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|
/**************************************************************************
* *
* Regina - A Normal Surface Theory Calculator *
* Computational Engine *
* *
* Copyright (c) 1999-2025, Ben Burton *
* For further details contact Ben Burton (bab@debian.org). *
* *
* This program is free software; you can redistribute it and/or *
* modify it under the terms of the GNU General Public License as *
* published by the Free Software Foundation; either version 2 of the *
* License, or (at your option) any later version. *
* *
* As an exception, when this program is distributed through (i) the *
* App Store by Apple Inc.; (ii) the Mac App Store by Apple Inc.; or *
* (iii) Google Play by Google Inc., then that store may impose any *
* digital rights management, device limits and/or redistribution *
* restrictions that are required by its terms of service. *
* *
* This program 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 *
* General Public License for more details. *
* *
* You should have received a copy of the GNU General Public License *
* along with this program. If not, see <https://www.gnu.org/licenses/>. *
* *
**************************************************************************/
#include <algorithm>
#include <bit> // for std::endian
#include <cctype>
#include <cstring>
#include <fstream>
#include <iostream>
#include "link/spatiallink.h"
#include "utilities/exception.h"
// Converts two successive bytes into a single unsigned 16-bit integer, where
// the input is treated as big-endian (regardless of the endianness of the
// current platform).
//
// PRE: the array c has length at least 2.
static constexpr uint16_t KPInt16(const char c[]) {
// The double-casts are to ensure that, if char is signed, then
// -1 casts up to 255 (and not 65535).
return (uint16_t(uint8_t(c[0])) << 8) |
(uint16_t(uint8_t(c[1])));
}
// Converts four successive bytes into a single unsigned 32-bit integer, where
// the input is treated as big-endian (regardless of the endianness of the
// current platform).
//
// PRE: the array c has length at least 4.
static constexpr uint32_t KPInt32(const char c[]) {
// The double-casts are to ensure that, if char is signed, then
// -1 casts up to 255 (and not 65535).
return (uint32_t(uint8_t(c[0])) << 24) |
(uint32_t(uint8_t(c[1])) << 16) |
(uint32_t(uint8_t(c[2])) << 8) |
(uint32_t(uint8_t(c[3])));
}
// Converts four successive bytes into a single 32-bit float, where the input
// is treated as big-endian (regardless of the endianness of the current
// platform).
//
// THIS NEEDS TESTING ON DIFFERENT PLATFORMS. I have seen a promise (on
// cppreference.com) that float and double should use IEEE-754 binary32 and
// IEEE-754 binary64 respectively.
//
// However, I believe endianness still matters. My own main platforms are
// all little-endian.
//
// PRE: the array c has length at least 4.
float KPFloat32(const char c[]) {
static_assert(std::endian::native == std::endian::big ||
std::endian::native == std::endian::little,
"Only big-endian and little-endian platforms are supported.");
if constexpr (std::endian::native == std::endian::big) {
return *(reinterpret_cast<const float*>(c));
} else {
const char x[4] = { c[3], c[2], c[1], c[0] };
return *(reinterpret_cast<const float*>(x));
}
}
// Converts eight successive bytes into a single 64-bit double, where the input
// is treated as big-endian (regardless of the endianness of the current
// platform).
//
// THIS NEEDS TESTING ON DIFFERENT PLATFORMS. See the comments above for
// KPFloat32().
//
// PRE: the array c has length at least 8.
double KPFloat64(const char c[]) {
static_assert(std::endian::native == std::endian::big ||
std::endian::native == std::endian::little,
"Only big-endian and little-endian platforms are supported.");
if constexpr (std::endian::native == std::endian::big) {
return *(reinterpret_cast<const double*>(c));
} else {
const char x[8] = { c[7], c[6], c[5], c[4], c[3], c[2], c[1], c[0] };
return *(reinterpret_cast<const double*>(x));
}
}
namespace regina {
SpatialLink SpatialLink::fromKnotPlot(const char* filename) {
// When we move to C++23, I think we get access to fixed-size floating-point
// types. I should check this.
if (sizeof(float) != 4 || sizeof(double) != 8)
throw NotImplemented("fromKnotPlot(): binary file format requires "
"a platform with 32-bit floats and 64-bit doubles");
std::ifstream in(filename, std::ios::binary);
if (! in)
throw FileError("fromKnotPlot(): could not open the given file");
// The file _must_ begin with "KnotPlot 1.0".
