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Revision e41bfd15dd148627b4f39c2a5837bddd8894d345 authored by Terry Jan Reedy on 30 November 2020, 17:09:43 UTC, committed by GitHub on 30 November 2020, 17:09:43 UTC
restart_subprocess is a method of self, the pyshell.InteractiveInterpreter instance. The latter does not have an interp attribute redundantly referring to itself. (The PyShell instance does have an interp attribute, referring to the InteractiveInterpreter instance.)
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Tip revision: e41bfd15dd148627b4f39c2a5837bddd8894d345 authored by Terry Jan Reedy on 30 November 2020, 17:09:43 UTC
bpo-42508: Remove bogus idlelib.pyshell.ModifiedInterpreter attribute (GH-23570)
Tip revision: e41bfd1
audioop.c

/* audioopmodule - Module to detect peak values in arrays */

#define PY_SSIZE_T_CLEAN

#include "Python.h"

#if defined(__CHAR_UNSIGNED__)
#if defined(signed)
/* This module currently does not work on systems where only unsigned
   characters are available.  Take it out of Setup.  Sorry. */
#endif
#endif

static const int maxvals[] = {0, 0x7F, 0x7FFF, 0x7FFFFF, 0x7FFFFFFF};
/* -1 trick is needed on Windows to support -0x80000000 without a warning */
static const int minvals[] = {0, -0x80, -0x8000, -0x800000, -0x7FFFFFFF-1};
static const unsigned int masks[] = {0, 0xFF, 0xFFFF, 0xFFFFFF, 0xFFFFFFFF};

static int
fbound(double val, double minval, double maxval)
{
    if (val > maxval) {
        val = maxval;
    }
    else if (val < minval + 1.0) {
        val = minval;
    }

    /* Round towards minus infinity (-inf) */
    val = floor(val);

    /* Cast double to integer: round towards zero */
    return (int)val;
}


/* Code shamelessly stolen from sox, 12.17.7, g711.c
** (c) Craig Reese, Joe Campbell and Jeff Poskanzer 1989 */

/* From g711.c:
 *
 * December 30, 1994:
 * Functions linear2alaw, linear2ulaw have been updated to correctly
 * convert unquantized 16 bit values.
 * Tables for direct u- to A-law and A- to u-law conversions have been
 * corrected.
 * Borge Lindberg, Center for PersonKommunikation, Aalborg University.
 * bli@cpk.auc.dk
 *
 */
#define BIAS 0x84   /* define the add-in bias for 16 bit samples */
#define CLIP 32635
#define SIGN_BIT        (0x80)          /* Sign bit for an A-law byte. */
#define QUANT_MASK      (0xf)           /* Quantization field mask. */
#define SEG_SHIFT       (4)             /* Left shift for segment number. */
#define SEG_MASK        (0x70)          /* Segment field mask. */

static const int16_t seg_aend[8] = {
    0x1F, 0x3F, 0x7F, 0xFF, 0x1FF, 0x3FF, 0x7FF, 0xFFF
};
static const int16_t seg_uend[8] = {
    0x3F, 0x7F, 0xFF, 0x1FF, 0x3FF, 0x7FF, 0xFFF, 0x1FFF
};

static int16_t
search(int16_t val, const int16_t *table, int size)
{
    int i;

    for (i = 0; i < size; i++) {
        if (val <= *table++)
            return (i);
    }
    return (size);
}
#define st_ulaw2linear16(uc) (_st_ulaw2linear16[uc])
#define st_alaw2linear16(uc) (_st_alaw2linear16[uc])

static const int16_t _st_ulaw2linear16[256] = {
    -32124,  -31100,  -30076,  -29052,  -28028,  -27004,  -25980,
    -24956,  -23932,  -22908,  -21884,  -20860,  -19836,  -18812,
    -17788,  -16764,  -15996,  -15484,  -14972,  -14460,  -13948,
    -13436,  -12924,  -12412,  -11900,  -11388,  -10876,  -10364,
     -9852,   -9340,   -8828,   -8316,   -7932,   -7676,   -7420,
     -7164,   -6908,   -6652,   -6396,   -6140,   -5884,   -5628,
     -5372,   -5116,   -4860,   -4604,   -4348,   -4092,   -3900,
     -3772,   -3644,   -3516,   -3388,   -3260,   -3132,   -3004,
     -2876,   -2748,   -2620,   -2492,   -2364,   -2236,   -2108,
     -1980,   -1884,   -1820,   -1756,   -1692,   -1628,   -1564,
     -1500,   -1436,   -1372,   -1308,   -1244,   -1180,   -1116,
     -1052,    -988,    -924,    -876,    -844,    -812,    -780,
      -748,    -716,    -684,    -652,    -620,    -588,    -556,
      -524,    -492,    -460,    -428,    -396,    -372,    -356,
      -340,    -324,    -308,    -292,    -276,    -260,    -244,
      -228,    -212,    -196,    -180,    -164,    -148,    -132,
      -120,    -112,    -104,     -96,     -88,     -80,     -72,
       -64,     -56,     -48,     -40,     -32,     -24,     -16,
    -8,       0,   32124,   31100,   30076,   29052,   28028,
     27004,   25980,   24956,   23932,   22908,   21884,   20860,
     19836,   18812,   17788,   16764,   15996,   15484,   14972,
     14460,   13948,   13436,   12924,   12412,   11900,   11388,
     10876,   10364,    9852,    9340,    8828,    8316,    7932,
      7676,    7420,    7164,    6908,    6652,    6396,    6140,
      5884,    5628,    5372,    5116,    4860,    4604,    4348,
      4092,    3900,    3772,    3644,    3516,    3388,    3260,
      3132,    3004,    2876,    2748,    2620,    2492,    2364,
      2236,    2108,    1980,    1884,    1820,    1756,    1692,
      1628,    1564,    1500,    1436,    1372,    1308,    1244,
      1180,    1116,    1052,     988,     924,     876,     844,
       812,     780,     748,     716,     684,     652,     620,
       588,     556,     524,     492,     460,     428,     396,
       372,     356,     340,     324,     308,     292,     276,
       260,     244,     228,     212,     196,     180,     164,
       148,     132,     120,     112,     104,      96,      88,
    80,      72,      64,      56,      48,      40,      32,
    24,      16,       8,       0
};

/*
 * linear2ulaw() accepts a 14-bit signed integer and encodes it as u-law data
 * stored in an unsigned char.  This function should only be called with
 * the data shifted such that it only contains information in the lower
 * 14-bits.
 *
 * In order to simplify the encoding process, the original linear magnitude
 * is biased by adding 33 which shifts the encoding range from (0 - 8158) to
 * (33 - 8191). The result can be seen in the following encoding table:
 *
 *      Biased Linear Input Code        Compressed Code
 *      ------------------------        ---------------
 *      00000001wxyza                   000wxyz
 *      0000001wxyzab                   001wxyz
 *      000001wxyzabc                   010wxyz
 *      00001wxyzabcd                   011wxyz
 *      0001wxyzabcde                   100wxyz
 *      001wxyzabcdef                   101wxyz
 *      01wxyzabcdefg                   110wxyz
 *      1wxyzabcdefgh                   111wxyz
 *
 * Each biased linear code has a leading 1 which identifies the segment
 * number. The value of the segment number is equal to 7 minus the number
 * of leading 0's. The quantization interval is directly available as the
 * four bits wxyz.  * The trailing bits (a - h) are ignored.
 *
 * Ordinarily the complement of the resulting code word is used for
 * transmission, and so the code word is complemented before it is returned.
 *
 * For further information see John C. Bellamy's Digital Telephony, 1982,
 * John Wiley & Sons, pps 98-111 and 472-476.
 */
static unsigned char
st_14linear2ulaw(int16_t pcm_val)       /* 2's complement (14-bit range) */
{
    int16_t         mask;
    int16_t         seg;
    unsigned char   uval;

    /* u-law inverts all bits */
    /* Get the sign and the magnitude of the value. */
    if (pcm_val < 0) {
        pcm_val = -pcm_val;
        mask = 0x7F;
    } else {
        mask = 0xFF;
    }
    if ( pcm_val > CLIP ) pcm_val = CLIP;           /* clip the magnitude */
    pcm_val += (BIAS >> 2);

    /* Convert the scaled magnitude to segment number. */
    seg = search(pcm_val, seg_uend, 8);

