pdfutils.c

/* $Id: pdfutils.c 9757 2009-03-19 12:10:17Z smekal $

    pdf_utils.c

    Copyright (C) 1992, 1993, 1994, 1995
    Maurice LeBrun          mjl@dino.ph.utexas.edu
    Institute for Fusion Studies    University of Texas at Austin

    Copyright (C) 2004  Joao Cardoso
    Copyright (C) 2004  Alan W. Irwin
    Copyright (C) 2004  Andrew Ross

    This file is part of PLplot.

    PLplot is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Library Public License as published
    by the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    PLplot is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Library General Public License for more details.

    You should have received a copy of the GNU Library General Public License
    along with PLplot; if not, write to the Free Software
    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

    These functions do the low-level reading/writing of portable data files.
    Data can be written to/read from either a file handle or memory buffer.
*/

#define NEED_PLDEBUG
#include "plplotP.h"

static void print_ieeef (void *, void *);
static int  pdf_wrx (const U_CHAR *x, long nitems, PDFstrm *pdfs);

static int debug = 0;

/*--------------------------------------------------------------------------*\
 * void pdf_set (string, value)
 *
 * Set an option.  Pretty sparse right now but you never know.
\*--------------------------------------------------------------------------*/

void
pdf_set(char *option, int value)
{
    if ( ! strcmp(option, "debug"))
    debug = value;
}

/*--------------------------------------------------------------------------*\
 * pdf_fopen()
 *
 * Initializes a PDFstrm for a file oriented device.
 * Used exactly like fopen().
\*--------------------------------------------------------------------------*/

PDFstrm *
pdf_fopen(const char *filename, const char *mode)
{
    PDFstrm *pdfs;

    dbug_enter("pdf_fopen");

    pdfs = (PDFstrm *) malloc(sizeof(PDFstrm));

    if (pdfs != NULL) {
    pdfs->buffer = NULL;
    pdfs->file = NULL;
    pdfs->bp = 0;
#ifdef PLPLOT_USE_TCL_CHANNELS
    pdfs->tclChan = NULL;
    if (1) {
        char new_mode[3];
        int binary = 0;
        char *m, *p;

        /* Copy over the mode, removing 'b' if needed */
        for (m = mode, p = new_mode; *m != 0; m++) {
            if (*m == 'b') {
                binary = 1;
            } else {
            *p = *m;
            p++;
            }
        }
        *p = 0;

        pdfs->tclChan = Tcl_OpenFileChannel(NULL, filename, new_mode, 0);
        if (pdfs->tclChan == NULL) {
        pdf_close(pdfs);
        pdfs = NULL;
        } else {
        if (binary) {
            Tcl_SetChannelOption(NULL, pdfs->tclChan, "-translation",
                     "binary");
        }
        }
    }
#else
    pdfs->file = fopen(filename, mode);
    if (pdfs->file == NULL) {
        pdf_close(pdfs);
        pdfs = NULL;
    }
#endif
    }

    return pdfs;
}

/*--------------------------------------------------------------------------*\
 * pdf_bopen()
 *
 * Initializes a PDFstrm for reading/writing to a memory buffer.
 * If buffer is NULL, a standard buffer is allocated.
\*--------------------------------------------------------------------------*/

PDFstrm *
pdf_bopen(U_CHAR *buffer, long bufmax)
{
    PDFstrm *pdfs;

    dbug_enter("pdf_bopen");

    pdfs = (PDFstrm *) malloc(sizeof(PDFstrm));

    if (pdfs != NULL) {
    pdfs->file = NULL;
#ifdef PLPLOT_USE_TCL_CHANNELS
    pdfs->tclChan = NULL;
#endif
    pdfs->bp = 0;

    if (buffer == NULL) {
        if (bufmax > 0)
        pdfs->bufmax = bufmax;
        else
        pdfs->bufmax = 2048;

        pdfs->buffer = (U_CHAR *) malloc(pdfs->bufmax);
        if (pdfs->buffer == NULL) {
        pdf_close(pdfs);
        pdfs = NULL;
        }
    }
    else {
        pdfs->bufmax = bufmax;
        pdfs->buffer = buffer;
    }
    }

    return pdfs;
}

/*--------------------------------------------------------------------------*\
 * pdf_finit()
 *
 * Initializes a PDFstrm for a file oriented device.
 * Like pdf_fopen() but an existing file handle is specified.
\*--------------------------------------------------------------------------*/

