LOLWUT: split the command from version-specific implementations.

3 files changed, 297 insertions, 241 deletions

diff --git a/src/Makefile b/src/Makefile
index e24dbe491..773d3b272 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -144,7 +144,7 @@ endif
 
 REDIS_SERVER_NAME=redis-server
 REDIS_SENTINEL_NAME=redis-sentinel
-REDIS_SERVER_OBJ=adlist.o quicklist.o ae.o anet.o dict.o server.o sds.o zmalloc.o lzf_c.o lzf_d.o pqsort.o zipmap.o sha1.o ziplist.o release.o networking.o util.o object.o db.o replication.o rdb.o t_string.o t_list.o t_set.o t_zset.o t_hash.o config.o aof.o pubsub.o multi.o debug.o sort.o intset.o syncio.o cluster.o crc16.o endianconv.o slowlog.o scripting.o bio.o rio.o rand.o memtest.o crc64.o bitops.o sentinel.o notify.o setproctitle.o blocked.o hyperloglog.o latency.o sparkline.o redis-check-rdb.o redis-check-aof.o geo.o lazyfree.o module.o evict.o expire.o geohash.o geohash_helper.o childinfo.o defrag.o siphash.o rax.o t_stream.o listpack.o localtime.o lolwut.o
+REDIS_SERVER_OBJ=adlist.o quicklist.o ae.o anet.o dict.o server.o sds.o zmalloc.o lzf_c.o lzf_d.o pqsort.o zipmap.o sha1.o ziplist.o release.o networking.o util.o object.o db.o replication.o rdb.o t_string.o t_list.o t_set.o t_zset.o t_hash.o config.o aof.o pubsub.o multi.o debug.o sort.o intset.o syncio.o cluster.o crc16.o endianconv.o slowlog.o scripting.o bio.o rio.o rand.o memtest.o crc64.o bitops.o sentinel.o notify.o setproctitle.o blocked.o hyperloglog.o latency.o sparkline.o redis-check-rdb.o redis-check-aof.o geo.o lazyfree.o module.o evict.o expire.o geohash.o geohash_helper.o childinfo.o defrag.o siphash.o rax.o t_stream.o listpack.o localtime.o lolwut.o lolwut5.o
 REDIS_CLI_NAME=redis-cli
 REDIS_CLI_OBJ=anet.o adlist.o dict.o redis-cli.o zmalloc.o release.o anet.o ae.o crc64.o siphash.o crc16.o
 REDIS_BENCHMARK_NAME=redis-benchmark
diff --git a/src/lolwut.c b/src/lolwut.c
index c8d036a27..19cbcf642 100644
--- a/src/lolwut.c
+++ b/src/lolwut.c
@@ -34,249 +34,23 @@
  */
 
 #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;
+void lolwut5Command(client *c);
 
-/* 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 lolwutCommand(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. ");
+/* The default target for LOLWUT if no matching version was found.
+ * This is what unstable versions of Redis will display. */
+void lolwutUnstableCommand(client *c) {
+    sds rendered = sdsnew("Redis ver. ");
     rendered = sdscat(rendered,REDIS_VERSION);
     rendered = sdscatlen(rendered,"\n",1);
     addReplyBulkSds(c,rendered);
-    lwFreeCanvas(canvas);
+}
+
+void lolwutCommand(client *c) {
+    char *v = REDIS_VERSION;
+    if ((v[0] == '5' && v[1] == '.') ||
+        (v[0] == '4' && v[1] == '.' && v[2] == '9'))
+        lolwut5Command(c);
+    else
+        lolwutUnstableCommand(c);
 }
diff --git a/src/lolwut5.c b/src/lolwut5.c
new file mode 100644
index 000000000..2cf7f5bd4
--- /dev/null
+++ b/src/lolwut5.c
@@ -0,0 +1,282 @@
+/*
+ * 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);
+}