    /*
     * Combine the sign, segment, quantization bits;
     * and complement the code word.
     */
    if (seg >= 8)           /* out of range, return maximum value. */
        return (unsigned char) (0x7F ^ mask);
    else {
        uval = (unsigned char) (seg << 4) | ((pcm_val >> (seg + 1)) & 0xF);
        return (uval ^ mask);
    }

}

static const int16_t _st_alaw2linear16[256] = {
     -5504,   -5248,   -6016,   -5760,   -4480,   -4224,   -4992,
     -4736,   -7552,   -7296,   -8064,   -7808,   -6528,   -6272,
     -7040,   -6784,   -2752,   -2624,   -3008,   -2880,   -2240,
     -2112,   -2496,   -2368,   -3776,   -3648,   -4032,   -3904,
     -3264,   -3136,   -3520,   -3392,  -22016,  -20992,  -24064,
    -23040,  -17920,  -16896,  -19968,  -18944,  -30208,  -29184,
    -32256,  -31232,  -26112,  -25088,  -28160,  -27136,  -11008,
    -10496,  -12032,  -11520,   -8960,   -8448,   -9984,   -9472,
    -15104,  -14592,  -16128,  -15616,  -13056,  -12544,  -14080,
    -13568,    -344,    -328,    -376,    -360,    -280,    -264,
      -312,    -296,    -472,    -456,    -504,    -488,    -408,
      -392,    -440,    -424,     -88,     -72,    -120,    -104,
       -24,      -8,     -56,     -40,    -216,    -200,    -248,
      -232,    -152,    -136,    -184,    -168,   -1376,   -1312,
     -1504,   -1440,   -1120,   -1056,   -1248,   -1184,   -1888,
     -1824,   -2016,   -1952,   -1632,   -1568,   -1760,   -1696,
      -688,    -656,    -752,    -720,    -560,    -528,    -624,
      -592,    -944,    -912,   -1008,    -976,    -816,    -784,
      -880,    -848,    5504,    5248,    6016,    5760,    4480,
      4224,    4992,    4736,    7552,    7296,    8064,    7808,
      6528,    6272,    7040,    6784,    2752,    2624,    3008,
      2880,    2240,    2112,    2496,    2368,    3776,    3648,
      4032,    3904,    3264,    3136,    3520,    3392,   22016,
     20992,   24064,   23040,   17920,   16896,   19968,   18944,
     30208,   29184,   32256,   31232,   26112,   25088,   28160,
     27136,   11008,   10496,   12032,   11520,    8960,    8448,
      9984,    9472,   15104,   14592,   16128,   15616,   13056,
     12544,   14080,   13568,     344,     328,     376,     360,
       280,     264,     312,     296,     472,     456,     504,
       488,     408,     392,     440,     424,      88,      72,
       120,     104,      24,       8,      56,      40,     216,
       200,     248,     232,     152,     136,     184,     168,
      1376,    1312,    1504,    1440,    1120,    1056,    1248,
      1184,    1888,    1824,    2016,    1952,    1632,    1568,
      1760,    1696,     688,     656,     752,     720,     560,
       528,     624,     592,     944,     912,    1008,     976,
       816,     784,     880,     848
};

/*
 * linear2alaw() accepts a 13-bit signed integer and encodes it as A-law data
 * stored in an unsigned char.  This function should only be called with
 * the data shifted such that it only contains information in the lower
 * 13-bits.
 *
 *              Linear Input Code       Compressed Code
 *      ------------------------        ---------------
 *      0000000wxyza                    000wxyz
 *      0000001wxyza                    001wxyz
 *      000001wxyzab                    010wxyz
 *      00001wxyzabc                    011wxyz
 *      0001wxyzabcd                    100wxyz
 *      001wxyzabcde                    101wxyz
 *      01wxyzabcdef                    110wxyz
 *      1wxyzabcdefg                    111wxyz
 *
 * For further information see John C. Bellamy's Digital Telephony, 1982,
 * John Wiley & Sons, pps 98-111 and 472-476.
 */
static unsigned char
st_linear2alaw(int16_t pcm_val) /* 2's complement (13-bit range) */
{
    int16_t         mask;
    int16_t         seg;
    unsigned char   aval;

    /* A-law using even bit inversion */
    if (pcm_val >= 0) {
        mask = 0xD5;            /* sign (7th) bit = 1 */
    } else {
        mask = 0x55;            /* sign bit = 0 */
        pcm_val = -pcm_val - 1;
    }

    /* Convert the scaled magnitude to segment number. */
    seg = search(pcm_val, seg_aend, 8);

    /* Combine the sign, segment, and quantization bits. */

    if (seg >= 8)           /* out of range, return maximum value. */
        return (unsigned char) (0x7F ^ mask);
    else {
        aval = (unsigned char) seg << SEG_SHIFT;
        if (seg < 2)
            aval |= (pcm_val >> 1) & QUANT_MASK;
        else
            aval |= (pcm_val >> seg) & QUANT_MASK;
        return (aval ^ mask);
    }
}
/* End of code taken from sox */

/* Intel ADPCM step variation table */
static const int indexTable[16] = {
    -1, -1, -1, -1, 2, 4, 6, 8,
    -1, -1, -1, -1, 2, 4, 6, 8,
};

static const int stepsizeTable[89] = {
    7, 8, 9, 10, 11, 12, 13, 14, 16, 17,
    19, 21, 23, 25, 28, 31, 34, 37, 41, 45,
    50, 55, 60, 66, 73, 80, 88, 97, 107, 118,
    130, 143, 157, 173, 190, 209, 230, 253, 279, 307,
    337, 371, 408, 449, 494, 544, 598, 658, 724, 796,
    876, 963, 1060, 1166, 1282, 1411, 1552, 1707, 1878, 2066,
    2272, 2499, 2749, 3024, 3327, 3660, 4026, 4428, 4871, 5358,
    5894, 6484, 7132, 7845, 8630, 9493, 10442, 11487, 12635, 13899,
    15289, 16818, 18500, 20350, 22385, 24623, 27086, 29794, 32767
};

#define GETINTX(T, cp, i)  (*(T *)((unsigned char *)(cp) + (i)))
#define SETINTX(T, cp, i, val)  do {                    \
        *(T *)((unsigned char *)(cp) + (i)) = (T)(val); \
    } while (0)


#define GETINT8(cp, i)          GETINTX(signed char, (cp), (i))
#define GETINT16(cp, i)         GETINTX(int16_t, (cp), (i))
#define GETINT32(cp, i)         GETINTX(int32_t, (cp), (i))

#if WORDS_BIGENDIAN
#define GETINT24(cp, i)  (                              \
        ((unsigned char *)(cp) + (i))[2] +              \
        (((unsigned char *)(cp) + (i))[1] << 8) +       \
        (((signed char *)(cp) + (i))[0] << 16) )
#else
#define GETINT24(cp, i)  (                              \
        ((unsigned char *)(cp) + (i))[0] +              \
        (((unsigned char *)(cp) + (i))[1] << 8) +       \
        (((signed char *)(cp) + (i))[2] << 16) )
#endif


#define SETINT8(cp, i, val)     SETINTX(signed char, (cp), (i), (val))
#define SETINT16(cp, i, val)    SETINTX(int16_t, (cp), (i), (val))
#define SETINT32(cp, i, val)    SETINTX(int32_t, (cp), (i), (val))

#if WORDS_BIGENDIAN
#define SETINT24(cp, i, val)  do {                              \
        ((unsigned char *)(cp) + (i))[2] = (int)(val);          \
        ((unsigned char *)(cp) + (i))[1] = (int)(val) >> 8;     \
        ((signed char *)(cp) + (i))[0] = (int)(val) >> 16;      \
    } while (0)
#else
#define SETINT24(cp, i, val)  do {                              \
        ((unsigned char *)(cp) + (i))[0] = (int)(val);          \
        ((unsigned char *)(cp) + (i))[1] = (int)(val) >> 8;     \
        ((signed char *)(cp) + (i))[2] = (int)(val) >> 16;      \
    } while (0)
#endif


#define GETRAWSAMPLE(size, cp, i)  (                    \
        (size == 1) ? (int)GETINT8((cp), (i)) :         \
        (size == 2) ? (int)GETINT16((cp), (i)) :        \
        (size == 3) ? (int)GETINT24((cp), (i)) :        \
                      (int)GETINT32((cp), (i)))

