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/*

 * Copyright (c) 2017 rxi

 *

 * Permission is hereby granted, free of charge, to any person obtaining a copy

 * of this software and associated documentation files (the "Software"), to

 * deal in the Software without restriction, including without limitation the

 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or

 * sell copies of the Software, and to permit persons to whom the Software is

 * furnished to do so, subject to the following conditions:

 *

 * The above copyright notice and this permission notice shall be included in

 * all copies or substantial portions of the Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING

 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS

 * IN THE SOFTWARE.

 */

#include 

#include 

#include 

#include 

#include 

#include "microtar.h"

typedef struct {

  char name[100];

  char mode[8];

  char owner[8];

  char group[8];

  char size[12];

  char mtime[12];

  char checksum[8];

  char type;

  char linkname[100];

  char _padding[255];

} mtar_raw_header_t;

static void * mtar_memset( void * s, int c, size_t n ){

  unsigned char * p = ( unsigned char * ) s;

  while ( n-- ){

      *p++ = ( unsigned char ) c;

  }

  return s;

}

#ifdef MTAR_OBJ

size_t (*fread)(void *restrict, size_t size, size_t count, FILE *restrict)=NULL;

size_t (*fwrite)(const void *restrict, size_t size, size_t count, FILE *restrict)=NULL;

int    (*fclose)(FILE *)=NULL;

FILE*  (*fopen)(const char *restrict, const char *restrict)=NULL;

int    (*fseek)(FILE *, long, int)=NULL;

long   (*ftell)(FILE *)=NULL;

int    (*sprintf)(char* buffer, const char* format, ...)=NULL;

int    (*sscanf)(const char*, const char *restrict, ...)=NULL;

int    (*strcmp)(const char * s1, const char* s2)=NULL;

char*  (*strchr)(const char* s, int c)=NULL;

char*  (*strcpy)(char*  s1, const char* s2)=NULL;

#endif

static unsigned round_up(unsigned n, unsigned incr) {

  return n + (incr - n % incr) % incr;

}

static unsigned checksum(const mtar_raw_header_t* rh) {

  unsigned i;

  unsigned char *p = (unsigned char*) rh;

  unsigned res = 256;

  for (i = 0; i < offsetof(mtar_raw_header_t, checksum); i++) {

    res += p[i];

  }

  for (i = offsetof(mtar_raw_header_t, type); i < sizeof(*rh); i++) {

    res += p[i];

  }

  return res;

}

static int tread(mtar_t *tar, void *data, unsigned size) {

  int err = tar->read(tar, data, size);

  tar->pos += size;

  return err;

}

static int twrite(mtar_t *tar, const void *data, unsigned size) {

  int err = tar->write(tar, data, size);

  tar->pos += size;

  return err;

}

static int write_null_bytes(mtar_t *tar, int n) {

  int i, err;

  char nul = '\0';

  for (i = 0; i < n; i++) {

    err = twrite(tar, &nul, 1);

    if (err) {

      return err;

    }

  }

  return MTAR_ESUCCESS;

}

static int raw_to_header(mtar_header_t *h, const mtar_raw_header_t *rh) {

  unsigned chksum1, chksum2;

  /* If the checksum starts with a null byte we assume the record is NULL */

  if (*rh->checksum == '\0') {

    return MTAR_ENULLRECORD;

  }

  /* Build and compare checksum */

  chksum1 = checksum(rh);

  sscanf(rh->checksum, "%o", &chksum2);

  if (chksum1 != chksum2) {

    return MTAR_EBADCHKSUM;

  }

  /* Load raw header into header */

  sscanf(rh->mode, "%o", &h->mode);

  sscanf(rh->owner, "%o", &h->owner);

  sscanf(rh->size, "%o", &h->size);

  sscanf(rh->mtime, "%o", &h->mtime);

  h->type = rh->type;

  strcpy(h->name, rh->name);

  strcpy(h->linkname, rh->linkname);

  return MTAR_ESUCCESS;

}

static int header_to_raw(mtar_raw_header_t *rh, const mtar_header_t *h) {

  unsigned chksum;

  /* Load header into raw header */

  mtar_memset(rh, 0, sizeof(*rh));

  sprintf(rh->mode, "%o", h->mode);

  sprintf(rh->owner, "%o", h->owner);

  sprintf(rh->size, "%o", h->size);

  sprintf(rh->mtime, "%o", h->mtime);

  rh->type = h->type ? h->type : MTAR_TREG;

  strcpy(rh->name, h->name);

  strcpy(rh->linkname, h->linkname);

