/*-
 * Copyright 2003,2004 Colin Percival
 * All rights reserved
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted providing 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
 *
 * Changelog:
 * 2005-04-26 - Define the header as a C structure, add a CRC32 checksum to
 *              the header, and make all the types 32-bit.
 *                --Benjamin Smedberg <benjamin@smedbergs.us>
 */

#include "bspatch.h"
#include "errors.h"

#include <algorithm>
#include <sys/stat.h>
#include <stdlib.h>
#include <stdio.h>
#include <fcntl.h>
#include <string.h>
#include <limits.h>

#if defined(_WIN32)
# include <io.h>
#else
# include <unistd.h>
#endif

#ifdef _WIN32
# include <winsock2.h>
#else
# include <arpa/inet.h>
#endif

#ifndef SSIZE_MAX
# define SSIZE_MAX LONG_MAX
#endif

int
MBS_ReadHeader(FILE* file, MBSPatchHeader *header)
{
    size_t s = fread(header, 1, sizeof(MBSPatchHeader), file);
    if (s != sizeof(MBSPatchHeader))
        return READ_ERROR;

    header->slen      = ntohl(header->slen);
    header->scrc32    = ntohl(header->scrc32);
    header->dlen      = ntohl(header->dlen);
    header->cblen     = ntohl(header->cblen);
    header->difflen   = ntohl(header->difflen);
    header->extralen  = ntohl(header->extralen);

    struct stat hs;
    s = fstat(fileno(file), &hs);
    if (s)
        return READ_ERROR;

    if (memcmp(header->tag, "MBDIFF10", 8) != 0)
        return UNEXPECTED_BSPATCH_ERROR;

    if (sizeof(MBSPatchHeader) +
            header->cblen +
            header->difflen +
            header->extralen != uint32_t(hs.st_size))
        return UNEXPECTED_BSPATCH_ERROR;

    return OK;
}

int
MBS_ApplyPatch(const MBSPatchHeader *header, FILE* patchFile,
               unsigned char *fbuffer, FILE* file)
{
    unsigned char *fbufend = fbuffer + header->slen;

    unsigned char *buf = (unsigned char*) malloc(header->cblen +
                         header->difflen +
                         header->extralen);
    if (!buf)
        return BSPATCH_MEM_ERROR;

    int rv = OK;

    size_t r = header->cblen + header->difflen + header->extralen;
    unsigned char *wb = buf;
    while (r)
    {
        const size_t count = std::min(r, size_t(SSIZE_MAX));
        size_t c = fread(wb, 1, count, patchFile);
        if (c != count)
        {
            rv = READ_ERROR;
            goto end;
        }

        r -= c;
        wb += c;
    }

    {
        MBSPatchTriple *ctrlsrc = (MBSPatchTriple*) buf;
        unsigned char *diffsrc = buf + header->cblen;
        unsigned char *extrasrc = diffsrc + header->difflen;

        MBSPatchTriple *ctrlend = (MBSPatchTriple*) diffsrc;
        unsigned char *diffend = extrasrc;
        unsigned char *extraend = extrasrc + header->extralen;

        do
        {
            ctrlsrc->x = ntohl(ctrlsrc->x);
            ctrlsrc->y = ntohl(ctrlsrc->y);
            ctrlsrc->z = ntohl(ctrlsrc->z);

#ifdef DEBUG_bsmedberg
            printf("Applying block:\n"
                   " x: %u\n"
                   " y: %u\n"
                   " z: %i\n",
                   ctrlsrc->x,
                   ctrlsrc->y,
                   ctrlsrc->z);
#endif

            /* Add x bytes from oldfile to x bytes from the diff block */

            if (fbuffer + ctrlsrc->x > fbufend ||
                    diffsrc + ctrlsrc->x > diffend)
            {
                rv = UNEXPECTED_BSPATCH_ERROR;
                goto end;
            }
            for (uint32_t i = 0; i < ctrlsrc->x; ++i)
            {
                diffsrc[i] += fbuffer[i];
            }
            if ((uint32_t) fwrite(diffsrc, 1, ctrlsrc->x, file) != ctrlsrc->x)
            {
                rv = WRITE_ERROR_PATCH_FILE;
                goto end;
            }
            fbuffer += ctrlsrc->x;
            diffsrc += ctrlsrc->x;

            /* Copy y bytes from the extra block */

            if (extrasrc + ctrlsrc->y > extraend)
            {
                rv = UNEXPECTED_BSPATCH_ERROR;
                goto end;
            }
            if ((uint32_t) fwrite(extrasrc, 1, ctrlsrc->y, file) != ctrlsrc->y)
            {
                rv = WRITE_ERROR_PATCH_FILE;
                goto end;
            }
            extrasrc += ctrlsrc->y;

            /* "seek" forwards in oldfile by z bytes */

            if (fbuffer + ctrlsrc->z > fbufend)
            {
                rv = UNEXPECTED_BSPATCH_ERROR;
                goto end;
            }
            fbuffer += ctrlsrc->z;

            /* and on to the next control block */

            ++ctrlsrc;
        }
        while (ctrlsrc < ctrlend);
    }

end:
    free(buf);
    return rv;
}