#define SETRAWSAMPLE(size, cp, i, val)  do {    \
        if (size == 1)                          \
            SETINT8((cp), (i), (val));          \
        else if (size == 2)                     \
            SETINT16((cp), (i), (val));         \
        else if (size == 3)                     \
            SETINT24((cp), (i), (val));         \
        else                                    \
            SETINT32((cp), (i), (val));         \
    } while(0)


#define GETSAMPLE32(size, cp, i)  (                     \
        (size == 1) ? (int)GETINT8((cp), (i)) << 24 :   \
        (size == 2) ? (int)GETINT16((cp), (i)) << 16 :  \
        (size == 3) ? (int)GETINT24((cp), (i)) << 8 :   \
                      (int)GETINT32((cp), (i)))

#define SETSAMPLE32(size, cp, i, val)  do {     \
        if (size == 1)                          \
            SETINT8((cp), (i), (val) >> 24);    \
        else if (size == 2)                     \
            SETINT16((cp), (i), (val) >> 16);   \
        else if (size == 3)                     \
            SETINT24((cp), (i), (val) >> 8);    \
        else                                    \
            SETINT32((cp), (i), (val));         \
    } while(0)

static PyModuleDef audioopmodule;

typedef struct {
    PyObject *AudioopError;
} audioop_state;

static inline audioop_state *
get_audioop_state(PyObject *module)
{
    void *state = PyModule_GetState(module);
    assert(state != NULL);
    return (audioop_state *)state;
}

static int
audioop_check_size(PyObject *module, int size)
{
    if (size < 1 || size > 4) {
        PyErr_SetString(get_audioop_state(module)->AudioopError,
                        "Size should be 1, 2, 3 or 4");
        return 0;
    }
    else
        return 1;
}

static int
audioop_check_parameters(PyObject *module, Py_ssize_t len, int size)
{
    if (!audioop_check_size(module, size))
        return 0;
    if (len % size != 0) {
        PyErr_SetString(get_audioop_state(module)->AudioopError,
                        "not a whole number of frames");
        return 0;
    }
    return 1;
}

/*[clinic input]
module audioop
[clinic start generated code]*/
/*[clinic end generated code: output=da39a3ee5e6b4b0d input=8fa8f6611be3591a]*/

/*[clinic input]
audioop.getsample

    fragment: Py_buffer
    width: int
    index: Py_ssize_t
    /

Return the value of sample index from the fragment.
[clinic start generated code]*/

static PyObject *
audioop_getsample_impl(PyObject *module, Py_buffer *fragment, int width,
                       Py_ssize_t index)
/*[clinic end generated code: output=8fe1b1775134f39a input=88edbe2871393549]*/
{
    int val;

    if (!audioop_check_parameters(module, fragment->len, width))
        return NULL;
    if (index < 0 || index >= fragment->len/width) {
        PyErr_SetString(get_audioop_state(module)->AudioopError,
                        "Index out of range");
        return NULL;
    }
    val = GETRAWSAMPLE(width, fragment->buf, index*width);
    return PyLong_FromLong(val);
}

/*[clinic input]
audioop.max

    fragment: Py_buffer
    width: int
    /

Return the maximum of the absolute value of all samples in a fragment.
[clinic start generated code]*/

static PyObject *
audioop_max_impl(PyObject *module, Py_buffer *fragment, int width)
/*[clinic end generated code: output=e6c5952714f1c3f0 input=32bea5ea0ac8c223]*/
{
    Py_ssize_t i;
    unsigned int absval, max = 0;

    if (!audioop_check_parameters(module, fragment->len, width))
        return NULL;
    for (i = 0; i < fragment->len; i += width) {
        int val = GETRAWSAMPLE(width, fragment->buf, i);
        /* Cast to unsigned before negating. Unsigned overflow is well-
        defined, but signed overflow is not. */
        if (val < 0) absval = (unsigned int)-(int64_t)val;
        else absval = val;
        if (absval > max) max = absval;
    }
    return PyLong_FromUnsignedLong(max);
}

/*[clinic input]
audioop.minmax

    fragment: Py_buffer
    width: int
    /

Return the minimum and maximum values of all samples in the sound fragment.
[clinic start generated code]*/

static PyObject *
audioop_minmax_impl(PyObject *module, Py_buffer *fragment, int width)
/*[clinic end generated code: output=473fda66b15c836e input=89848e9b927a0696]*/
{
    Py_ssize_t i;
    /* -1 trick below is needed on Windows to support -0x80000000 without
    a warning */
    int min = 0x7fffffff, max = -0x7FFFFFFF-1;

    if (!audioop_check_parameters(module, fragment->len, width))
        return NULL;
    for (i = 0; i < fragment->len; i += width) {
        int val = GETRAWSAMPLE(width, fragment->buf, i);
        if (val > max) max = val;
        if (val < min) min = val;
    }
    return Py_BuildValue("(ii)", min, max);
}

/*[clinic input]
audioop.avg

    fragment: Py_buffer
    width: int
    /

Return the average over all samples in the fragment.
[clinic start generated code]*/

static PyObject *
audioop_avg_impl(PyObject *module, Py_buffer *fragment, int width)
/*[clinic end generated code: output=4410a4c12c3586e6 input=1114493c7611334d]*/
{
    Py_ssize_t i;
    int avg;
    double sum = 0.0;

    if (!audioop_check_parameters(module, fragment->len, width))
        return NULL;
    for (i = 0; i < fragment->len; i += width)
        sum += GETRAWSAMPLE(width, fragment->buf, i);
    if (fragment->len == 0)
        avg = 0;
    else
        avg = (int)floor(sum / (double)(fragment->len/width));
    return PyLong_FromLong(avg);
}

/*[clinic input]
audioop.rms

    fragment: Py_buffer
    width: int
    /

Return the root-mean-square of the fragment, i.e. sqrt(sum(S_i^2)/n).
[clinic start generated code]*/

static PyObject *
audioop_rms_impl(PyObject *module, Py_buffer *fragment, int width)
/*[clinic end generated code: output=1e7871c826445698 input=4cc57c6c94219d78]*/
{
    Py_ssize_t i;
    unsigned int res;
    double sum_squares = 0.0;

    if (!audioop_check_parameters(module, fragment->len, width))
        return NULL;
    for (i = 0; i < fragment->len; i += width) {
        double val = GETRAWSAMPLE(width, fragment->buf, i);
        sum_squares += val*val;
    }
    if (fragment->len == 0)
        res = 0;
    else
        res = (unsigned int)sqrt(sum_squares / (double)(fragment->len/width));
    return PyLong_FromUnsignedLong(res);
}

static double _sum2(const int16_t *a, const int16_t *b, Py_ssize_t len)
{
    Py_ssize_t i;
    double sum = 0.0;

    for( i=0; i<len; i++) {
        sum = sum + (double)a[i]*(double)b[i];
    }
    return sum;
}

/*
** Findfit tries to locate a sample within another sample. Its main use
** is in echo-cancellation (to find the feedback of the output signal in
** the input signal).
** The method used is as follows:
**
** let R be the reference signal (length n) and A the input signal (length N)
** with N > n, and let all sums be over i from 0 to n-1.
**
** Now, for each j in {0..N-n} we compute a factor fj so that -fj*R matches A
** as good as possible, i.e. sum( (A[j+i]+fj*R[i])^2 ) is minimal. This
** equation gives fj = sum( A[j+i]R[i] ) / sum(R[i]^2).
**
** Next, we compute the relative distance between the original signal and
** the modified signal and minimize that over j:
** vj = sum( (A[j+i]-fj*R[i])^2 ) / sum( A[j+i]^2 )  =>
** vj = ( sum(A[j+i]^2)*sum(R[i]^2) - sum(A[j+i]R[i])^2 ) / sum( A[j+i]^2 )
**
** In the code variables correspond as follows:
** cp1          A
** cp2          R
** len1         N
** len2         n
** aj_m1        A[j-1]
** aj_lm1       A[j+n-1]
** sum_ri_2     sum(R[i]^2)
** sum_aij_2    sum(A[i+j]^2)
** sum_aij_ri   sum(A[i+j]R[i])
**
** sum_ri is calculated once, sum_aij_2 is updated each step and sum_aij_ri
** is completely recalculated each step.
*/
/*[clinic input]
audioop.findfit

