Update FLAC to 1.3.1

src/libFLAC/lpc.c

 /* libFLAC - Free Lossless Audio Codec library
- * Copyright (C) 2000,2001,2002,2003,2004,2005,2006,2007  Josh Coalson
+ * Copyright (C) 2000-2009  Josh Coalson
+ * Copyright (C) 2011-2014  Xiph.Org Foundation
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * - Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *
  * - Redistributions in binary form must reproduce the above copyright
  * notice, this list of conditions and the following disclaimer in the
  * documentation and/or other materials provided with the distribution.
  *
  * - Neither the name of the Xiph.org Foundation nor the names of its
  * contributors may be used to endorse or promote products derived from
  * this software without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  * A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR
  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
  * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#if HAVE_CONFIG_H
+#ifdef HAVE_CONFIG_H
 #  include <config.h>
 #endif
 
 #include <math.h>
+
 #include "FLAC/assert.h"
 #include "FLAC/format.h"
+#include "share/compat.h"
 #include "private/bitmath.h"
 #include "private/lpc.h"
+#include "private/macros.h"
 #if defined DEBUG || defined FLAC__OVERFLOW_DETECT || defined FLAC__OVERFLOW_DETECT_VERBOSE
 #include <stdio.h>
 #endif
 
-#ifndef FLAC__INTEGER_ONLY_LIBRARY
-
-#ifndef M_LN2
-/* math.h in VC++ doesn't seem to have this (how Microsoft is that?) */
-#define M_LN2 0.69314718055994530942
-#endif
-
 /* OPT: #undef'ing this may improve the speed on some architectures */
 #define FLAC__LPC_UNROLLED_FILTER_LOOPS
 
+#ifndef FLAC__INTEGER_ONLY_LIBRARY
+
+#if !defined(HAVE_LROUND)
+#if defined(_MSC_VER)
+#include <float.h>
+#define copysign _copysign
+#elif defined(__GNUC__)
+#define copysign __builtin_copysign
+#endif
+static inline long int lround(double x) {
+    return (long)(x + copysign (0.5, x));
+}
+/* If this fails, we are in the presence of a mid 90's compiler, move along... */
+#endif
 
 void FLAC__lpc_window_data(const FLAC__int32 in[], const FLAC__real window[], FLAC__real out[], unsigned data_len)
 {
         unsigned i;
         for(i = 0; i < data_len; i++)
                 out[i] = in[i] * window[i];
 }
 
 void FLAC__lpc_compute_autocorrelation(const FLAC__real data[], unsigned data_len, unsigned lag, FLAC__real autoc[])
 {
@@ skipping 40 matching lines @@
         for(; sample < data_len; sample++) {
                 d = data[sample];
                 for(coeff = 0; coeff < data_len - sample; coeff++)
                         autoc[coeff] += d * data[sample+coeff];
         }
 }
 
 void FLAC__lpc_compute_lp_coefficients(const FLAC__real autoc[], unsigned *max_order, FLAC__real lp_coeff[][FLAC__MAX_LPC_ORDER], FLAC__double error[])
 {
         unsigned i, j;
-        FLAC__double r, err, ref[FLAC__MAX_LPC_ORDER], lpc[FLAC__MAX_LPC_ORDER];
+        FLAC__double r, err, lpc[FLAC__MAX_LPC_ORDER];
 
         FLAC__ASSERT(0 != max_order);
         FLAC__ASSERT(0 < *max_order);
         FLAC__ASSERT(*max_order <= FLAC__MAX_LPC_ORDER);
         FLAC__ASSERT(autoc[0] != 0.0);
 
         err = autoc[0];
 
         for(i = 0; i < *max_order; i++) {
                 /* Sum up this iteration's reflection coefficient. */
                 r = -autoc[i+1];
                 for(j = 0; j < i; j++)
                         r -= lpc[j] * autoc[i-j];
-                ref[i] = (r/=err);
+                r /= err;
 
                 /* Update LPC coefficients and total error. */
                 lpc[i]=r;
                 for(j = 0; j < (i>>1); j++) {
                         FLAC__double tmp = lpc[j];
                         lpc[j] += r * lpc[i-1-j];
                         lpc[i-1-j] += r * tmp;
                 }
                 if(i & 1)
                         lpc[j] += lpc[j] * r;
 
                 err *= (1.0 - r * r);
 
