zdf.c

/**
 * @file zdf.c
 * @author Ricardo
 * @brief ZDF file library
 * @version 1.0
 * @date 2022-02-04
 * 
 * @copyright Copyright (c) 2022
 * 
 * This ZDF version is totally self contained. It does not depend on XDR or any other
 * external libraries. Current implementation should also work on big endian systems (untested)
 * This version is not compatible is version 0 (files have the opposite endianess)
 */

/**
 * @brief  Use 2008 edition of the POSIX standard (IEEE Standard 1003.1-2008)
 * 
 */
#define _POSIX_C_SOURCE 200809L

/**
 * @brief  Use 64 bit file interface
 * 
 */
#define _FILE_OFFSET_BITS 64

#include "zdf.h"

#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <string.h>
#include <errno.h>
#include <inttypes.h>

/**
 * On Windows we cannot use the POSIX.1 mkdir command, so use _mkdir instead
 */
#if defined(_MSC_VER) || defined(_WIN32) || defined(_WIN64)
#include <direct.h>
#define mkdir(path,mode) _mkdir(path)

// Windows also lacks the 'fseeko', 'ftello' functions so replace with Windows
// equivalent.
#define fseeko _fseeki64
#define ftello _ftelli64

#endif

/**
 * Number of bytes required for writing data to ZDF file
 * (round up to multiple of BYTES_PER_ZDF_UNIT)
 */
#define RNDUP(x)  ((((x) + BYTES_PER_ZDF_UNIT - 1) / BYTES_PER_ZDF_UNIT) \
            * BYTES_PER_ZDF_UNIT)


/**
 * Buffer size for converting big endian to little endian data
 */
#define ENDIAN_CONV_BUF_SIZE 1024

/**
 * Sizes of datatypes
 */
const unsigned size_zdf_int32   = 4;    ///< size of zdf_int32
const unsigned size_zdf_uint32  = 4;    ///< size of zdf_uint32
// const unsigned size_zdf_int64   = 8;    ///< size of zdf_int64
const unsigned size_zdf_uint64  = 8;    ///< size of zdf_uint64
const unsigned size_zdf_double  = 8;    ///< size of zdf_double
// const unsigned size_zdf_float   = 4;    ///< size of zdf_float


/**
 * IDs of ZDF records
 */
#define ZDF_INT32_ID         0x00010000  ///< Int32 record ID
#define ZDF_DOUBLE_ID        0x00020000  ///< Double record ID
#define ZDF_STRING_ID        0x00030000  ///< String record ID

#define ZDF_DATASET_ID      0x00100002  ///< Dataset record ID
#define ZDF_CDSET_START_ID  0x00110000  ///< Chunked dataset start record ID
#define ZDF_CDSET_CHUNK_ID  0x00120000  ///< Chunked dataset data chunk record ID
#define ZDF_CDSET_END_ID    0x00130000  ///< Chunked dataset end record ID

#define ZDF_ITERATION_ID     0x00200001  ///< Iteration record ID
#define ZDF_GRID_INFO_ID     0x00210001  ///< Grid information record ID
#define ZDF_PART_INFO_ID     0x00220002  ///< Particle set information record ID
#define ZDF_TRACK_INFO_ID     0x00230001  ///< Particle tracks information record ID

/* -----------------------------------------------------------------------------------------------
  recursively create path if required
-------------------------------------------------------------------------------------------------- */

/**
 * @brief Recursively creates a path if required
 * @param  path path to create
 * @return      returns 0 on success, otherwise returns the value returned by mkdir
 */
int create_path( const char path[] )
{
    if ( path[0] == '\0' ) return 0;
    
    char uppath[256], *p;
    int ierr = 0;

    if (mkdir(path,S_IRWXU | (S_IRGRP | S_IXGRP ) | (S_IROTH | S_IXOTH) )) {
        switch (errno) {
            case ENOENT : // A component of the path does not exist 

                // get upper path
                strncpy(uppath, path, 255);
                p = uppath + strlen(uppath);
                while(*p!='/') p--;
                *p=0;

                //recursively build the path
                if ( !create_path( uppath ) ) ierr = create_path( path );
                break;

            case EEXIST : /* if directory already exists ignore the error */
                ierr = 0;
                break;
            default: ierr = errno;
        }
    }
    return ierr;
}


/**
 * Returns size of ZDF datatype
 * @param  data_type Data type id
 * @return           Returns type size in bytes or 0 for an invalid data type
 */
size_t zdf_sizeof( enum zdf_data_type data_type ) {
    switch( data_type ) {
        case zdf_null:
            return(0);
        case zdf_int8:
        case zdf_uint8:
            return(1);
        case zdf_int16:
        case zdf_uint16:
            return(2);
        case zdf_int32:
        case zdf_uint32:
        case zdf_float32:
            return(4);
        case zdf_int64:
        case zdf_uint64:
        case zdf_float64:
            return(8);
    }
    return(0);
}

/* -----------------------------------------------------------------------------------------------
  Open / Close ZDF file
-------------------------------------------------------------------------------------------------- */

/**
 * Closes ZDF file
 * @param  zdf ZDF file to close
 * @return     Returns 1 on success, 0 on error
 */
int zdf_close_file( t_zdf_file* zdf ) {

    if ( fclose( zdf->fp ) ) {
        perror("(*error*) Unable to close ZDF file");
        return(0);
    }
    zdf -> fp = NULL;
    return(1);
}

/**
 * Opens ZDF file
 * @param  zdf      ZDF file to open
 * @param  filename Filename of the ZDF file to open, including path
 * @param  mode     Can be one of ZDF_CREATE, ZDF_READ, or ZDF_UPDATE
 * @return          Returns 1 on success, 0 on error
 */
int zdf_open_file( t_zdf_file* zdf, const char* filename, enum zdf_file_access_mode mode ){

    char test_magic[4];

    zdf -> mode = mode;

    switch( mode ) {
        case ZDF_CREATE :
            // Open file for writing
            // The "wb" mode must be used for compatibility with Windows
            if (!(zdf->fp = fopen( filename, "w+b"))) {
                perror("(*error*) Unable to open ZDF file for writing");
                return(0);
            }

            // Write magic number
            if ( fwrite( (void *) zdf_magic, sizeof(char), ZDF_MAGIC_LENGTH, zdf->fp )
                 != ZDF_MAGIC_LENGTH ) {
                fprintf(stderr, "(*error*) Unable to write magic number to ZDF file.\n");
                zdf_close_file( zdf );
                return(0);
            }

            break;

        case ZDF_READ :
            // Open file for reading
            if (!(zdf->fp = fopen( filename, "r"))) {
                perror("(*error*) Unable to open ZDF file for reading");
                return(0);
            }

            // Read magic number
            if ( fread( (void *) test_magic, sizeof(char), ZDF_MAGIC_LENGTH, zdf->fp )
                != ZDF_MAGIC_LENGTH) {
                fprintf(stderr, "(*error*) Unable to read magic number from ZDF file.\n");
                zdf_close_file( zdf );
                return(0);
            }

            // Check magic number
            for( int i = 0; i < ZDF_MAGIC_LENGTH; i++) {
                if ( test_magic[i] != zdf_magic[i] ) {
                    fprintf(stderr, "(*error*) Invalid magic number, file is not a proper ZDF file.\n");
                    zdf_close_file( zdf );
                    return(0);
                }
            }
            break;

        case ZDF_UPDATE :
            // Open file for reading and writing
            if (!(zdf->fp = fopen( filename, "r+"))) {
                perror("(*error*) Unable to open ZDF file for reading / writing.\n");
                return(0);
            }