    fragment: Py_buffer
    reference: Py_buffer
    /

Try to match reference as well as possible to a portion of fragment.
[clinic start generated code]*/

static PyObject *
audioop_findfit_impl(PyObject *module, Py_buffer *fragment,
                     Py_buffer *reference)
/*[clinic end generated code: output=5752306d83cbbada input=62c305605e183c9a]*/
{
    const int16_t *cp1, *cp2;
    Py_ssize_t len1, len2;
    Py_ssize_t j, best_j;
    double aj_m1, aj_lm1;
    double sum_ri_2, sum_aij_2, sum_aij_ri, result, best_result, factor;

    if (fragment->len & 1 || reference->len & 1) {
        PyErr_SetString(get_audioop_state(module)->AudioopError,
                        "Strings should be even-sized");
        return NULL;
    }
    cp1 = (const int16_t *)fragment->buf;
    len1 = fragment->len >> 1;
    cp2 = (const int16_t *)reference->buf;
    len2 = reference->len >> 1;

    if (len1 < len2) {
        PyErr_SetString(get_audioop_state(module)->AudioopError,
                        "First sample should be longer");
        return NULL;
    }
    sum_ri_2 = _sum2(cp2, cp2, len2);
    sum_aij_2 = _sum2(cp1, cp1, len2);
    sum_aij_ri = _sum2(cp1, cp2, len2);

    result = (sum_ri_2*sum_aij_2 - sum_aij_ri*sum_aij_ri) / sum_aij_2;

    best_result = result;
    best_j = 0;

    for ( j=1; j<=len1-len2; j++) {
        aj_m1 = (double)cp1[j-1];
        aj_lm1 = (double)cp1[j+len2-1];

        sum_aij_2 = sum_aij_2 + aj_lm1*aj_lm1 - aj_m1*aj_m1;
        sum_aij_ri = _sum2(cp1+j, cp2, len2);

        result = (sum_ri_2*sum_aij_2 - sum_aij_ri*sum_aij_ri)
            / sum_aij_2;

        if ( result < best_result ) {
            best_result = result;
            best_j = j;
        }

    }

    factor = _sum2(cp1+best_j, cp2, len2) / sum_ri_2;

    return Py_BuildValue("(nf)", best_j, factor);
}

/*
** findfactor finds a factor f so that the energy in A-fB is minimal.
** See the comment for findfit for details.
*/
/*[clinic input]
audioop.findfactor

    fragment: Py_buffer
    reference: Py_buffer
    /

Return a factor F such that rms(add(fragment, mul(reference, -F))) is minimal.
[clinic start generated code]*/

static PyObject *
audioop_findfactor_impl(PyObject *module, Py_buffer *fragment,
                        Py_buffer *reference)
/*[clinic end generated code: output=14ea95652c1afcf8 input=816680301d012b21]*/
{
    const int16_t *cp1, *cp2;
    Py_ssize_t len;
    double sum_ri_2, sum_aij_ri, result;

    if (fragment->len & 1 || reference->len & 1) {
        PyErr_SetString(get_audioop_state(module)->AudioopError,
                        "Strings should be even-sized");
        return NULL;
    }
    if (fragment->len != reference->len) {
        PyErr_SetString(get_audioop_state(module)->AudioopError,
                        "Samples should be same size");
        return NULL;
    }
    cp1 = (const int16_t *)fragment->buf;
    cp2 = (const int16_t *)reference->buf;
    len = fragment->len >> 1;
    sum_ri_2 = _sum2(cp2, cp2, len);
    sum_aij_ri = _sum2(cp1, cp2, len);

    result = sum_aij_ri / sum_ri_2;

    return PyFloat_FromDouble(result);
}

/*
** findmax returns the index of the n-sized segment of the input sample
** that contains the most energy.
*/
/*[clinic input]
audioop.findmax

    fragment: Py_buffer
    length: Py_ssize_t
    /

Search fragment for a slice of specified number of samples with maximum energy.
[clinic start generated code]*/

static PyObject *
audioop_findmax_impl(PyObject *module, Py_buffer *fragment,
                     Py_ssize_t length)
/*[clinic end generated code: output=f008128233523040 input=2f304801ed42383c]*/
{
    const int16_t *cp1;
    Py_ssize_t len1;
    Py_ssize_t j, best_j;
    double aj_m1, aj_lm1;
    double result, best_result;

    if (fragment->len & 1) {
        PyErr_SetString(get_audioop_state(module)->AudioopError,
                        "Strings should be even-sized");
        return NULL;
    }
    cp1 = (const int16_t *)fragment->buf;
    len1 = fragment->len >> 1;

    if (length < 0 || len1 < length) {
        PyErr_SetString(get_audioop_state(module)->AudioopError,
                        "Input sample should be longer");
        return NULL;
    }

    result = _sum2(cp1, cp1, length);

    best_result = result;
    best_j = 0;

    for ( j=1; j<=len1-length; j++) {
        aj_m1 = (double)cp1[j-1];
        aj_lm1 = (double)cp1[j+length-1];

        result = result + aj_lm1*aj_lm1 - aj_m1*aj_m1;

        if ( result > best_result ) {
            best_result = result;
            best_j = j;
        }

    }

    return PyLong_FromSsize_t(best_j);
}

/*[clinic input]
audioop.avgpp

    fragment: Py_buffer
    width: int
    /

Return the average peak-peak value over all samples in the fragment.
[clinic start generated code]*/

static PyObject *
audioop_avgpp_impl(PyObject *module, Py_buffer *fragment, int width)
/*[clinic end generated code: output=269596b0d5ae0b2b input=0b3cceeae420a7d9]*/
{
    Py_ssize_t i;
    int prevval, prevextremevalid = 0, prevextreme = 0;
    double sum = 0.0;
    unsigned int avg;
    int diff, prevdiff, nextreme = 0;

    if (!audioop_check_parameters(module, fragment->len, width))
        return NULL;
    if (fragment->len <= width)
        return PyLong_FromLong(0);
    prevval = GETRAWSAMPLE(width, fragment->buf, 0);
    prevdiff = 17; /* Anything != 0, 1 */
    for (i = width; i < fragment->len; i += width) {
        int val = GETRAWSAMPLE(width, fragment->buf, i);
        if (val != prevval) {
            diff = val < prevval;
            if (prevdiff == !diff) {
                /* Derivative changed sign. Compute difference to last
                ** extreme value and remember.
                */
                if (prevextremevalid) {
                    if (prevval < prevextreme)
                        sum += (double)((unsigned int)prevextreme -
                                        (unsigned int)prevval);
                    else
                        sum += (double)((unsigned int)prevval -
                                        (unsigned int)prevextreme);
                    nextreme++;
                }
                prevextremevalid = 1;
                prevextreme = prevval;
            }
            prevval = val;
            prevdiff = diff;
        }
    }
    if ( nextreme == 0 )
        avg = 0;
    else
        avg = (unsigned int)(sum / (double)nextreme);
    return PyLong_FromUnsignedLong(avg);
}

/*[clinic input]
audioop.maxpp

    fragment: Py_buffer
    width: int
    /

Return the maximum peak-peak value in the sound fragment.
[clinic start generated code]*/

static PyObject *
audioop_maxpp_impl(PyObject *module, Py_buffer *fragment, int width)
/*[clinic end generated code: output=5b918ed5dbbdb978 input=671a13e1518f80a1]*/
{
    Py_ssize_t i;
    int prevval, prevextremevalid = 0, prevextreme = 0;
    unsigned int max = 0, extremediff;
    int diff, prevdiff;

    if (!audioop_check_parameters(module, fragment->len, width))
        return NULL;
    if (fragment->len <= width)
        return PyLong_FromLong(0);
    prevval = GETRAWSAMPLE(width, fragment->buf, 0);
    prevdiff = 17; /* Anything != 0, 1 */
    for (i = width; i < fragment->len; i += width) {
        int val = GETRAWSAMPLE(width, fragment->buf, i);
        if (val != prevval) {
            diff = val < prevval;
            if (prevdiff == !diff) {
                /* Derivative changed sign. Compute difference to
                ** last extreme value and remember.
                */
                if (prevextremevalid) {
                    if (prevval < prevextreme)
                        extremediff = (unsigned int)prevextreme -
                                      (unsigned int)prevval;
                    else
                        extremediff = (unsigned int)prevval -
                                      (unsigned int)prevextreme;
                    if ( extremediff > max )
                        max = extremediff;
                }
                prevextremevalid = 1;
                prevextreme = prevval;
            }
            prevval = val;
            prevdiff = diff;
        }
    }
    return PyLong_FromUnsignedLong(max);
}