PDFstrm *
pdf_finit(FILE *file)
{
    PDFstrm *pdfs;

    dbug_enter("pdf_finit");

    pdfs = (PDFstrm *) malloc(sizeof(PDFstrm));

    if (pdfs != NULL) {
    pdfs->buffer = NULL;
    pdfs->file = file;
#ifdef PLPLOT_USE_TCL_CHANNELS
    pdfs->tclChan = NULL;
#endif
    pdfs->bp = 0;
    }

    return pdfs;
}

/*--------------------------------------------------------------------------*\
 * pdf_close()
 *
 * Closes a PDFstrm.
 * Used exactly like fclose().
\*--------------------------------------------------------------------------*/

int
pdf_close(PDFstrm *pdfs)
{
    dbug_enter("pdf_close");

    if (pdfs != NULL) {
    if (pdfs->file != NULL) {
        fclose(pdfs->file);
#ifdef PLPLOT_USE_TCL_CHANNELS
    } else if (pdfs->tclChan != NULL) {
        Tcl_Close(NULL, pdfs->tclChan);
#endif
    } else if (pdfs->buffer != NULL) {
        free ((void *) pdfs->buffer);
    }
    free((void *) pdfs);
    }
    return 0;
}

/*--------------------------------------------------------------------------*\
 * int pdf_putc()
 *
 * Writes a single character.
\*--------------------------------------------------------------------------*/

int
pdf_putc(int c, PDFstrm *pdfs)
{
    int result = EOF;

    if (pdfs->file != NULL) {
    result = putc(c, pdfs->file);
    pdfs->bp++;
#ifdef PLPLOT_USE_TCL_CHANNELS
    } else if (pdfs->tclChan != NULL) {
    result = Tcl_WriteChars(pdfs->tclChan, &c, 1);
    pdfs->bp++;
#endif
    } else if (pdfs->buffer != NULL) {
    if (pdfs->bp >= pdfs->bufmax) {
        pldebug("pdf_putc",
            "Increasing buffer to %d bytes\n", pdfs->bufmax);
        pdfs->bufmax += 512;
        if ((pdfs->buffer = (U_CHAR *) realloc((void *) pdfs->buffer, pdfs->bufmax))==NULL)
        {
          plexit("pdf_putc: Insufficient memory");
        }
    }
    pdfs->buffer[pdfs->bp++] = c;
    result = c;
    }
    else
    plexit("pdf_putc: Illegal operation");

    return result;
}

/*--------------------------------------------------------------------------*\
 * int pdf_getc()
 *
 * Reads a single character.
\*--------------------------------------------------------------------------*/

int
pdf_getc(PDFstrm *pdfs)
{
    int result = EOF;

    if (pdfs->file != NULL) {
    result = getc(pdfs->file);
    pdfs->bp++;
#ifdef PLPLOT_USE_TCL_CHANNELS
    } else if (pdfs->tclChan != NULL) {
    result = Tcl_Read(pdfs->tclChan, &result, 1);
    pdfs->bp++;
#endif
    } else if (pdfs->buffer != NULL) {
    if (pdfs->bp < pdfs->bufmax)
        result = pdfs->buffer[pdfs->bp++];
    }
    else
    plexit("pdf_getc: Illegal operation");

    return result;
}

/*--------------------------------------------------------------------------*\
 * int pdf_ungetc()
 *
 * Push back the last command read.
\*--------------------------------------------------------------------------*/