            // Read magic number
            if (fread( (void *) test_magic, sizeof(char), ZDF_MAGIC_LENGTH, zdf->fp )
                != ZDF_MAGIC_LENGTH) {
                fprintf(stderr, "(*error*) Unable to read magic number from ZDF file.\n");
                zdf_close_file( zdf );
                return(0);
            }

            // Check magic number
              for( int i = 0; i < ZDF_MAGIC_LENGTH; i++) {
                if ( test_magic[i] != zdf_magic[i] ) {
                    fprintf(stderr, "(*error*) Invalid magic number, file is not a proper ZDF file.\n");
                    zdf_close_file( zdf );
                    return(0);
                }
            }

            // Position the file pointer at the end of the file
            fseeko( zdf->fp, 0, SEEK_END );

            break;

        default:
            fprintf(stderr, "(*error*) zdf_open_file: unsupported mode.\n");
            return(0);
    }

    zdf -> ndatasets = 0;

    return(1);
}

/* -----------------------------------------------------------------------------------------------
  Elemental types
-------------------------------------------------------------------------------------------------- */


#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__

/**
 * Implementation for little endian systems (e.g. x86)
 *
 * For these systems just writing the data to disk is sufficient
 */

/**
 * Writes scalar int32 value to file
 * @param  zdf ZDF file descriptor
 * @param  i   int32_t value to write
 * @return     Returns number of bytes written on success, 0 on error
 */
size_t zdf_int32_write( t_zdf_file* zdf, const int32_t i ){
    if ( fwrite( (void *) &i, sizeof(int32_t), 1, zdf -> fp ) != 1 )
        return(0);
    return ( sizeof(int32_t) );
}

/**
 * Reads scalar int32 value from file
 * @param  zdf ZDF file descriptor
 * @param  i   int32_t value read
 * @return     Returns number of bytes written on success, 0 on error
 */
size_t zdf_int32_read( t_zdf_file* zdf, int32_t* i ){
    if ( fread( (void *) i, sizeof(int32_t), 1, zdf -> fp ) != 1 )
        return(0);
    return ( sizeof(int32_t) );
}

/**
 * Writes scalar uint32 value to file
 * @param  zdf ZDF file descriptor
 * @param  u   uint32_t value to write
 * @return     Returns number of bytes written on success, 0 on error
 */
size_t zdf_uint32_write( t_zdf_file* zdf, const uint32_t u ){
    if ( fwrite( (void *) &u, sizeof(uint32_t), 1, zdf -> fp ) != 1 )
        return(0);
    return(sizeof(uint32_t));
}

/**
 * Reads scalar uint32 value from file
 * @param  zdf ZDF file descriptor
 * @param  u   uint32_t value read
 * @return     Returns number of bytes written on success, 0 on error
 */
size_t zdf_uint32_read( t_zdf_file* zdf, uint32_t* u ){
    if ( fread( (void *) u, sizeof(uint32_t), 1, zdf -> fp ) != 1 )
        return(0);
    return(sizeof(uint32_t));
}

/**
 * Writes scalar int64 value to file
 * @param  zdf ZDF file descriptor
 * @param  i   int64_t value to write
 * @return     Returns number of bytes written on success, 0 on error
 */
size_t zdf_int64_write( t_zdf_file* zdf, const int64_t i ){
    if ( fwrite( (void *) &i, sizeof(int64_t), 1, zdf -> fp ) != 1 )
        return(0);
    return(sizeof(int64_t));
}

/**
 * Reads scalar int64 value from file
 * @param  zdf ZDF file descriptor
 * @param  i   int64_t value read
 * @return     Returns number of bytes written on success, 0 on error
 */
size_t zdf_int64_read( t_zdf_file* zdf, int64_t *i ){
    if ( fread( (void *) i, sizeof(int64_t), 1, zdf -> fp ) != 1 )
        return(0);
    return(sizeof(int64_t));
}

/**
 * Writes scalar uint64_t value to file
 * @param  zdf ZDF file descriptor
 * @param  u   uint64_t value to write
 * @return     Returns number of bytes written on success, 0 on error
 */
size_t zdf_uint64_write( t_zdf_file* zdf, const uint64_t u ){
    if ( fwrite( (void *) &u, sizeof(uint64_t), 1, zdf -> fp ) != 1 )
        return(0);
    return(sizeof(uint64_t));
}

/**
 * Reads scalar int64 value from file
 * @param  zdf ZDF file descriptor
 * @param  u   uint64_t value read
 * @return     Returns number of bytes written on success, 0 on error
 */
size_t zdf_uint64_read( t_zdf_file* zdf, uint64_t *u ){
    if ( fread( (void *) u, sizeof(int64_t), 1, zdf -> fp ) != 1 )
        return(0);
    return(sizeof(uint64_t));
}


/**
 * Writes scalar double (float64) value to file
 * @param  zdf ZDF file descriptor
 * @param  d   double value to write
 * @return     Returns number of bytes written on success, 0 on error
 */
size_t zdf_double_write( t_zdf_file* zdf, const double d ){
    if ( fwrite( (void *) &d, sizeof(double), 1, zdf -> fp ) != 1 )
        return(0);
    return(sizeof(double));
}

/**
 * Write arbitraty 16bit type vector to file
 * @param  zdf          ZDF file descriptor
 * @param  data         Pointer to data to write
 * @param  len          Number of vector elements
 * @return              Returns number of bytes written on success, 0 on error
 */
size_t zdf_vector16_write( t_zdf_file* zdf, void const * const data, size_t len ) {
    if ( fwrite( data, sizeof(int16_t), len, zdf -> fp ) != len )
        return(0);
    return( len * sizeof(int16_t) );
}

/**
 * Write arbitraty 32bit type vector to file
 * @param  zdf          ZDF file descriptor
 * @param  data         Pointer to data to write
 * @param  len          Number of vector elements
 * @return              Returns number of bytes written on success, 0 on error
 */
size_t zdf_vector32_write( t_zdf_file* zdf, void const * const data, size_t len ) {
    if ( fwrite( data, sizeof(int32_t), len, zdf -> fp ) != len )
        return(0);
    return( len * sizeof(int32_t) );
}

/**
 * Write arbitraty 64bit type vector to file
 * @param  zdf          ZDF file descriptor
 * @param  data         Pointer to data to write
 * @param  len          Number of vector elements
 * @return              Returns number of bytes written on success, 0 on error
 */
size_t zdf_vector64_write( t_zdf_file* zdf, void const * const data, size_t len ) {
    if( fwrite( data, sizeof(int64_t), len, zdf -> fp ) != len )
        return(0);
    return( len * sizeof(int64_t) );
}

#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__

/**
 * Implementation for big endian systems (e.g. PowerPC)
 *
 * For these systems we need to swap the bytes before writing. For vectors, conversion
 * is done in chunks of ENDIAN_CONV_BUF_SIZE values.
 *
 * The system may provide hardware optimized bswap_* routines, these are usually found in
 * the <byteswap.h> header, but they are missing on many platforms.
 */


