jpgd.h - external/github.com/BinomialLLC/basis_universal - Git at Google

 // jpgd.h - C++ class for JPEG decompression.
 // Public domain, Rich Geldreich <richgel99@gmail.com>
 #ifndef JPEG_DECODER_H
 #define JPEG_DECODER_H

 #include <stdlib.h>
 #include <stdio.h>
 #include <setjmp.h>
 #include <assert.h>
 #include <stdint.h>

 #ifdef _MSC_VER
 #define JPGD_NORETURN __declspec(noreturn)
 #elif defined(__GNUC__)
 #define JPGD_NORETURN __attribute__ ((noreturn))
 #else
 #define JPGD_NORETURN
 #endif

 #define JPGD_HUFF_TREE_MAX_LENGTH 512
 #define JPGD_HUFF_CODE_SIZE_MAX_LENGTH 256

 namespace jpgd
 {
 	typedef unsigned char  uint8;
 	typedef   signed short int16;
 	typedef unsigned short uint16;
 	typedef unsigned int   uint;
 	typedef   signed int   int32;

 	// Loads a JPEG image from a memory buffer or a file.
 	// req_comps can be 1 (grayscale), 3 (RGB), or 4 (RGBA).
 	// On return, width/height will be set to the image's dimensions, and actual_comps will be set to the either 1 (grayscale) or 3 (RGB).
 	// Notes: For more control over where and how the source data is read, see the decompress_jpeg_image_from_stream() function below, or call the jpeg_decoder class directly.
 	// Requesting a 8 or 32bpp image is currently a little faster than 24bpp because the jpeg_decoder class itself currently always unpacks to either 8 or 32bpp.
 	unsigned char* decompress_jpeg_image_from_memory(const unsigned char* pSrc_data, int src_data_size, int* width, int* height, int* actual_comps, int req_comps, uint32_t flags = 0);
 	unsigned char* decompress_jpeg_image_from_file(const char* pSrc_filename, int* width, int* height, int* actual_comps, int req_comps, uint32_t flags = 0);

 	// Success/failure error codes.
 	enum jpgd_status
 	{
 		JPGD_SUCCESS = 0, JPGD_FAILED = -1, JPGD_DONE = 1,
 		JPGD_BAD_DHT_COUNTS = -256, JPGD_BAD_DHT_INDEX, JPGD_BAD_DHT_MARKER, JPGD_BAD_DQT_MARKER, JPGD_BAD_DQT_TABLE,
 		JPGD_BAD_PRECISION, JPGD_BAD_HEIGHT, JPGD_BAD_WIDTH, JPGD_TOO_MANY_COMPONENTS,
 		JPGD_BAD_SOF_LENGTH, JPGD_BAD_VARIABLE_MARKER, JPGD_BAD_DRI_LENGTH, JPGD_BAD_SOS_LENGTH,
 		JPGD_BAD_SOS_COMP_ID, JPGD_W_EXTRA_BYTES_BEFORE_MARKER, JPGD_NO_ARITHMITIC_SUPPORT, JPGD_UNEXPECTED_MARKER,
 		JPGD_NOT_JPEG, JPGD_UNSUPPORTED_MARKER, JPGD_BAD_DQT_LENGTH, JPGD_TOO_MANY_BLOCKS,
 		JPGD_UNDEFINED_QUANT_TABLE, JPGD_UNDEFINED_HUFF_TABLE, JPGD_NOT_SINGLE_SCAN, JPGD_UNSUPPORTED_COLORSPACE,
 		JPGD_UNSUPPORTED_SAMP_FACTORS, JPGD_DECODE_ERROR, JPGD_BAD_RESTART_MARKER,
 		JPGD_BAD_SOS_SPECTRAL, JPGD_BAD_SOS_SUCCESSIVE, JPGD_STREAM_READ, JPGD_NOTENOUGHMEM, JPGD_TOO_MANY_SCANS
 	};

 	// Input stream interface.
 	// Derive from this class to read input data from sources other than files or memory. Set m_eof_flag to true when no more data is available.
 	// The decoder is rather greedy: it will keep on calling this method until its internal input buffer is full, or until the EOF flag is set.
 	// It the input stream contains data after the JPEG stream's EOI (end of image) marker it will probably be pulled into the internal buffer.
 	// Call the get_total_bytes_read() method to determine the actual size of the JPEG stream after successful decoding.
 	class jpeg_decoder_stream
 	{
 	public:
 		jpeg_decoder_stream() { }
 		virtual ~jpeg_decoder_stream() { }

