text: // basisu.h
  // Copyright (C) 2019-2021 Binomial LLC. All Rights Reserved.
  // Important: If compiling with gcc, be sure strict aliasing is disabled: -fno-strict-aliasing
  //
  // Licensed under the Apache License, Version 2.0 (the "License");
  // you may not use this file except in compliance with the License.
  // You may obtain a copy of the License at
  //
  //    http://www.apache.org/licenses/LICENSE-2.0
  //
  // Unless required by applicable law or agreed to in writing, software
  // distributed under the License is distributed on an "AS IS" BASIS,
  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  // See the License for the specific language governing permissions and
  // limitations under the License.
  #pragma once
  
  #ifdef _MSC_VER
  
  	#pragma warning (disable : 4201)
  	#pragma warning (disable : 4127) // warning C4127: conditional expression is constant
  	#pragma warning (disable : 4530) // C++ exception handler used, but unwind semantics are not enabled.
  
  	#ifndef BASISU_NO_ITERATOR_DEBUG_LEVEL
  		//#define _HAS_ITERATOR_DEBUGGING 0
  
  		#if defined(_DEBUG) || defined(DEBUG)
  			// This is madness, but we need to disable iterator debugging in debug builds or the encoder is unsable because MSVC's iterator debugging implementation is totally broken.
  			#ifndef _ITERATOR_DEBUG_LEVEL
  			#define _ITERATOR_DEBUG_LEVEL 1
  			#endif
  			#ifndef _SECURE_SCL
  			#define _SECURE_SCL 1
  			#endif
  		#else // defined(_DEBUG) || defined(DEBUG)
  			#ifndef _SECURE_SCL
  			#define _SECURE_SCL 0
  			#endif
  			#ifndef _ITERATOR_DEBUG_LEVEL
  			#define _ITERATOR_DEBUG_LEVEL 0
  			#endif
  		#endif // defined(_DEBUG) || defined(DEBUG)
  
  	#endif // BASISU_NO_ITERATOR_DEBUG_LEVEL
  
  #endif // _MSC_VER
  
  #include <stdlib.h>
  #include <stdio.h>
  #include <math.h>
  #include <stdarg.h>
  #include <string.h>
  #include <memory.h>
  #include <limits.h>
  #include <stdint.h>
  
  #include <algorithm>
  #include <limits>
  #include <functional>
  #include <iterator>
  #include <type_traits>
  #include <assert.h>
  #include <random>
  
  #include "basisu_containers.h"
  
  #ifdef max
  #undef max
  #endif
  
  #ifdef min
  #undef min
  #endif
  
  #ifdef _WIN32
  #define strcasecmp _stricmp
  #endif
  
  // Set to one to enable debug printf()'s when any errors occur, for development/debugging. Especially useful for WebGL development.
  #ifndef BASISU_FORCE_DEVEL_MESSAGES
  #define BASISU_FORCE_DEVEL_MESSAGES 0
  #endif
  
  #define BASISU_NOTE_UNUSED(x) (void)(x)
  #define BASISU_ARRAY_SIZE(x) (sizeof(x) / sizeof(x[0]))
  #define BASISU_NO_EQUALS_OR_COPY_CONSTRUCT(x) x(const x &) = delete; x& operator= (const x &) = delete;
  #define BASISU_ASSUME(x) static_assert(x, #x);
  #define BASISU_OFFSETOF(s, m) offsetof(s, m)
  #define BASISU_STRINGIZE(x) #x
  #define BASISU_STRINGIZE2(x) BASISU_STRINGIZE(x)
  
  #if BASISU_FORCE_DEVEL_MESSAGES
  	#define BASISU_DEVEL_ERROR(...) do { basisu::debug_printf(__VA_ARGS__); } while(0)
  #else
  	#define BASISU_DEVEL_ERROR(...)
  #endif
  
  namespace basisu
  {
  	// Types/utilities
  
  #ifdef _WIN32
  	const char BASISU_PATH_SEPERATOR_CHAR = '\\';
  #else
  	const char BASISU_PATH_SEPERATOR_CHAR = '/';
  #endif
  
  	typedef basisu::vector<uint8_t> uint8_vec;
  	typedef basisu::vector<int16_t> int16_vec;
  	typedef basisu::vector<uint16_t> uint16_vec;
  	typedef basisu::vector<uint32_t> uint_vec;
  	typedef basisu::vector<uint64_t> uint64_vec;
  	typedef basisu::vector<int> int_vec;
  	typedef basisu::vector<bool> bool_vec;
  