                 /* save this order */
                 for(j = 0; j <= i; j++)
                         lp_coeff[i][j] = (FLAC__real)(-lpc[j]); /* negate FIR filter coeff to get predictor coeff */
                 error[i] = err;
 
-                /* see SF bug #1601812 http://sourceforge.net/tracker/index.php?func=detail&aid=1601812&group_id=13478&atid=113478 */
+                /* see SF bug https://sourceforge.net/p/flac/bugs/234/ */
                 if(err == 0.0) {
                         *max_order = i+1;
                         return;
                 }
         }
 }
 
 int FLAC__lpc_quantize_coefficients(const FLAC__real lp_coeff[], unsigned order, unsigned precision, FLAC__int32 qlp_coeff[], int *shift)
 {
         unsigned i;
@@ skipping 34 matching lines @@
                         *shift = max_shiftlimit;
                 else if(*shift < min_shiftlimit)
                         return 1;
         }
 
         if(*shift >= 0) {
                 FLAC__double error = 0.0;
                 FLAC__int32 q;
                 for(i = 0; i < order; i++) {
                         error += lp_coeff[i] * (1 << *shift);
-#if 1 /* unfortunately lround() is C99 */
-                        if(error >= 0.0)
-                                q = (FLAC__int32)(error + 0.5);
-                        else
-                                q = (FLAC__int32)(error - 0.5);
-#else
                         q = lround(error);
-#endif
+
 #ifdef FLAC__OVERFLOW_DETECT
                         if(q > qmax+1) /* we expect q==qmax+1 occasionally due to rounding */
                                 fprintf(stderr,"FLAC__lpc_quantize_coefficients: quantizer overflow: q>qmax %d>%d shift=%d cmax=%f precision=%u lpc[%u]=%f\n",q,qmax,*shift,cmax,precision+1,i,lp_coeff[i]);
                         else if(q < qmin)
                                 fprintf(stderr,"FLAC__lpc_quantize_coefficients: quantizer overflow: q<qmin %d<%d shift=%d cmax=%f precision=%u lpc[%u]=%f\n",q,qmin,*shift,cmax,precision+1,i,lp_coeff[i]);
 #endif
                         if(q > qmax)
                                 q = qmax;
                         else if(q < qmin)
                                 q = qmin;
                         error -= q;
                         qlp_coeff[i] = q;
                 }
         }
         /* negative shift is very rare but due to design flaw, negative shift is
          * a NOP in the decoder, so it must be handled specially by scaling down
          * coeffs
          */
         else {
                 const int nshift = -(*shift);
                 FLAC__double error = 0.0;
                 FLAC__int32 q;
 #ifdef DEBUG
                 fprintf(stderr,"FLAC__lpc_quantize_coefficients: negative shift=%d order=%u cmax=%f\n", *shift, order, cmax);
 #endif
                 for(i = 0; i < order; i++) {
                         error += lp_coeff[i] / (1 << nshift);
-#if 1 /* unfortunately lround() is C99 */
-                        if(error >= 0.0)
-                                q = (FLAC__int32)(error + 0.5);
-                        else
-                                q = (FLAC__int32)(error - 0.5);
-#else
                         q = lround(error);
-#endif
 #ifdef FLAC__OVERFLOW_DETECT
                         if(q > qmax+1) /* we expect q==qmax+1 occasionally due to rounding */
                                 fprintf(stderr,"FLAC__lpc_quantize_coefficients: quantizer overflow: q>qmax %d>%d shift=%d cmax=%f precision=%u lpc[%u]=%f\n",q,qmax,*shift,cmax,precision+1,i,lp_coeff[i]);
                         else if(q < qmin)
                                 fprintf(stderr,"FLAC__lpc_quantize_coefficients: quantizer overflow: q<qmin %d<%d shift=%d cmax=%f precision=%u lpc[%u]=%f\n",q,qmin,*shift,cmax,precision+1,i,lp_coeff[i]);
 #endif
                         if(q > qmax)
                                 q = qmax;
                         else if(q < qmin)
                                 q = qmin;
                         error -= q;
                         qlp_coeff[i] = q;
                 }
                 *shift = 0;
         }
 