 		// The read() method is called when the internal input buffer is empty.
 		// Parameters:
 		// pBuf - input buffer
 		// max_bytes_to_read - maximum bytes that can be written to pBuf
 		// pEOF_flag - set this to true if at end of stream (no more bytes remaining)
 		// Returns -1 on error, otherwise return the number of bytes actually written to the buffer (which may be 0).
 		// Notes: This method will be called in a loop until you set *pEOF_flag to true or the internal buffer is full.
 		virtual int read(uint8* pBuf, int max_bytes_to_read, bool* pEOF_flag) = 0;
 	};

 	// stdio FILE stream class.
 	class jpeg_decoder_file_stream : public jpeg_decoder_stream
 	{
 		jpeg_decoder_file_stream(const jpeg_decoder_file_stream&);
 		jpeg_decoder_file_stream& operator =(const jpeg_decoder_file_stream&);

 		FILE* m_pFile;
 		bool m_eof_flag, m_error_flag;

 	public:
 		jpeg_decoder_file_stream();
 		virtual ~jpeg_decoder_file_stream();

 		bool open(const char* Pfilename);
 		void close();

 		virtual int read(uint8* pBuf, int max_bytes_to_read, bool* pEOF_flag);
 	};

 	// Memory stream class.
 	class jpeg_decoder_mem_stream : public jpeg_decoder_stream
 	{
 		const uint8* m_pSrc_data;
 		uint m_ofs, m_size;

 	public:
 		jpeg_decoder_mem_stream() : m_pSrc_data(NULL), m_ofs(0), m_size(0) { }
 		jpeg_decoder_mem_stream(const uint8* pSrc_data, uint size) : m_pSrc_data(pSrc_data), m_ofs(0), m_size(size) { }

 		virtual ~jpeg_decoder_mem_stream() { }

 		bool open(const uint8* pSrc_data, uint size);
 		void close() { m_pSrc_data = NULL; m_ofs = 0; m_size = 0; }

 		virtual int read(uint8* pBuf, int max_bytes_to_read, bool* pEOF_flag);
 	};

 	// Loads JPEG file from a jpeg_decoder_stream.
 	unsigned char* decompress_jpeg_image_from_stream(jpeg_decoder_stream* pStream, int* width, int* height, int* actual_comps, int req_comps, uint32_t flags = 0);

 	enum
 	{
 		JPGD_IN_BUF_SIZE = 8192, JPGD_MAX_BLOCKS_PER_MCU = 10, JPGD_MAX_HUFF_TABLES = 8, JPGD_MAX_QUANT_TABLES = 4,
 		JPGD_MAX_COMPONENTS = 4, JPGD_MAX_COMPS_IN_SCAN = 4, JPGD_MAX_BLOCKS_PER_ROW = 16384, JPGD_MAX_HEIGHT = 32768, JPGD_MAX_WIDTH = 32768
 	};

 	typedef int16 jpgd_quant_t;
 	typedef int16 jpgd_block_t;

 	class jpeg_decoder
 	{
 	public:
 		enum
 		{
 			cFlagLinearChromaFiltering = 1
 		};

 		// Call get_error_code() after constructing to determine if the stream is valid or not. You may call the get_width(), get_height(), etc.
 		// methods after the constructor is called. You may then either destruct the object, or begin decoding the image by calling begin_decoding(), then decode() on each scanline.
 		jpeg_decoder(jpeg_decoder_stream* pStream, uint32_t flags = cFlagLinearChromaFiltering);

 		~jpeg_decoder();

 		// Call this method after constructing the object to begin decompression.
 		// If JPGD_SUCCESS is returned you may then call decode() on each scanline.

 		int begin_decoding();

 		// Returns the next scan line.
 		// For grayscale images, pScan_line will point to a buffer containing 8-bit pixels (get_bytes_per_pixel() will return 1).
 		// Otherwise, it will always point to a buffer containing 32-bit RGBA pixels (A will always be 255, and get_bytes_per_pixel() will return 4).
 		// Returns JPGD_SUCCESS if a scan line has been returned.
 		// Returns JPGD_DONE if all scan lines have been returned.
 		// Returns JPGD_FAILED if an error occurred. Call get_error_code() for a more info.
 		int decode(const void** pScan_line, uint* pScan_line_len);

 		inline jpgd_status get_error_code() const { return m_error_code; }

 		inline int get_width() const { return m_image_x_size; }
 		inline int get_height() const { return m_image_y_size; }

 		inline int get_num_components() const { return m_comps_in_frame; }

 		inline int get_bytes_per_pixel() const { return m_dest_bytes_per_pixel; }
 		inline int get_bytes_per_scan_line() const { return m_image_x_size * get_bytes_per_pixel(); }