  	void enable_debug_printf(bool enabled);
  	void debug_printf(const char *pFmt, ...);
  		
  
  	template <typename T> inline void clear_obj(T& obj) { memset(&obj, 0, sizeof(obj)); }
  
  	template <typename T0, typename T1> inline T0 lerp(T0 a, T0 b, T1 c) { return a + (b - a) * c; }
  
  	template <typename S> inline S maximum(S a, S b) { return (a > b) ? a : b; }
  	template <typename S> inline S maximum(S a, S b, S c) { return maximum(maximum(a, b), c); }
  	template <typename S> inline S maximum(S a, S b, S c, S d) { return maximum(maximum(maximum(a, b), c), d); }
  	
  	template <typename S> inline S minimum(S a, S b) {	return (a < b) ? a : b; }
  	template <typename S> inline S minimum(S a, S b, S c) {	return minimum(minimum(a, b), c); }
  	template <typename S> inline S minimum(S a, S b, S c, S d) { return minimum(minimum(minimum(a, b), c), d); }
  
  	inline float clampf(float value, float low, float high) { if (value < low) value = low; else if (value > high) value = high;	return value; }
  	inline float saturate(float value) { return clampf(value, 0, 1.0f); }
  	inline uint8_t minimumub(uint8_t a, uint8_t b) { return (a < b) ? a : b; }
  	inline uint32_t minimumu(uint32_t a, uint32_t b) { return (a < b) ? a : b; }
  	inline int32_t minimumi(int32_t a, int32_t b) { return (a < b) ? a : b; }
  	inline float minimumf(float a, float b) { return (a < b) ? a : b; }
  	inline uint8_t maximumub(uint8_t a, uint8_t b) { return (a > b) ? a : b; }
  	inline uint32_t maximumu(uint32_t a, uint32_t b) { return (a > b) ? a : b; }
  	inline int32_t maximumi(int32_t a, int32_t b) { return (a > b) ? a : b; }
  	inline float maximumf(float a, float b) { return (a > b) ? a : b; }
  	inline int squarei(int i) { return i * i; }
  	inline float squaref(float i) { return i * i; }
  	template<typename T> inline T square(T a) { return a * a; }
  
  	template <typename S> inline S clamp(S value, S low, S high) { return (value < low) ? low : ((value > high) ? high : value); }
  
  	inline uint32_t iabs(int32_t i) { return (i < 0) ? static_cast<uint32_t>(-i) : static_cast<uint32_t>(i);	}
  	inline uint64_t iabs64(int64_t i) {	return (i < 0) ? static_cast<uint64_t>(-i) : static_cast<uint64_t>(i); }
  
  	template<typename T> inline void clear_vector(T &vec) { vec.erase(vec.begin(), vec.end()); }		
  	template<typename T> inline typename T::value_type *enlarge_vector(T &vec, size_t n) { size_t cs = vec.size(); vec.resize(cs + n); return &vec[cs]; }
  
  	inline bool is_pow2(uint32_t x) { return x && ((x & (x - 1U)) == 0U); }
  	inline bool is_pow2(uint64_t x) { return x && ((x & (x - 1U)) == 0U); }
  
  	template<typename T> inline T open_range_check(T v, T minv, T maxv) { assert(v >= minv && v < maxv); BASISU_NOTE_UNUSED(minv); BASISU_NOTE_UNUSED(maxv); return v; }
  	template<typename T> inline T open_range_check(T v, T maxv) { assert(v < maxv); BASISU_NOTE_UNUSED(maxv); return v; }
  
  	inline uint32_t total_bits(uint32_t v) { uint32_t l = 0; for ( ; v > 0U; ++l) v >>= 1; return l; }
  
  	template<typename T> inline T saturate(T val) { return clamp(val, 0.0f, 1.0f); }
  
  	template<typename T, typename R> inline void append_vector(T &vec, const R *pObjs, size_t n) 
  	{ 
  		if (n)
  		{
  			const size_t cur_s = vec.size();
  			vec.resize(cur_s + n);
  			memcpy(&vec[cur_s], pObjs, sizeof(R) * n);
  		}
  	}
  
  	template<typename T> inline void append_vector(T &vec, const T &other_vec)
  	{
  		if (other_vec.size())
  			append_vector(vec, &other_vec[0], other_vec.size());
  	}
  
  	template<typename T> inline void vector_ensure_element_is_valid(T &vec, size_t idx)
  	{
  		if (idx >= vec.size())
  			vec.resize(idx + 1);
  	}
  
  	template<typename T> inline void vector_sort(T &vec)
  	{
  		if (vec.size())
  			std::sort(vec.begin(), vec.end());
  	}
  