/**
 * Swap bytes for 16 bit number
 * @param  x 16 bit number to convert
 * @return   byte-swapped version of x
 */
#define bswap_16(x) \
({ \
    uint16_t __x = (x); \
    ((uint16_t)( \
        (((uint16_t)(__x) & (uint16_t)0x00ffU) << 8) | \
        (((uint16_t)(__x) & (uint16_t)0xff00U) >> 8) )); \
})

/**
 * Swap bytes for 32 bit number
 * @param  x 32 bit number to convert
 * @return   byte-swapped version of x
 */
#define bswap_32(x) \
({ \
    uint32_t __x = (x); \
    ((uint32_t)( \
        (((uint32_t)(__x) & (uint32_t)0x000000ffUL) << 24) | \
        (((uint32_t)(__x) & (uint32_t)0x0000ff00UL) <<  8) | \
        (((uint32_t)(__x) & (uint32_t)0x00ff0000UL) >>  8) | \
        (((uint32_t)(__x) & (uint32_t)0xff000000UL) >> 24) )); \
})

/**
 * Swap bytes for 64 bit number
 * @param  x 64 bit number to convert
 * @return   byte-swapped version of x
 */
#define bswap_64(x) \
({ \
    uint64_t __x = (x); \
    ((uint64_t)( \
        (uint64_t)(((uint64_t)(__x) & (uint64_t)0x00000000000000ffULL) << 56) | \
        (uint64_t)(((uint64_t)(__x) & (uint64_t)0x000000000000ff00ULL) << 40) | \
        (uint64_t)(((uint64_t)(__x) & (uint64_t)0x0000000000ff0000ULL) << 24) | \
        (uint64_t)(((uint64_t)(__x) & (uint64_t)0x00000000ff000000ULL) <<  8) | \
        (uint64_t)(((uint64_t)(__x) & (uint64_t)0x000000ff00000000ULL) >>  8) | \
        (uint64_t)(((uint64_t)(__x) & (uint64_t)0x0000ff0000000000ULL) >> 24) | \
        (uint64_t)(((uint64_t)(__x) & (uint64_t)0x00ff000000000000ULL) >> 40) | \
        (uint64_t)(((uint64_t)(__x) & (uint64_t)0xff00000000000000ULL) >> 56) )); \
})

/**
 * Writes int32 value to file
 * @param  zdf ZDF file descriptor
 * @param  i   int32_t value to write
 * @return     Returns number of bytes written on success, 0 on error
 */
size_t zdf_int32_write( t_zdf_file* zdf, const int32_t i ){
    uint32_t tmp = bswap_32((uint32_t)i);
    if ( fwrite( (void *) &tmp, sizeof(uint32_t), 1, zdf -> fp ) != 1 )
        return(0);
    return( sizeof(uint32_t));
}

/**
 * Reads scalar int32 value from file
 * @param  zdf ZDF file descriptor
 * @param  i   int32_t value read
 * @return     Returns number of bytes read on success, 0 on error
 */
size_t zdf_int32_read( t_zdf_file* zdf, int32_t* i ){
    uint32_t tmp;
    if ( fread( (void *) &tmp, sizeof(uint32_t), 1, zdf -> fp ) != 1 )
        return(0);
    *i = (int32_t) bswap_32(tmp);
    return( sizeof(uint32_t));
}

/**
 * Writes uint32 value to file
 * @param  zdf ZDF file descriptor
 * @param  u   uint32_t value to write
 * @return     Returns number of bytes written on success, 0 on error
 */
size_t zdf_uint32_write( t_zdf_file* zdf, const uint32_t u ){
    uint32_t tmp = bswap_32(u);
    if ( fwrite( (void *) &tmp, sizeof(uint32_t), 1, zdf -> fp ) != 1 )
        return(0);
    return(sizeof(uint32_t));
}

/**
 * Reads scalar uint32 value from file
 * @param  zdf ZDF file descriptor
 * @param  i   uint32_t value read
 * @return     Returns number of bytes read on success, 0 on error
 */
size_t zdf_uint32_read( t_zdf_file* zdf, uint32_t* u ){
    uint32_t tmp;
    if ( fread( (void *) &tmp, sizeof(uint32_t), 1, zdf -> fp ) != 1 )
        return(0);
    *u = bswap_32(tmp);
    return(sizeof(uint32_t));
}

/**
 * Writes int64 value to file
 * @param  zdf ZDF file descriptor
 * @param  i   int64_t value to write
 * @return     Returns number of bytes written on success, 0 on error
 */
size_t zdf_int64_write( t_zdf_file* zdf, const int64_t i ){
    uint64_t tmp = bswap_64((uint64_t)i);
    if ( fwrite( (void *) &tmp, sizeof(uint64_t), 1, zdf -> fp ) != 1 )
        return(0);
    return(sizeof(uint64_t));
}

/**
 * Reads scalar int64 value from file
 * @param  zdf ZDF file descriptor
 * @param  i   int64_t value read
 * @return     Returns number of bytes read on success, 0 on error
 */
size_t zdf_int64_read( t_zdf_file* zdf, int64_t* i ){
    uint64_t tmp;
    if ( fread( (void *) &tmp, sizeof(uint64_t), 1, zdf -> fp ) != 1 )
        return(0);
    *i = (int64_t) bswap_64(tmp);
    return(sizeof(uint64_t));
}

/**
 * Writes uint64_t value to file
 * @param  zdf ZDF file descriptor
 * @param  u   uint64_t value to write
 * @return     Returns number of bytes read on success, 0 on error
 */
size_t zdf_uint64_write( t_zdf_file* zdf, const uint64_t u ){
    uint64_t tmp = bswap_64(u);
    if ( fwrite( (void *) &tmp, sizeof(uint64_t), 1, zdf -> fp ) != 1 )
        return(0);
    return(sizeof(uint64_t));
}

/**
 * Reads scalar uint64 value from file
 * @param  zdf ZDF file descriptor
 * @param  i   uint64_t value read
 * @return     Returns number of bytes read on success, 0 on error
 */
size_t zdf_uint64_read( t_zdf_file* zdf, uint64_t* i ){
    uint64_t tmp;
    if ( fread( (void *) &tmp, sizeof(uint64_t), 1, zdf -> fp ) != 1 )
        return(0);
    *i = bswap_64(tmp);
    return(sizeof(uint64_t));
}

/**
 * Writes double (float64) value to file
 * @param  zdf ZDF file descriptor
 * @param  d   double value to write
 * @return     Returns number of bytes written on success, 0 on error
 */
size_t zdf_double_write( t_zdf_file* zdf, const double d ){
    uint64_t tmp = bswap_64((uint64_t)d);
    if ( fwrite( (void *) &tmp, sizeof(uint64_t), 1, zdf -> fp ) != 1 )
        return(0);
    return(sizeof(uint64_t));
}

/**
 * Write arbitraty 16bit type vector to file
 * @param  zdf  ZDF file descriptor
 * @param  data Pointer to 16 bit data to write
 * @param  len  Number of vector elements
 * @return      Returns number of bytes written on success, 0 on error
 */
size_t zdf_vector16_write( t_zdf_file* zdf,  void const * const data, size_t len ) {

    uint16_t buffer[ENDIAN_CONV_BUF_SIZE];

    for( size_t offset = 0; offset < len; offset += ENDIAN_CONV_BUF_SIZE ) {

        // Number of values in chunk
        size_t chunk_len = (offset + ENDIAN_CONV_BUF_SIZE < len ) ? ENDIAN_CONV_BUF_SIZE : len - offset;