 		// Returns the total number of bytes actually consumed by the decoder (which should equal the actual size of the JPEG file).
 		inline int get_total_bytes_read() const { return m_total_bytes_read; }

 	private:
 		jpeg_decoder(const jpeg_decoder&);
 		jpeg_decoder& operator =(const jpeg_decoder&);

 		typedef void (*pDecode_block_func)(jpeg_decoder*, int, int, int);

 		struct huff_tables
 		{
 			bool ac_table;
 			uint  look_up[256];
 			uint  look_up2[256];
 			uint8 code_size[JPGD_HUFF_CODE_SIZE_MAX_LENGTH];
 			uint  tree[JPGD_HUFF_TREE_MAX_LENGTH];
 		};

 		struct coeff_buf
 		{
 			uint8* pData;
 			int block_num_x, block_num_y;
 			int block_len_x, block_len_y;
 			int block_size;
 		};

 		struct mem_block
 		{
 			mem_block* m_pNext;
 			size_t m_used_count;
 			size_t m_size;
 			char m_data[1];
 		};

 		jmp_buf m_jmp_state;
 		uint32_t m_flags;
 		mem_block* m_pMem_blocks;
 		int m_image_x_size;
 		int m_image_y_size;
 		jpeg_decoder_stream* m_pStream;

 		int m_progressive_flag;

 		uint8 m_huff_ac[JPGD_MAX_HUFF_TABLES];
 		uint8* m_huff_num[JPGD_MAX_HUFF_TABLES];      // pointer to number of Huffman codes per bit size
 		uint8* m_huff_val[JPGD_MAX_HUFF_TABLES];      // pointer to Huffman codes per bit size
 		jpgd_quant_t* m_quant[JPGD_MAX_QUANT_TABLES]; // pointer to quantization tables
 		int m_scan_type;                              // Gray, Yh1v1, Yh1v2, Yh2v1, Yh2v2 (CMYK111, CMYK4114 no longer supported)
 		int m_comps_in_frame;                         // # of components in frame
 		int m_comp_h_samp[JPGD_MAX_COMPONENTS];       // component's horizontal sampling factor
 		int m_comp_v_samp[JPGD_MAX_COMPONENTS];       // component's vertical sampling factor
 		int m_comp_quant[JPGD_MAX_COMPONENTS];        // component's quantization table selector
 		int m_comp_ident[JPGD_MAX_COMPONENTS];        // component's ID
 		int m_comp_h_blocks[JPGD_MAX_COMPONENTS];
 		int m_comp_v_blocks[JPGD_MAX_COMPONENTS];
 		int m_comps_in_scan;                          // # of components in scan
 		int m_comp_list[JPGD_MAX_COMPS_IN_SCAN];      // components in this scan
 		int m_comp_dc_tab[JPGD_MAX_COMPONENTS];       // component's DC Huffman coding table selector
 		int m_comp_ac_tab[JPGD_MAX_COMPONENTS];       // component's AC Huffman coding table selector
 		int m_spectral_start;                         // spectral selection start
 		int m_spectral_end;                           // spectral selection end
 		int m_successive_low;                         // successive approximation low
 		int m_successive_high;                        // successive approximation high
 		int m_max_mcu_x_size;                         // MCU's max. X size in pixels
 		int m_max_mcu_y_size;                         // MCU's max. Y size in pixels
 		int m_blocks_per_mcu;
 		int m_max_blocks_per_row;
 		int m_mcus_per_row, m_mcus_per_col;
 		int m_mcu_org[JPGD_MAX_BLOCKS_PER_MCU];
 		int m_total_lines_left;                       // total # lines left in image
 		int m_mcu_lines_left;                         // total # lines left in this MCU
 		int m_num_buffered_scanlines;
 		int m_real_dest_bytes_per_scan_line;
 		int m_dest_bytes_per_scan_line;               // rounded up
 		int m_dest_bytes_per_pixel;                   // 4 (RGB) or 1 (Y)
 		huff_tables* m_pHuff_tabs[JPGD_MAX_HUFF_TABLES];
 		coeff_buf* m_dc_coeffs[JPGD_MAX_COMPONENTS];
 		coeff_buf* m_ac_coeffs[JPGD_MAX_COMPONENTS];
 		int m_eob_run;
 		int m_block_y_mcu[JPGD_MAX_COMPONENTS];
 		uint8* m_pIn_buf_ofs;
 		int m_in_buf_left;
 		int m_tem_flag;