/*[clinic input]
audioop.cross

    fragment: Py_buffer
    width: int
    /

Return the number of zero crossings in the fragment passed as an argument.
[clinic start generated code]*/

static PyObject *
audioop_cross_impl(PyObject *module, Py_buffer *fragment, int width)
/*[clinic end generated code: output=5938dcdd74a1f431 input=b1b3f15b83f6b41a]*/
{
    Py_ssize_t i;
    int prevval;
    Py_ssize_t ncross;

    if (!audioop_check_parameters(module, fragment->len, width))
        return NULL;
    ncross = -1;
    prevval = 17; /* Anything <> 0,1 */
    for (i = 0; i < fragment->len; i += width) {
        int val = GETRAWSAMPLE(width, fragment->buf, i) < 0;
        if (val != prevval) ncross++;
        prevval = val;
    }
    return PyLong_FromSsize_t(ncross);
}

/*[clinic input]
audioop.mul

    fragment: Py_buffer
    width: int
    factor: double
    /

Return a fragment that has all samples in the original fragment multiplied by the floating-point value factor.
[clinic start generated code]*/

static PyObject *
audioop_mul_impl(PyObject *module, Py_buffer *fragment, int width,
                 double factor)
/*[clinic end generated code: output=6cd48fe796da0ea4 input=c726667baa157d3c]*/
{
    signed char *ncp;
    Py_ssize_t i;
    double maxval, minval;
    PyObject *rv;

    if (!audioop_check_parameters(module, fragment->len, width))
        return NULL;

    maxval = (double) maxvals[width];
    minval = (double) minvals[width];

    rv = PyBytes_FromStringAndSize(NULL, fragment->len);
    if (rv == NULL)
        return NULL;
    ncp = (signed char *)PyBytes_AsString(rv);

    for (i = 0; i < fragment->len; i += width) {
        double val = GETRAWSAMPLE(width, fragment->buf, i);
        int ival = fbound(val * factor, minval, maxval);
        SETRAWSAMPLE(width, ncp, i, ival);
    }
    return rv;
}

/*[clinic input]
audioop.tomono

    fragment: Py_buffer
    width: int
    lfactor: double
    rfactor: double
    /

Convert a stereo fragment to a mono fragment.
[clinic start generated code]*/

static PyObject *
audioop_tomono_impl(PyObject *module, Py_buffer *fragment, int width,
                    double lfactor, double rfactor)
/*[clinic end generated code: output=235c8277216d4e4e input=c4ec949b3f4dddfa]*/
{
    signed char *cp, *ncp;
    Py_ssize_t len, i;
    double maxval, minval;
    PyObject *rv;

    cp = fragment->buf;
    len = fragment->len;
    if (!audioop_check_parameters(module, len, width))
        return NULL;
    if (((len / width) & 1) != 0) {
        PyErr_SetString(get_audioop_state(module)->AudioopError,
                        "not a whole number of frames");
        return NULL;
    }

    maxval = (double) maxvals[width];
    minval = (double) minvals[width];

    rv = PyBytes_FromStringAndSize(NULL, len/2);
    if (rv == NULL)
        return NULL;
    ncp = (signed char *)PyBytes_AsString(rv);

    for (i = 0; i < len; i += width*2) {
        double val1 = GETRAWSAMPLE(width, cp, i);
        double val2 = GETRAWSAMPLE(width, cp, i + width);
        double val = val1 * lfactor + val2 * rfactor;
        int ival = fbound(val, minval, maxval);
        SETRAWSAMPLE(width, ncp, i/2, ival);
    }
    return rv;
}

/*[clinic input]
audioop.tostereo

    fragment: Py_buffer
    width: int
    lfactor: double
    rfactor: double
    /

Generate a stereo fragment from a mono fragment.
[clinic start generated code]*/

static PyObject *
audioop_tostereo_impl(PyObject *module, Py_buffer *fragment, int width,
                      double lfactor, double rfactor)
/*[clinic end generated code: output=046f13defa5f1595 input=27b6395ebfdff37a]*/
{
    signed char *ncp;
    Py_ssize_t i;
    double maxval, minval;
    PyObject *rv;

    if (!audioop_check_parameters(module, fragment->len, width))
        return NULL;

    maxval = (double) maxvals[width];
    minval = (double) minvals[width];

    if (fragment->len > PY_SSIZE_T_MAX/2) {
        PyErr_SetString(PyExc_MemoryError,
                        "not enough memory for output buffer");
        return NULL;
    }

    rv = PyBytes_FromStringAndSize(NULL, fragment->len*2);
    if (rv == NULL)
        return NULL;
    ncp = (signed char *)PyBytes_AsString(rv);

    for (i = 0; i < fragment->len; i += width) {
        double val = GETRAWSAMPLE(width, fragment->buf, i);
        int val1 = fbound(val * lfactor, minval, maxval);
        int val2 = fbound(val * rfactor, minval, maxval);
        SETRAWSAMPLE(width, ncp, i*2, val1);
        SETRAWSAMPLE(width, ncp, i*2 + width, val2);
    }
    return rv;
}

/*[clinic input]
audioop.add

    fragment1: Py_buffer
    fragment2: Py_buffer
    width: int
    /

Return a fragment which is the addition of the two samples passed as parameters.
[clinic start generated code]*/

static PyObject *
audioop_add_impl(PyObject *module, Py_buffer *fragment1,
                 Py_buffer *fragment2, int width)
/*[clinic end generated code: output=60140af4d1aab6f2 input=4a8d4bae4c1605c7]*/
{
    signed char *ncp;
    Py_ssize_t i;
    int minval, maxval, newval;
    PyObject *rv;

    if (!audioop_check_parameters(module, fragment1->len, width))
        return NULL;
    if (fragment1->len != fragment2->len) {
        PyErr_SetString(get_audioop_state(module)->AudioopError,
                        "Lengths should be the same");
        return NULL;
    }

    maxval = maxvals[width];
    minval = minvals[width];

    rv = PyBytes_FromStringAndSize(NULL, fragment1->len);
    if (rv == NULL)
        return NULL;
    ncp = (signed char *)PyBytes_AsString(rv);

    for (i = 0; i < fragment1->len; i += width) {
        int val1 = GETRAWSAMPLE(width, fragment1->buf, i);
        int val2 = GETRAWSAMPLE(width, fragment2->buf, i);

        if (width < 4) {
            newval = val1 + val2;
            /* truncate in case of overflow */
            if (newval > maxval)
                newval = maxval;
            else if (newval < minval)
                newval = minval;
        }
        else {
            double fval = (double)val1 + (double)val2;
            /* truncate in case of overflow */
            newval = fbound(fval, minval, maxval);
        }

        SETRAWSAMPLE(width, ncp, i, newval);
    }
    return rv;
}

/*[clinic input]
audioop.bias

    fragment: Py_buffer
    width: int
    bias: int
    /

Return a fragment that is the original fragment with a bias added to each sample.
[clinic start generated code]*/

static PyObject *
audioop_bias_impl(PyObject *module, Py_buffer *fragment, int width, int bias)
/*[clinic end generated code: output=6e0aa8f68f045093 input=2b5cce5c3bb4838c]*/
{
    signed char *ncp;
    Py_ssize_t i;
    unsigned int val = 0, mask;
    PyObject *rv;

    if (!audioop_check_parameters(module, fragment->len, width))
        return NULL;

    rv = PyBytes_FromStringAndSize(NULL, fragment->len);
    if (rv == NULL)
        return NULL;
    ncp = (signed char *)PyBytes_AsString(rv);

    mask = masks[width];

    for (i = 0; i < fragment->len; i += width) {
        if (width == 1)
            val = GETINTX(unsigned char, fragment->buf, i);
        else if (width == 2)
            val = GETINTX(uint16_t, fragment->buf, i);
        else if (width == 3)
            val = ((unsigned int)GETINT24(fragment->buf, i)) & 0xffffffu;
        else {
            assert(width == 4);
            val = GETINTX(uint32_t, fragment->buf, i);
        }

        val += (unsigned int)bias;
        /* wrap around in case of overflow */
        val &= mask;

        if (width == 1)
            SETINTX(unsigned char, ncp, i, val);
        else if (width == 2)
            SETINTX(uint16_t, ncp, i, val);
        else if (width == 3)
            SETINT24(ncp, i, (int)val);
        else {
            assert(width == 4);
            SETINTX(uint32_t, ncp, i, val);
        }
    }
    return rv;
}

