paysages3d/src/rendering/tools/pack.c

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#include "pack.h"
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <inttypes.h>
#include <math.h>
#include <unistd.h>
#include "color.h"
#include "euclid.h"
struct PackStream
{
FILE* fd;
int write;
};
#define pack754_32(f) (pack754((f), 32, 8))
#define pack754_64(f) (pack754((f), 64, 11))
#define unpack754_32(i) (unpack754((i), 32, 8))
#define unpack754_64(i) (unpack754((i), 64, 11))
static uint64_t pack754(double f, unsigned bits, unsigned expbits)
{
double fnorm;
int shift;
long long sign, exp, significand;
unsigned significandbits = bits - expbits - 1; // -1 for sign bit
if (f == 0.0) return 0; // get this special case out of the way
// check sign and begin normalization
if (f < 0) { sign = 1; fnorm = -f; }
else { sign = 0; fnorm = f; }
// get the normalized form of f and track the exponent
shift = 0;
while(fnorm >= 2.0) { fnorm /= 2.0; shift++; }
while(fnorm < 1.0) { fnorm *= 2.0; shift--; }
fnorm = fnorm - 1.0;
// calculate the binary form (non-double) of the significand data
significand = fnorm * ((1LL<<significandbits) + 0.5f);
// get the biased exponent
exp = shift + ((1<<(expbits-1)) - 1); // shift + bias
// return the final answer
return (sign<<(bits-1)) | (exp<<(bits-expbits-1)) | significand;
}
static double unpack754(uint64_t i, unsigned bits, unsigned expbits)
{
double result;
long long shift;
unsigned bias;
unsigned significandbits = bits - expbits - 1; // -1 for sign bit
if (i == 0) return 0.0;
// pull the significand
result = (i&((1LL<<significandbits)-1)); // mask
result /= (1LL<<significandbits); // convert back to double
result += 1.0f; // add the one back on
// deal with the exponent
bias = (1<<(expbits-1)) - 1;
shift = ((i>>significandbits)&((1LL<<expbits)-1)) - bias;
while(shift > 0) { result *= 2.0; shift--; }
while(shift < 0) { result /= 2.0; shift++; }
// sign it
result *= (i>>(bits-1))&1? -1.0: 1.0;
return result;
}
PackStream* packReadFile(const char* filepath)
{
PackStream* result;
result = malloc(sizeof(PackStream));
result->fd = fopen(filepath, "rb");
result->write = 0;
return result;
}
PackStream* packWriteFile(const char* filepath)
{
PackStream* result;
result = malloc(sizeof(PackStream));
result->fd = fopen(filepath, "wb");
result->write = 1;
return result;
}
void packCloseStream(PackStream* stream)
{
if (stream->write)
{
fflush(stream->fd);
}
fclose(stream->fd);
free(stream);
}
void packWriteDouble(PackStream* stream, double* value)
{
int written;
uint64_t servalue;
servalue = pack754_64(*value);
written = fwrite(&servalue, sizeof(uint64_t), 1, stream->fd);
assert(written == 1);
}
void packReadDouble(PackStream* stream, double* value)
{
int read;
uint64_t servalue;
read = fread(&servalue, sizeof(uint64_t), 1, stream->fd);
assert(read == 1);
*value = unpack754_64(servalue);
}
void packWriteInt(PackStream* stream, int* value)
{
int written;
written = fprintf(stream->fd, "%d;", *value);
assert(written > 1);
}
void packReadInt(PackStream* stream, int* value)
{
int read;
read = fscanf(stream->fd, "%d;", value);
assert(read == 1);
}
void packWriteString(PackStream* stream, char* value, int max_length)
{
int written;
int len = strnlen(value, max_length - 1) + 1;
packWriteInt(stream, &len);
written = fwrite(value, 1, len, stream->fd);
assert(written == len);
}
void packReadString(PackStream* stream, char* value, int max_length)
{
int read;
int len;
packReadInt(stream, &len);
if (len > max_length)
{
len = max_length;
}
read = fread(value, 1, len, stream->fd);
assert(read == len);
}