redis/src/sparkline.c

/* sparkline.c -- ASCII Sparklines
 * This code is modified from http://github.com/antirez/aspark and adapted
 * in order to return SDS strings instead of outputting directly to
 * the terminal.
 *
 * ---------------------------------------------------------------------------
 *
 * Copyright (c) 2011-Present, Redis Ltd.
 * All rights reserved.
 *
 * Licensed under your choice of the Redis Source Available License 2.0
 * (RSALv2) or the Server Side Public License v1 (SSPLv1).
 */

#include "server.h"

#include <math.h>

/* This is the charset used to display the graphs, but multiple rows are used
 * to increase the resolution. */
static char charset[] = "_-`";
static char charset_fill[] = "_o#";
static int charset_len = sizeof(charset)-1;
static int label_margin_top = 1;

/* ----------------------------------------------------------------------------
 * Sequences are arrays of samples we use to represent data to turn
 * into sparklines. This is the API in order to generate a sparkline:
 *
 * struct sequence *seq = createSparklineSequence();
 * sparklineSequenceAddSample(seq, 10, NULL);
 * sparklineSequenceAddSample(seq, 20, NULL);
 * sparklineSequenceAddSample(seq, 30, "last sample label");
 * sds output = sparklineRender(sdsempty(), seq, 80, 4, SPARKLINE_FILL);
 * freeSparklineSequence(seq);
 * ------------------------------------------------------------------------- */

/* Create a new sequence. */
struct sequence *createSparklineSequence(void) {
    struct sequence *seq = zmalloc(sizeof(*seq));
    seq->length = 0;
    seq->labels = 0;
    seq->samples = NULL;
    seq->min = 0.0f;
    seq->max = 0.0f;
    return seq;
}

/* Add a new sample into a sequence. */
void sparklineSequenceAddSample(struct sequence *seq, double value, char *label) {
    label = (label == NULL || label[0] == '\0') ? NULL : zstrdup(label);
    if (seq->length == 0) {
        seq->min = seq->max = value;
    } else {
        if (value < seq->min) seq->min = value;
        else if (value > seq->max) seq->max = value;
    }
    seq->samples = zrealloc(seq->samples,sizeof(struct sample)*(seq->length+1));
    seq->samples[seq->length].value = value;
    seq->samples[seq->length].label = label;
    seq->length++;
    if (label) seq->labels++;
}

/* Free a sequence. */
void freeSparklineSequence(struct sequence *seq) {
    int j;

    for (j = 0; j < seq->length; j++)
        zfree(seq->samples[j].label);
    zfree(seq->samples);
    zfree(seq);
}

/* ----------------------------------------------------------------------------
 * ASCII rendering of sequence
 * ------------------------------------------------------------------------- */

/* Render part of a sequence, so that render_sequence() call call this function
 * with different parts in order to create the full output without overflowing
 * the current terminal columns. */
sds sparklineRenderRange(sds output, struct sequence *seq, int rows, int offset, int len, int flags) {
    int j;
    double relmax = seq->max - seq->min;
    int steps = charset_len*rows;
    int row = 0;
    char *chars = zmalloc(len);
    int loop = 1;
    int opt_fill = flags & SPARKLINE_FILL;
    int opt_log = flags & SPARKLINE_LOG_SCALE;

    if (opt_log) {
        relmax = log(relmax+1);
    } else if (relmax == 0) {
        relmax = 1;
    }

    while(loop) {
        loop = 0;
        memset(chars,' ',len);
        for (j = 0; j < len; j++) {
            struct sample *s = &seq->samples[j+offset];
            double relval = s->value - seq->min;
            int step;

            if (opt_log) relval = log(relval+1);
            step = (int) (relval*steps)/relmax;
            if (step < 0) step = 0;
            if (step >= steps) step = steps-1;

            if (row < rows) {
                /* Print the character needed to create the sparkline */
                int charidx = step-((rows-row-1)*charset_len);
                loop = 1;
                if (charidx >= 0 && charidx < charset_len) {
                    chars[j] = opt_fill ? charset_fill[charidx] :
                                          charset[charidx];
                } else if(opt_fill && charidx >= charset_len) {
                    chars[j] = '|';
                }
            } else {
                /* Labels spacing */
                if (seq->labels && row-rows < label_margin_top) {
                    loop = 1;
                    break;
                }
                /* Print the label if needed. */
                if (s->label) {
                    int label_len = strlen(s->label);
                    int label_char = row - rows - label_margin_top;

                    if (label_len > label_char) {
                        loop = 1;
                        chars[j] = s->label[label_char];
                    }
                }
            }
        }
        if (loop) {
            row++;
            output = sdscatlen(output,chars,len);
            output = sdscatlen(output,"\n",1);
        }
    }
    zfree(chars);
    return output;
}

/* Turn a sequence into its ASCII representation */
sds sparklineRender(sds output, struct sequence *seq, int columns, int rows, int flags) {
    int j;

    for (j = 0; j < seq->length; j += columns) {
        int sublen = (seq->length-j) < columns ? (seq->length-j) : columns;

        if (j != 0) output = sdscatlen(output,"\n",1);
        output = sparklineRenderRange(output, seq, rows, j, sublen, flags);
    }
    return output;
}