  	template<typename T, typename U> inline bool unordered_set_contains(T& set, const U&obj)
  	{
  		return set.find(obj) != set.end();
  	}
  
  	template<typename T> int vector_find(const T &vec, const typename T::value_type &obj)
  	{
  		assert(vec.size() <= INT_MAX);
  		for (size_t i = 0; i < vec.size(); i++)
  			if (vec[i] == obj)
  				return static_cast<int>(i);
  		return -1;
  	}
  
  	template<typename T> void vector_set_all(T &vec, const typename T::value_type &obj)
  	{
  		for (size_t i = 0; i < vec.size(); i++)
  			vec[i] = obj;
  	}
  		
  	inline uint64_t read_be64(const void *p)
  	{
  		uint64_t val = 0;
  		for (uint32_t i = 0; i < 8; i++)
  			val |= (static_cast<uint64_t>(static_cast<const uint8_t *>(p)[7 - i]) << (i * 8));
  		return val;
  	}
  
  	inline void write_be64(void *p, uint64_t x)
  	{
  		for (uint32_t i = 0; i < 8; i++)
  			static_cast<uint8_t *>(p)[7 - i] = static_cast<uint8_t>(x >> (i * 8));
  	}
  
  	static inline uint16_t byteswap16(uint16_t x) { return static_cast<uint16_t>((x << 8) | (x >> 8)); }
  	static inline uint32_t byteswap32(uint32_t x) { return ((x << 24) | ((x << 8) & 0x00FF0000) | ((x >> 8) & 0x0000FF00) | (x >> 24)); }
  
  	inline uint32_t floor_log2i(uint32_t v)
  	{
  		uint32_t b = 0;
  		for (; v > 1U; ++b)
  			v >>= 1;
  		return b;
  	}
  
  	inline uint32_t ceil_log2i(uint32_t v)
  	{
  		uint32_t b = floor_log2i(v);
  		if ((b != 32) && (v > (1U << b)))
  			++b;
  		return b;
  	}
  
  	inline int posmod(int x, int y)
  	{
  		if (x >= 0)
  			return (x < y) ? x : (x % y);
  		int m = (-x) % y;
  		return (m != 0) ? (y - m) : m;
  	}
  
  	inline bool do_excl_ranges_overlap(int la, int ha, int lb, int hb)
  	{
  		assert(la < ha && lb < hb);
  		if ((ha <= lb) || (la >= hb)) return false;
  		return true;
  	}
  		
  	// Always little endian 2-4 byte unsigned int
  	template<uint32_t NumBytes>
  	struct packed_uint
  	{
  		uint8_t m_bytes[NumBytes];
  
  		inline packed_uint() { static_assert(NumBytes <= 4, "NumBytes <= 4"); }
  		inline packed_uint(uint32_t v) { *this = v; }
  		inline packed_uint(const packed_uint& other) { *this = other; }
  
  		inline packed_uint& operator= (uint32_t v) { for (uint32_t i = 0; i < NumBytes; i++) m_bytes[i] = static_cast<uint8_t>(v >> (i * 8)); return *this; }
  		inline packed_uint& operator= (const packed_uint& rhs) { memcpy(m_bytes, rhs.m_bytes, sizeof(m_bytes)); return *this; }
  
  		inline operator uint32_t() const
  		{
  			switch (NumBytes)
  			{
  				case 1:  return  m_bytes[0];
  				case 2:  return (m_bytes[1] << 8U) | m_bytes[0];
  				case 3:  return (m_bytes[2] << 16U) | (m_bytes[1] << 8U) | (m_bytes[0]);
  				default: return (m_bytes[3] << 24U) | (m_bytes[2] << 16U) | (m_bytes[1] << 8U) | (m_bytes[0]);
  			}
  		}
  	};
  
  	enum eZero { cZero };
  	enum eNoClamp { cNoClamp };
  	
  	// Rice/Huffman entropy coding
  		
  	// This is basically Deflate-style canonical Huffman, except we allow for a lot more symbols.
  	enum
  	{
  		cHuffmanMaxSupportedCodeSize = 16, cHuffmanMaxSupportedInternalCodeSize = 31, 
  		cHuffmanFastLookupBits = 10, 
  		cHuffmanMaxSymsLog2 = 14, cHuffmanMaxSyms = 1 << cHuffmanMaxSymsLog2,
  
  		// Small zero runs
  		cHuffmanSmallZeroRunSizeMin = 3, cHuffmanSmallZeroRunSizeMax = 10, cHuffmanSmallZeroRunExtraBits = 3,
  