        // Convert chunk to little endian
        for( size_t i = 0; i < chunk_len; i++) buffer[i] = bswap_16( data[offset+i]);

        // Write chunk
        if ( fwrite( (void *) buffer, sizeof(uint16_t), chunk_len, zdf -> fp) != chunk_len ) 
            return(0);
    }

    return( len * sizeof(uint16_t) );
}

/**
 * Write arbitraty 32bit type vector to file
 * @param  zdf  ZDF file descriptor
 * @param  data Pointer to 32 bit data to write
 * @param  len  Number of vector elements
 * @return      Returns number of bytes written on success, 0 on error
 */
size_t zdf_vector32_write( t_zdf_file* zdf,  void const * const data, size_t len ) {

    uint32_t buffer[ENDIAN_CONV_BUF_SIZE];

    for( size_t offset = 0; offset < len; offset += ENDIAN_CONV_BUF_SIZE ) {

        // Number of values in chunk
        size_t chunk_len = (offset + ENDIAN_CONV_BUF_SIZE < len ) ? ENDIAN_CONV_BUF_SIZE : len - offset;

        // Convert chunk to little endian
        for( size_t i = 0; i < chunk_len; i++) buffer[i] = bswap_32( data[offset+i]);

        // Write chunk
        if ( fwrite( (void *) buffer, sizeof(uint32_t), chunk_len, zdf -> fp) != chunk_len ) 
            return(0);
    }

    return( len * sizeof(uint32_t) );
}

/**
 * Write arbitraty 64bit type vector to file
 * @param  zdf  ZDF file descriptor
 * @param  data Pointer to 64 bit data to write
 * @param  len  Number of vector elements
 * @return      Returns number of bytes written on success, 0 on error
 */
size_t zdf_vector64_write( t_zdf_file* zdf,  void const * const data, size_t len ) {
    uint64_t buffer[ENDIAN_CONV_BUF_SIZE];

    for( size_t offset = 0; offset < len; offset += ENDIAN_CONV_BUF_SIZE ) {

        // Number of values in chunk
        size_t chunk_len = (offset + ENDIAN_CONV_BUF_SIZE < len ) ? ENDIAN_CONV_BUF_SIZE : len - offset;

        // Convert chunk to little endian
        for( size_t i = 0; i < chunk_len; i++) buffer[i] = bswap_64( data[offset+i] );

        // Write chunk
        if ( fwrite( (void *) buffer, sizeof(uint64_t), chunk_len, zdf -> fp) != chunk_len ) 
            return(0);
    }

    return( len * sizeof(uint64_t) );
}


#else

#error "System is neither little endian nor big endian, aborting."

#endif

/**
 * Write arbitraty 8bit type vector to file. Adds padding at the end of the vector if
 * necessary to maitain alignment.
 * @param  zdf ZDF file descriptor
 * @param  u   Pointer to 8 bit data
 * @param  len Number of vector elements
 * @return     Returns number of bytes written (including padding), 0 on error
 */
size_t zdf_vector8_write( t_zdf_file* zdf, void const * const u, size_t len ){

    if ( fwrite( u, sizeof(uint8_t), len, zdf -> fp ) != len ) {
        return(0);
    }

    size_t npad = RNDUP(len) - len;

    if ( npad > 0 ) {
        const uint8_t pad[BYTES_PER_ZDF_UNIT] = {0};
        if ( fwrite( (void *) pad, sizeof(uint8_t), npad, zdf -> fp ) != npad ) {
            return(0);
        }
    }

    return( RNDUP(len) );
}

/**
 * Writes a vector of the specified datatype to file
 * @param  zdf       ZDF file descriptor
 * @param  data      Pointer to data
 * @param  data_type Data type descriptor
 * @param  len       Number of elements in vector
 * @return           Returns number of bytes written on success, 0 on error
 */
size_t zdf_vector_write( t_zdf_file* zdf, const void * data, enum zdf_data_type data_type, size_t len ){

     switch ( data_type ) {
        case zdf_int8:
        case zdf_uint8:
            return ( zdf_vector8_write( zdf, data, len ));
        case zdf_int16:
        case zdf_uint16:
            return ( zdf_vector16_write( zdf, data, len ) );
        case zdf_int32:
        case zdf_uint32:
        case zdf_float32:
            return ( zdf_vector32_write( zdf, data, len ) );
        case zdf_int64:
        case zdf_uint64:
        case zdf_float64:
            return ( zdf_vector64_write( zdf, data, len ) );
        default:
            fprintf(stderr,"(*error*) zdf_vector_write: Unsupported datatype.\n");
     }
    return(0);
 }


/* -----------------------------------------------------------------------------------------------
  zdf_string
-------------------------------------------------------------------------------------------------- */

/**
 * Write a string to file
 * @param  zdf ZDF file descriptor
 * @param  str C string (char *) to write
 * @return     Returns number of bytes written on success, 0 on error
 */
size_t zdf_string_write( t_zdf_file* zdf, const char * str ){

    uint32_t len;
    int count;

    len = ( str ) ? strlen( str ) : 0;
    if ( ! zdf_uint32_write( zdf, len ) ) return(0);

    if ( len > 0 ) {
        if ( !(count = zdf_vector8_write( zdf, (void *) str, len ) ) )
            return(0);
    } else {
        count = 0;
    }

    return( sizeof(uint32_t) + count );
}

/**
 * Read a string from file
 * @param  zdf ZDF file descriptor
 * @param  str C string (char *) to read. The routine will allocate memory using
 *             malloc() for storing the string data.
 * @return     Returns number of bytes read on success, 0 on error
 */
size_t zdf_string_read( t_zdf_file* zdf, char * * str ){

    uint32_t len;
    if ( ! zdf_uint32_read( zdf, &len) ) return(0);

    uint32_t flen = RNDUP(len);

    char * buffer = (char *) malloc( (flen+1) * sizeof(uint8_t) );

    if ( len > 0 ) {
        if ( fread( (void *) buffer, sizeof(uint8_t), flen, zdf -> fp ) != flen ) return(0);
    }

    buffer[len] = 0;

    *str = buffer;

    return( sizeof(uint32_t) + flen );
}

/**
 * Calculate size of string record
 * @param  s C string (char *) to write
 * @return   The number of bytes required for writing the string data
 */
size_t size_zdf_string( const char *s )
{
    unsigned len = ( s ) ? strlen( s ) : 0;
    return size_zdf_uint32 + ((len > 0) ? RNDUP(len) : 0);
}


/* -----------------------------------------------------------------------------------------------
  zdf records
-------------------------------------------------------------------------------------------------- */

/**
 * @brief ZDF Record
 * 
 */
typedef struct ZDF_Record{
    uint32_t id_version;    ///< id & version
    char*    name;          ///< Name
    uint64_t length;        ///< Record length
} t_zdf_record;

