parse_color: refactor color storage
When we parse a color name like "red" into its ANSI color value, we pack the storage into a single int that may take on many values: 1. If it's "-2", no value has been specified. 2. If it's "-1", the value is "normal" (i.e., no color). 3. If it's 0 through 7, the value is a standard ANSI color. 4. If it's larger (up to 255), it is a 256-color extended value. Given these magic numbers, it is often hard to see what is going on in the code. Let's refactor this into a struct with a flag that tells which scheme we are using, along with a numeric value. This is more verbose, but should hopefully be simpler to follow. It will also allow us to easily add support for more schemes, like 24-bit RGB values. The result is also slightly less efficient to store, but that's OK; we only store this intermediate state during the parse, after which we write out the actual ANSI bytes. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Jeff King committed
Nov 20, 2014 at 10:17 UTC
695d95df19b74485be62aba0f978044ff1215ea0
1 file changed
+106
-32
color.c
+106
-32
@@ -26,23 +26,77 @@ const char *column_colors_ansi[] = {
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/* Ignore the RESET at the end when giving the size */
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const int column_colors_ansi_max = ARRAY_SIZE(column_colors_ansi) - 1;
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-static int parse_color(const char *name, int len)
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+/* An individual foreground or background color. */
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+struct color {
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+ enum {
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+ COLOR_UNSPECIFIED = 0,
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+ COLOR_NORMAL,
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+ COLOR_ANSI, /* basic 0-7 ANSI colors */
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+ COLOR_256
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+ } type;
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+ /* The numeric value for ANSI and 256-color modes */
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+ unsigned char value;
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+};
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+
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+/*
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+ * "word" is a buffer of length "len"; does it match the NUL-terminated
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+ * "match" exactly?
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+ */
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+static int match_word(const char *word, int len, const char *match)
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{
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+ return !strncasecmp(word, match, len) && !match[len];
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+}
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+
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+static int parse_color(struct color *out, const char *name, int len)
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+{
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+ /* Positions in array must match ANSI color codes */
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static const char * const color_names[] = {
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- "normal", "black", "red", "green", "yellow",
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+ "black", "red", "green", "yellow",
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"blue", "magenta", "cyan", "white"
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};
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char *end;
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int i;
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+ long val;
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+
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+ /* First try the special word "normal"... */
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+ if (match_word(name, len, "normal")) {
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+ out->type = COLOR_NORMAL;
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+ return 0;
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+ }
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+
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+ /* Then pick from our human-readable color names... */
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for (i = 0; i < ARRAY_SIZE(color_names); i++) {
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- const char *str = color_names[i];
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- if (!strncasecmp(name, str, len) && !str[len])
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- return i - 1;
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+ if (match_word(name, len, color_names[i])) {
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+ out->type = COLOR_ANSI;
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+ out->value = i;
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+ return 0;
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+ }
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}
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- i = strtol(name, &end, 10);
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- if (end - name == len && i >= -1 && i <= 255)
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- return i;
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- return -2;
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+
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+ /* And finally try a literal 256-color-mode number */
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+ val = strtol(name, &end, 10);
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+ if (end - name == len) {
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+ /*
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+ * Allow "-1" as an alias for "normal", but other negative
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+ * numbers are bogus.
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+ */
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+ if (val < -1)
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+ ; /* fall through to error */
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+ else if (val < 0) {
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+ out->type = COLOR_NORMAL;
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+ return 0;
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+ /* Rewrite low numbers as more-portable standard colors. */
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+ } else if (val < 8) {
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+ out->type = COLOR_ANSI;
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+ out->value = val;
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+ } else if (val < 256) {
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+ out->type = COLOR_256;
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+ out->value = val;
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+ return 0;
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+ }
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+ }
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+
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+ return -1;
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}
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static int parse_attr(const char *name, int len)
@@ -65,13 +119,43 @@ int color_parse(const char *value, char *dst)
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return color_parse_mem(value, strlen(value), dst);
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}
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+#define COLOR_FOREGROUND '3'
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+#define COLOR_BACKGROUND '4'
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+
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+/*
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+ * Write the ANSI color codes for "c" to "out"; the string should
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+ * already have the ANSI escape code in it. "out" should have enough
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+ * space in it to fit any color.
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+ */
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+static char *color_output(char *out, const struct color *c, char type)
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+{
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+ switch (c->type) {
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+ case COLOR_UNSPECIFIED:
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+ case COLOR_NORMAL:
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+ break;
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+ case COLOR_ANSI:
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+ *out++ = type;
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+ *out++ = '0' + c->value;
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+ break;
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+ case COLOR_256:
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+ out += sprintf(out, "%c8;5;%d", type, c->value);
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+ break;
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+ }
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+ return out;
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+}
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+
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+static int color_empty(const struct color *c)
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+{
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+ return c->type <= COLOR_NORMAL;
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+}
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+
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int color_parse_mem(const char *value, int value_len, char *dst)
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{
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const char *ptr = value;
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int len = value_len;
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unsigned int attr = 0;
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- int fg = -2;
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- int bg = -2;
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+ struct color fg = { COLOR_UNSPECIFIED };
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+ struct color bg = { COLOR_UNSPECIFIED };
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if (!strncasecmp(value, "reset", len)) {
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strcpy(dst, GIT_COLOR_RESET);
@@ -81,6 +165,7 @@ int color_parse_mem(const char *value, int value_len, char *dst)
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/* [fg [bg]] [attr]... */
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while (len > 0) {
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const char *word = ptr;
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+ struct color c;
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int val, wordlen = 0;
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while (len > 0 && !isspace(word[wordlen])) {
@@ -94,14 +179,13 @@ int color_parse_mem(const char *value, int value_len, char *dst)
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len--;
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}
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- val = parse_color(word, wordlen);
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- if (val >= -1) {
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- if (fg == -2) {
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- fg = val;
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+ if (!parse_color(&c, word, wordlen)) {
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+ if (fg.type == COLOR_UNSPECIFIED) {
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+ fg = c;
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continue;
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}
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- if (bg == -2) {
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- bg = val;
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+ if (bg.type == COLOR_UNSPECIFIED) {
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+ bg = c;
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continue;
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}
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goto bad;
@@ -113,7 +197,7 @@ int color_parse_mem(const char *value, int value_len, char *dst)
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goto bad;
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}
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- if (attr || fg >= 0 || bg >= 0) {
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+ if (attr || !color_empty(&fg) || !color_empty(&bg)) {
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int sep = 0;
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int i;
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@@ -129,25 +213,15 @@ int color_parse_mem(const char *value, int value_len, char *dst)
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*dst++ = ';';
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*dst++ = '0' + i;
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}
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- if (fg >= 0) {
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+ if (!color_empty(&fg)) {
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if (sep++)
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*dst++ = ';';
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- if (fg < 8) {
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- *dst++ = '3';
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- *dst++ = '0' + fg;
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- } else {
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- dst += sprintf(dst, "38;5;%d", fg);
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- }
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+ dst = color_output(dst, &fg, COLOR_FOREGROUND);
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}
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- if (bg >= 0) {
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+ if (!color_empty(&bg)) {
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if (sep++)
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*dst++ = ';';
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- if (bg < 8) {
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- *dst++ = '4';
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- *dst++ = '0' + bg;
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- } else {
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- dst += sprintf(dst, "48;5;%d", bg);
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- }
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+ dst = color_output(dst, &bg, COLOR_BACKGROUND);
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}
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*dst++ = 'm';
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}