ovs-ofctl: Declare / set up colors for command output.

OVS_COLORS environment variable is parsed to extract user-defined
preferences regarding colors (this is used to set up a color theme, not
to replace the `--color` option for activating color output).

The string should be of a format similar to LS_COLORS or GREP_COLORS,
with available colors being as follows:

* ac: action field
* dr: drop keyword
* le: learn keyword
* pm: parameters receiving attributes
* pr: keyword having parenthesis
* sp: some special keywords
* vl: lone values with no parameter name

For color whose idendifier does not appear in the string, the default
hardcoded value is used instead.

As an example, setting OVS_COLORS to the following string is equivalent
to using the default values:

    OVS_COLORS="ac:01;31:dr=34:le=31:pm=36:pr=35:sp=33:vl=32"

Signed-off-by: Quentin Monnet <quentin.monnet@6wind.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>

1 files changed, 138 insertions, 0 deletions

diff --git a/lib/colors.c b/lib/colors.c
new file mode 100644
index 000000000..4ea1880d8
--- /dev/null
+++ b/lib/colors.c
@@ -0,0 +1,138 @@
+/*
+ * Copyright (c) 2016 6WIND S.A.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/* Handle color setup for output. */
+
+#include <config.h>
+
+#include "colors.h"
+
+#include <stdlib.h>
+#include <string.h>
+
+#include "util.h"
+
+struct color_key {
+    const char *name;
+    char **var_ptr;
+};
+
+/* Returns a pointer to the variable containing a given color. */
+static char **get_color(const struct color_key color_dic[], const char * name);
+
+/* Extract user-defined colors from OVS_COLORS environment variable. */
+static void colors_parse_from_env(const struct color_key color_dic[]);
+
+/* Global holder for colors. Declared in header file. */
+struct colors colors = { "", "", "", "", "", "", "", "" };
+
+static char **
+get_color(const struct color_key color_dic[], const char *name)
+{
+    const struct color_key *color;
+    for (color = color_dic; color->name; color++) {
+        if (!strcmp(color->name, name)) {
+            return color->var_ptr;
+        }
+    }
+    return NULL;
+}
+
+void
+colors_init(bool enable_color)
+{
+    /* If colored output is not enabled, just keep empty strings for color
+     * markers, including end marker.
+     */
+    if (!enable_color) {
+        return;
+    }
+
+    /* Color IDs to use in OVS_COLORS environment variable to overwrite
+     * defaults with custom colors.
+     */
+    const struct color_key color_dic[] = {
+        { "ac", &colors.actions },
+        { "dr", &colors.drop },
+        { "le", &colors.learn },
+        { "pm", &colors.param },
+        { "pr", &colors.paren },
+        { "sp", &colors.special },
+        { "vl", &colors.value },
+        { NULL, NULL }
+    };
+
+    /* Actual color to use. First we define default values. */
+    colors.actions = "\33[1;31m\33[K";  /* bold red */
+    colors.drop    = "\33[34m\33[K";    /* blue */
+    colors.learn   = "\33[31m\33[K";    /* red */
+    colors.param   = "\33[36m\33[K";    /* cyan */
+    colors.paren   = "\33[35m\33[K";    /* magenta */
+    colors.special = "\33[33m\33[K";    /* yellow */
+    colors.value   = "\33[32m\33[K";    /* green */
+    colors.end     = "\33[m\33[K";      /* end marker */
+
+    /* Now, overwrite with user-defined color markers. */
+    colors_parse_from_env(color_dic);
+}
+
+/* Colorized output: get user-defined colors from OVS_COLORS environment
+ * variable. This must be a string of the form:
+ *     ac=01;31:r=34:le=:pm=02;32:pr=01;30
+ * (see color_dic[] in colors_init() function for all color names)
+ * If a color is missing from this string, default value is used instead.
+ * If a color name is assigned an empty or incorrect value (i.e. something
+ * containing characters other than decimals and ';'), fields using this color
+ * will not be highlighted.
+ * If a color is assigned more than once, the last (rightmost) value appearing
+ * in the string is kept.
+ * Unknown color names are ignored so as to ensure forward compatibility.
+ * (Feeling adventurous? Try combining markers: "ac=1;3;5;7;38;2;30;150;100".)
+ */
+static void
+colors_parse_from_env(const struct color_key color_dic[])
+{
+    const char *color_str = getenv("OVS_COLORS");
+    if (color_str == NULL || *color_str == '\0') {
+        return;
+    }
+
+    /* Loop on tokens: they are separated by columns ':' */
+    char *s = xstrdup(color_str);
+    for (char *token = strsep(&s, ":");
+         token != NULL;
+         token = strsep(&s, ":")) {
+        char *name = strsep(&token, "=");
+        for (char *ptr = token; ptr != NULL && *ptr != '\0'; ptr++) {
+            /* We accept only decimals and ';' for color marker. */
+            if (*ptr == ';' || (*ptr >= '0' && *ptr <= '9')) {
+                continue;
+            }
+            name = NULL;
+            break;
+        }
+        if (name != NULL) {
+            /* We found a name and marker contains only decimals and ';'.
+             * Try to get a pointer to associated color variable. */
+            char **color_var_ptr = get_color(color_dic, name);
+            /* If we know that color, update its value. */
+            if (color_var_ptr != NULL) {
+                *color_var_ptr = xasprintf("\33[%sm\33[K", token);
+            }
+        }
+    }
+    free(s);
+}