/**
 * Adds ZDF record header to file
 * @param  zdf ZDF file descriptor
 * @param  rec ZDF record
 * @return     Returns number of bytes written on success, 0 on error
 */
size_t zdf_record_write( t_zdf_file* zdf, const t_zdf_record* rec ){

  if ( ! zdf_uint32_write( zdf, rec -> id_version ) ) return(0);
  size_t len;    if ( ! (len=zdf_string_write( zdf, rec -> name )) ) return(0);
    if ( ! zdf_uint64_write( zdf, rec -> length )     ) return(0);

     return( sizeof(uint32_t) + len + sizeof(uint64_t) );
}

/**
 * Reads ZDF record header from file
 * @param  zdf ZDF file descriptor
 * @param  rec ZDF record
 * @return     Returns number of bytes read on success, 0 on error
 */
size_t zdf_record_read( t_zdf_file* zdf, t_zdf_record* rec ){

  if ( ! zdf_uint32_read( zdf, & rec -> id_version ) ) return(0);
  size_t len; if ( ! (len=zdf_string_read( zdf, & rec -> name )) ) return(0);
    if ( ! zdf_uint64_read( zdf, & rec -> length )     ) return(0);

     return( sizeof(uint32_t) + len + sizeof(uint64_t) );
}

/**
 * Skips to the end of ZDF record. File pointer is assumed to be after the record header.
 * @param  zdf ZDF file descriptor
 * @param  rec ZDF record
 * @return     Returns 1 on success, 0 on error
 */
int zdf_record_skip( t_zdf_file* zdf, const t_zdf_record* rec ){

    off_t offset = rec -> length;
    return ( ! fseeko( zdf -> fp, offset, SEEK_CUR ) ? 1 : 0 );
}

/* -----------------------------------------------------------------------------------------------
  zdf basic data tags
-------------------------------------------------------------------------------------------------- */

/**
 * Adds string element to ZDF file
 * @param  zdf  ZDF File handle
 * @param  name Element name
 * @param  str  String value
 * @return      Returns number of bytes written on success, 0 on error
 */
size_t zdf_add_string( t_zdf_file* zdf, const char* name, const char* str ){

    t_zdf_record rec = {
        .id_version = ZDF_STRING_ID,
        .name = (char *)name,
        .length = size_zdf_string( str )
    };

    size_t ok, len;
    len = ( ok = zdf_record_write( zdf, &rec ) );
    if ( !ok ) return(0);

    len += ( ok = zdf_string_write( zdf, str) );
    if ( !ok ) return(0);

    return(len);
}

/**
 * Adds int32 element to ZDF file
 * @param  zdf    ZDF File handle
 * @param  name   Element name
 * @param  value  int32 value
 * @return        Returns number of bytes written on success, 0 on error
 */
size_t zdf_add_int32( t_zdf_file* zdf, const char* name, const int32_t value ){

    t_zdf_record rec = {
        .id_version = ZDF_INT32_ID,
        .name = (char *)name,
        .length = size_zdf_int32
    };

    size_t ok, len;
    len = ( ok = zdf_record_write(zdf, &rec) );
    if (!ok) return(0);

    len += ( ok = zdf_int32_write(zdf, value) );
    if (!ok) return(0);

    return( len );
}

/**
 * Adds float64 element to ZDF file
 * @param  zdf    ZDF file handle
 * @param  name   Element name
 * @param  value  float64 value
 * @return        Returns number of bytes written on success, 0 on error
 */
size_t zdf_add_double( t_zdf_file* zdf, const char* name, const double value )
{
    t_zdf_record rec = {
        .id_version = ZDF_DOUBLE_ID,
        .name = (char *)name,
        .length = size_zdf_double
    };

    size_t ok, len;
    len = (ok = zdf_record_write(zdf, &rec) );    if ( !ok ) return(0);
    len += ( ok = zdf_double_write(zdf, value) ); if ( !ok ) return(0);

    return(len);
}


/* -----------------------------------------------------------------------------------------------
  zdf compound metadata tags
-------------------------------------------------------------------------------------------------- */

/**
 * Adds iteration metadata group to ZDF file
 * @param  zdf  ZDF file handle
 * @param  iter Iteration info
 * @return      Number of bytes written on success, 0 on error
 */
size_t zdf_add_iteration( t_zdf_file* zdf, const t_zdf_iteration* iter ){

    t_zdf_record rec = {
        .id_version = ZDF_ITERATION_ID,
        .name = (char *) iter -> name,
        .length = size_zdf_uint32 +
                     size_zdf_double +
                     size_zdf_string( iter -> time_units )
    };

    // Default name
    if ( ! rec.name ) rec.name = "Iteration";

    size_t ok, len;

    len = ( ok = zdf_record_write( zdf, &rec) );      if ( !ok ) return(0);
    len += ( ok = zdf_int32_write( zdf, iter ->n ) ); if ( !ok ) return(0);
    len += ( ok = zdf_double_write( zdf, iter->t ) ); if ( !ok ) return(0);
    len += ( ok = zdf_string_write( zdf, iter->time_units ) ); if ( !ok ) return(0);

     return(len);
}

/**
 * Returns size of grid information metadata element
 * @param  grid Grid info
 * @return Metadata group size in bytes
 */
size_t size_zdf_grid_info(const t_zdf_grid_info* grid) {
    size_t size;

    size = size_zdf_uint32 + grid -> ndims * size_zdf_uint64 +
            size_zdf_string(grid->label) +  size_zdf_string(grid->units);

    // Includes axis information
    size += size_zdf_int32;
    if ( grid -> axis ) {

        for(unsigned i=0; i<grid -> ndims; i++)
            size += size_zdf_string( grid->axis[i].name ) +
                    size_zdf_int32 +
                    2 * size_zdf_double +
                    size_zdf_string( grid -> axis[i].label ) +
                    size_zdf_string( grid -> axis[i].units );
    }

    return size;
}

/**
 * Adds grid information metadata group to file
 * @param  zdf  File handle
 * @param  grid Grid information
 * @return      Number of bytes written on success, 0 on error
 */
size_t zdf_add_grid_info( t_zdf_file* zdf, const t_zdf_grid_info* grid ){

    t_zdf_record rec = {
        .id_version = ZDF_GRID_INFO_ID,
        .name = (char *) grid -> name,
        .length = size_zdf_grid_info( grid )
    };

    size_t reclen;
    if ( !( reclen = zdf_record_write( zdf, &rec ) )  ) return(0);

    if ( ! zdf_uint32_write( zdf, grid -> ndims ) ) return(0);
    for( unsigned i=0; i < grid -> ndims; i++) {
        if ( ! zdf_uint64_write( zdf, grid -> count[i] ) ) return(0);
    }

    if ( !zdf_string_write( zdf, grid->label ) ) return(0);
    if ( !zdf_string_write( zdf, grid->units ) ) return(0);

    int32_t has_axis = ( grid -> axis != NULL);
    if ( !zdf_int32_write( zdf, has_axis ) ) return(0);

    if ( has_axis ) {

        for( unsigned i=0; i < grid -> ndims; i++) {
            if ( !zdf_string_write( zdf, grid -> axis[i].name  ) ) return(0);
            if ( !zdf_int32_write(  zdf, grid -> axis[i].type  ) ) return(0);
            if ( !zdf_double_write( zdf, grid -> axis[i].min   ) ) return(0);
            if ( !zdf_double_write( zdf, grid -> axis[i].max   ) ) return(0);
            if ( !zdf_string_write( zdf, grid -> axis[i].label ) ) return(0);
            if ( !zdf_string_write( zdf, grid -> axis[i].units ) ) return(0);
        }
    }

