subsurface/uemis.c

/*
 * uemis.c
 *
 * UEMIS SDA file importer
 * AUTHOR:  Dirk Hohndel - Copyright 2011
 *
 * Licensed under the MIT license.
 */

#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <stdint.h>
#include <stdlib.h>
#define __USE_XOPEN
#include <time.h>
#include <regex.h>

#include "dive.h"
#include "uemis.h"

/*
 * following code is based on code found in at base64.sourceforge.net/b64.c
 * AUTHOR:         Bob Trower 08/04/01
 * COPYRIGHT:      Copyright (c) Trantor Standard Systems Inc., 2001
 * NOTE:           This source code may be used as you wish, subject to
 *                 the MIT license.
 */
/*
 * Translation Table to decode (created by Bob Trower)
 */
static const char cd64[]="|$$$}rstuvwxyz{$$$$$$$>?@ABCDEFGHIJKLMNOPQRSTUVW$$$$$$XYZ[\\]^_`abcdefghijklmnopq";

/*
 * decodeblock -- decode 4 '6-bit' characters into 3 8-bit binary bytes
 */
static void decodeblock( unsigned char in[4], unsigned char out[3] ) {
	out[ 0 ] = (unsigned char ) (in[0] << 2 | in[1] >> 4);
	out[ 1 ] = (unsigned char ) (in[1] << 4 | in[2] >> 2);
	out[ 2 ] = (unsigned char ) (((in[2] << 6) & 0xc0) | in[3]);
}

/*
 * decode a base64 encoded stream discarding padding, line breaks and noise
 */
static void decode( uint8_t *inbuf, uint8_t *outbuf, int inbuf_len ) {
	uint8_t in[4], out[3], v;
	int i,len,indx_in=0,indx_out=0;

	while (indx_in < inbuf_len) {
		for (len = 0, i = 0; i < 4 && (indx_in < inbuf_len); i++ ) {
			v = 0;
			while ((indx_in < inbuf_len) && v == 0) {
				v = inbuf[indx_in++];
				v = ((v < 43 || v > 122) ? 0 : cd64[ v - 43 ]);
				if (v)
					v = ((v == '$') ? 0 : v - 61);
			}
			if (indx_in < inbuf_len) {
				len++;
				if (v)
					in[i] = (v - 1);
			}
			else
				in[i] = 0;
		}
		if( len ) {
			decodeblock( in, out );
			for( i = 0; i < len - 1; i++ )
				outbuf[indx_out++] = out[i];
		}
	}
}
/* end code from Bob Trower */

/*
 * pressure_to_depth: In centibar. And when converting to
 * depth, I'm just going to always use saltwater, because I
 * think "true depth" is just stupid. From a diving standpoint,
 * "true depth" is pretty much completely pointless, unless
 * you're doing some kind of underwater surveying work.
 *
 * So I give water depths in "pressure depth", always assuming
 * salt water. So one atmosphere per 10m.
 */
static int pressure_to_depth(uint16_t value)
{
	double atm, cm;

	atm = (value / 100.0) / 1.01325;
	cm = 100 * atm + 0.5;
	return( (cm > 0) ? 10 * (long)cm : 0);
}

/*
 * convert the base64 data blog
 */
int uemis_convert_base64(char *base64, uint8_t **data) {
	int len,datalen;

	len = strlen(base64);
	datalen = (len/4 + 1)*3;
	if (datalen < 0x123+0x25) {
		/* less than header + 1 sample??? */
		fprintf(stderr,"suspiciously short data block\n");
	}
	*data = malloc(datalen);
	if (! *data) {
		datalen = 0;
		fprintf(stderr,"Out of memory\n");
		goto bail;
	}
	decode(base64, *data, len);

	if (memcmp(*data,"Dive\01\00\00",7))
		fprintf(stderr,"Missing Dive100 header\n");

bail:
	return datalen;
}

/*
 * parse uemis base64 data blob into struct dive
 */
void uemis_parse_divelog_binary(char *base64, void *datap) {
	int datalen;
	int i;
	uint8_t *data;
	struct sample *sample;
	struct dive **divep = datap;
	struct dive *dive = *divep;
	int template, gasoffset;

	datalen = uemis_convert_base64(base64, &data);

	/* dive template in use:
	   0 = air
	   1 = nitrox (B)
	   2 = nitrox (B+D)
	   3 = nitrox (B+T+D)
	   uemis cylinder data is insane - it stores seven tank settings in a block
	   and the template tells us which of the four groups of tanks we need to look at
	 */
	gasoffset = template = *(uint8_t *)(data+115);
	if (template == 3)
		gasoffset = 4;
	for (i = 0; i < template; i++) {
		float volume = *(float *)(data+116+25*(gasoffset + i)) * 1000.0;
		/* uemis always assumes a working pressure of 202.6bar (!?!?) - I first thought
		 * it was 3000psi, but testing against all my dives gets me that strange number.
		 * Still, that's of course completely bogus and shows they don't get how
		 * cylinders are named in non-metric parts of the world...
		 * we store the incorrect working pressure to get the SAC calculations "close"
		 * but the user will have to correct this manually
		 */
		dive->cylinder[i].type.size.mliter = volume;
		dive->cylinder[i].type.workingpressure.mbar = 202600;
		dive->cylinder[i].gasmix.o2.permille = *(uint8_t *)(data+120+25*(gasoffset + i)) * 10 + 0.5;
		dive->cylinder[i].gasmix.he.permille = 0;
	}
	/* first byte of divelog data is at offset 0x123 */
	i = 0x123;
	while ((i < datalen) && (*(uint16_t *)(data+i))) {
		/* it seems that a dive_time of 0 indicates the end of the valid readings */
		/* the SDA usually records more samples after the end of the dive --
		 * we want to discard those, but not cut the dive short; sadly the dive
		 * duration in the header is a) in minutes and b) up to 3 minutes short */
		if (*(uint16_t *)(data+i) > dive->duration.seconds + 180)
			break;
		sample = prepare_sample(divep);
		dive = *divep; /* prepare_sample might realloc the dive */
		sample->time.seconds = *(uint16_t *)(data+i);
		sample->depth.mm = pressure_to_depth(*(uint16_t *)(data+i+2));
		sample->temperature.mkelvin = (*(uint16_t *)(data+i+4) * 100) + 273150;
		sample->cylinderpressure.mbar= *(uint16_t *)(data+i+23) * 10;
		sample->cylinderindex = *(uint8_t *)(data+i+22);
		finish_sample(dive, sample);
		i += 0x25;
	}
	dive->duration.seconds = sample->time.seconds - 1;
	return;
}