//  * jdct.h
//  *
//  * Copyright (C) 1994, Thomas G. Lane.
//  * This file is part of the Independent JPEG Group's software.
//  * For conditions of distribution and use, see the accompanying README file.
//  *
//  * This include file contains common declarations for the forward and
//  * inverse DCT modules.  These declarations are private to the DCT managers
//  * (jcdctmgr.c, jddctmgr.c) and the individual DCT algorithms.
//  * The individual DCT algorithms are kept in separate files to ease
//  * machine-dependent tuning (e.g., assembly coding).


//  * A forward DCT routine is given a pointer to a work area of type DCTELEM[];
//  * the DCT is to be performed in-place in that buffer.  Type DCTELEM is int
//  * for 8-bit samples, INT32 for 12-bit samples.  (NOTE: Floating-point DCT
//  * implementations use an array of type FAST_FLOAT, instead.)
//  * The DCT inputs are expected to be signed (range +-CENTERJSAMPLE).
//  * The DCT outputs are returned scaled up by a factor of 8; they therefore
//  * have a range of +-8K for 8-bit data, +-128K for 12-bit data.  This
//  * convention improves accuracy in integer implementations and saves some
//  * work in floating-point ones.
//  * Quantization of the output coefficients is done by jcdctmgr.c.

#if BITS_IN_JSAMPLE == 8
typedef int DCTELEM;		// 16 or 32 bits is fine 
#else
typedef INT32 DCTELEM;		// must have 32 bits 
#endif

typedef JMETHOD(void, forward_DCT_method_ptr, (DCTELEM * data));
typedef JMETHOD(void, float_DCT_method_ptr, (FAST_FLOAT * data));


//  * An inverse DCT routine is given a pointer to the input JBLOCK and a pointer
//  * to an output sample array.  The routine must dequantize the input data as
//  * well as perform the IDCT; for dequantization, it uses the multiplier table
//  * pointed to by compptr->dct_table.  The output data is to be placed into the
//  * sample array starting at a specified column.  (Any row offset needed will
//  * be applied to the array pointer before it is passed to the IDCT code.)
//  * Note that the number of samples emitted by the IDCT routine is
//  * DCT_scaled_size * DCT_scaled_size.

// typedef inverse_DCT_method_ptr is declared in jpegint.h 

//  * Each IDCT routine has its own ideas about the best dct_table element type.

typedef MULTIPLIER ISLOW_MULT_TYPE; // short or int, whichever is faster 
#if BITS_IN_JSAMPLE == 8
typedef MULTIPLIER IFAST_MULT_TYPE; // 16 bits is OK, use short if faster 
#define IFAST_SCALE_BITS  2	// fractional bits in scale factors 
#else
typedef INT32 IFAST_MULT_TYPE;	// need 32 bits for scaled quantizers 
#define IFAST_SCALE_BITS  13	// fractional bits in scale factors 
#endif
typedef FAST_FLOAT FLOAT_MULT_TYPE; // preferred floating type 


//  * Each IDCT routine is responsible for range-limiting its results and
//  * converting them to unsigned form (0..MAXJSAMPLE).  The raw outputs could
//  * be quite far out of range if the input data is corrupt, so a bulletproof
//  * range-limiting step is required.  We use a mask-and-table-lookup method
//  * to do the combined operations quickly.  See the comments with
//  * prepare_range_limit_table (in jdmaster.c) for more info.

#define IDCT_range_limit(cinfo)  ((cinfo)->sample_range_limit + CENTERJSAMPLE)

#define RANGE_MASK  (MAXJSAMPLE * 4 + 3) // 2 bits wider than legal samples 


// Short forms of external names for systems with brain-damaged linkers. 

#ifdef NEED_SHORT_EXTERNAL_NAMES
#define jpeg_fdct_islow		jFDislow
#define jpeg_fdct_ifast		jFDifast
#define jpeg_fdct_float		jFDfloat
#define jpeg_idct_islow		jRDislow
#define jpeg_idct_ifast		jRDifast
#define jpeg_idct_float		jRDfloat
#define jpeg_idct_4x4		jRD4x4
#define jpeg_idct_2x2		jRD2x2
#define jpeg_idct_1x1		jRD1x1
#endif // NEED_SHORT_EXTERNAL_NAMES 

// Extern declarations for the forward and inverse DCT routines. 

EXTERN void jpeg_fdct_islow JPP((DCTELEM * data));
EXTERN void jpeg_fdct_ifast JPP((DCTELEM * data));
EXTERN void jpeg_fdct_float JPP((FAST_FLOAT * data));

EXTERN void jpeg_idct_islow
    JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
	 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
EXTERN void jpeg_idct_ifast
    JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
	 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
EXTERN void jpeg_idct_float
    JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
	 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
EXTERN void jpeg_idct_4x4
    JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
	 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
EXTERN void jpeg_idct_2x2
    JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
	 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
EXTERN void jpeg_idct_1x1
    JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
	 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));


//  * Macros for handling fixed-point arithmetic; these are used by many
//  * but not all of the DCT/IDCT modules.
//  *
//  * All values are expected to be of type INT32.
//  * Fractional constants are scaled left by CONST_BITS bits.
//  * CONST_BITS is defined within each module using these macros,
//  * and may differ from one module to the next.

#define ONE	((INT32) 1)
#define CONST_SCALE (ONE << CONST_BITS)

//  Convert a positive real constant to an integer scaled by CONST_SCALE.
//  * Caution: some C compilers fail to reduce "FIX(constant)" at compile time,
//  * thus causing a lot of useless floating-point operations at run time.

#define FIX(x)	((INT32) ((x) * CONST_SCALE + 0.5))

//  Descale and correctly round an INT32 value that's scaled by N bits.
//  * We assume RIGHT_SHIFT rounds towards minus infinity, so adding
//  * the fudge factor is correct for either sign of X.

#define DESCALE(x,n)  RIGHT_SHIFT((x) + (ONE << ((n)-1)), n)

//  Multiply an INT32 variable by an INT32 constant to yield an INT32 result.
//  * This macro is used only when the two inputs will actually be no more than
//  * 16 bits wide, so that a 16x16->32 bit multiply can be used instead of a
//  * full 32x32 multiply.  This provides a useful speedup on many machines.
//  * Unfortunately there is no way to specify a 16x16->32 multiply portably
//  * in C, but some C compilers will do the right thing if you provide the
//  * correct combination of casts.

#ifdef SHORTxSHORT_32		// may work if 'int' is 32 bits 
#define MULTIPLY16C16(var,const)  (((INT16) (var)) * ((INT16) (const)))
#endif
#ifdef SHORTxLCONST_32		// known to work with Microsoft C 6.0 
#define MULTIPLY16C16(var,const)  (((INT16) (var)) * ((INT32) (const)))
#endif

#ifndef MULTIPLY16C16		// default definition 
#define MULTIPLY16C16(var,const)  ((var) * (const))
#endif

// Same except both inputs are variables. 

#ifdef SHORTxSHORT_32		// may work if 'int' is 32 bits 
#define MULTIPLY16V16(var1,var2)  (((INT16) (var1)) * ((INT16) (var2)))
#endif

#ifndef MULTIPLY16V16		// default definition 
#define MULTIPLY16V16(var1,var2)  ((var1) * (var2))
#endif