/*[clinic input]
audioop.reverse

    fragment: Py_buffer
    width: int
    /

Reverse the samples in a fragment and returns the modified fragment.
[clinic start generated code]*/

static PyObject *
audioop_reverse_impl(PyObject *module, Py_buffer *fragment, int width)
/*[clinic end generated code: output=b44135698418da14 input=668f890cf9f9d225]*/
{
    unsigned char *ncp;
    Py_ssize_t i;
    PyObject *rv;

    if (!audioop_check_parameters(module, fragment->len, width))
        return NULL;

    rv = PyBytes_FromStringAndSize(NULL, fragment->len);
    if (rv == NULL)
        return NULL;
    ncp = (unsigned char *)PyBytes_AsString(rv);

    for (i = 0; i < fragment->len; i += width) {
        int val = GETRAWSAMPLE(width, fragment->buf, i);
        SETRAWSAMPLE(width, ncp, fragment->len - i - width, val);
    }
    return rv;
}

/*[clinic input]
audioop.byteswap

    fragment: Py_buffer
    width: int
    /

Convert big-endian samples to little-endian and vice versa.
[clinic start generated code]*/

static PyObject *
audioop_byteswap_impl(PyObject *module, Py_buffer *fragment, int width)
/*[clinic end generated code: output=50838a9e4b87cd4d input=fae7611ceffa5c82]*/
{
    unsigned char *ncp;
    Py_ssize_t i;
    PyObject *rv;

    if (!audioop_check_parameters(module, fragment->len, width))
        return NULL;

    rv = PyBytes_FromStringAndSize(NULL, fragment->len);
    if (rv == NULL)
        return NULL;
    ncp = (unsigned char *)PyBytes_AsString(rv);

    for (i = 0; i < fragment->len; i += width) {
        int j;
        for (j = 0; j < width; j++)
            ncp[i + width - 1 - j] = ((unsigned char *)fragment->buf)[i + j];
    }
    return rv;
}

/*[clinic input]
audioop.lin2lin

    fragment: Py_buffer
    width: int
    newwidth: int
    /

Convert samples between 1-, 2-, 3- and 4-byte formats.
[clinic start generated code]*/

static PyObject *
audioop_lin2lin_impl(PyObject *module, Py_buffer *fragment, int width,
                     int newwidth)
/*[clinic end generated code: output=17b14109248f1d99 input=5ce08c8aa2f24d96]*/
{
    unsigned char *ncp;
    Py_ssize_t i, j;
    PyObject *rv;

    if (!audioop_check_parameters(module, fragment->len, width))
        return NULL;
    if (!audioop_check_size(module, newwidth))
        return NULL;

    if (fragment->len/width > PY_SSIZE_T_MAX/newwidth) {
        PyErr_SetString(PyExc_MemoryError,
                        "not enough memory for output buffer");
        return NULL;
    }
    rv = PyBytes_FromStringAndSize(NULL, (fragment->len/width)*newwidth);
    if (rv == NULL)
        return NULL;
    ncp = (unsigned char *)PyBytes_AsString(rv);

    for (i = j = 0; i < fragment->len; i += width, j += newwidth) {
        int val = GETSAMPLE32(width, fragment->buf, i);
        SETSAMPLE32(newwidth, ncp, j, val);
    }
    return rv;
}

static int
gcd(int a, int b)
{
    while (b > 0) {
        int tmp = a % b;
        a = b;
        b = tmp;
    }
    return a;
}

/*[clinic input]
audioop.ratecv

    fragment: Py_buffer
    width: int
    nchannels: int
    inrate: int
    outrate: int
    state: object
    weightA: int = 1
    weightB: int = 0
    /

Convert the frame rate of the input fragment.
[clinic start generated code]*/

static PyObject *
audioop_ratecv_impl(PyObject *module, Py_buffer *fragment, int width,
                    int nchannels, int inrate, int outrate, PyObject *state,
                    int weightA, int weightB)
/*[clinic end generated code: output=624038e843243139 input=aff3acdc94476191]*/
{
    char *cp, *ncp;
    Py_ssize_t len;
    int chan, d, *prev_i, *cur_i, cur_o;
    PyObject *samps, *str, *rv = NULL, *channel;
    int bytes_per_frame;

    if (!audioop_check_size(module, width))
        return NULL;
    if (nchannels < 1) {
        PyErr_SetString(get_audioop_state(module)->AudioopError,
                        "# of channels should be >= 1");
        return NULL;
    }
    if (width > INT_MAX / nchannels) {
        /* This overflow test is rigorously correct because
           both multiplicands are >= 1.  Use the argument names
           from the docs for the error msg. */
        PyErr_SetString(PyExc_OverflowError,
                        "width * nchannels too big for a C int");
        return NULL;
    }
    bytes_per_frame = width * nchannels;
    if (weightA < 1 || weightB < 0) {
        PyErr_SetString(get_audioop_state(module)->AudioopError,
            "weightA should be >= 1, weightB should be >= 0");
        return NULL;
    }
    assert(fragment->len >= 0);
    if (fragment->len % bytes_per_frame != 0) {
        PyErr_SetString(get_audioop_state(module)->AudioopError,
                        "not a whole number of frames");
        return NULL;
    }
    if (inrate <= 0 || outrate <= 0) {
        PyErr_SetString(get_audioop_state(module)->AudioopError,
                        "sampling rate not > 0");
        return NULL;
    }
    /* divide inrate and outrate by their greatest common divisor */
    d = gcd(inrate, outrate);
    inrate /= d;
    outrate /= d;
    /* divide weightA and weightB by their greatest common divisor */
    d = gcd(weightA, weightB);
    weightA /= d;
    weightB /= d;

    if ((size_t)nchannels > SIZE_MAX/sizeof(int)) {
        PyErr_SetString(PyExc_MemoryError,
                        "not enough memory for output buffer");
        return NULL;
    }
    prev_i = (int *) PyMem_Malloc(nchannels * sizeof(int));
    cur_i = (int *) PyMem_Malloc(nchannels * sizeof(int));
    if (prev_i == NULL || cur_i == NULL) {
        (void) PyErr_NoMemory();
        goto exit;
    }

    len = fragment->len / bytes_per_frame; /* # of frames */

    if (state == Py_None) {
        d = -outrate;
        for (chan = 0; chan < nchannels; chan++)
            prev_i[chan] = cur_i[chan] = 0;
    }
    else {
        if (!PyTuple_Check(state)) {
            PyErr_SetString(PyExc_TypeError, "state must be a tuple or None");
            goto exit;
        }
        if (!PyArg_ParseTuple(state,
                        "iO!;ratecv(): illegal state argument",
                        &d, &PyTuple_Type, &samps))
            goto exit;
        if (PyTuple_Size(samps) != nchannels) {
            PyErr_SetString(get_audioop_state(module)->AudioopError,
                            "illegal state argument");
            goto exit;
        }
        for (chan = 0; chan < nchannels; chan++) {
            channel = PyTuple_GetItem(samps, chan);
            if (!PyTuple_Check(channel)) {
                PyErr_SetString(PyExc_TypeError,
                                "ratecv(): illegal state argument");
                goto exit;
            }
            if (!PyArg_ParseTuple(channel,
                                  "ii;ratecv(): illegal state argument",
                                  &prev_i[chan], &cur_i[chan]))
            {
                goto exit;
            }
        }
    }

    /* str <- Space for the output buffer. */
    if (len == 0)
        str = PyBytes_FromStringAndSize(NULL, 0);
    else {
        /* There are len input frames, so we need (mathematically)
           ceiling(len*outrate/inrate) output frames, and each frame
           requires bytes_per_frame bytes.  Computing this
           without spurious overflow is the challenge; we can
           settle for a reasonable upper bound, though, in this
           case ceiling(len/inrate) * outrate. */