    return( reclen + size_zdf_grid_info( grid ) );
}

/**
 * Returns size of particles information metadata group
 * @param  part Particles information
 * @return      Metadata group size in bytes
 */
size_t size_zdf_part_info(const t_zdf_part_info* part) {
    size_t size = size_zdf_string(part->label) +    // label
            size_zdf_uint64 +                       // np
            size_zdf_uint32;                        // nquants

    for( unsigned i = 0; i < part -> nquants; i++) {
        size += size_zdf_string( part -> quants[i] ) +
                size_zdf_string( part -> qlabels[i] ) +
                size_zdf_string( part -> qunits[i] );
    }

    return size;
}

/**
 * Adds particle information metadata group to file
 * @param  zdf  File handle
 * @param  part Particle information
 * @return      Number of bytes written on success, 0 on error
 */
size_t zdf_add_part_info( t_zdf_file* zdf, const t_zdf_part_info* part ){

    size_t reclen;

    t_zdf_record rec = {
        .id_version = ZDF_PART_INFO_ID,
        .name = (char *) part->name,
        .length = size_zdf_part_info( part )
    };

    if ( !( reclen = zdf_record_write( zdf, &rec ) ) ) return(0);
    if ( !zdf_string_write( zdf, part -> label )     ) return(0);
    if ( !zdf_uint64_write( zdf, part -> np )        ) return(0);
    if ( !zdf_uint32_write( zdf, part -> nquants )   ) return(0);

    for( unsigned i=0; i < part -> nquants; i++) {
        if ( !zdf_string_write( zdf, part -> quants[i] ) ) return(0);
    }
    for( unsigned i=0; i < part -> nquants; i++) {
        if ( !zdf_string_write( zdf, part -> qlabels[i] ) ) return(0);
    }
    for( unsigned i=0; i < part -> nquants; i++) {
        if ( !zdf_string_write( zdf, part -> qunits[i] )  ) return(0);
    }

     return( reclen + size_zdf_part_info( part ) );
}

/**
 * Returns size of tracks information metadata group
 * @param  tracks Tracks information
 * @return        Metadata group size in bytes
 */
size_t size_zdf_track_info(const t_zdf_track_info* tracks) {
    size_t size = size_zdf_string(tracks->label) +    // label
            4 * size_zdf_uint32; // ntracks, ndump, niter, nquants

    for( unsigned i = 0; i < tracks -> nquants; i++) {
        size += size_zdf_string( tracks -> quants[i] ) +
                size_zdf_string( tracks -> qlabels[i] ) +
                size_zdf_string( tracks -> qunits[i] );
    }

    return size;
}

/**
 * Adds tracks information metadata group to file
 * @param  zdf    File handle
 * @param  tracks Tracks information
 * @return        Number of bytes written on success, 0 on error
 */
size_t zdf_add_track_info( t_zdf_file* zdf, const t_zdf_track_info* tracks ){

    int reclen;

    t_zdf_record rec = {
        .id_version = ZDF_TRACK_INFO_ID,
        .name = (char *)tracks -> name,
        .length = size_zdf_track_info( tracks )
    };

    if ( !( reclen = zdf_record_write( zdf, &rec ) ) ) return(0);
    if ( !zdf_string_write( zdf, tracks -> label )   ) return(0);
     if ( !zdf_uint32_write( zdf, tracks -> ntracks ) ) return(0);
     if ( !zdf_uint32_write( zdf, tracks -> ndump )   ) return(0);
     if ( !zdf_uint32_write( zdf, tracks -> niter )   ) return(0);
     if ( !zdf_uint32_write( zdf, tracks -> nquants ) ) return(0);

    for( unsigned i=0; i < tracks -> nquants; i++) {
        if ( !zdf_string_write( zdf, tracks -> quants[i] ) ) return(0);
    }
    for( unsigned i=0; i < tracks -> nquants; i++) {
        if ( !zdf_string_write( zdf, tracks -> qlabels[i] ) ) return(0);
    }
    for( unsigned i=0; i < tracks -> nquants; i++) {
        if ( !zdf_string_write( zdf, tracks -> qunits[i] ) ) return(0);
    }

     return( reclen + size_zdf_track_info( tracks ) );
}
/* -----------------------------------------------------------------------------------------------
  zdf dataset
-------------------------------------------------------------------------------------------------- */

/**
 * [size_zdf_dataset_header description]
 * @param  dataset [description]
 * @return         [description]
 */
size_t size_zdf_dataset_header( const t_zdf_dataset* dataset ) {
    return size_zdf_uint32 + size_zdf_int32 + size_zdf_uint32 +
        dataset -> ndims * size_zdf_uint64;
}

/**
 * Write dataset header to file and modify the dataset object to include the
 * file position where the dataset is stored.
 *
 * @param  zdf     ZDF file handle
 * @param  dataset Dataset object
 * @return         Number of bytes written on success, 0 on error
 */
size_t zdf_dataset_header_write( t_zdf_file* zdf, t_zdf_dataset* dataset ) {

    // Get the file position for the dataset header and store it
    off_t offset = ftello( zdf -> fp );
    if ( offset < 0 ) return(0);
    dataset -> offset = offset;

     // Version 0x0001
     uint32_t id = dataset -> id;
     if ( !zdf_uint32_write( zdf, id )                  ) return(0);
     if ( !zdf_int32_write( zdf, dataset -> data_type ) ) return(0);
    if ( !zdf_uint32_write( zdf, dataset -> ndims )    ) return(0);

    for( unsigned i=0; i < dataset -> ndims; i++) {
         if ( !zdf_uint64_write( zdf, dataset -> count[i] ) ) return(0);
    }
    return( size_zdf_dataset_header( dataset ) );
}

/**
 * Read dataset header from file and store the file position where the dataset
 * header is stored.
 *
 * @param  zdf     ZDF file handle
 * @param  dataset Dataset object
 * @return         Number of bytes written on success, 0 on error
 */
size_t zdf_dataset_header_read( t_zdf_file* zdf, t_zdf_dataset* dataset ) {

    // Get the file position for the dataset header and store it
    off_t offset = ftello( zdf -> fp );
    if ( offset < 0 ) return(0);
    dataset -> offset = offset;

     // Version 0x0001
     uint32_t id;
    if ( !zdf_uint32_read( zdf, &id ) ) return(0);
    dataset -> id = id;

     if ( !zdf_int32_read( zdf, (int32_t *) &dataset -> data_type ) ) return(0);
    if ( !zdf_uint32_read( zdf, &dataset -> ndims ) ) return(0);

    for( unsigned i=0; i < dataset -> ndims; i++) {
         if ( !zdf_uint64_read( zdf, &dataset -> count[i] ) ) return(0);
    }
    return( size_zdf_dataset_header( dataset ) );
}