int
pdf_ungetc(int c, PDFstrm *pdfs)
{
    int result = EOF;

    if (pdfs->file != NULL) {
    result = ungetc(c, pdfs->file);
    if (pdfs->bp > 0)
        pdfs->bp--;
#ifdef PLPLOT_USE_TCL_CHANNELS
    } else if (pdfs->tclChan != NULL) {
    result = Tcl_Ungets(pdfs->tclChan, &c, 1, 0);
    if (pdfs->bp > 0)
        pdfs->bp--;
#endif
    } else if (pdfs->buffer != NULL) {
    if (pdfs->bp > 0) {
        pdfs->buffer[--pdfs->bp] = c;
        result = c;
    }
    }
    else
    plexit("pdf_ungetc: Illegal operation");

    return result;
}

/*--------------------------------------------------------------------------*\
 * int pdf_wrx()
 *
 * Writes a record.
\*--------------------------------------------------------------------------*/

static int
pdf_wrx(const U_CHAR *x, long nitems, PDFstrm *pdfs)
{
    int i, result = 0;

    if (pdfs->file != NULL) {
    result = fwrite(x, 1, nitems, pdfs->file);
    pdfs->bp += nitems;
#ifdef PLPLOT_USE_TCL_CHANNELS
    } else if (pdfs->tclChan != NULL) {
    result = Tcl_Write(pdfs->tclChan, x, nitems);
    pdfs->bp += nitems;
#endif
    } else if (pdfs->buffer != NULL) {
    for (i = 0; i < nitems; i++) {
        if (pdfs->bp >= pdfs->bufmax) {
        pldebug("pdf_wrx",
            "Increasing buffer to %d bytes\n", pdfs->bufmax);
        pdfs->bufmax += 512;
        if ((pdfs->buffer = (U_CHAR *)
            realloc((void *) (pdfs->buffer), pdfs->bufmax))==NULL)
            {
            plexit("pdf_wrx: Insufficient memory");
          }
        }
        pdfs->buffer[pdfs->bp++] = x[i];
    }
    result = i;
    }

    return result;
}

/*--------------------------------------------------------------------------*\
 * int pdf_rdx()
 *
 * Reads a record.
\*--------------------------------------------------------------------------*/

int
pdf_rdx(U_CHAR *x, long nitems, PDFstrm *pdfs)
{
    int i, result = 0;

    if (pdfs->file != NULL) {
    result = fread(x, 1, nitems, pdfs->file);
    pdfs->bp += nitems;
#ifdef PLPLOT_USE_TCL_CHANNELS
    } else if (pdfs->tclChan != NULL) {
    result = Tcl_ReadRaw(pdfs->tclChan, x, nitems);
    pdfs->bp += nitems;
#endif
    } else if (pdfs->buffer != NULL) {
    for (i = 0; i < nitems; i++) {
        if (pdfs->bp > pdfs->bufmax)
        break;
        x[i] = pdfs->buffer[pdfs->bp++];
    }
    result = i;
    }

    return result;
}

/*--------------------------------------------------------------------------*\
 * pdf_wr_header()
 *
 * Writes a header string.  Input string must be NULL-terminated.  The
 * written string is terminated by a new-line, not a NULL.  This is done
 * so you can type e.g. "% strings <file> | head" and get sensible output.
\*--------------------------------------------------------------------------*/

int
pdf_wr_header(PDFstrm *pdfs, char *header)
{
    int i;

    dbug_enter("pdf_wr_header");

    for (i = 0; i < 79; i++) {
    if (header[i] == '\0')
        break;
    if (pdf_putc(header[i], pdfs) == EOF)
        return PDF_WRERR;
    }
    if (pdf_putc('\n', pdfs) == EOF)
    return PDF_WRERR;