         return 0;
 }
 
-void FLAC__lpc_compute_residual_from_qlp_coefficients(const FLAC__int32 *data, unsigned data_len, const FLAC__int32 qlp_coeff[], unsigned order, int lp_quantization, FLAC__int32 residual[])
+#if defined(_MSC_VER)
+// silence MSVC warnings about __restrict modifier
+#pragma warning ( disable : 4028 )
+#endif
+
+void FLAC__lpc_compute_residual_from_qlp_coefficients(const FLAC__int32 * flac_restrict data, unsigned data_len, const FLAC__int32 * flac_restrict qlp_coeff, unsigned order, int lp_quantization, FLAC__int32 * flac_restrict residual)
 #if defined(FLAC__OVERFLOW_DETECT) || !defined(FLAC__LPC_UNROLLED_FILTER_LOOPS)
 {
         FLAC__int64 sumo;
         unsigned i, j;
         FLAC__int32 sum;
         const FLAC__int32 *history;
 
 #ifdef FLAC__OVERFLOW_DETECT_VERBOSE
         fprintf(stderr,"FLAC__lpc_compute_residual_from_qlp_coefficients: data_len=%d, order=%u, lpq=%d",data_len,order,lp_quantization);
         for(i=0;i<order;i++)
                 fprintf(stderr,", q[%u]=%d",i,qlp_coeff[i]);
         fprintf(stderr,"\n");
 #endif
         FLAC__ASSERT(order > 0);
 
         for(i = 0; i < data_len; i++) {
                 sumo = 0;
                 sum = 0;
                 history = data;
                 for(j = 0; j < order; j++) {
                         sum += qlp_coeff[j] * (*(--history));
                         sumo += (FLAC__int64)qlp_coeff[j] * (FLAC__int64)(*history);
-#if defined _MSC_VER
-                        if(sumo > 2147483647I64 || sumo < -2147483648I64)
-                                fprintf(stderr,"FLAC__lpc_compute_residual_from_qlp_coefficients: OVERFLOW, i=%u, j=%u, c=%d, d=%d, sumo=%I64d\n",i,j,qlp_coeff[j],*history,sumo);
-#else
-                        if(sumo > 2147483647ll || sumo < -2147483648ll)
-                                fprintf(stderr,"FLAC__lpc_compute_residual_from_qlp_coefficients: OVERFLOW, i=%u, j=%u, c=%d, d=%d, sumo=%lld\n",i,j,qlp_coeff[j],*history,(long long)sumo);
-#endif
+                                fprintf(stderr,"FLAC__lpc_compute_residual_from_qlp_coefficients: OVERFLOW, i=%u, j=%u, c=%d, d=%d, sumo=%" PRId64 "\n",i,j,qlp_coeff[j],*history,sumo);
                 }
                 *(residual++) = *(data++) - (sum >> lp_quantization);
         }
 
         /* Here's a slower but clearer version:
         for(i = 0; i < data_len; i++) {
                 sum = 0;
                 for(j = 0; j < order; j++)
                         sum += qlp_coeff[j] * data[i-j-1];
                 residual[i] = data[i] - (sum >> lp_quantization);
@@ skipping 216 matching lines @@
                                          sum += qlp_coeff[ 2] * data[i- 3];
                                          sum += qlp_coeff[ 1] * data[i- 2];
                                          sum += qlp_coeff[ 0] * data[i- 1];
                         }
                         residual[i] = data[i] - (sum >> lp_quantization);
                 }
         }
 }
 #endif
 
-void FLAC__lpc_compute_residual_from_qlp_coefficients_wide(const FLAC__int32 *data, unsigned data_len, const FLAC__int32 qlp_coeff[], unsigned order, int lp_quantization, FLAC__int32 residual[])
+void FLAC__lpc_compute_residual_from_qlp_coefficients_wide(const FLAC__int32 * flac_restrict data, unsigned data_len, const FLAC__int32 * flac_restrict qlp_coeff, unsigned order, int lp_quantization, FLAC__int32 * flac_restrict residual)
 #if defined(FLAC__OVERFLOW_DETECT) || !defined(FLAC__LPC_UNROLLED_FILTER_LOOPS)
 {
         unsigned i, j;
         FLAC__int64 sum;
         const FLAC__int32 *history;
 
