstr(ringq_t *rq, char_t *str)
{
        int             rc;

        a_assert(rq);
        a_assert(str);
        a_assert(rq->buflen == (rq->endbuf - rq->buf));

        rc = ringqPutBlk(rq, (unsigned char*) str, gstrlen(str) * sizeof(char_t));
        *((char_t*) rq->endp) = (char_t) '\0';
        return rc;
}

/******************************************************************************/
#if UNICODE
/*
 *      Get a byte from the queue
 */

int ringqGetcA(ringq_t *rq)
{
        unsigned char   c;

        a_assert(rq);
        a_assert(rq->buflen == (rq->endbuf - rq->buf));

        if (rq->servp == rq->endp) {
                return -1;
        }

        c = *rq->servp++;
        if (rq->servp >= rq->endbuf) {
                rq->servp = rq->buf;
        }
        return c;
}

/******************************************************************************/
/*
 *      Add a byte to the queue. Note if being used to store strings this does not
 *      add a trailing '\0'. Grow the q as required.
 */

int ringqPutcA(ringq_t *rq, char c)
{
        a_assert(rq);
        a_assert(rq->buflen == (rq->endbuf - rq->buf));

        if (ringqPutBlkMax(rq) == 0 && !ringq_grow(rq)) {
                return -1;
        }

        *rq->endp++ = (unsigned char) c;
        if (rq->endp >= rq->endbuf) {
                rq->endp = rq->buf;
        }
        return 0;
}

/******************************************************************************/
/*
 *      Insert a byte at the front of the queue
 */

int ringqInsertcA(ringq_t *rq, char c)
{
        a_assert(rq);
        a_assert(rq->buflen == (rq->endbuf - rq->buf));

        if (ringqPutBlkMax(rq) == 0 && !ringq_grow(rq)) {
                return -1;
        }
        if (rq->servp <= rq->buf) {
                rq->servp = rq->endbuf;
        }
        *--rq->servp = (unsigned char) c;
        return 0;
}

/******************************************************************************/
/*
 *      Add a string to the queue. Add a trailing null (not really in the q).
 *      ie. beyond the last valid byte.
 */

int ringqPutstrA(ringq_t *rq, char *str)
{
        int             rc;

        a_assert(rq);
        a_assert(str);
        a_assert(rq->buflen == (rq->endbuf - rq->buf));

        rc = ringqPutBlk(rq, (unsigned char*) str, strlen(str));
        rq->endp[0] = '\0';
        return rc;
}

#endif /* UNICODE */
/******************************************************************************/
/*
 *      Add a block of data to the ringq. Return the number of bytes added.
 *      Grow the q as required.
 */

int ringqPutBlk(ringq_t *rq, unsigned char *buf, int size)
{
        int             this, bytes_put;

        a_assert(rq);
        a_assert(rq->buflen == (rq->endbuf - rq->buf));
        a_assert(buf);
        a_assert(0 <= size);

/*
 *      Loop adding the maximum bytes we can add in a single straight line copy
 */
        bytes_put = 0;
        while (size > 0) {
                this = min(ringqPutBlkMax(rq), size);
                if (this <= 0) {
                        if (! ringq_grow(rq)) {
                                break;
                        }
                        this = min(ringqPutBlkMax(rq), size);
                }

                memcpy(rq->endp, buf, this);
                buf += this;
                rq->endp += this;
                size -= this;
                bytes_put += this;

                if (rq->endp >= rq->endbuf) {
                        rq->endp = rq->buf;
                }
        }
        return bytes_put;
}

/******************************************************************************/
/*
 *      Get a block of data from the ringq. Return the number of bytes returned.
 */

int ringqGetBlk(ringq_t *rq, unsigned char *buf, int size)
{
        int             this, bytes_read;

        a_assert(rq);
        a_assert(rq->buflen == (rq->endbuf - rq->buf));
        a_assert(buf);
        a_assert(0 <= size && size < rq->buflen);