    return 0;
}

/*--------------------------------------------------------------------------*\
 * int pdf_rd_header
 *
 * Reads a newline-terminated header string from PDFstrm *pdfs, and
 * converts to a usual NULL-terminated string.  80 chars maximum assumed.
\*--------------------------------------------------------------------------*/

int
pdf_rd_header(PDFstrm *pdfs, char *header)
{
    int i, c;

    dbug_enter("pdf_rd_header");

    for (i = 0; i < 79; i++) {
    if ((c = pdf_getc(pdfs)) == EOF)
        return PDF_RDERR;

    header[i] = c;
    if (header[i] == '\n')
        break;
    }
    header[i] = '\0';       /* NULL terminate */
    return 0;
}

/*--------------------------------------------------------------------------*\
 * pdf_wr_string()
 *
 * Writes a null-terminated string.
\*--------------------------------------------------------------------------*/

int
pdf_wr_string(PDFstrm *pdfs, const char *string)
{
    int i;

    dbug_enter("pdf_wr_string");

    for (i = 0; i <= (int) strlen(string); i++) {
    if (pdf_putc(string[i], pdfs) == EOF)
        return PDF_WRERR;
    }

    return 0;
}

/*--------------------------------------------------------------------------*\
 * int pdf_rd_string
 *
 * Reads a null-terminated string from PDFstrm *pdfs.
 * A max of nmax chars are read.
\*--------------------------------------------------------------------------*/

int
pdf_rd_string(PDFstrm *pdfs, char *string, int nmax)
{
    int i, c;

    dbug_enter("pdf_rd_string");

    for (i = 0; i < nmax; i++) {
    if ((c = pdf_getc(pdfs)) == EOF)
        return PDF_RDERR;

    string[i] = c;
    if (c == '\0')
        break;
    }
    string[i] = '\0';       /* handle boundary case */
    return 0;
}

/*--------------------------------------------------------------------------*\
 * int pdf_wr_1byte()
 *
 * Writes a U_CHAR as a single byte.
\*--------------------------------------------------------------------------*/

int
pdf_wr_1byte(PDFstrm *pdfs, U_CHAR s)
{
    U_CHAR x[1];

    x[0] = s;
    if (pdf_wrx(x, 1, pdfs) != 1)
    return PDF_WRERR;

    return 0;
}

/*--------------------------------------------------------------------------*\
 * int pdf_rd_1byte()
 *
 * Reads a single byte, storing into a U_CHAR.
\*--------------------------------------------------------------------------*/

int
pdf_rd_1byte(PDFstrm *pdfs, U_CHAR *ps)
{
    U_CHAR x[1];

    if ( ! pdf_rdx(x, 1, pdfs))
    return PDF_RDERR;

    *ps = ((U_CHAR) x[0]);
    return 0;
}

/*--------------------------------------------------------------------------*\
 * pdf_wr_2bytes()
 *
 * Writes a U_SHORT as two single bytes, low end first.
\*--------------------------------------------------------------------------*/

int
pdf_wr_2bytes(PDFstrm *pdfs, U_SHORT s)
{
    U_CHAR x[2];

    x[0] = (U_CHAR) ((U_LONG) (s & (U_LONG) 0x00FF));
    x[1] = (U_CHAR) ((U_LONG) (s & (U_LONG) 0xFF00) >> 8);

    if (pdf_wrx(x, 2, pdfs) != 2)
    return PDF_WRERR;

    return 0;
}

/*--------------------------------------------------------------------------*\
 * pdf_rd_2bytes()
 *
 * Reads a U_SHORT from two single bytes, low end first.
\*--------------------------------------------------------------------------*/

int
pdf_rd_2bytes(PDFstrm *pdfs, U_SHORT *ps)
{
    U_CHAR x[2];

    if ( ! pdf_rdx(x, 2, pdfs))
    return PDF_RDERR;