 		uint8 m_in_buf_pad_start[64];
 		uint8 m_in_buf[JPGD_IN_BUF_SIZE + 128];
 		uint8 m_in_buf_pad_end[64];

 		int m_bits_left;
 		uint m_bit_buf;
 		int m_restart_interval;
 		int m_restarts_left;
 		int m_next_restart_num;
 		int m_max_mcus_per_row;
 		int m_max_blocks_per_mcu;

 		int m_max_mcus_per_col;
 		uint m_last_dc_val[JPGD_MAX_COMPONENTS];
 		jpgd_block_t* m_pMCU_coefficients;
 		int m_mcu_block_max_zag[JPGD_MAX_BLOCKS_PER_MCU];
 		uint8* m_pSample_buf;
 		uint8* m_pSample_buf_prev;
 		int m_crr[256];
 		int m_cbb[256];
 		int m_crg[256];
 		int m_cbg[256];
 		uint8* m_pScan_line_0;
 		uint8* m_pScan_line_1;
 		jpgd_status m_error_code;
 		int m_total_bytes_read;

 		bool m_ready_flag;
 		bool m_eof_flag;
 		bool m_sample_buf_prev_valid;

 		inline int check_sample_buf_ofs(int ofs) const { assert(ofs >= 0); assert(ofs < m_max_blocks_per_row * 64); return ofs; }
 		void free_all_blocks();
 		JPGD_NORETURN void stop_decoding(jpgd_status status);
 		void* alloc(size_t n, bool zero = false);
 		void word_clear(void* p, uint16 c, uint n);
 		void prep_in_buffer();
 		void read_dht_marker();
 		void read_dqt_marker();
 		void read_sof_marker();
 		void skip_variable_marker();
 		void read_dri_marker();
 		void read_sos_marker();
 		int next_marker();
 		int process_markers();
 		void locate_soi_marker();
 		void locate_sof_marker();
 		int locate_sos_marker();
 		void init(jpeg_decoder_stream* pStream, uint32_t flags);
 		void create_look_ups();
 		void fix_in_buffer();
 		void transform_mcu(int mcu_row);
 		coeff_buf* coeff_buf_open(int block_num_x, int block_num_y, int block_len_x, int block_len_y);
 		inline jpgd_block_t* coeff_buf_getp(coeff_buf* cb, int block_x, int block_y);
 		void load_next_row();
 		void decode_next_row();
 		void make_huff_table(int index, huff_tables* pH);
 		void check_quant_tables();
 		void check_huff_tables();
 		bool calc_mcu_block_order();
 		int init_scan();
 		void init_frame();
 		void process_restart();
 		void decode_scan(pDecode_block_func decode_block_func);
 		void init_progressive();
 		void init_sequential();
 		void decode_start();
 		void decode_init(jpeg_decoder_stream* pStream, uint32_t flags);
 		void H2V2Convert();
 		uint32_t H2V2ConvertFiltered();
 		void H2V1Convert();
 		void H2V1ConvertFiltered();
 		void H1V2Convert();
 		void H1V2ConvertFiltered();
 		void H1V1Convert();
 		void gray_convert();
 		void find_eoi();
 		inline uint get_char();
 		inline uint get_char(bool* pPadding_flag);
 		inline void stuff_char(uint8 q);
 		inline uint8 get_octet();
 		inline uint get_bits(int num_bits);
 		inline uint get_bits_no_markers(int numbits);
 		inline int huff_decode(huff_tables* pH);
 		inline int huff_decode(huff_tables* pH, int& extrabits);

