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FEAT: new natives rgb-to-hsv and hsv-to-rgb
These natives were in Rebol2 and so why not to have them in Rebol3 again. Could be enhanced in future for batch conversion and or more precise version not depending on tuple value for HSV. Implements wish: metaeducation/rebol-issues#2342
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‎src/core/n-image.c

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/***********************************************************************
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**
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** REBOL [R3] Language Interpreter and Run-time Environment
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**
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** Copyright 2012 REBOL Technologies
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** Copyright 2012-2019 Rebol Open Source Contributors
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** REBOL is a trademark of REBOL Technologies
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**
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** Licensed under the Apache License, Version 2.0 (the "License");
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** you may not use this file except in compliance with the License.
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** You may obtain a copy of the License at
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**
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** http://www.apache.org/licenses/LICENSE-2.0
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**
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** Unless required by applicable law or agreed to in writing, software
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** distributed under the License is distributed on an "AS IS" BASIS,
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** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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** See the License for the specific language governing permissions and
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** limitations under the License.
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**
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************************************************************************
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**
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** Module: n-image.c
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** Summary: image related native functions
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** Section: natives
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** Author: Oldes
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** Notes:
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**
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***********************************************************************/
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#include "sys-core.h"
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typedef struct REBCLR {
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union {
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unsigned char r;
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unsigned char h;
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};
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union {
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unsigned char g;
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unsigned char s;
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};
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union {
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unsigned char b;
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unsigned char v;
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};
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unsigned char a;
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} REBCLR;
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// Conversion using raw tuple bytes is (a little bit) faster but less precise
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// using decimals in conversions is producing results closer to Rebol2
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#define HSV_CONVERSION_USING_DECIMAL
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// Currently HSW is using tuple datatype, which is limited to range 0-255
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// That is also adding some precision lost for round-trip conversions.
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// Code based on: https://stackoverflow.com/q/3018313/494472
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/***********************************************************************
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**
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*/ REBNATIVE(hsv_to_rgb)
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/*
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// hsv-to-rgb: native [
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// "Converts HSV (hue, saturation, value) to RGB"
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// hsv [tuple!]
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// ]
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***********************************************************************/
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{
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REBCLR *val = (REBCLR*)VAL_TUPLE(D_ARG(1));
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if (val->s == 0) {
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// achromatic (grey)
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val->r = val->v;
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val->g = val->v;
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val->b = val->v;
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return R_ARG1;
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}
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#ifdef HSV_CONVERSION_USING_DECIMAL
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REBDEC h = (float)val->h;
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REBDEC s = (float)val->s / 255.0;
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REBDEC v = (float)val->v / 255.0;
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int i;
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REBDEC f, p, q, t;
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h /= 42.5; // sector 0 to 5; we are using 255 instead of 360 because the value is in tuple's byte ! (255 / 6)
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i = floor(h);
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f = h - i; // factorial part of h
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p = v * (1 - s);
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q = v * (1 - s * f);
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t = v * (1 - s * (1 - f));
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switch (i) {
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case 0: val->r = (REBYTE)(255.0 * v); val->g = (REBYTE)(255.0 * t); val->b = (REBYTE)(255.0 * p); break;
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case 1: val->r = (REBYTE)(255.0 * q); val->g = (REBYTE)(255.0 * v); val->b = (REBYTE)(255.0 * p); break;
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case 2: val->r = (REBYTE)(255.0 * p); val->g = (REBYTE)(255.0 * v); val->b = (REBYTE)(255.0 * t); break;
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case 3: val->r = (REBYTE)(255.0 * p); val->g = (REBYTE)(255.0 * q); val->b = (REBYTE)(255.0 * v); break;
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case 4: val->r = (REBYTE)(255.0 * t); val->g = (REBYTE)(255.0 * p); val->b = (REBYTE)(255.0 * v); break;
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default: val->r = (REBYTE)(255.0 * v); val->g = (REBYTE)(255.0 * p); val->b = (REBYTE)(255.0 * q); break; // case 5
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}
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#else
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REBYTE region, remainder, p, q, t;
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region = val->h / 43; // six regions: 255 / 6
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remainder = (val->h - (region * 43)) * 6;
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p = (val->v * (255 - val->s)) >> 8;
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q = (val->v * (255 - ((val->s * remainder) >> 8))) >> 8;
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t = (val->v * (255 - ((val->s * (255 - remainder)) >> 8))) >> 8;
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switch (region) {
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case 0: val->r = val->v; val->g = t; val->b = p; break;
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case 1: val->r = q; val->g = val->v; val->b = p; break;
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case 2: val->r = p; val->g = val->v; val->b = t; break;
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case 3: val->r = p; val->g = q; val->b = val->v; break;
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case 4: val->r = t; val->g = p; val->b = val->v; break;
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default: // case 5
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val->r = val->v; val->g = p; val->b = q;
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break;
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}
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#endif
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return R_ARG1;
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}
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/***********************************************************************
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**
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*/ REBNATIVE(rgb_to_hsv)
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/*
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// rgb-to-hsv: native [
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// "Converts RGB value to HSV (hue, saturation, value)"
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// rgb [tuple!]
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// ]
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***********************************************************************/
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{
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REBCLR *val = (REBCLR*)VAL_TUPLE(D_ARG(1));
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REBYTE rgbMin, rgbMax, r, g, b;
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r = val->r;
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g = val->g;
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b = val->b;
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rgbMax = r > g ? (r > b ? r : b) : (g > b ? g : b);
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rgbMin = r < g ? (r < b ? r : b) : (g < b ? g : b);
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val->v = rgbMax;
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if (val->v == 0 || rgbMax == rgbMin) {
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val->h = val->s = 0;
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return R_ARG1;
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}
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#ifdef HSV_CONVERSION_USING_DECIMAL
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REBDEC delta = rgbMax - rgbMin;
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val->s = (REBYTE)(255.0 * delta / rgbMax);
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if (rgbMax == r)
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val->h = (REBYTE)(42.5 * (g - b) / delta);
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else if (rgbMax == g)
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val->h = (REBYTE)(85.0 + 42.5 * (b - r) / delta);
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else
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val->h = (REBYTE)(170.0 + 42.5 * (r - g) / delta);
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#else
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REBINT delta = rgbMax - rgbMin;
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val->s = (REBYTE)(255 * delta / rgbMax);
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if (rgbMax == r)
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val->h = 0 + 43 * (g - b) / delta;
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else if (rgbMax == g)
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val->h = 85 + 43 * (b - r) / delta;
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else
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val->h = 171 + 43 * (r - g) / delta;
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#endif
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return R_ARG1;
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}