  		// Big zero run
  		cHuffmanBigZeroRunSizeMin = 11, cHuffmanBigZeroRunSizeMax = 138, cHuffmanBigZeroRunExtraBits = 7,
  
  		// Small non-zero run
  		cHuffmanSmallRepeatSizeMin = 3, cHuffmanSmallRepeatSizeMax = 6, cHuffmanSmallRepeatExtraBits = 2,
  
  		// Big non-zero run
  		cHuffmanBigRepeatSizeMin = 7, cHuffmanBigRepeatSizeMax = 134, cHuffmanBigRepeatExtraBits = 7,
  
  		cHuffmanTotalCodelengthCodes = 21, cHuffmanSmallZeroRunCode = 17, cHuffmanBigZeroRunCode = 18, cHuffmanSmallRepeatCode = 19, cHuffmanBigRepeatCode = 20
  	};
  
  	static const uint8_t g_huffman_sorted_codelength_codes[] = { cHuffmanSmallZeroRunCode, cHuffmanBigZeroRunCode,	cHuffmanSmallRepeatCode, cHuffmanBigRepeatCode, 0, 8, 7, 9, 6, 0xA, 5, 0xB, 4, 0xC, 3, 0xD, 2, 0xE, 1, 0xF, 0x10 };
  	const uint32_t cHuffmanTotalSortedCodelengthCodes = sizeof(g_huffman_sorted_codelength_codes) / sizeof(g_huffman_sorted_codelength_codes[0]);
  
  	// GPU texture formats
  
  	enum class texture_format
  	{
  		cInvalidTextureFormat = -1,
  		
  		// Block-based formats
  		cETC1,			// ETC1
  		cETC1S,			// ETC1 (subset: diff colors only, no subblocks)
  		cETC2_RGB,		// ETC2 color block (basisu doesn't support ETC2 planar/T/H modes - just basic ETC1)
  		cETC2_RGBA,		// ETC2 EAC alpha block followed by ETC2 color block
  		cETC2_ALPHA,	// ETC2 EAC alpha block 
  		cBC1,				// DXT1
  		cBC3,				// DXT5 (BC4/DXT5A block followed by a BC1/DXT1 block)
  		cBC4,				// DXT5A
  		cBC5,				// 3DC/DXN (two BC4/DXT5A blocks)
  		cBC7,
  		cASTC4x4,		// LDR only
  		cPVRTC1_4_RGB,
  		cPVRTC1_4_RGBA,
  		cATC_RGB,
  		cATC_RGBA_INTERPOLATED_ALPHA,
  		cFXT1_RGB,
  		cPVRTC2_4_RGBA,
  		cETC2_R11_EAC,
  		cETC2_RG11_EAC,
  		cUASTC4x4,		
  		cBC1_NV,
  		cBC1_AMD,
  		
  		// Uncompressed/raw pixels
  		cRGBA32,
  		cRGB565,
  		cBGR565,
  		cRGBA4444,
  		cABGR4444
  	};
  
  	inline uint32_t get_bytes_per_block(texture_format fmt)
  	{
  		switch (fmt)
  		{
  		case texture_format::cETC1:
  		case texture_format::cETC1S:
  		case texture_format::cETC2_RGB:
  		case texture_format::cETC2_ALPHA:
  		case texture_format::cBC1:
  		case texture_format::cBC1_NV:
  		case texture_format::cBC1_AMD:
  		case texture_format::cBC4:
  		case texture_format::cPVRTC1_4_RGB:
  		case texture_format::cPVRTC1_4_RGBA:
  		case texture_format::cATC_RGB:
  		case texture_format::cPVRTC2_4_RGBA:
  		case texture_format::cETC2_R11_EAC:
  			return 8;
  		case texture_format::cRGBA32:
  			return sizeof(uint32_t) * 16;
  		default:
  			break;
  		}
  		return 16;
  	}
  
  	inline uint32_t get_qwords_per_block(texture_format fmt)
  	{
  		return get_bytes_per_block(fmt) >> 3;
  	}
  
  	inline uint32_t get_block_width(texture_format fmt)
  	{
  		BASISU_NOTE_UNUSED(fmt);
  		switch (fmt)
  		{
  		case texture_format::cFXT1_RGB:
  			return 8;
  		default:
  			break;
  		}
  		return 4;
  	}
  
  	inline uint32_t get_block_height(texture_format fmt)
  	{
  		BASISU_NOTE_UNUSED(fmt);
  		return 4;
  	}
  							
  } // namespace basisu
  
  