/**
 * Adds dataset to file
 * @param  zdf     ZDF file handle
 * @param  dataset Dataset object (includes pointer to data)
 * @return         Number of bytes written on success, 0 on error. The dataset object is also
 *                 modified to include a unique id.
 */
size_t zdf_add_dataset( t_zdf_file* zdf, t_zdf_dataset* dataset ){

    size_t length = zdf_sizeof( dataset -> data_type );
    for( unsigned i = 0; i < dataset -> ndims; i++ ) {
        length *= dataset -> count[i];
    }

    length += size_zdf_dataset_header( dataset ) ;

    t_zdf_record rec = {
        .id_version = ZDF_DATASET_ID,
        .name       = (char *) dataset -> name,
        .length     = length
    };

  size_t reclen;
  if ( !( reclen = zdf_record_write( zdf, &rec ) ) ) return(0);

  dataset -> id = ++ zdf -> ndatasets;
  if ( !zdf_dataset_header_write( zdf, dataset ) ) return(0);

  size_t count = 1;
  for( unsigned i=0; i < dataset -> ndims; i++) count *= dataset -> count[i];

     if ( !zdf_vector_write( zdf, dataset -> data, dataset -> data_type, count ) ) return(0);

     return( reclen + length );
}

/**
 * Adds a chunked dataset header to file
 * @param  zdf     ZDF file handle
 * @param  dataset Dataset object
 * @return         Number of bytes written on success, 0 on error. The dataset object is also
 *                 modified to include a unique id.
 */
size_t zdf_start_cdset( t_zdf_file* zdf, t_zdf_dataset* dataset ) {

    t_zdf_record rec = {
        .id_version = ZDF_CDSET_START_ID,
        .name       = (char *) dataset -> name,
        .length     = size_zdf_dataset_header( dataset )
    };

    size_t ok, len;

    len = ( ok =  zdf_record_write( zdf, &rec ) );
    if ( !ok ) return(0);

     dataset -> id = ++ zdf -> ndatasets;
    len += (ok = zdf_dataset_header_write( zdf, dataset ) );
    if ( !ok ) return(0);

    return( len );
}

/**
 * Returns size of chunk header
 * @param  dataset Dataset object
 * @return         Chunk header size in bytes
 */
size_t size_zdf_chunk_header(const t_zdf_dataset* dataset) {

    return size_zdf_uint32 + (size_zdf_uint32 + 16) + size_zdf_uint64 + 
           size_zdf_uint32 + 3 * dataset -> ndims * size_zdf_uint64;
}

/**
 * Adds a chunk header to file
 * @param  zdf     ZDF file handle
 * @param  dataset Dataset object
 * @param  chunk   Chunk object
 * @return         Number of bytes written on success, 0 on error.
 */
size_t zdf_write_chunk_header( t_zdf_file* zdf, t_zdf_dataset* dataset, t_zdf_chunk* chunk ){

    char name[16];
    snprintf( name, 16, "%08" PRIx64 "-chunk", dataset -> id);

    size_t length;
    length = zdf_sizeof( dataset -> data_type );
    for( unsigned i = 0; i < dataset -> ndims; i++ ) {
            length *= chunk -> count[i];
        }
    length += size_zdf_uint32 + 3 * dataset -> ndims * size_zdf_uint64;

    t_zdf_record rec = {
        .id_version = ZDF_CDSET_CHUNK_ID,
        .name       = (char *)name,
        .length     = length
    };

    size_t reclen;
    if ( !( reclen = zdf_record_write( zdf, &rec ) ) ) return(0);

    // ID of dataset this chunk belongs to
    if ( !zdf_uint32_write( zdf, dataset -> id ) ) return(0);

    // Size of chunk
    for( unsigned i=0; i < dataset -> ndims; i++) {
         if ( !zdf_uint64_write( zdf, chunk -> count[i] ) ) return(0);
    }

    // Start position
    for( unsigned i = 0; i < dataset -> ndims; i++) {
        if ( !zdf_uint64_write( zdf, chunk -> start[i] ) ) return(0);
    }

    // Stride
    for( unsigned i = 0; i < dataset -> ndims; i++) {
        if ( !zdf_uint64_write( zdf, chunk -> stride[i] ) ) return(0);
    }

    return( reclen + size_zdf_uint32 + 3 * dataset -> ndims * size_zdf_uint64 );

}


/**
 * Adds a chunk of dataset data to file
 * @param  zdf     ZDF file handle
 * @param  dataset Dataset object
 * @param  chunk   Chunk object (includes pointer to data). Data is expected to be contiguos in memory
 * @return         Number of bytes written on success, 0 on error.
 */
size_t zdf_write_cdset( t_zdf_file* zdf, t_zdf_dataset* dataset, t_zdf_chunk* chunk ){

    size_t headerlen = zdf_write_chunk_header( zdf, dataset, chunk );
    if ( !headerlen ) return(0);

     // Chunk data
     size_t count = 1;
     for( unsigned i = 0; i < dataset -> ndims; i++ ) count *= chunk -> count[i];

     size_t vectorlen;
     if ( !( vectorlen = zdf_vector_write( zdf, chunk -> data, dataset -> data_type, count ) ) )
             return(0);

     return( headerlen + vectorlen );
}

/**
 * Add an end marker for a chunked dataset to file
 * @param  zdf     ZDF file handle
 * @param  dataset Dataset object
 * @return         Number of bytes written on success, 0 on error.
 */
size_t zdf_end_cdset( t_zdf_file* zdf, t_zdf_dataset* dataset ){

    char name[16];
    snprintf( name, 16, "%08" PRIx64 "-end", dataset -> id);

    t_zdf_record rec = {
        .id_version = ZDF_CDSET_END_ID,
        .name       = name,
        .length     = 0
    };

    size_t reclen;
    if ( !( reclen = zdf_record_write( zdf, &rec ) ) ) return(0);

     return(reclen);
}


/**
 * Open a dataset and read the header. The dataset is selected by name.
 * 
 * If the dataset is not found the routine returns 0
 * 
 * @param  zdf     ZDF file handle
 * @param  dataset Dataset object
 * @return         Returns 1 if successful, 0 on error.
 */
size_t zdf_open_dataset( t_zdf_file* zdf, t_zdf_dataset* dataset ) {

    // Set file position after the magic number
    if ( fseek( zdf -> fp, 4, SEEK_SET ) ) return(-1);

    // Locate the requested dataset
    // If the dataset is not found there will be an EOF error signaled
    // and the routine returns 0
    int found = 0;
    while(!feof(zdf -> fp)) {
        t_zdf_record rec = { .name = NULL };

        if ( !zdf_record_read( zdf, &rec ) ) return(0);

        if ( rec.id_version == ZDF_CDSET_START_ID || rec.id_version == ZDF_DATASET_ID ) {
            int diff = strcmp( dataset -> name, rec.name );
            free( rec.name );

            if ( diff == 0 ) {
                // Read the dataset header
                if ( !zdf_dataset_header_read( zdf, dataset ) ) return(0);
                found = 1;
                break;
            } else {
                // Skip the record
                if ( !zdf_record_skip( zdf, &rec ) ) return(0);
            }
        } else {
            free( rec.name );
            if ( !zdf_record_skip( zdf, &rec ) ) return(0);
        }
    }

    if ( !found ) {
        fprintf(stderr,"(*error*) Unable to find dataset %s\n", dataset -> name);
        return(-1);
    }

    // re-position the file pointer at the end of the file
    if ( fseeko( zdf->fp, 0, SEEK_END ) ) return(0);
    return(1);

