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annotate libgsmefr/pow2.c @ 585:3c6bf0d26ee7 default tip

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TW-TS-005 reader: fix maximum line length bug TW-TS-005 section 4.1 states: The maximum allowed length of each line is 80 characters, not including the OS-specific newline encoding. The implementation of this line length limit in the TW-TS-005 hex file reader function in the present suite was wrong, such that lines of the full maximum length could not be read. Fix it. Note that this bug affects comment lines too, not just actual RTP payloads. Neither Annex A nor Annex B features an RTP payload format that goes to the maximum of 40 bytes, but if a comment line goes to the maximum allowed length of 80 characters not including the terminating newline, the bug will be triggered, necessitating the present fix.
author Mychaela Falconia <falcon@freecalypso.org>
date Tue, 25 Feb 2025 07:49:28 +0000
parents 33714b36841a
children
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1 /*************************************************************************
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2 *
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3 * FUNCTION: Pow2()
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4 *
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5 * PURPOSE: computes L_x = pow(2.0, exponent.fraction)
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6 *
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7 * DESCRIPTION:
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8 * The function Pow2(L_x) is approximated by a table and linear
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9 * interpolation.
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10 * 1- i = bit10-b15 of fraction, 0 <= i <= 31
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11 * 2- a = bit0-b9 of fraction
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12 * 3- L_x = table[i]<<16 - (table[i] - table[i+1]) * a * 2
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13 * 4- L_x = L_x >> (30-exponent) (with rounding)
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14 *
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15 *************************************************************************/
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16
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17 #include "gsm_efr.h"
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18 #include "typedef.h"
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19 #include "namespace.h"
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20 #include "basic_op.h"
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21 #include "no_count.h"
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22 #include "sig_proc.h"
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24 #include "pow2.tab" /* Table for Pow2() */
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26 Word32 Pow2 ( /* (o) : result (range: 0<=val<=0x7fffffff) */
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27 Word16 exponent, /* (i) : Integer part. (range: 0<=val<=30) */
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28 Word16 fraction /* (i) : Fractional part. (range: 0.0<=val<1.0) */
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29 )
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30 {
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31 Word16 exp, i, a, tmp;
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32 Word32 L_x;
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34 L_x = L_mult (fraction, 32);/* L_x = fraction<<6 */
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35 i = extract_h (L_x); /* Extract b10-b16 of fraction */
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36 L_x = L_shr (L_x, 1);
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37 a = extract_l (L_x); /* Extract b0-b9 of fraction */
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38 a = a & (Word16) 0x7fff; logic16 ();
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40 L_x = L_deposit_h (table[i]); /* table[i] << 16 */
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41 tmp = sub (table[i], table[i + 1]); /* table[i] - table[i+1] */
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42 L_x = L_msu (L_x, tmp, a); /* L_x -= tmp*a*2 */
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44 exp = sub (30, exponent);
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45 L_x = L_shr_r (L_x, exp);
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47 return (L_x);
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48 }