 		// Clamps a value between 0-255.
 		static inline uint8 clamp(int i)
 		{
 			if (static_cast<uint>(i) > 255)
 				i = (((~i) >> 31) & 0xFF);
 			return static_cast<uint8>(i);
 		}
 		int decode_next_mcu_row();

 		static void decode_block_dc_first(jpeg_decoder* pD, int component_id, int block_x, int block_y);
 		static void decode_block_dc_refine(jpeg_decoder* pD, int component_id, int block_x, int block_y);
 		static void decode_block_ac_first(jpeg_decoder* pD, int component_id, int block_x, int block_y);
 		static void decode_block_ac_refine(jpeg_decoder* pD, int component_id, int block_x, int block_y);
 	};

 } // namespace jpgd

 #endif // JPEG_DECODER_H
	// jpgd.h - C++ class for JPEG decompression.
	// Public domain, Rich Geldreich <richgel99@gmail.com>
	#ifndef JPEG_DECODER_H
	#define JPEG_DECODER_H

	#include <stdlib.h>
	#include <stdio.h>
	#include <setjmp.h>
	#include <assert.h>
	#include <stdint.h>

	#ifdef _MSC_VER
	#define JPGD_NORETURN __declspec(noreturn)
	#elif defined(__GNUC__)
	#define JPGD_NORETURN __attribute__ ((noreturn))
	#else
	#define JPGD_NORETURN
	#endif

	#define JPGD_HUFF_TREE_MAX_LENGTH 512
	#define JPGD_HUFF_CODE_SIZE_MAX_LENGTH 256

	namespace jpgd
	{
	typedef unsigned char uint8;
	typedef signed short int16;
	typedef unsigned short uint16;
	typedef unsigned int uint;
	typedef signed int int32;

	// Loads a JPEG image from a memory buffer or a file.
	// req_comps can be 1 (grayscale), 3 (RGB), or 4 (RGBA).
	// On return, width/height will be set to the image's dimensions, and actual_comps will be set to the either 1 (grayscale) or 3 (RGB).
	// Notes: For more control over where and how the source data is read, see the decompress_jpeg_image_from_stream() function below, or call the jpeg_decoder class directly.
	// Requesting a 8 or 32bpp image is currently a little faster than 24bpp because the jpeg_decoder class itself currently always unpacks to either 8 or 32bpp.
	unsigned char* decompress_jpeg_image_from_memory(const unsigned char* pSrc_data, int src_data_size, int* width, int* height, int* actual_comps, int req_comps, uint32_t flags = 0);
	unsigned char* decompress_jpeg_image_from_file(const char* pSrc_filename, int* width, int* height, int* actual_comps, int req_comps, uint32_t flags = 0);

	// Success/failure error codes.
	enum jpgd_status
	{
	JPGD_SUCCESS = 0, JPGD_FAILED = -1, JPGD_DONE = 1,
	JPGD_BAD_DHT_COUNTS = -256, JPGD_BAD_DHT_INDEX, JPGD_BAD_DHT_MARKER, JPGD_BAD_DQT_MARKER, JPGD_BAD_DQT_TABLE,
	JPGD_BAD_PRECISION, JPGD_BAD_HEIGHT, JPGD_BAD_WIDTH, JPGD_TOO_MANY_COMPONENTS,
	JPGD_BAD_SOF_LENGTH, JPGD_BAD_VARIABLE_MARKER, JPGD_BAD_DRI_LENGTH, JPGD_BAD_SOS_LENGTH,
	JPGD_BAD_SOS_COMP_ID, JPGD_W_EXTRA_BYTES_BEFORE_MARKER, JPGD_NO_ARITHMITIC_SUPPORT, JPGD_UNEXPECTED_MARKER,
	JPGD_NOT_JPEG, JPGD_UNSUPPORTED_MARKER, JPGD_BAD_DQT_LENGTH, JPGD_TOO_MANY_BLOCKS,
	JPGD_UNDEFINED_QUANT_TABLE, JPGD_UNDEFINED_HUFF_TABLE, JPGD_NOT_SINGLE_SCAN, JPGD_UNSUPPORTED_COLORSPACE,
	JPGD_UNSUPPORTED_SAMP_FACTORS, JPGD_DECODE_ERROR, JPGD_BAD_RESTART_MARKER,
	JPGD_BAD_SOS_SPECTRAL, JPGD_BAD_SOS_SUCCESSIVE, JPGD_STREAM_READ, JPGD_NOTENOUGHMEM, JPGD_TOO_MANY_SCANS
	};