    *ps = 0;
    *ps |= (U_LONG) x[0];
    *ps |= (U_LONG) x[1] << 8;

    return 0;
}

/*--------------------------------------------------------------------------*\
 * pdf_wr_2nbytes()
 *
 * Writes n U_SHORT's as 2n single bytes, low end first.
\*--------------------------------------------------------------------------*/

int
pdf_wr_2nbytes(PDFstrm *pdfs, U_SHORT *s, PLINT n)
{
    PLINT i;
    U_CHAR x[2];

    for (i = 0; i < n; i++) {
    x[0] = (U_CHAR) ((U_LONG) (s[i] & (U_LONG) 0x00FF));
    x[1] = (U_CHAR) ((U_LONG) (s[i] & (U_LONG) 0xFF00) >> 8);

    if (pdf_wrx(x, 2, pdfs) != 2)
        return PDF_WRERR;
    }
    return 0;
}

/*--------------------------------------------------------------------------*\
 * pdf_rd_2nbytes()
 *
 * Reads n U_SHORT's from 2n single bytes, low end first.
\*--------------------------------------------------------------------------*/

int
pdf_rd_2nbytes(PDFstrm *pdfs, U_SHORT *s, PLINT n)
{
    PLINT i;
    U_CHAR x[2];

    for (i = 0; i < n; i++) {
    if ( ! pdf_rdx(x, 2, pdfs))
        return PDF_RDERR;

    s[i] = 0;
    s[i] |= (U_SHORT) x[0];
    s[i] |= (U_SHORT) x[1] << 8;
    }
    return 0;
}

/*--------------------------------------------------------------------------*\
 * pdf_wr_4bytes()
 *
 * Writes an unsigned long as four single bytes, low end first.
\*--------------------------------------------------------------------------*/

int
pdf_wr_4bytes(PDFstrm *pdfs, U_LONG s)
{
    U_CHAR x[4];

    x[0] = (U_CHAR) ((s & (U_LONG) 0x000000FF));
    x[1] = (U_CHAR) ((s & (U_LONG) 0x0000FF00) >> 8);
    x[2] = (U_CHAR) ((s & (U_LONG) 0x00FF0000) >> 16);
    x[3] = (U_CHAR) ((s & (U_LONG) 0xFF000000) >> 24);

    if (pdf_wrx(x, 4, pdfs) != 4)
    return PDF_WRERR;

    return 0;
}

/*--------------------------------------------------------------------------*\
 * pdf_rd_4bytes()
 *
 * Reads an unsigned long from 4 single bytes, low end first.
\*--------------------------------------------------------------------------*/

int
pdf_rd_4bytes(PDFstrm *pdfs, U_LONG *ps)
{
    U_CHAR x[4];

    if ( ! pdf_rdx(x, 4, pdfs))
    return PDF_RDERR;

    *ps = 0;
    *ps |= (U_LONG) x[0];
    *ps |= (U_LONG) x[1] << 8;
    *ps |= (U_LONG) x[2] << 16;
    *ps |= (U_LONG) x[3] << 24;

    return 0;
}

/*--------------------------------------------------------------------------*\
 * Here is the IEEE floating point specification in both 32 bit and 64 bit
 * precisions, from page 9 of "IEEE Standard for Binary Floating-Point
 * Arithmetic", copyright 1985, IEEE Std 754-1985:
 *
 *
 *                             Single Format
 *
 * msb means most significant bit
 * lsb means least significant bit
 *
 *   1         8                                23
 * _____________________________________________________________________
 * |   |                |                                              |
 * | s |       e        |                        f                     |
 * |___|________________|______________________________________________|
 *      msb          lsb msb                                        lsb
 *
 *
 *
 *                             Double Format
 *
 * msb means most significant bit
 * lsb means least significant bit
 *
 *   1        11                                52
 * _____________________________________________________________________
 * |   |                |                                              |
 * | s |       e        |                        f                     |
 * |___|________________|______________________________________________|
 *      msb          lsb msb                                        lsb
 *
 *
 * (Thanks to: Andy Mai (mai@ncar.ucar.edu))
 *
 *
 * According to "inmos: Transputer instruction set" the IEEE standard
 * specifies the floating format as:
 *
 *      s exp frac
 *
 * Where: s = sign bit  (1 bit)
 *      exp = exponent (8 bits for 32 bit float / 11 bits for 64 bit float)
 *      frac = fraction (23 bits for 32 bit float / 52 bits for 64 bit float)
 *
 * value of (s exp frac) = (-1)^s * 1.frac * 2^(exp-bias) ; if exp not 0
 *                         (-1)^s * 0.frac * 2^(1-bias) ; if exp = 0
 *
 * where bias = 127 for 32 bit float
 *       bias = 1023 for 64 bit float
 *
 * (Thanks to: Tom Bjorkholm(TBJORKHOLM@abo.fi))
 *
\*--------------------------------------------------------------------------*/