char banner[12];
in.read(banner, 12);
if (! in)
throw InvalidInput("fromKnotPlot(): unexpected end of file");
if (std::memcmp(banner, "KnotPlot 1.0", 12) != 0)
throw InvalidInput("fromKnotPlot(): file has no KnotPlot header");
// The header ends with '\f' followed by another arbitrary character.
in.ignore(std::numeric_limits<std::streamsize>::max(), '\f');
if (! in)
throw InvalidInput("fromKnotPlot(): unexpected end of file");
in.get();
if (! in)
throw InvalidInput("fromKnotPlot(): unexpected end of file");
SpatialLink ans;
bool finished = false;
while (! finished) {
// Extract the next field.
char field[4];
in.read(field, 4);
if (! in)
throw InvalidInput("fromKnotPlot(): unexpected end of file");
if (std::islower(field[0])) {
if (std::islower(field[1])) {
// This field contains no data at all.
switch (KPInt32(field)) {
case KPInt32("endf"):
// End of data file.
finished = true;
break;
case KPInt32("comp"):
ans.components_.emplace_back();
break;
}
} else
throw InvalidInput("fromKnotPlot(): invalid field name");
} else if (std::isupper(field[0])) {
if (std::islower(field[1])) {
// This field contains exactly 4 bytes of data.
char data[4];
in.read(data, 4);
if (! in)
throw InvalidInput(
"fromKnotPlot(): unexpected end of file");
switch (KPInt32(field)) {
case KPInt32("Attr"):
// Attributes are stored as a 4-byte integer:
// the lowest order bit is 1 for closed, or 0 for open.
// If the attributes are missing entirely then the
// component is assumed to be closed.
uint32_t attr = KPInt32(data);
if (! (attr & 1))
throw InvalidInput("fromKnotPlot(): file contains "
"an open link component, with free ends");
break;
}
} else if (std::isupper(field[1])) {
// This field contains a 4-byte integer indicating how many
// _subsequent_ bytes the field contains.
char lenData[4];
in.read(lenData, 4);
if (! in)
throw InvalidInput("fromKnotPlot(): "
"unexpected end of file");
uint32_t len = KPInt32(lenData);
switch (KPInt32(field)) {
#if 0
case KPInt32("NAME"):
// Name of the knot/link.
// For now we do not actually use this.
{
char* data = new char[len];
in.read(data, len);
if (! in) {
delete [] data;
throw InvalidInput("fromKnotPlot(): "
"unexpected end of file");
}
std::string name(data, len);
delete[] data;
// ... send name to wherever it needs to go.
}
break;
#endif
case KPInt32("LOCS"):
// 2-byte unsigned integers for coordinates.
// Preceeded by scale and offset data; I am assuming
// based on inspecting some KnotPlot sample files that
// these are stored as four 4-byte floats (scale,
// offset_x, offset_y, offset_z).
if (ans.components_.empty())
throw InvalidInput("fromKnotPlot(): found "
"coordinates before the first component");
if (len % 6 != 4)
throw InvalidInput("fromKnotPlot(): invalid "
"LOCS field length");
{
char data[16];
in.read(data, 16);
if (! in)
throw InvalidInput(
"fromKnotPlot(): unexpected end of file");
float scale = KPFloat32(data);
float offset[3] = {
KPFloat32(data + 4),
KPFloat32(data + 8),
KPFloat32(data + 12) };
for (size_t i = 16; i < len; i += 6) {
in.read(data, 6);
if (! in)
throw InvalidInput("fromKnotPlot(): "
"unexpected end of file");
// Note: we already tested above that
// components_ is non-empty.
ans.components_.back().emplace_back(
float(KPInt16(data)) * scale + offset[0],
float(KPInt16(data + 2)) * scale +
offset[1],
float(KPInt16(data + 4)) * scale +
offset[2]);
}
}
break;
case KPInt32("LOCF"):
// 4-byte floats for coordinates.
