/*-
 * 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 "updatererrors.h"

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

#if defined(XP_WIN)
#  include <io.h>
#endif

#ifdef XP_WIN
#  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 != 0) {
    return READ_ERROR;
  }

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

  if (hs.st_size > INT_MAX) {
    return UNEXPECTED_BSPATCH_ERROR;
  }

  size_t size = static_cast<size_t>(hs.st_size);
  if (size < sizeof(MBSPatchHeader)) {
    return UNEXPECTED_BSPATCH_ERROR;
  }
  size -= sizeof(MBSPatchHeader);

  if (size < header->cblen) {
    return UNEXPECTED_BSPATCH_ERROR;
  }
  size -= header->cblen;

  if (size < header->difflen) {
    return UNEXPECTED_BSPATCH_ERROR;
  }
  size -= header->difflen;

  if (size < header->extralen) {
    return UNEXPECTED_BSPATCH_ERROR;
  }
  size -= header->extralen;

  if (size != 0) {
    return UNEXPECTED_BSPATCH_ERROR;
  }

  return OK;
}

int MBS_ApplyPatch(const MBSPatchHeader* header, FILE* patchFile,
                   const unsigned char* fbuffer, FILE* file) {
  const unsigned char* fbufstart = fbuffer;
  const 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 = (r > SSIZE_MAX) ? SSIZE_MAX : r;
    size_t c = fread(wb, 1, count, patchFile);
    if (c != count) {
      rv = READ_ERROR;
      goto end;
    }

    r -= c;
    wb += c;

    if (c == 0 && r) {
      rv = UNEXPECTED_BSPATCH_ERROR;
      goto end;
    }
  }

  {
    MBSPatchTriple* ctrlsrc = (MBSPatchTriple*)buf;
    if (header->cblen % sizeof(MBSPatchTriple) != 0) {
      rv = UNEXPECTED_BSPATCH_ERROR;
      goto end;
    }

    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;

    while (ctrlsrc < ctrlend) {
      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 (ctrlsrc->x > static_cast<size_t>(fbufend - fbuffer) ||
          ctrlsrc->x > static_cast<size_t>(diffend - diffsrc)) {
        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 (ctrlsrc->y > static_cast<size_t>(extraend - extrasrc)) {
        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 (ctrlsrc->z < fbufstart - fbuffer || ctrlsrc->z > fbufend - fbuffer) {
        rv = UNEXPECTED_BSPATCH_ERROR;
        goto end;
      }
      fbuffer += ctrlsrc->z;

      /* and on to the next control block */

      ++ctrlsrc;
    }
  }

end:
  free(buf);
  return rv;
}