/*

 *  Copyright (c) 2018, Sam Kumar <samkumar@cs.berkeley.edu>

 *  Copyright (c) 2018, University of California, Berkeley

 *  All rights reserved.

 *

 *  Redistribution and use in source and binary forms, with or without

 *  modification, are permitted provided that the following conditions are met:

 *  1. Redistributions of source code must retain the above copyright

 *     notice, this list of conditions and the following disclaimer.

 *  2. Redistributions in binary form must reproduce the above copyright

 *     notice, this list of conditions and the following disclaimer in the

 *     documentation and/or other materials provided with the distribution.

 *  3. Neither the name of the copyright holder nor the

 *     names of its contributors may be used to endorse or promote products

 *     derived from this software without specific prior written permission.

 *

 *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"

 *  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

 *  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

 *  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE

 *  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR

 *  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

 *  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS

 *  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN

 *  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

 *  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE

 *  POSSIBILITY OF SUCH DAMAGE.

 */

/* LINKED BUFFER */

#include "lbuf.h"

#include <string.h>

#include <openthread/tcp.h>

void lbuf_init(struct lbufhead* buffer) {

    memset(buffer, 0x00, sizeof(struct lbufhead));

}

void lbuf_append(struct lbufhead* buffer, otLinkedBuffer* newentry) {

    otLinkedBuffer* tail = buffer->tail;

    if (tail == NULL) {

        buffer->head = newentry;

        buffer->tail = newentry;

        buffer->offset = 0;

        buffer->length = newentry->mLength;

        newentry->mNext = NULL;

    } else {

        tail->mNext = newentry;

        buffer->tail = newentry;

        buffer->length += newentry->mLength;

        newentry->mNext = NULL;

    }

}

void lbuf_extend(struct lbufhead* buffer, size_t numbytes) {

    buffer->tail->mLength += numbytes;

    buffer->length += numbytes;

}

size_t lbuf_pop(struct lbufhead* buffer, size_t numbytes, uint32_t* ntraversed) {

    otLinkedBuffer* curr = buffer->head;

    size_t bytesleft = numbytes;

    size_t curroffset = buffer->offset;

    if (curr == NULL) {

        return 0;

    }

    while (bytesleft >= curr->mLength - curroffset) {

        ++*ntraversed;

        bytesleft -= (curr->mLength - curroffset);

        buffer->length -= (curr->mLength - curroffset);

        if (buffer->tail == curr) {

            buffer->head = NULL;

            buffer->tail = NULL;

            buffer->offset = 0;

            return numbytes - bytesleft;

        }

        curr = curr->mNext;

        curroffset = 0;

    }

    /* Handle the last entry. */

    buffer->head = curr;

    buffer->offset = curroffset + bytesleft;

    buffer->length -= bytesleft;

    return numbytes;

}

int lbuf_getrange(struct lbufhead* buffer, size_t offset, size_t numbytes,

                  otLinkedBuffer** first, size_t* firstoffset,

                  otLinkedBuffer** last, size_t* lastextra) {

    otLinkedBuffer* curr = buffer->head;

    size_t offsetleft = offset + buffer->offset;

    size_t bytesleft = numbytes;

    if (buffer->length < offset + numbytes) {

        return 1; // out of range

    }

    while (offsetleft > 0 && offsetleft >= curr->mLength) {

        offsetleft -= curr->mLength;

        curr = curr->mNext;

    }

    *first = curr;

    *firstoffset = offsetleft;

    bytesleft += offsetleft;

    while (bytesleft > 0 && bytesleft > curr->mLength) {

        bytesleft -= curr->mLength;

        curr = curr->mNext;

    }

    *last = curr;

    *lastextra = curr->mLength - bytesleft;

    return 0;

}

size_t lbuf_used_space(const struct lbufhead* buffer) {

    return buffer->length;

}