    /*
     * jdct.h
     *
     * Copyright (C) 1994-1996, 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, long 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 long 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 long 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 long.
     * 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	((long) 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)	((long) ((x) * CONST_SCALE + 0.5))

    /* Descale and correctly round an long 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 long variable by an long constant to yield an long 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)  (((short) (var)) * ((short) (const)))
    #endif
    #ifdef SHORTxLCONST_32		/* known to work with Microsoft C 6.0 */
    #define MULTIPLY16C16(var,const)  (((short) (var)) * ((long) (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)  (((short) (var1)) * ((short) (var2)))
    #endif

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