        /* compute ceiling(len/inrate) without overflow */
        Py_ssize_t q = 1 + (len - 1) / inrate;
        if (outrate > PY_SSIZE_T_MAX / q / bytes_per_frame)
            str = NULL;
        else
            str = PyBytes_FromStringAndSize(NULL,
                                            q * outrate * bytes_per_frame);
    }
    if (str == NULL) {
        PyErr_SetString(PyExc_MemoryError,
            "not enough memory for output buffer");
        goto exit;
    }
    ncp = PyBytes_AsString(str);
    cp = fragment->buf;

    for (;;) {
        while (d < 0) {
            if (len == 0) {
                samps = PyTuple_New(nchannels);
                if (samps == NULL)
                    goto exit;
                for (chan = 0; chan < nchannels; chan++)
                    PyTuple_SetItem(samps, chan,
                        Py_BuildValue("(ii)",
                                      prev_i[chan],
                                      cur_i[chan]));
                if (PyErr_Occurred())
                    goto exit;
                /* We have checked before that the length
                 * of the string fits into int. */
                len = (Py_ssize_t)(ncp - PyBytes_AsString(str));
                rv = PyBytes_FromStringAndSize
                    (PyBytes_AsString(str), len);
                Py_DECREF(str);
                str = rv;
                if (str == NULL)
                    goto exit;
                rv = Py_BuildValue("(O(iO))", str, d, samps);
                Py_DECREF(samps);
                Py_DECREF(str);
                goto exit; /* return rv */
            }
            for (chan = 0; chan < nchannels; chan++) {
                prev_i[chan] = cur_i[chan];
                cur_i[chan] = GETSAMPLE32(width, cp, 0);
                cp += width;
                /* implements a simple digital filter */
                cur_i[chan] = (int)(
                    ((double)weightA * (double)cur_i[chan] +
                     (double)weightB * (double)prev_i[chan]) /
                    ((double)weightA + (double)weightB));
            }
            len--;
            d += outrate;
        }
        while (d >= 0) {
            for (chan = 0; chan < nchannels; chan++) {
                cur_o = (int)(((double)prev_i[chan] * (double)d +
                         (double)cur_i[chan] * (double)(outrate - d)) /
                    (double)outrate);
                SETSAMPLE32(width, ncp, 0, cur_o);
                ncp += width;
            }
            d -= inrate;
        }
    }
  exit:
    PyMem_Free(prev_i);
    PyMem_Free(cur_i);
    return rv;
}

/*[clinic input]
audioop.lin2ulaw

    fragment: Py_buffer
    width: int
    /

Convert samples in the audio fragment to u-LAW encoding.
[clinic start generated code]*/

static PyObject *
audioop_lin2ulaw_impl(PyObject *module, Py_buffer *fragment, int width)
/*[clinic end generated code: output=14fb62b16fe8ea8e input=2450d1b870b6bac2]*/
{
    unsigned char *ncp;
    Py_ssize_t i;
    PyObject *rv;

    if (!audioop_check_parameters(module, fragment->len, width))
        return NULL;

    rv = PyBytes_FromStringAndSize(NULL, fragment->len/width);
    if (rv == NULL)
        return NULL;
    ncp = (unsigned char *)PyBytes_AsString(rv);

    for (i = 0; i < fragment->len; i += width) {
        int val = GETSAMPLE32(width, fragment->buf, i);
        *ncp++ = st_14linear2ulaw(val >> 18);
    }
    return rv;
}

/*[clinic input]
audioop.ulaw2lin

    fragment: Py_buffer
    width: int
    /

Convert sound fragments in u-LAW encoding to linearly encoded sound fragments.
[clinic start generated code]*/

static PyObject *
audioop_ulaw2lin_impl(PyObject *module, Py_buffer *fragment, int width)
/*[clinic end generated code: output=378356b047521ba2 input=45d53ddce5be7d06]*/
{
    unsigned char *cp;
    signed char *ncp;
    Py_ssize_t i;
    PyObject *rv;

    if (!audioop_check_size(module, width))
        return NULL;

    if (fragment->len > PY_SSIZE_T_MAX/width) {
        PyErr_SetString(PyExc_MemoryError,
                        "not enough memory for output buffer");
        return NULL;
    }
    rv = PyBytes_FromStringAndSize(NULL, fragment->len*width);
    if (rv == NULL)
        return NULL;
    ncp = (signed char *)PyBytes_AsString(rv);

    cp = fragment->buf;
    for (i = 0; i < fragment->len*width; i += width) {
        int val = st_ulaw2linear16(*cp++) << 16;
        SETSAMPLE32(width, ncp, i, val);
    }
    return rv;
}

/*[clinic input]
audioop.lin2alaw

    fragment: Py_buffer
    width: int
    /

Convert samples in the audio fragment to a-LAW encoding.
[clinic start generated code]*/

static PyObject *
audioop_lin2alaw_impl(PyObject *module, Py_buffer *fragment, int width)
/*[clinic end generated code: output=d076f130121a82f0 input=ffb1ef8bb39da945]*/
{
    unsigned char *ncp;
    Py_ssize_t i;
    PyObject *rv;

    if (!audioop_check_parameters(module, fragment->len, width))
        return NULL;

    rv = PyBytes_FromStringAndSize(NULL, fragment->len/width);
    if (rv == NULL)
        return NULL;
    ncp = (unsigned char *)PyBytes_AsString(rv);

    for (i = 0; i < fragment->len; i += width) {
        int val = GETSAMPLE32(width, fragment->buf, i);
        *ncp++ = st_linear2alaw(val >> 19);
    }
    return rv;
}

/*[clinic input]
audioop.alaw2lin

    fragment: Py_buffer
    width: int
    /

Convert sound fragments in a-LAW encoding to linearly encoded sound fragments.
[clinic start generated code]*/

static PyObject *
audioop_alaw2lin_impl(PyObject *module, Py_buffer *fragment, int width)
/*[clinic end generated code: output=85c365ec559df647 input=4140626046cd1772]*/
{
    unsigned char *cp;
    signed char *ncp;
    Py_ssize_t i;
    int val;
    PyObject *rv;

    if (!audioop_check_size(module, width))
        return NULL;

    if (fragment->len > PY_SSIZE_T_MAX/width) {
        PyErr_SetString(PyExc_MemoryError,
                        "not enough memory for output buffer");
        return NULL;
    }
    rv = PyBytes_FromStringAndSize(NULL, fragment->len*width);
    if (rv == NULL)
        return NULL;
    ncp = (signed char *)PyBytes_AsString(rv);
    cp = fragment->buf;

    for (i = 0; i < fragment->len*width; i += width) {
        val = st_alaw2linear16(*cp++) << 16;
        SETSAMPLE32(width, ncp, i, val);
    }
    return rv;
}

/*[clinic input]
audioop.lin2adpcm

    fragment: Py_buffer
    width: int
    state: object
    /

Convert samples to 4 bit Intel/DVI ADPCM encoding.
[clinic start generated code]*/

static PyObject *
audioop_lin2adpcm_impl(PyObject *module, Py_buffer *fragment, int width,
                       PyObject *state)
/*[clinic end generated code: output=cc19f159f16c6793 input=12919d549b90c90a]*/
{
    signed char *ncp;
    Py_ssize_t i;
    int step, valpred, delta,
        index, sign, vpdiff, diff;
    PyObject *rv = NULL, *str;
    int outputbuffer = 0, bufferstep;

    if (!audioop_check_parameters(module, fragment->len, width))
        return NULL;

    /* Decode state, should have (value, step) */
    if ( state == Py_None ) {
        /* First time, it seems. Set defaults */
        valpred = 0;
        index = 0;
    }
    else if (!PyTuple_Check(state)) {
        PyErr_SetString(PyExc_TypeError, "state must be a tuple or None");
        return NULL;
    }
    else if (!PyArg_ParseTuple(state, "ii;lin2adpcm(): illegal state argument",
                               &valpred, &index))
    {
        return NULL;
    }
    else if (valpred >= 0x8000 || valpred < -0x8000 ||
             (size_t)index >= Py_ARRAY_LENGTH(stepsizeTable)) {
        PyErr_SetString(PyExc_ValueError, "bad state");
        return NULL;
    }

    str = PyBytes_FromStringAndSize(NULL, fragment->len/(width*2));
    if (str == NULL)
        return NULL;
    ncp = (signed char *)PyBytes_AsString(str);

    step = stepsizeTable[index];
    bufferstep = 1;

    for (i = 0; i < fragment->len; i += width) {
        int val = GETSAMPLE32(width, fragment->buf, i) >> 16;