/*
 *      Loop getting the maximum bytes we can get in a single straight line copy
 */
        bytes_read = 0;
        while (size > 0) {
                this = ringqGetBlkMax(rq);
                this = min(this, size);
                if (this <= 0) {
                        break;
                }

                memcpy(buf, rq->servp, this);
                buf += this;
                rq->servp += this;
                size -= this;
                bytes_read += this;

                if (rq->servp >= rq->endbuf) {
                        rq->servp = rq->buf;
                }
        }
        return bytes_read;
}

/******************************************************************************/
/*
 *      Return the maximum number of bytes the ring q can accept via a single 
 *      block copy. Useful if the user is doing their own data insertion.
 */

int ringqPutBlkMax(ringq_t *rq)
{
        int             space, in_a_line;

        a_assert(rq);
        a_assert(rq->buflen == (rq->endbuf - rq->buf));
        
        space = rq->buflen - RINGQ_LEN(rq) - 1;
        in_a_line = rq->endbuf - rq->endp;

        return min(in_a_line, space);
}

/******************************************************************************/
/*
 *      Return the maximum number of bytes the ring q can provide via a single 
 *      block copy. Useful if the user is doing their own data retrieval.
 */

int ringqGetBlkMax(ringq_t *rq)
{
        int             len, in_a_line;

        a_assert(rq);
        a_assert(rq->buflen == (rq->endbuf - rq->buf));

        len = RINGQ_LEN(rq);
        in_a_line = rq->endbuf - rq->servp;

        return min(in_a_line, len);
}

/******************************************************************************/
/*
 *      Adjust the endp pointer after the user has copied data into the queue.
 */

void ringqPutBlkAdj(ringq_t *rq, int size)
{
        a_assert(rq);
        a_assert(rq->buflen == (rq->endbuf - rq->buf));
        a_assert(0 <= size && size < rq->buflen);

        rq->endp += size;
        if (rq->endp >= rq->endbuf) {
                rq->endp -= rq->buflen;
        }
/*
 *      Flush the queue if the endp pointer is corrupted via a bad size
 */
        if (rq->endp >= rq->endbuf) {
                error(E_L, E_LOG, T("Bad end pointer"));
                ringqFlush(rq);
        }
}

/******************************************************************************/
/*
 *      Adjust the servp pointer after the user has copied data from the queue.
 */

void ringqGetBlkAdj(ringq_t *rq, int size)
{
        a_assert(rq);
        a_assert(rq->buflen == (rq->endbuf - rq->buf));
        a_assert(0 < size && size < rq->buflen);

        rq->servp += size;
        if (rq->servp >= rq->endbuf) {
                rq->servp -= rq->buflen;
        }
/*
 *      Flush the queue if the servp pointer is corrupted via a bad size
 */
        if (rq->servp >= rq->endbuf) {
                error(E_L, E_LOG, T("Bad serv pointer"));
                ringqFlush(rq);
        }
}

/******************************************************************************/
/*
 *      Flush all data in a ring q.  Reset the pointers.
 */

void ringqFlush(ringq_t *rq)
{
        a_assert(rq);

        rq->servp = rq->buf;
        rq->endp = rq->buf;
        *rq->servp = '\0';
}

/******************************************************************************/
/*
 *      Grow the buffer. Return true if the buffer can be grown. Grow using
 *      the increment size specified when opening the ringq. Don't grow beyond
 *      the maximum possible size.
 */

static int ringq_grow(ringq_t *rq)
{
        unsigned char   *newbuf;
        int                     len;

        a_assert(rq);

        if (rq->maxsize >= 0 && rq->buflen >= rq->maxsize) {
                return 0;
        }

        len = ringqLen(rq);

        if ((newbuf = balloc(B_L, rq->buflen + rq->increment)) == NULL) {
                return 0;
        }
        ringqGetBlk(rq, newbuf, ringqLen(rq));
        bfree(B_L, (char*) rq->buf);

#if OLD
        rq->endp = &newbuf[endp];
        rq->servp = &newbuf[servp];
        rq->endbuf = &newbuf[rq->buflen];
        rq->buf = newbuf;
#endif

        rq->buflen += rq->increment;
        rq->endp = newbuf;
        rq->servp = newbuf;
        rq->buf = newbuf;
        rq->endbuf = &rq->buf[rq->buflen];

        ringqPutBlk(rq, newbuf, len);
        return 1;
}

/******************************************************************************/