/* $Header$ */

/* Purpose: Description (definition) of Precision-Preserving Compression (PPC) functions */

/* Copyright (C) 2015--present Charlie Zender
   This file is part of NCO, the netCDF Operators. NCO is free software.
   You may redistribute and/or modify NCO under the terms of the 
   3-Clause BSD License with exceptions described in the LICENSE file */

/* Usage:
   #include "nco_ppc.h" *//* Precision-Preserving Compression */

#ifndef NCO_PPC_H
#define NCO_PPC_H

/* Standard header files */
#include <ctype.h> /* isalnum(), isdigit(), tolower() */
#include <float.h> /* FLT_RADIX */
#include <math.h> /* sin cos cos sin 3.14159 */
#include <stdio.h> /* stderr, FILE, NULL, printf */
#include <stdlib.h> /* abs, getopt, malloc, strtol */
#include <string.h> /* strcmp() */

/* 3rd party vendors */
#include <netcdf.h> /* netCDF definitions and C library */
#include "nco_netcdf.h" /* NCO wrappers for netCDF C library */

/* Personal headers */
#include "nco.h" /* netCDF Operator (NCO) definitions */
#include "nco_mmr.h" /* Memory management */
#include "nco_mta.h" /* Multi-argument parsing */
#include "nco_sng_utl.h" /* String utilities */

/* Minimum number of explicit significand bits to preserve when zeroing/bit-masking floating point values
   Codes will preserve at least two explicit bits, IEEE significand representation contains one implicit bit
   Thus preserving at least three bits would preserve approximately one sigificant decimal digit
   20211231: Allow only one explicit bit to be preserved (useful for NSB algorithms like BitRound)
   Used in nco_ppc_bitmask() and nco_ppc_bitmask_scl() */
#define NCO_PPC_BIT_XPL_NBR_MIN 1

/* Macro to return sign of floating point values, used in Digit Round */
#define SIGN(x)	((x) < 0 ? -1 : 1)

#ifdef __cplusplus
extern "C" {
#endif /* __cplusplus */

  void 
  nco_ppc_ini /* [fnc] Set PPC based on user specifications */
  (const int nc_id, /* I [id] netCDF input file ID */
   int *dfl_lvl, /* O [enm] Deflate level */
   const int fl_out_fmt, /* I [enm] Output file format */
   char *const ppc_arg[], /* I [sng] List of user-specified ppc */
   const int ppc_nbr, /* I [nbr] Number of ppc specified */
   trv_tbl_sct * const trv_tbl); /* I/O [sct] Traversal table */
  
  void
  nco_ppc_att_prc /* [fnc] create ppc att from trv_tbl */
  (const int nc_id, /* I [id] Input netCDF file ID */
   const trv_tbl_sct * const trv_tbl); /* I [sct] GTT (Group Traversal Table) */
  
  void
  nco_ppc_set_dflt /* Set the ppc value for all non-coordinate vars */
  (const int nc_id, /* I [id] netCDF input file ID */
   const char * const ppc_arg, /* I [sng] user input for precision-preserving compression */
   trv_tbl_sct * const trv_tbl); /* I/O [sct] Traversal table */
  
  void
  nco_ppc_set_var
  (const char * const var_nm_fll, /* I [sng] Variable name to find */
   const char * const ppc_arg, /* I [sng] user input for precision-preserving compression */
   trv_tbl_sct * const trv_tbl); /* I/O [sct] Traversal table */

  void
  nco_ppc_around /* [fnc] Replace op1 values by their values rounded to decimal precision prc */
  (const int prc, /* I [nbr] Precision-preserving compression, i.e., number of total or decimal significant digits */
   const nc_type type, /* I [enm] netCDF type of operand */
   const long sz, /* I [nbr] Size (in elements) of operand */
   const int has_mss_val, /* I [flg] Flag for missing values */
   ptr_unn mss_val, /* I [val] Value of missing value */
   ptr_unn op1); /* I/O [val] Values of first operand */

  void
  nco_ppc_bitmask /* [fnc] Mask-out insignificant bits of significand */
  (const int nsd, /* I [nbr] Number of significant digits, i.e., arithmetic precision */
   const nc_type type, /* I [enm] netCDF type of operand */
   const long sz, /* I [nbr] Size (in elements) of operand */
   const int has_mss_val, /* I [flg] Flag for missing values */
   ptr_unn mss_val, /* I [val] Value of missing value */
   ptr_unn op1); /* I/O [val] Values of first operand */
  
  double /* [frc] Rounded value */
  nco_ppc_bitmask_scl /* [fnc] Round input value significand by specified number of bits */
  (const double val_xct, /* I [frc] Exact value to round */
   const int bit_xpl_nbr_zro); /* I [nbr] Bits to round */

#ifdef __cplusplus
} /* end extern "C" */
#endif /* __cplusplus */

#endif /* NCO_PPC_H */
