/*
* Copyright (c) 2018, Salvatore Sanfilippo <antirez at gmail dot com>
* All rights reserved.
*
* 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 Redis 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 COPYRIGHT OWNER 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.
*
* ----------------------------------------------------------------------------
*
* This file implements the LOLWUT command. The command should do something
* fun and interesting, and should be replaced by a new implementation at
* each new version of Redis.
*/
#include "server.h"
#include <math.h>
/* This structure represents our canvas. Drawing functions will take a pointer
* to a canvas to write to it. Later the canvas can be rendered to a string
* suitable to be printed on the screen, using unicode Braille characters. */
typedef struct lwCanvas {
int width;
int height;
char *pixels;
} lwCanvas;
/* Translate a group of 8 pixels (2x4 vertical rectangle) to the corresponding
* braille character. The byte should correspond to the pixels arranged as
* follows, where 0 is the least significant bit, and 7 the most significant
* bit:
*
* 0 3
* 1 4
* 2 5
* 6 7
*
* The corresponding utf8 encoded character is set into the three bytes
* pointed by 'output'.
*/
#include <stdio.h>
void lwTranslatePixelsGroup(int byte, char *output) {
int code = 0x2800 + byte;
/* Convert to unicode. This is in the U0800-UFFFF range, so we need to
* emit it like this in three bytes:
* 1110xxxx 10xxxxxx 10xxxxxx. */
output[0] = 0xE0 | (code >> 12); /* 1110-xxxx */
output[1] = 0x80 | ((code >> 6) & 0x3F); /* 10-xxxxxx */
output[2] = 0x80 | (code & 0x3F); /* 10-xxxxxx */
}
/* Allocate and return a new canvas of the specified size. */
lwCanvas *lwCreateCanvas(int width, int height) {
lwCanvas *canvas = zmalloc(sizeof(*canvas));
canvas->width = width;
canvas->height = height;
canvas->pixels = zmalloc(width*height);
memset(canvas->pixels,0,width*height);
return canvas;
}
/* Free the canvas created by lwCreateCanvas(). */
void lwFreeCanvas(lwCanvas *canvas) {
zfree(canvas->pixels);
zfree(canvas);
}
/* Set a pixel to the specified color. Color is 0 or 1, where zero means no
* dot will be displyed, and 1 means dot will be displayed.
* Coordinates are arranged so that left-top corner is 0,0. You can write
* out of the size of the canvas without issues. */
void lwDrawPixel(lwCanvas *canvas, int x, int y, int color) {
if (x < 0 || x >= canvas->width ||
y < 0 || y >= canvas->height) return;
canvas->pixels[x+y*canvas->width] = color;
}
/* Return the value of the specified pixel on the canvas. */
int lwGetPixel(lwCanvas *canvas, int x, int y) {
if (x < 0 || x >= canvas->width ||
y < 0 || y >= canvas->height) return 0;
return canvas->pixels[x+y*canvas->width];
}
/* Draw a line from x1,y1 to x2,y2 using the Bresenham algorithm. */
void lwDrawLine(lwCanvas *canvas, int x1, int y1, int x2, int y2, int color) {
int dx = abs(x2-x1);
int dy = abs(y2-y1);
int sx = (x1 < x2) ? 1 : -1;
int sy = (y1 < y2) ? 1 : -1;
int err = dx-dy, e2;
while(1) {
lwDrawPixel(canvas,x1,y1,color);
if (x1 == x2 && y1 == y2) break;
e2 = err*2;
if (e2 > -dy) {
err -= dy;
x1 += sx;
}
if (e2 < dx) {
err += dx;
y1 += sy;
}
}
}
/* Draw a square centered at the specified x,y coordinates, with the specified
* rotation angle and size. In order to write a rotated square, we use the
* trivial fact that the parametric equation:
*
* x = sin(k)
* y = cos(k)
*
* Describes a circle for values going from 0 to 2*PI. So basically if we start
* at 45 degrees, that is k = PI/4, with the first point, and then we find
* the other three points incrementing K by PI/2 (90 degrees), we'll have the
* points of the square. In order to rotate the square, we just start with
* k = PI/4 + rotation_angle, and we are done.
*
* Of course the vanilla equations above will describe the square inside a
* circle of radius 1, so in order to draw larger squares we'll have to
* multiply the obtained coordinates, and then translate them. However this
* is much simpler than implementing the abstract concept of 2D shape and then
* performing the rotation/translation transformation, so for LOLWUT it's
* a good approach. */
void lwDrawSquare(lwCanvas *canvas, int x, int y, float size, float angle) {
int px[4], py[4];
/* Adjust the desired size according to the fact that the square inscribed
* into a circle of radius 1 has the side of length SQRT(2). This way
* size becomes a simple multiplication factor we can use with our
* coordinates to magnify them. */
size /= 1.4142135623;
size = round(size);
/* Compute the four points. */
float k = M_PI/4 + angle;
for (int j = 0; j < 4; j++) {
px[j] = round(sin(k) * size + x);
py[j] = round(cos(k) * size + y);
k += M_PI/2;
}
/* Draw the square. */
for (int j = 0; j < 4; j++)
lwDrawLine(canvas,px[j],py[j],px[(j+1)%4],py[(j+1)%4],1);
}
/* Schotter, the output of LOLWUT of Redis 5, is a computer graphic art piece
* generated by Georg Nees in the 60s. It explores the relationship between
* caos and order.