}

/**
 * Extends dataset dimensions. After this call the file pointer is positioned at the
 * end of the file.
 *
 * @param  zdf       ZDF file handle
 * @param  dataset   Datasete object
 * @param  new_count New dimensions for the dataset, must be >= than the previous
 *                   dimensions.
 * @return           Returns 1 if successful, 0 otherwise.
 */
int zdf_extend_dataset( t_zdf_file* zdf, t_zdf_dataset* dataset, uint64_t* new_count ) {

    for( unsigned i = 0; i < dataset -> ndims; i++ ) {
        if ( new_count[i] < dataset -> count[i] ) {
               fprintf(stderr,"(*error*) Invalid value for zdf_extend_dataset.\n");
               fprintf(stderr,"(*error*) New size is smaller than original size.\n");
             return(-1);
        }
        dataset -> count[i] = new_count[i];
    }

    off_t offset = dataset -> offset;
    if ( fseeko( zdf -> fp, offset , SEEK_SET ) ) return(0);
    if ( ! zdf_dataset_header_write( zdf, dataset ) ) return(0);
    if ( fseeko( zdf->fp, 0, SEEK_END ) ) return(0);

    return(1);
}

/* -----------------------------------------------------------------------------------------------
  zdf high level interface
-------------------------------------------------------------------------------------------------- */

/**
 * Opens ZDF file and adds TYPE, GRID, and ITERATION metadata
 * @param  zdf       File handle
 * @param  info      Grid information
 * @param  iteration Iteration information
 * @param  path      File path
 * @return           Returns 1 on success, 0 on error
 */
int zdf_open_grid_file( t_zdf_file *zdf, const t_zdf_grid_info *info,
    const t_zdf_iteration *iteration, char const path[] ){

    char filename[1024];

    // Ensure that the path is available
    create_path( path );

    // Build filename
    sprintf( filename, "%s/%s-%06u.zdf", path, info->name, (unsigned) iteration -> n );
    // printf("Saving filename %s\n", filename );

    // Create ZDF file
    if ( !zdf_open_file( zdf, filename, ZDF_CREATE ) ) {
        fprintf(stderr,"(*error*) Unable to open ZDF file, aborting.\n");
        return(-1);
    }

    // Add file type
    if ( !zdf_add_string( zdf, "TYPE", "grid") ) return(0);

    // Add grid info
    if ( !zdf_add_grid_info( zdf, info ) ) return(0);

    // Add iteration info
    if ( !zdf_add_iteration( zdf, iteration ) ) return(0);

    return( 1 );
}


/**
 * @brief Saves a ZDF grid file
 * 
 * @param  data       Pointer to grid data
 * @param  data_type  ZDF Data type of grid data
 * @param  info       Grid information
 * @param  iteration  Iteration information
 * @param  path       File path
 * @return            Returns 1 on success, 0 on error
 */
int zdf_save_grid( const void * data, const enum zdf_data_type data_type, const t_zdf_grid_info *info,
    const t_zdf_iteration *iteration, char const path[] )
{

    t_zdf_file zdf;

    // Open grid file
    if ( !zdf_open_grid_file( &zdf, info, iteration, path ) ) return(0);

    // Add dataset
    t_zdf_dataset dataset = {
        .name = info -> name,
        .data_type = data_type,
        .ndims = info->ndims,
        .data = (void *) data
    };
    for( unsigned i = 0; i < info->ndims; i ++) dataset.count[i] = info->count[i];

    if ( !zdf_add_dataset( &zdf, &dataset ) ) return(0);

    // Close ZDF file and return
    return( zdf_close_file( &zdf ) );
}

/**
 * Opens ZDF file and adds TYPE, PARTICLES, and ITERATION metadata
 * @param  zdf        File handle
 * @param  info       Particles information
 * @param  iteration  Iteration information
 * @param  path       File path
 * @return            1 on sucess, 0 on error
 */
int zdf_open_part_file( t_zdf_file *zdf, t_zdf_part_info *info,
    const t_zdf_iteration *iteration, char const path[] ){

    char filename[1024];

    // Ensure that the path is available
    create_path( path );

    // Build filename
    sprintf( filename, "%s/%s-%s-%06u.zdf", path, "particles", info->name, (unsigned) iteration -> n );
    //printf("Saving filename %s\n", filename );

    // Create ZDF file
    if ( !zdf_open_file( zdf, filename, ZDF_CREATE ) ) {
        fprintf(stderr,"(*error*) Unable to open ZDF file, aborting.\n");
        return(-1);
    }

    // Add file type
    if ( !zdf_add_string( zdf, "TYPE", "particles") ) return(0);

    // Add particle info
    if ( !zdf_add_part_info( zdf, info ) ) return(0);

    // Add iteration info
    if ( !zdf_add_iteration( zdf, iteration ) ) return(0);

    return(1);
}

/**
 * Adds individual particle quantity to file
 * @param  zdf  File handle
 * @param  name Quantity name
 * @param  data Quantity data (float32)
 * @param  np   Number of particles
 * @return      Number of bytes written on success, 0 on error
 */
int zdf_add_quant_part_file( t_zdf_file *zdf, const char *name, const float* data,
    const uint64_t np ) {

    t_zdf_dataset dataset = {
        .name = (char *) name,
        .data_type = zdf_float32,
        .ndims = 1,
        .data = (void *) data
    };

    dataset.count[0] = np;

    return( zdf_add_dataset( zdf, &dataset ) );

}

#ifdef __TEST_ZDF__

#include <math.h>

int main (int argc, const char * argv[]) {

    const unsigned NX = 128;
    float buf[NX];

    for(unsigned i = 0; i < NX; i++) {
        float x = 8 * (M_PI/NX) * (i+1);
        buf[i] = sin(x)/x;
    }

    t_zdf_grid_axis axis[1];
    axis[0] = (t_zdf_grid_axis) {
        .min = -1.0,
        .max =  1.0,
        .label = "axis label",
        .units = "axis units"
    };

    t_zdf_grid_info info = {
        .ndims = 1,
        .label = "data label",
        .units = "data units",
        .axis = axis
    };

    info.count[0] = NX;

    t_zdf_iteration iter = {
        .n = 123,
        .t = 12.3,
        .time_units = "time units"
    };

    zdf_save_grid( (void *) buf, zdf_float32, &info, &iter, "V1TEST" );

    return 0;
}


#if 0
int main (int argc, const char * argv[]) {

    const unsigned NX = 128;
    float buf[NX];

    for(unsigned i = 0; i < NX; i++) {
        float x = 8 * (M_PI/NX) * (i+1);
        buf[i] = sin(x)/x;
    }

    t_zdf_grid_axis axis[1];
    axis[0] = (t_zdf_grid_axis) {
        .min = -1.0,
        .max =  1.0,
        .label = "axis label",
        .units = "axis units"
    };

    t_zdf_grid_info info = {
        .ndims = 1,
        .label = "data label",
        .units = "data units",
        .axis = axis
    };

    info.count[0] = NX;

    t_zdf_iteration iter = {
        .n = 123,
        .t = 12.3,
        .time_units = "time units"
    };

    // Open file
    t_zdf_file file;
    zdf_open_grid_file( &file, &info, &iter, "chunk_test" );

    // Write chunked dataset header
    t_zdf_dataset dset = {
        .data_type = zdf_float32,
        .ndims = 1
    };
    dset.count[0] = 128;
    zdf_start_cdset( &file, "DATA", &dset );

    // Write chunks
    t_zdf_chunk chunk;
    chunk.count[0] = 16;
    chunk.start[0] = 0;
    chunk.stride[0] = 1;
    for( int i = 0; i < 8; i ++) {
        chunk.data = &buf[i*16];
        zdf_write_cdset( &file, &dset, &chunk );
        chunk.start[0] += 16;
    }

    // End dataset (optional)
    zdf_end_cdset( &file, &dset );

    // Close file
    zdf_close_file( &file );

    return 0;
}

#endif

#endif