 #ifdef FLAC__OVERFLOW_DETECT_VERBOSE
         fprintf(stderr,"FLAC__lpc_compute_residual_from_qlp_coefficients_wide: data_len=%d, order=%u, lpq=%d",data_len,order,lp_quantization);
         for(i=0;i<order;i++)
                 fprintf(stderr,", q[%u]=%d",i,qlp_coeff[i]);
         fprintf(stderr,"\n");
 #endif
         FLAC__ASSERT(order > 0);
 
         for(i = 0; i < data_len; i++) {
                 sum = 0;
                 history = data;
                 for(j = 0; j < order; j++)
                         sum += (FLAC__int64)qlp_coeff[j] * (FLAC__int64)(*(--history));
                 if(FLAC__bitmath_silog2_wide(sum >> lp_quantization) > 32) {
-#if defined _MSC_VER
-                        fprintf(stderr,"FLAC__lpc_compute_residual_from_qlp_coefficients_wide: OVERFLOW, i=%u, sum=%I64d\n", i, sum >> lp_quantization);
-#else
-                        fprintf(stderr,"FLAC__lpc_compute_residual_from_qlp_coefficients_wide: OVERFLOW, i=%u, sum=%lld\n", i, (long long)(sum >> lp_quantization));
-#endif
+                        fprintf(stderr,"FLAC__lpc_compute_residual_from_qlp_coefficients_wide: OVERFLOW, i=%u, sum=%" PRId64 "\n", i, (sum >> lp_quantization));
                         break;
                 }
                 if(FLAC__bitmath_silog2_wide((FLAC__int64)(*data) - (sum >> lp_quantization)) > 32) {
-#if defined _MSC_VER
-                        fprintf(stderr,"FLAC__lpc_compute_residual_from_qlp_coefficients_wide: OVERFLOW, i=%u, data=%d, sum=%I64d, residual=%I64d\n", i, *data, sum >> lp_quantization, (FLAC__int64)(*data) - (sum >> lp_quantization));
-#else
-                        fprintf(stderr,"FLAC__lpc_compute_residual_from_qlp_coefficients_wide: OVERFLOW, i=%u, data=%d, sum=%lld, residual=%lld\n", i, *data, (long long)(sum >> lp_quantization), (long long)((FLAC__int64)(*data) - (sum >> lp_quantization)));
-#endif
+                        fprintf(stderr,"FLAC__lpc_compute_residual_from_qlp_coefficients_wide: OVERFLOW, i=%u, data=%d, sum=%" PRId64 ", residual=%" PRId64 "\n", i, *data, (int64_t)(sum >> lp_quantization), ((FLAC__int64)(*data) - (sum >> lp_quantization)));
                         break;
                 }
                 *(residual++) = *(data++) - (FLAC__int32)(sum >> lp_quantization);
         }
 }
 #else /* fully unrolled version for normal use */
 {
         int i;
         FLAC__int64 sum;
 
@@ skipping 210 matching lines @@
                                          sum += qlp_coeff[ 0] * (FLAC__int64)data[i- 1];
                         }
                         residual[i] = data[i] - (FLAC__int32)(sum >> lp_quantization);
                 }
         }
 }
 #endif
 
 #endif /* !defined FLAC__INTEGER_ONLY_LIBRARY */
 
-void FLAC__lpc_restore_signal(const FLAC__int32 residual[], unsigned data_len, const FLAC__int32 qlp_coeff[], unsigned order, int lp_quantization, FLAC__int32 data[])
+void FLAC__lpc_restore_signal(const FLAC__int32 * flac_restrict residual, unsigned data_len, const FLAC__int32 * flac_restrict qlp_coeff, unsigned order, int lp_quantization, FLAC__int32 * flac_restrict data)
 #if defined(FLAC__OVERFLOW_DETECT) || !defined(FLAC__LPC_UNROLLED_FILTER_LOOPS)
 {
         FLAC__int64 sumo;
         unsigned i, j;
         FLAC__int32 sum;
         const FLAC__int32 *r = residual, *history;
 