*
* The function creates the canvas itself, depending on the columns available
* in the output display and the number of squares per row and per column
* requested by the caller. */
lwCanvas *lwDrawSchotter(int console_cols, int squares_per_row, int squares_per_col) {
/* Calculate the canvas size. */
int canvas_width = console_cols*2;
int padding = canvas_width > 4 ? 2 : 0;
float square_side = (float)(canvas_width-padding*2) / squares_per_row;
int canvas_height = square_side * squares_per_col + padding*2;
lwCanvas *canvas = lwCreateCanvas(canvas_width, canvas_height);
for (int y = 0; y < squares_per_col; y++) {
for (int x = 0; x < squares_per_row; x++) {
int sx = x * square_side + square_side/2 + padding;
int sy = y * square_side + square_side/2 + padding;
/* Rotate and translate randomly as we go down to lower
* rows. */
float angle = 0;
if (y > 1) {
float r1 = (float)rand() / RAND_MAX / squares_per_col * y;
float r2 = (float)rand() / RAND_MAX / squares_per_col * y;
float r3 = (float)rand() / RAND_MAX / squares_per_col * y;
if (rand() % 2) r1 = -r1;
if (rand() % 2) r2 = -r2;
if (rand() % 2) r3 = -r3;
angle = r1;
sx += r2*square_side/3;
sy += r3*square_side/3;
}
lwDrawSquare(canvas,sx,sy,square_side,angle);
}
}
return canvas;
}
/* Converts the canvas to an SDS string representing the UTF8 characters to
* print to the terminal in order to obtain a graphical representaiton of the
* logical canvas. The actual returned string will require a terminal that is
* width/2 large and height/4 tall in order to hold the whole image without
* overflowing or scrolling, since each Barille character is 2x4. */
sds lwRenderCanvas(lwCanvas *canvas) {
sds text = sdsempty();
for (int y = 0; y < canvas->height; y += 4) {
for (int x = 0; x < canvas->width; x += 2) {
/* We need to emit groups of 8 bits according to a specific
* arrangement. See lwTranslatePixelsGroup() for more info. */
int byte = 0;
if (lwGetPixel(canvas,x,y)) byte |= (1<<0);
if (lwGetPixel(canvas,x,y+1)) byte |= (1<<1);
if (lwGetPixel(canvas,x,y+2)) byte |= (1<<2);
if (lwGetPixel(canvas,x+1,y)) byte |= (1<<3);
if (lwGetPixel(canvas,x+1,y+1)) byte |= (1<<4);
if (lwGetPixel(canvas,x+1,y+2)) byte |= (1<<5);
if (lwGetPixel(canvas,x,y+3)) byte |= (1<<6);
if (lwGetPixel(canvas,x+1,y+3)) byte |= (1<<7);
char unicode[3];
lwTranslatePixelsGroup(byte,unicode);
text = sdscatlen(text,unicode,3);
}
if (y != canvas->height-1) text = sdscatlen(text,"\n",1);
}
return text;
}
/* The LOLWUT command:
*
* LOLWUT [terminal columns] [squares-per-row] [squares-per-col]
*
* By default the command uses 66 columns, 8 squares per row, 12 squares
* per column.
*/
void lolwut5Command(client *c) {
long cols = 66;
long squares_per_row = 8;
long squares_per_col = 12;
/* Parse the optional arguments if any. */
if (c->argc > 1 &&
getLongFromObjectOrReply(c,c->argv[1],&cols,NULL) != C_OK)
return;
if (c->argc > 2 &&
getLongFromObjectOrReply(c,c->argv[2],&squares_per_row,NULL) != C_OK)
return;
if (c->argc > 3 &&
getLongFromObjectOrReply(c,c->argv[3],&squares_per_col,NULL) != C_OK)
return;
/* Limits. We want LOLWUT to be always reasonably fast and cheap to execute
* so we have maximum number of columns, rows, and output resulution. */
if (cols < 1) cols = 1;
if (cols > 1000) cols = 1000;
if (squares_per_row < 1) squares_per_row = 1;
if (squares_per_row > 200) squares_per_row = 200;
if (squares_per_col < 1) squares_per_col = 1;
if (squares_per_col > 200) squares_per_col = 200;
/* Generate some computer art and reply. */
lwCanvas *canvas = lwDrawSchotter(cols,squares_per_row,squares_per_col);
sds rendered = lwRenderCanvas(canvas);
rendered = sdscat(rendered,
"\nGeorg Nees - schotter, plotter on paper, 1968. Redis ver. ");
rendered = sdscat(rendered,REDIS_VERSION);
rendered = sdscatlen(rendered,"\n",1);
addReplyBulkSds(c,rendered);
lwFreeCanvas(canvas);
}