	// Input stream interface.
	// Derive from this class to read input data from sources other than files or memory. Set m_eof_flag to true when no more data is available.
	// The decoder is rather greedy: it will keep on calling this method until its internal input buffer is full, or until the EOF flag is set.
	// It the input stream contains data after the JPEG stream's EOI (end of image) marker it will probably be pulled into the internal buffer.
	// Call the get_total_bytes_read() method to determine the actual size of the JPEG stream after successful decoding.
	class jpeg_decoder_stream
	{
	public:
	jpeg_decoder_stream() { }
	virtual ~jpeg_decoder_stream() { }

	// The read() method is called when the internal input buffer is empty.
	// Parameters:
	// pBuf - input buffer
	// max_bytes_to_read - maximum bytes that can be written to pBuf
	// pEOF_flag - set this to true if at end of stream (no more bytes remaining)
	// Returns -1 on error, otherwise return the number of bytes actually written to the buffer (which may be 0).
	// Notes: This method will be called in a loop until you set *pEOF_flag to true or the internal buffer is full.
	virtual int read(uint8* pBuf, int max_bytes_to_read, bool* pEOF_flag) = 0;
	};

	// stdio FILE stream class.
	class jpeg_decoder_file_stream : public jpeg_decoder_stream
	{
	jpeg_decoder_file_stream(const jpeg_decoder_file_stream&);
	jpeg_decoder_file_stream& operator =(const jpeg_decoder_file_stream&);

	FILE* m_pFile;
	bool m_eof_flag, m_error_flag;

	public:
	jpeg_decoder_file_stream();
	virtual ~jpeg_decoder_file_stream();

	bool open(const char* Pfilename);
	void close();

	virtual int read(uint8* pBuf, int max_bytes_to_read, bool* pEOF_flag);
	};

	// Memory stream class.
	class jpeg_decoder_mem_stream : public jpeg_decoder_stream
	{
	const uint8* m_pSrc_data;
	uint m_ofs, m_size;

	public:
	jpeg_decoder_mem_stream() : m_pSrc_data(NULL), m_ofs(0), m_size(0) { }
	jpeg_decoder_mem_stream(const uint8* pSrc_data, uint size) : m_pSrc_data(pSrc_data), m_ofs(0), m_size(size) { }

	virtual ~jpeg_decoder_mem_stream() { }

	bool open(const uint8* pSrc_data, uint size);
	void close() { m_pSrc_data = NULL; m_ofs = 0; m_size = 0; }

	virtual int read(uint8* pBuf, int max_bytes_to_read, bool* pEOF_flag);
	};

	// Loads JPEG file from a jpeg_decoder_stream.
	unsigned char* decompress_jpeg_image_from_stream(jpeg_decoder_stream* pStream, int* width, int* height, int* actual_comps, int req_comps, uint32_t flags = 0);

	enum
	{
	JPGD_IN_BUF_SIZE = 8192, JPGD_MAX_BLOCKS_PER_MCU = 10, JPGD_MAX_HUFF_TABLES = 8, JPGD_MAX_QUANT_TABLES = 4,
	JPGD_MAX_COMPONENTS = 4, JPGD_MAX_COMPS_IN_SCAN = 4, JPGD_MAX_BLOCKS_PER_ROW = 16384, JPGD_MAX_HEIGHT = 32768, JPGD_MAX_WIDTH = 32768
	};

	typedef int16 jpgd_quant_t;
	typedef int16 jpgd_block_t;

	class jpeg_decoder
	{
	public:
	enum
	{
	cFlagLinearChromaFiltering = 1
	};

	// Call get_error_code() after constructing to determine if the stream is valid or not. You may call the get_width(), get_height(), etc.
	// methods after the constructor is called. You may then either destruct the object, or begin decoding the image by calling begin_decoding(), then decode() on each scanline.
	jpeg_decoder(jpeg_decoder_stream* pStream, uint32_t flags = cFlagLinearChromaFiltering);

	~jpeg_decoder();

	// Call this method after constructing the object to begin decompression.
	// If JPGD_SUCCESS is returned you may then call decode() on each scanline.

	int begin_decoding();