 #ifdef FLAC__OVERFLOW_DETECT_VERBOSE
         fprintf(stderr,"FLAC__lpc_restore_signal: data_len=%d, order=%u, lpq=%d",data_len,order,lp_quantization);
         for(i=0;i<order;i++)
                 fprintf(stderr,", q[%u]=%d",i,qlp_coeff[i]);
         fprintf(stderr,"\n");
 #endif
         FLAC__ASSERT(order > 0);
 
         for(i = 0; i < data_len; i++) {
                 sumo = 0;
                 sum = 0;
                 history = data;
                 for(j = 0; j < order; j++) {
                         sum += qlp_coeff[j] * (*(--history));
                         sumo += (FLAC__int64)qlp_coeff[j] * (FLAC__int64)(*history);
-#if defined _MSC_VER
-                        if(sumo > 2147483647I64 || sumo < -2147483648I64)
-                                fprintf(stderr,"FLAC__lpc_restore_signal: OVERFLOW, i=%u, j=%u, c=%d, d=%d, sumo=%I64d\n",i,j,qlp_coeff[j],*history,sumo);
-#else
                         if(sumo > 2147483647ll || sumo < -2147483648ll)
-                                fprintf(stderr,"FLAC__lpc_restore_signal: OVERFLOW, i=%u, j=%u, c=%d, d=%d, sumo=%lld\n",i,j,qlp_coeff[j],*history,(long long)sumo);
-#endif
+                                fprintf(stderr,"FLAC__lpc_restore_signal: OVERFLOW, i=%u, j=%u, c=%d, d=%d, sumo=%" PRId64 "\n",i,j,qlp_coeff[j],*history,sumo);
                 }
                 *(data++) = *(r++) + (sum >> lp_quantization);
         }
 
         /* Here's a slower but clearer version:
         for(i = 0; i < data_len; i++) {
                 sum = 0;
                 for(j = 0; j < order; j++)
                         sum += qlp_coeff[j] * data[i-j-1];
                 data[i] = residual[i] + (sum >> lp_quantization);
@@ skipping 216 matching lines @@
                                          sum += qlp_coeff[ 2] * data[i- 3];
                                          sum += qlp_coeff[ 1] * data[i- 2];
                                          sum += qlp_coeff[ 0] * data[i- 1];
                         }
                         data[i] = residual[i] + (sum >> lp_quantization);
                 }
         }
 }
 #endif
 
-void FLAC__lpc_restore_signal_wide(const FLAC__int32 residual[], unsigned data_len, const FLAC__int32 qlp_coeff[], unsigned order, int lp_quantization, FLAC__int32 data[])
+void FLAC__lpc_restore_signal_wide(const FLAC__int32 * flac_restrict residual, unsigned data_len, const FLAC__int32 * flac_restrict qlp_coeff, unsigned order, int lp_quantization, FLAC__int32 * flac_restrict data)
 #if defined(FLAC__OVERFLOW_DETECT) || !defined(FLAC__LPC_UNROLLED_FILTER_LOOPS)
 {
         unsigned i, j;
         FLAC__int64 sum;
         const FLAC__int32 *r = residual, *history;
 
 #ifdef FLAC__OVERFLOW_DETECT_VERBOSE
         fprintf(stderr,"FLAC__lpc_restore_signal_wide: data_len=%d, order=%u, lpq=%d",data_len,order,lp_quantization);
         for(i=0;i<order;i++)
                 fprintf(stderr,", q[%u]=%d",i,qlp_coeff[i]);
         fprintf(stderr,"\n");
 #endif
         FLAC__ASSERT(order > 0);
 