        /* Step 1 - compute difference with previous value */
        if (val < valpred) {
            diff = valpred - val;
            sign = 8;
        }
        else {
            diff = val - valpred;
            sign = 0;
        }

        /* Step 2 - Divide and clamp */
        /* Note:
        ** This code *approximately* computes:
        **    delta = diff*4/step;
        **    vpdiff = (delta+0.5)*step/4;
        ** but in shift step bits are dropped. The net result of this
        ** is that even if you have fast mul/div hardware you cannot
        ** put it to good use since the fixup would be too expensive.
        */
        delta = 0;
        vpdiff = (step >> 3);

        if ( diff >= step ) {
            delta = 4;
            diff -= step;
            vpdiff += step;
        }
        step >>= 1;
        if ( diff >= step  ) {
            delta |= 2;
            diff -= step;
            vpdiff += step;
        }
        step >>= 1;
        if ( diff >= step ) {
            delta |= 1;
            vpdiff += step;
        }

        /* Step 3 - Update previous value */
        if ( sign )
            valpred -= vpdiff;
        else
            valpred += vpdiff;

        /* Step 4 - Clamp previous value to 16 bits */
        if ( valpred > 32767 )
            valpred = 32767;
        else if ( valpred < -32768 )
            valpred = -32768;

        /* Step 5 - Assemble value, update index and step values */
        delta |= sign;

        index += indexTable[delta];
        if ( index < 0 ) index = 0;
        if ( index > 88 ) index = 88;
        step = stepsizeTable[index];

        /* Step 6 - Output value */
        if ( bufferstep ) {
            outputbuffer = (delta << 4) & 0xf0;
        } else {
            *ncp++ = (delta & 0x0f) | outputbuffer;
        }
        bufferstep = !bufferstep;
    }
    rv = Py_BuildValue("(O(ii))", str, valpred, index);
    Py_DECREF(str);
    return rv;
}

/*[clinic input]
audioop.adpcm2lin

    fragment: Py_buffer
    width: int
    state: object
    /

Decode an Intel/DVI ADPCM coded fragment to a linear fragment.
[clinic start generated code]*/

static PyObject *
audioop_adpcm2lin_impl(PyObject *module, Py_buffer *fragment, int width,
                       PyObject *state)
/*[clinic end generated code: output=3440ea105acb3456 input=f5221144f5ca9ef0]*/
{
    signed char *cp;
    signed char *ncp;
    Py_ssize_t i, outlen;
    int valpred, step, delta, index, sign, vpdiff;
    PyObject *rv, *str;
    int inputbuffer = 0, bufferstep;

    if (!audioop_check_size(module, width))
        return NULL;

    /* Decode state, should have (value, step) */
    if ( state == Py_None ) {
        /* First time, it seems. Set defaults */
        valpred = 0;
        index = 0;
    }
    else if (!PyTuple_Check(state)) {
        PyErr_SetString(PyExc_TypeError, "state must be a tuple or None");
        return NULL;
    }
    else if (!PyArg_ParseTuple(state, "ii;adpcm2lin(): illegal state argument",
                               &valpred, &index))
    {
        return NULL;
    }
    else if (valpred >= 0x8000 || valpred < -0x8000 ||
             (size_t)index >= Py_ARRAY_LENGTH(stepsizeTable)) {
        PyErr_SetString(PyExc_ValueError, "bad state");
        return NULL;
    }

    if (fragment->len > (PY_SSIZE_T_MAX/2)/width) {
        PyErr_SetString(PyExc_MemoryError,
                        "not enough memory for output buffer");
        return NULL;
    }
    outlen = fragment->len*width*2;
    str = PyBytes_FromStringAndSize(NULL, outlen);
    if (str == NULL)
        return NULL;
    ncp = (signed char *)PyBytes_AsString(str);
    cp = fragment->buf;

    step = stepsizeTable[index];
    bufferstep = 0;

    for (i = 0; i < outlen; i += width) {
        /* Step 1 - get the delta value and compute next index */
        if ( bufferstep ) {
            delta = inputbuffer & 0xf;
        } else {
            inputbuffer = *cp++;
            delta = (inputbuffer >> 4) & 0xf;
        }

        bufferstep = !bufferstep;

        /* Step 2 - Find new index value (for later) */
        index += indexTable[delta];
        if ( index < 0 ) index = 0;
        if ( index > 88 ) index = 88;

        /* Step 3 - Separate sign and magnitude */
        sign = delta & 8;
        delta = delta & 7;

        /* Step 4 - Compute difference and new predicted value */
        /*
        ** Computes 'vpdiff = (delta+0.5)*step/4', but see comment
        ** in adpcm_coder.
        */
        vpdiff = step >> 3;
        if ( delta & 4 ) vpdiff += step;
        if ( delta & 2 ) vpdiff += step>>1;
        if ( delta & 1 ) vpdiff += step>>2;

        if ( sign )
            valpred -= vpdiff;
        else
            valpred += vpdiff;

        /* Step 5 - clamp output value */
        if ( valpred > 32767 )
            valpred = 32767;
        else if ( valpred < -32768 )
            valpred = -32768;

        /* Step 6 - Update step value */
        step = stepsizeTable[index];

        /* Step 6 - Output value */
        SETSAMPLE32(width, ncp, i, valpred << 16);
    }

    rv = Py_BuildValue("(O(ii))", str, valpred, index);
    Py_DECREF(str);
    return rv;
}

#include "clinic/audioop.c.h"

static PyMethodDef audioop_methods[] = {
    AUDIOOP_MAX_METHODDEF
    AUDIOOP_MINMAX_METHODDEF
    AUDIOOP_AVG_METHODDEF
    AUDIOOP_MAXPP_METHODDEF
    AUDIOOP_AVGPP_METHODDEF
    AUDIOOP_RMS_METHODDEF
    AUDIOOP_FINDFIT_METHODDEF
    AUDIOOP_FINDMAX_METHODDEF
    AUDIOOP_FINDFACTOR_METHODDEF
    AUDIOOP_CROSS_METHODDEF
    AUDIOOP_MUL_METHODDEF
    AUDIOOP_ADD_METHODDEF
    AUDIOOP_BIAS_METHODDEF
    AUDIOOP_ULAW2LIN_METHODDEF
    AUDIOOP_LIN2ULAW_METHODDEF
    AUDIOOP_ALAW2LIN_METHODDEF
    AUDIOOP_LIN2ALAW_METHODDEF
    AUDIOOP_LIN2LIN_METHODDEF
    AUDIOOP_ADPCM2LIN_METHODDEF
    AUDIOOP_LIN2ADPCM_METHODDEF
    AUDIOOP_TOMONO_METHODDEF
    AUDIOOP_TOSTEREO_METHODDEF
    AUDIOOP_GETSAMPLE_METHODDEF
    AUDIOOP_REVERSE_METHODDEF
    AUDIOOP_BYTESWAP_METHODDEF
    AUDIOOP_RATECV_METHODDEF
    { 0,          0 }
};

static int
audioop_traverse(PyObject *module, visitproc visit, void *arg)
{
    audioop_state *state = get_audioop_state(module);
    Py_VISIT(state->AudioopError);
    return 0;
}

static int
audioop_clear(PyObject *module)
{
    audioop_state *state = get_audioop_state(module);
    Py_CLEAR(state->AudioopError);
    return 0;
}

static void
audioop_free(void *module) {
    audioop_clear((PyObject *)module);
}

static int
audioop_exec(PyObject* module)
{
    audioop_state *state = get_audioop_state(module);

    state->AudioopError = PyErr_NewException("audioop.error", NULL, NULL);
    if (state->AudioopError == NULL) {
        return -1;
    }

    Py_INCREF(state->AudioopError);
    if (PyModule_AddObject(module, "error", state->AudioopError) < 0) {
        Py_DECREF(state->AudioopError);
        return -1;
    }

    return 0;
}

static PyModuleDef_Slot audioop_slots[] = {
    {Py_mod_exec, audioop_exec},
    {0, NULL}
};

static struct PyModuleDef audioopmodule = {
    PyModuleDef_HEAD_INIT,
    "audioop",
    NULL,
    sizeof(audioop_state),
    audioop_methods,
    audioop_slots,
    audioop_traverse,
    audioop_clear,
    audioop_free
};

PyMODINIT_FUNC
PyInit_audioop(void)
{
    return PyModuleDef_Init(&audioopmodule);
}
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