‎src/tests/run-tests.r3

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wrap load %units/series-test.r3
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wrap load %units/compress-test.r3
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wrap load %units/date-test.r3
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wrap load %units/image-test.r3
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recycle/torture
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recycle

‎src/tests/units/image-test.r3

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Rebol [
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Title: "Rebol image test script"
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Author: "Oldes"
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File: %image-test.r3
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Tabs: 4
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Needs: [%../quick-test-module.r3]
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]
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~~~start-file~~~ "Image"
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===start-group=== "RGB - HSV conversions"
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;@@ https://github.com/rebol/rebol-issues/issues/2342
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--test-- "RGB-TO-HSV"
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--assert 36.235.134 = rgb-to-hsv 134.116.10
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--assert 36.235.134.100 = rgb-to-hsv 134.116.10.100
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--assert 0.0.134 = rgb-to-hsv 134.134.134
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--assert 42.253.134 = rgb-to-hsv 134.134.1
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--test-- "HSV-TO-RGB"
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--assert 5.9.10 = hsv-to-rgb 134.116.10
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--assert 5.9.10.100 = hsv-to-rgb 134.116.10.100
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--assert 63.123.134 = hsv-to-rgb 134.134.134
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--assert 0.1.2 = hsv-to-rgb 134.134.2
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===end-group===
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~~~end-file~~~

‎src/tools/file-base.r

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n-control.c
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n-crypt.c
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n-data.c
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n-image.c
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n-io.c
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n-loop.c
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n-math.c

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