	// Returns the next scan line.
	// For grayscale images, pScan_line will point to a buffer containing 8-bit pixels (get_bytes_per_pixel() will return 1).
	// Otherwise, it will always point to a buffer containing 32-bit RGBA pixels (A will always be 255, and get_bytes_per_pixel() will return 4).
	// Returns JPGD_SUCCESS if a scan line has been returned.
	// Returns JPGD_DONE if all scan lines have been returned.
	// Returns JPGD_FAILED if an error occurred. Call get_error_code() for a more info.
	int decode(const void** pScan_line, uint* pScan_line_len);

	inline jpgd_status get_error_code() const { return m_error_code; }

	inline int get_width() const { return m_image_x_size; }
	inline int get_height() const { return m_image_y_size; }

	inline int get_num_components() const { return m_comps_in_frame; }

	inline int get_bytes_per_pixel() const { return m_dest_bytes_per_pixel; }
	inline int get_bytes_per_scan_line() const { return m_image_x_size * get_bytes_per_pixel(); }

	// Returns the total number of bytes actually consumed by the decoder (which should equal the actual size of the JPEG file).
	inline int get_total_bytes_read() const { return m_total_bytes_read; }

	private:
	jpeg_decoder(const jpeg_decoder&);
	jpeg_decoder& operator =(const jpeg_decoder&);

	typedef void (pDecode_block_func)(jpeg_decoder, int, int, int);

	struct huff_tables
	{
	bool ac_table;
	uint look_up[256];
	uint look_up2[256];
	uint8 code_size[JPGD_HUFF_CODE_SIZE_MAX_LENGTH];
	uint tree[JPGD_HUFF_TREE_MAX_LENGTH];
	};

	struct coeff_buf
	{
	uint8* pData;
	int block_num_x, block_num_y;
	int block_len_x, block_len_y;
	int block_size;
	};

	struct mem_block
	{
	mem_block* m_pNext;
	size_t m_used_count;
	size_t m_size;
	char m_data[1];
	};

	jmp_buf m_jmp_state;
	uint32_t m_flags;
	mem_block* m_pMem_blocks;
	int m_image_x_size;
	int m_image_y_size;
	jpeg_decoder_stream* m_pStream;

	int m_progressive_flag;

	uint8 m_huff_ac[JPGD_MAX_HUFF_TABLES];
	uint8* m_huff_num[JPGD_MAX_HUFF_TABLES]; // pointer to number of Huffman codes per bit size
	uint8* m_huff_val[JPGD_MAX_HUFF_TABLES]; // pointer to Huffman codes per bit size
	jpgd_quant_t* m_quant[JPGD_MAX_QUANT_TABLES]; // pointer to quantization tables
	int m_scan_type; // Gray, Yh1v1, Yh1v2, Yh2v1, Yh2v2 (CMYK111, CMYK4114 no longer supported)
	int m_comps_in_frame; // # of components in frame
	int m_comp_h_samp[JPGD_MAX_COMPONENTS]; // component's horizontal sampling factor
	int m_comp_v_samp[JPGD_MAX_COMPONENTS]; // component's vertical sampling factor
	int m_comp_quant[JPGD_MAX_COMPONENTS]; // component's quantization table selector
	int m_comp_ident[JPGD_MAX_COMPONENTS]; // component's ID
	int m_comp_h_blocks[JPGD_MAX_COMPONENTS];
	int m_comp_v_blocks[JPGD_MAX_COMPONENTS];
	int m_comps_in_scan; // # of components in scan
	int m_comp_list[JPGD_MAX_COMPS_IN_SCAN]; // components in this scan
	int m_comp_dc_tab[JPGD_MAX_COMPONENTS]; // component's DC Huffman coding table selector
	int m_comp_ac_tab[JPGD_MAX_COMPONENTS]; // component's AC Huffman coding table selector
	int m_spectral_start; // spectral selection start
	int m_spectral_end; // spectral selection end
	int m_successive_low; // successive approximation low
	int m_successive_high; // successive approximation high
	int m_max_mcu_x_size; // MCU's max. X size in pixels
	int m_max_mcu_y_size; // MCU's max. Y size in pixels
	int m_blocks_per_mcu;
	int m_max_blocks_per_row;
	int m_mcus_per_row, m_mcus_per_col;
	int m_mcu_org[JPGD_MAX_BLOCKS_PER_MCU];
	int m_total_lines_left; // total # lines left in image
	int m_mcu_lines_left; // total # lines left in this MCU
	int m_num_buffered_scanlines;
	int m_real_dest_bytes_per_scan_line;
	int m_dest_bytes_per_scan_line; // rounded up
	int m_dest_bytes_per_pixel; // 4 (RGB) or 1 (Y)
	huff_tables* m_pHuff_tabs[JPGD_MAX_HUFF_TABLES];
	coeff_buf* m_dc_coeffs[JPGD_MAX_COMPONENTS];
	coeff_buf* m_ac_coeffs[JPGD_MAX_COMPONENTS];
	int m_eob_run;
	int m_block_y_mcu[JPGD_MAX_COMPONENTS];
	uint8* m_pIn_buf_ofs;
	int m_in_buf_left;
	int m_tem_flag;

