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#include <stdint.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include "terragen.h"
// Some custom types and helper macros that
// allow for a portable file to number variable
// read procedure
typedef uint8_t DUET[2];
typedef uint8_t QUARTET[4];
typedef uint8_t OCTET[8];
#define DUET_TO_NUMBER(duet) ((duet[0]|duet[1]<<8))
#define QUARTET_TO_NUMBER(quartet) ((quartet[0])|(quartet[1]<<8)|(quartet[2]<<16)|(quartet[3]<<24))
int read_terrain(char const *filename, double **pbuffer, int *width, int *height, double *scale)
// [in] filename: path to the file to be read in
// [out] pbuffer: address of new allocated data buffer
// [out] width: width of the terrain
// [out] heigt: height of the terrain
// [out] return value: 0 if read in successfully 1 otherwise
{
FILE *file=fopen(filename, "rb");
if(!file)
return -1;
OCTET octet;
QUARTET quartet;
QUARTET quartet_marker;
DUET duet;
fread(octet, 8, 1, file);
if(memcmp(octet, "TERRAGEN", 8))
return -1;
fread(octet, 8, 1, file);
if(memcmp(octet, "TERRAIN ", 8))
return -1;
fread(quartet, 4, 1, file);
if(memcmp(quartet, "SIZE", 4))
return -1;
fread(duet, 2, 1, file);
fseek(file, 2, SEEK_CUR);
int size=DUET_TO_NUMBER(duet);
int xpts=0, ypts=0;
do
{
fread(quartet_marker, 4, 1, file);
if(memcmp(quartet_marker, "XPTS", 4)==0)
{
fread(duet, 2, 1, file);
fseek(file, 2, SEEK_CUR);
xpts=DUET_TO_NUMBER(duet);
continue;
}
if(memcmp(quartet_marker, "YPTS", 4)==0)
{
fread(duet, 2, 1, file);
fseek(file, 2, SEEK_CUR);
ypts=DUET_TO_NUMBER(duet);
continue;
}
// I'm going to ignore the other segments so long
// so we can leave the quartet marker test to the
// while condition
//if(strcmp(quartet_marker, "SIZE")) // Ignore SIZE
// fseek(file, 4, SEEK_CUR);
if(memcmp(quartet_marker, "SCAL", 4)==0&&scale) // Ignore SCAL
{
float fscale[3];
fread(&(fscale[0]), 4, 1, file);
fread(&(fscale[1]), 4, 1, file);
fread(&(fscale[2]), 4, 1, file);
scale[0]=fscale[0];
scale[1]=fscale[1];
scale[2]=fscale[2];
}
//if(strcmp(quartet_marker, "CRAD")) // Ignore CRAD
// fseek(file, 4, SEEK_CUR);
//if(strcmp(quartet_marker, "CRVM")) // Ignore CRVM
// fseek(file, 4, SEEK_CUR);
}while(memcmp(quartet_marker, "ALTW", 4));
int16_t height_scale, base_height;
fread(duet, 2, 1, file);
height_scale = DUET_TO_NUMBER(duet);
fread(duet, 2, 1, file);
base_height = DUET_TO_NUMBER(duet);
if(xpts==0&&ypts==0)
{
xpts=size+1;
ypts=size+1;
}
*width=xpts;
*height=ypts;
// The caller of this function is responsible
// to free the memory consumed by buffer
DUET *buffer=new DUET[xpts*ypts];
fread(buffer, 2, xpts*ypts, file);
*pbuffer=new double[xpts*ypts];
for(int y=0; y<ypts; y++)
{
for(int x=0; x<xpts; x++)
{
int16_t elev = (int16_t)DUET_TO_NUMBER( buffer[y*xpts+x] );
//memcpy(&elev, (buffer+(y*xpts+x)), 2);
(*pbuffer)[y*xpts+x]=
static_cast<double>(base_height+elev*height_scale/65536);
}
}
delete[] buffer;
// a last test, the next we read should be "EOF ", since currently the Terragen
// file format says, that "ALTW" must be the last segment of a file
// however it's no problem for _us_ if we've no "EOF " here, because it doesn't matter
fread(quartet, 4, 1, file);
if(memcmp(quartet, "EOF ", 4))
printf("read terrain file with \"EOF \" at the end\n");
fclose(file);
return 0;
}
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