  /* Calculate and write checksum */

  chksum = checksum(rh);

  sprintf(rh->checksum, "%06o", chksum);

  rh->checksum[7] = ' ';

  return MTAR_ESUCCESS;

}

const char* mtar_strerror(int err) {

  switch (err) {

    case MTAR_ESUCCESS     : return "success";

    case MTAR_EFAILURE     : return "failure";

    case MTAR_EOPENFAIL    : return "could not open";

    case MTAR_EREADFAIL    : return "could not read";

    case MTAR_EWRITEFAIL   : return "could not write";

    case MTAR_ESEEKFAIL    : return "could not seek";

    case MTAR_EBADCHKSUM   : return "bad checksum";

    case MTAR_ENULLRECORD  : return "null record";

    case MTAR_ENOTFOUND    : return "file not found";

  }

  return "unknown error";

}

static int file_write(mtar_t *tar, const void *data, unsigned size) {

  unsigned res = fwrite(data, 1, size, tar->stream);

  return (res == size) ? MTAR_ESUCCESS : MTAR_EWRITEFAIL;

}

static int file_read(mtar_t *tar, void *data, unsigned size) {

  unsigned res = fread(data, 1, size, tar->stream);

  return (res == size) ? MTAR_ESUCCESS : MTAR_EREADFAIL;

}

static int file_seek(mtar_t *tar, unsigned offset) {

    int res = fseek(tar->stream, offset, SEEK_SET);

  return (res == 0) ? MTAR_ESUCCESS : MTAR_ESEEKFAIL;

}

static int file_close(mtar_t *tar) {

  fclose(tar->stream);

  return MTAR_ESUCCESS;

}

int mtar_open(mtar_t *tar, const char *filename, const char *mode) {

  int err;

  mtar_header_t h;

  /* Init tar struct and functions */

  mtar_memset(tar, 0, sizeof(*tar));

  tar->write = file_write;

  tar->read = file_read;

  tar->seek = file_seek;

  tar->close = file_close;

  /* Assure mode is always binary */

  if ( strchr(mode, 'r') ) mode = "rb";

  if ( strchr(mode, 'w') ) mode = "wb";

  if ( strchr(mode, 'a') ) mode = "ab";

  /* Open file */

  tar->stream = fopen(filename, mode);

  if (!tar->stream) {

    return MTAR_EOPENFAIL;

  }

  /* Read first header to check it is valid if mode is `r` */

  if (*mode == 'r') {

    err = mtar_read_header(tar, &h);

    if (err != MTAR_ESUCCESS) {

      mtar_close(tar);

      return err;

    }

  }

  /* Return ok */

  return MTAR_ESUCCESS;

}

int mtar_close(mtar_t *tar) {

  return tar->close(tar);

}

int mtar_seek(mtar_t *tar, unsigned pos) {

  int err = tar->seek(tar, pos);

  tar->pos = pos;

  return err;

}

int mtar_rewind(mtar_t *tar) {

  tar->remaining_data = 0;

  tar->last_header = 0;

  return mtar_seek(tar, 0);

}

int mtar_next(mtar_t *tar) {

  int err, n;

  mtar_header_t h;

  /* Load header */

  err = mtar_read_header(tar, &h);

  if (err) {

    return err;

  }

  /* Seek to next record */

  n = round_up(h.size, 512) + sizeof(mtar_raw_header_t);

  return mtar_seek(tar, tar->pos + n);

}

int mtar_find(mtar_t *tar, const char *name, mtar_header_t *h) {

  int err;

  mtar_header_t header;

  /* Start at beginning */

  err = mtar_rewind(tar);

  if (err) {

    return err;

  }

  /* Iterate all files until we hit an error or find the file */

  while ( (err = mtar_read_header(tar, &header)) == MTAR_ESUCCESS ) {

    if ( !strcmp(header.name, name) ) {

      if (h) {

        *h = header;

      }

      return MTAR_ESUCCESS;

    }

    mtar_next(tar);

  }

  /* Return error */

  if (err == MTAR_ENULLRECORD) {

    err = MTAR_ENOTFOUND;

  }

  return err;

}

int mtar_read_header(mtar_t *tar, mtar_header_t *h) {

  int err;

  mtar_raw_header_t rh;

  /* Save header position */

  tar->last_header = tar->pos;

  /* Read raw header */

  err = tread(tar, &rh, sizeof(rh));

  if (err) {

    return err;

  }

  /* Seek back to start of header */

  err = mtar_seek(tar, tar->last_header);

  if (err) {

    return err;