if (ans.components_.empty())
throw InvalidInput("fromKnotPlot(): found "
"coordinates before the first component");
if (len % 12 != 0)
throw InvalidInput("fromKnotPlot(): invalid "
"LOCF field length");
{
char data[12];
for (size_t i = 0; i < len; i += 12) {
in.read(data, 12);
if (! in)
throw InvalidInput("fromKnotPlot(): "
"unexpected end of file");
// Note: we already tested above that
// components_ is non-empty.
ans.components_.back().emplace_back(
KPFloat32(data),
KPFloat32(data + 4),
KPFloat32(data + 8));
}
}
break;
case KPInt32("LOCD"):
// 8-byte doubles for coordinates.
if (ans.components_.empty())
throw InvalidInput("fromKnotPlot(): found "
"coordinates before the first component");
if (len % 24 != 0)
throw InvalidInput("fromKnotPlot(): invalid "
"LOCD field length");
{
char data[24];
for (size_t i = 0; i < len; i += 24) {
in.read(data, 24);
if (! in)
throw InvalidInput("fromKnotPlot(): "
"unexpected end of file");
// Note: we already tested above that
// components_ is non-empty.
ans.components_.back().emplace_back(
KPFloat64(data),
KPFloat64(data + 8),
KPFloat64(data + 16));
}
}
break;
case KPInt32("LOCC"):
// This format is not documented alongside the others,
// and I'm not convinced I'm interpreting it correctly.
// For now we explicitly disable it until such a time
// as we can find out exactly what it is meant to store.
//
// Below is the code for what I _thought_ it was meant
// to hold, but some tests on KnotPlot files from the
// wild suggest this is not actually what's going on.
//
// The good news: AFAICT this is used more often with
// open paths (not closed loops), which we do not
// support anyway.
throw InvalidInput("fromKnotPlot(): found a block "
"of translations (not coordinates), which "
"are not currently supported");
#if 0
// This appears to hold a series of translations,
// not absolute coordinates.
// The translations use signed 1-byte integers for
// coordinates.
// Before the translations we have two triples of
// 4-byte floats:
// - scaling factors for x, y, z translations;
// - the starting coordinates.
if (ans.components_.empty())
throw InvalidInput("fromKnotPlot(): found "
"coordinates before the first component");
if (len % 3 != 0)
throw InvalidInput("fromKnotPlot(): invalid "
"LOCC field length");
{
char data[12];
in.read(data, 12);
if (! in)
throw InvalidInput(
"fromKnotPlot(): unexpected end of file");
float scale[3] = {
KPFloat32(data + 4),
KPFloat32(data + 8),
KPFloat32(data + 12) };
in.read(data, 12);
if (! in)
throw InvalidInput(
"fromKnotPlot(): unexpected end of file");
Node pos(
KPFloat32(data + 4),
KPFloat32(data + 8),
KPFloat32(data + 12));
// Note: we already tested above that
// components_ is non-empty.
ans.components_.back().push_back(pos);
for (size_t i = 24; i < len; i += 3) {
in.read(data, 3);
if (! in)
throw InvalidInput("fromKnotPlot(): "
"unexpected end of file");
// Cast from char to int8_t, because we have
// no guarantee that char is signed.
pos.x += (float(int8_t(data[0])) * scale[0]);
pos.y += (float(int8_t(data[1])) * scale[1]);
pos.z += (float(int8_t(data[2])) * scale[2]);
ans.components_.back().push_back(pos);
}
}
break;
#endif
/*
case KPInt32("COLR"):
// This holds an RGB triple specifying the colour of
// the current component. We might wish to support
// this at some later date.
*/
default:
// Skip over the remainder of this field.
in.ignore(len);
if (! in)
throw InvalidInput(
"fromKnotPlot(): unexpected end of file");
break;
}
} else
throw InvalidInput("fromKnotPlot(): invalid field name");
} else
throw InvalidInput("fromKnotPlot(): invalid field name");
}
if (ans.components_.empty()) {
// Assume the file used some other method of storing coordinates, and
// that we were not able to read it.
throw InvalidInput("fromKnotPlot(): no coordinates could be read");
}
// A final basic sanity check: to be embedded, each component must have at
// least three nodes.
for (const auto& c : ans.components_)
if (c.size() < 3)
throw InvalidInput("fromKnotPlot(): read a component with "
"< 3 nodes");
return ans;
}
} // namespace regina
|