	uint8 m_in_buf_pad_start[64];
	uint8 m_in_buf[JPGD_IN_BUF_SIZE + 128];
	uint8 m_in_buf_pad_end[64];

	int m_bits_left;
	uint m_bit_buf;
	int m_restart_interval;
	int m_restarts_left;
	int m_next_restart_num;
	int m_max_mcus_per_row;
	int m_max_blocks_per_mcu;

	int m_max_mcus_per_col;
	uint m_last_dc_val[JPGD_MAX_COMPONENTS];
	jpgd_block_t* m_pMCU_coefficients;
	int m_mcu_block_max_zag[JPGD_MAX_BLOCKS_PER_MCU];
	uint8* m_pSample_buf;
	uint8* m_pSample_buf_prev;
	int m_crr[256];
	int m_cbb[256];
	int m_crg[256];
	int m_cbg[256];
	uint8* m_pScan_line_0;
	uint8* m_pScan_line_1;
	jpgd_status m_error_code;
	int m_total_bytes_read;

	bool m_ready_flag;
	bool m_eof_flag;
	bool m_sample_buf_prev_valid;

	inline int check_sample_buf_ofs(int ofs) const { assert(ofs >= 0); assert(ofs < m_max_blocks_per_row * 64); return ofs; }
	void free_all_blocks();
	JPGD_NORETURN void stop_decoding(jpgd_status status);
	void* alloc(size_t n, bool zero = false);
	void word_clear(void* p, uint16 c, uint n);
	void prep_in_buffer();
	void read_dht_marker();
	void read_dqt_marker();
	void read_sof_marker();
	void skip_variable_marker();
	void read_dri_marker();
	void read_sos_marker();
	int next_marker();
	int process_markers();
	void locate_soi_marker();
	void locate_sof_marker();
	int locate_sos_marker();
	void init(jpeg_decoder_stream* pStream, uint32_t flags);
	void create_look_ups();
	void fix_in_buffer();
	void transform_mcu(int mcu_row);
	coeff_buf* coeff_buf_open(int block_num_x, int block_num_y, int block_len_x, int block_len_y);
	inline jpgd_block_t* coeff_buf_getp(coeff_buf* cb, int block_x, int block_y);
	void load_next_row();
	void decode_next_row();
	void make_huff_table(int index, huff_tables* pH);
	void check_quant_tables();
	void check_huff_tables();
	bool calc_mcu_block_order();
	int init_scan();
	void init_frame();
	void process_restart();
	void decode_scan(pDecode_block_func decode_block_func);
	void init_progressive();
	void init_sequential();
	void decode_start();
	void decode_init(jpeg_decoder_stream* pStream, uint32_t flags);
	void H2V2Convert();
	uint32_t H2V2ConvertFiltered();
	void H2V1Convert();
	void H2V1ConvertFiltered();
	void H1V2Convert();
	void H1V2ConvertFiltered();
	void H1V1Convert();
	void gray_convert();
	void find_eoi();
	inline uint get_char();
	inline uint get_char(bool* pPadding_flag);
	inline void stuff_char(uint8 q);
	inline uint8 get_octet();
	inline uint get_bits(int num_bits);
	inline uint get_bits_no_markers(int numbits);
	inline int huff_decode(huff_tables* pH);
	inline int huff_decode(huff_tables* pH, int& extrabits);

	// Clamps a value between 0-255.
	static inline uint8 clamp(int i)
	{
	if (static_cast<uint>(i) > 255)
	i = (((~i) >> 31) & 0xFF);
	return static_cast<uint8>(i);
	}
	int decode_next_mcu_row();

	static void decode_block_dc_first(jpeg_decoder* pD, int component_id, int block_x, int block_y);
	static void decode_block_dc_refine(jpeg_decoder* pD, int component_id, int block_x, int block_y);
	static void decode_block_ac_first(jpeg_decoder* pD, int component_id, int block_x, int block_y);
	static void decode_block_ac_refine(jpeg_decoder* pD, int component_id, int block_x, int block_y);
	};

	} // namespace jpgd

	#endif // JPEG_DECODER_H