/*--------------------------------------------------------------------------*\
 * int pdf_wr_ieeef()
 *
 * Writes a float in IEEE single precision (32 bit) format.
\*--------------------------------------------------------------------------*/

int
pdf_wr_ieeef(PDFstrm *pdfs, float f)
{
    double fdbl, fmant, f_new;
    float fsgl, f_tmp;
    int istat, exp, e_new, e_off, bias = 127;
    U_LONG value, s_ieee, e_ieee, f_ieee;

    if (f == 0.0) {
    value = 0;
    return (pdf_wr_4bytes(pdfs, value));
    }
    fdbl = f;
    fsgl = (float)fdbl;
    fmant = frexp(fdbl, &exp);

    if (fmant < 0)
    s_ieee = 1;
    else
    s_ieee = 0;

    fmant = fabs(fmant);
    f_new = 2 * fmant;
    e_new = exp - 1;

    if (e_new < 1 - bias) {
    e_off = e_new - (1 - bias);
    e_ieee = 0;
    f_tmp = (float)(f_new * pow((double) 2.0, (double) e_off));
    }
    else {
    e_ieee = e_new + bias;
    f_tmp = (float)(f_new - 1);
    }
    f_ieee = (U_LONG)(f_tmp * 8388608);     /* multiply by 2^23 */

    if (e_ieee > 255) {
    if (debug)
        fprintf(stderr, "pdf_wr_ieeef: Warning -- overflow\n");
    e_ieee = 255;
    }

    s_ieee = s_ieee << 31;
    e_ieee = e_ieee << 23;

    value = s_ieee | e_ieee | f_ieee;

    if ((istat = pdf_wr_4bytes(pdfs, value)))
    return (istat);

    if (debug) {
    fprintf(stderr, "Float value (written):      %g\n", fsgl);
    print_ieeef(&fsgl, &value);
    }

    return 0;
}

/*--------------------------------------------------------------------------*\
 * int pdf_rd_ieeef()
 *
 * Reads a float from a IEEE single precision (32 bit) format.
\*--------------------------------------------------------------------------*/

int
pdf_rd_ieeef(PDFstrm *pdfs, float *pf)
{
    double f_new, f_tmp;
    float fsgl;
    int istat, exp, bias = 127;
    U_LONG value, s_ieee, e_ieee, f_ieee;

    if ((istat = pdf_rd_4bytes(pdfs, &value)))
    return (istat);

    s_ieee = (value & (U_LONG) 0x80000000) >> 31;
    e_ieee = (value & (U_LONG) 0x7F800000) >> 23;
    f_ieee = (value & (U_LONG) 0x007FFFFF);

    f_tmp = (double) f_ieee / 8388608.0;    /* divide by 2^23 */

    if (e_ieee == 0) {
    exp = 1 - bias;
    f_new = f_tmp;
    }
    else {
    exp = (int) e_ieee - bias;
    f_new = 1.0 + f_tmp;
    }

    fsgl = (float)(f_new * pow(2.0, (double) exp));
    if (s_ieee == 1)
    fsgl = -fsgl;