  }

  /* Load raw header into header struct and return */

  return raw_to_header(h, &rh);

}

int mtar_read_data(mtar_t *tar, void *ptr, unsigned size) {

  int err;

  /* If we have no remaining data then this is the first read, we get the size,

   * set the remaining data and seek to the beginning of the data */

  if (tar->remaining_data == 0) {

    mtar_header_t h;

    /* Read header */

    err = mtar_read_header(tar, &h);

    if (err) {

      return err;

    }

    /* Seek past header and init remaining data */

    err = mtar_seek(tar, tar->pos + sizeof(mtar_raw_header_t));

    if (err) {

      return err;

    }

    tar->remaining_data = h.size;

  }

  /* Read data */

  err = tread(tar, ptr, size);

  if (err) {

    return err;

  }

  tar->remaining_data -= size;

  /* If there is no remaining data we've finished reading and seek back to the

   * header */

  if (tar->remaining_data == 0) {

    return mtar_seek(tar, tar->last_header);

  }

  return MTAR_ESUCCESS;

}

int mtar_write_header(mtar_t *tar, const mtar_header_t *h) {

  mtar_raw_header_t rh;

  /* Build raw header and write */

  header_to_raw(&rh, h);

  tar->remaining_data = h->size;

  return twrite(tar, &rh, sizeof(rh));

}

int mtar_write_file_header(mtar_t *tar, const char *name, unsigned size) {

  mtar_header_t h;

  /* Build header */

  mtar_memset(&h, 0, sizeof(h));

  strcpy(h.name, name);

  h.size = size;

  h.type = MTAR_TREG;

  h.mode = 0664;

  /* Write header */

  return mtar_write_header(tar, &h);

}

int mtar_write_dir_header(mtar_t *tar, const char *name) {

  mtar_header_t h;

  /* Build header */

  mtar_memset(&h, 0, sizeof(h));

  strcpy(h.name, name);

  h.type = MTAR_TDIR;

  h.mode = 0775;

  /* Write header */

  return mtar_write_header(tar, &h);

}

int mtar_write_data(mtar_t *tar, const void *data, unsigned size) {

  int err;

  /* Write data */

  err = twrite(tar, data, size);

  if (err) {

    return err;

  }

  tar->remaining_data -= size;

  /* Write padding if we've written all the data for this file */

  if (tar->remaining_data == 0) {

    return write_null_bytes(tar, round_up(tar->pos, 512) - tar->pos);

  }

  return MTAR_ESUCCESS;

}

int mtar_finalize(mtar_t *tar) {

  /* Write two NULL records */

  return write_null_bytes(tar, sizeof(mtar_raw_header_t) * 2);

}

/* Load libc.obj */

#ifdef MTAR_OBJ

#include 

int mtar_init(){

  ksys_dll_t *libc = _ksys_dlopen("/sys/lib/libc.obj");

  if(!libc){

    _ksys_debug_puts("mtar.obj: libc.obj not loaded!");

    return 1;

  }

  fread  = _ksys_dlsym(libc, "fread");

  fwrite = _ksys_dlsym(libc, "fwrite");

  fclose = _ksys_dlsym(libc, "fclose");

  fopen  = _ksys_dlsym(libc, "fopen");

  fseek  = _ksys_dlsym(libc, "fseek");

  ftell  = _ksys_dlsym(libc, "ftell");

  sprintf= _ksys_dlsym(libc, "sprintf");

  sscanf = _ksys_dlsym(libc, "sscanf");

  strcmp = _ksys_dlsym(libc, "strcmp");

  strchr = _ksys_dlsym(libc, "strchr");

  strcpy = _ksys_dlsym(libc, "strcpy");

  return 0;

}

ksys_dll_t EXPORTS[] = {

  {"mtar_init", mtar_init},

  {"mtar_open", mtar_open},

  {"mtar_close", mtar_close},

  {"mtar_seek", mtar_seek},

  {"mtar_rewind", mtar_rewind},

  {"mtar_next", mtar_next},

  {"mtar_find", mtar_find},

  {"mtar_read_header", mtar_read_header},

  {"mtar_read_data", mtar_read_data},

  {"mtar_write_header", mtar_write_header},

  {"mtar_write_file_header", mtar_write_file_header},

  {"mtar_write_dir_header",  mtar_write_dir_header},

  {"mtar_write_data",mtar_write_data},

  {"mtar_finalize", mtar_finalize},

  {"mtar_strerror", mtar_strerror},

  NULL

};

#endif