         for(i = 0; i < data_len; i++) {
                 sum = 0;
                 history = data;
                 for(j = 0; j < order; j++)
                         sum += (FLAC__int64)qlp_coeff[j] * (FLAC__int64)(*(--history));
                 if(FLAC__bitmath_silog2_wide(sum >> lp_quantization) > 32) {
-#ifdef _MSC_VER
-                        fprintf(stderr,"FLAC__lpc_restore_signal_wide: OVERFLOW, i=%u, sum=%I64d\n", i, sum >> lp_quantization);
-#else
-                        fprintf(stderr,"FLAC__lpc_restore_signal_wide: OVERFLOW, i=%u, sum=%lld\n", i, (long long)(sum >> lp_quantization));
-#endif
+                        fprintf(stderr,"FLAC__lpc_restore_signal_wide: OVERFLOW, i=%u, sum=%" PRId64 "\n", i, (sum >> lp_quantization));
                         break;
                 }
                 if(FLAC__bitmath_silog2_wide((FLAC__int64)(*r) + (sum >> lp_quantization)) > 32) {
-#ifdef _MSC_VER
-                        fprintf(stderr,"FLAC__lpc_restore_signal_wide: OVERFLOW, i=%u, residual=%d, sum=%I64d, data=%I64d\n", i, *r, sum >> lp_quantization, (FLAC__int64)(*r) + (sum >> lp_quantization));
-#else
-                        fprintf(stderr,"FLAC__lpc_restore_signal_wide: OVERFLOW, i=%u, residual=%d, sum=%lld, data=%lld\n", i, *r, (long long)(sum >> lp_quantization), (long long)((FLAC__int64)(*r) + (sum >> lp_quantization)));
-#endif
+                        fprintf(stderr,"FLAC__lpc_restore_signal_wide: OVERFLOW, i=%u, residual=%d, sum=%" PRId64 ", data=%" PRId64 "\n", i, *r, (sum >> lp_quantization), ((FLAC__int64)(*r) + (sum >> lp_quantization)));
                         break;
                 }
                 *(data++) = *(r++) + (FLAC__int32)(sum >> lp_quantization);
         }
 }
 #else /* fully unrolled version for normal use */
 {
         int i;
         FLAC__int64 sum;
 
@@ skipping 208 matching lines @@
                                          sum += qlp_coeff[ 2] * (FLAC__int64)data[i- 3];
                                          sum += qlp_coeff[ 1] * (FLAC__int64)data[i- 2];
                                          sum += qlp_coeff[ 0] * (FLAC__int64)data[i- 1];
                         }
                         data[i] = residual[i] + (FLAC__int32)(sum >> lp_quantization);
                 }
         }
 }
 #endif
 
+#if defined(_MSC_VER)
+#pragma warning ( default : 4028 )
+#endif
+
 #ifndef FLAC__INTEGER_ONLY_LIBRARY
 
 FLAC__double FLAC__lpc_compute_expected_bits_per_residual_sample(FLAC__double lpc_error, unsigned total_samples)
 {
         FLAC__double error_scale;
 
         FLAC__ASSERT(total_samples > 0);
 
         error_scale = 0.5 * M_LN2 * M_LN2 / (FLAC__double)total_samples;
 
@@ skipping 12 matching lines @@
         else if(lpc_error < 0.0) { /* error should not be negative but can happen due to inadequate floating-point resolution */
                 return 1e32;
         }
         else {
                 return 0.0;
         }
 }
 
 unsigned FLAC__lpc_compute_best_order(const FLAC__double lpc_error[], unsigned max_order, unsigned total_samples, unsigned overhead_bits_per_order)
 {
-        unsigned order, index, best_index; /* 'index' the index into lpc_error; index==order-1 since lpc_error[0] is for order==1, lpc_error[1] is for order==2, etc */
+        unsigned order, indx, best_index; /* 'index' the index into lpc_error; index==order-1 since lpc_error[0] is for order==1, lpc_error[1] is for order==2, etc */
         FLAC__double bits, best_bits, error_scale;
 
         FLAC__ASSERT(max_order > 0);
         FLAC__ASSERT(total_samples > 0);
 
         error_scale = 0.5 * M_LN2 * M_LN2 / (FLAC__double)total_samples;
 
         best_index = 0;
         best_bits = (unsigned)(-1);
 
-        for(index = 0, order = 1; index < max_order; index++, order++) {
-                bits = FLAC__lpc_compute_expected_bits_per_residual_sample_with_error_scale(lpc_error[index], error_scale) * (FLAC__double)(total_samples - order) + (FLAC__double)(order * overhead_bits_per_order);
+        for(indx = 0, order = 1; indx < max_order; indx++, order++) {
+                bits = FLAC__lpc_compute_expected_bits_per_residual_sample_with_error_scale(lpc_error[indx], error_scale) * (FLAC__double)(total_samples - order) + (FLAC__double)(order * overhead_bits_per_order);
                 if(bits < best_bits) {
-                        best_index = index;
+                        best_index = indx;
                         best_bits = bits;
                 }
         }
 
-        return best_index+1; /* +1 since index of lpc_error[] is order-1 */
+        return best_index+1; /* +1 since indx of lpc_error[] is order-1 */
 }
 
 #endif /* !defined FLAC__INTEGER_ONLY_LIBRARY */