    *pf = fsgl;

    if (debug) {
    fprintf(stderr, "Float value (read):      %g\n", fsgl);
    print_ieeef(&fsgl, &value);
    }

    return 0;
}

/*--------------------------------------------------------------------------*\
 * print_ieeef()
 *
 * Prints binary representation for numbers pointed to by arguments.
 * The first argument is the original float, the second is the
 * IEEE representation.  They should be the same on any machine that
 * uses IEEE floats.
\*--------------------------------------------------------------------------*/

static void
print_ieeef(void *vx, void *vy)
{
    int i;
    U_LONG f, *x = (U_LONG *) vx, *y = (U_LONG *) vy;
    char bitrep[33];

    bitrep[32] = '\0';

    f = *x;
    for (i = 0; i < 32; i++) {
    if (f & 1)
        bitrep[32 - i - 1] = '1';
    else
        bitrep[32 - i - 1] = '0';
    f = f >> 1;
    }
    fprintf(stderr, "Binary representation:      ");
    fprintf(stderr, "%s\n", bitrep);

    f = *y;
    for (i = 0; i < 32; i++) {
    if (f & 1)
        bitrep[32 - i - 1] = '1';
    else
        bitrep[32 - i - 1] = '0';
    f = f >> 1;
    }
    fprintf(stderr, "Converted representation:   ");
    fprintf(stderr, "%s\n\n", bitrep);

    return;
}

/*--------------------------------------------------------------------------*\
 * plAlloc2dGrid()
 *
 * Allocates a block of memory for use as a 2-d grid of PLFLT's.
 * Resulting array can be indexed as f[i][j] anywhere.  This is to be used
 * instead of PLFLT f[nx][ny], which is less useful.  Note that this type
 * of allocation is required by the PLplot functions which take a 2-d
 * grids of PLFLT's as an argument, such as plcont() and plot3d().
 * Example usage:
 *
 *   PLFLT **z;
 *
 *   Alloc2dGrid(&z, XPTS, YPTS);
\*--------------------------------------------------------------------------*/

void
plAlloc2dGrid(PLFLT ***f, PLINT nx, PLINT ny)
{
    PLINT i;

    if ((*f = (PLFLT **) calloc(nx, sizeof(PLFLT *)))==NULL)
        plexit("Memory allocation error in \"plAlloc2dGrid\"");

    for (i = 0; i < nx; i++) {
    if (((*f)[i] = (PLFLT *) calloc(ny ,sizeof(PLFLT)))==NULL)
       plexit("Memory allocation error in \"plAlloc2dGrid\"");
    }

}

/*--------------------------------------------------------------------------*\
 * Free2dGrid()
 *
 * Frees a block of memory allocated with Alloc2dGrid().
\*--------------------------------------------------------------------------*/

void
plFree2dGrid(PLFLT **f, PLINT nx, PLINT ny)
{
    PLINT i;

    for (i = 0; i < nx; i++)
    free((void *) f[i]);

    free((void *) f);
}

/*--------------------------------------------------------------------------*\
 * MinMax2dGrid()
 *
 * Finds the maximum and minimum of a 2d matrix allocated with plAllc2dGrid().
 * NaN and +/- infinity values are ignored.
\*--------------------------------------------------------------------------*/

void
plMinMax2dGrid(PLFLT **f, PLINT nx, PLINT ny, PLFLT *fmax, PLFLT *fmin)
{
    int i, j;
    PLFLT m, M;

    if (!finite(f[0][0])) {
        M = -HUGE_VAL;
        m = HUGE_VAL;
    }
    else
        M = m = f[0][0];

    for (i = 0; i < nx; i++) {
    for (j = 0; j < ny; j++) {
        if (!finite(f[i][j])) continue;
        if (f[i][j] > M) M = f[i][j];
        if (f[i][j] < m) m = f[i][j];
    }
    }
    *fmax = M;
    *fmin = m;
}

---