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@xxxxxxxx>
---
color.c | 138 +++++++++++++++++++++++++++++++++++++++++++++++++---------------
1 file changed, 106 insertions(+), 32 deletions(-)
diff --git a/color.c b/color.c
index 7941e93..6edbcae 100644
--- a/color.c
+++ b/color.c
@@ -26,23 +26,77 @@ const char *column_colors_ansi[] = {
/* Ignore the RESET at the end when giving the size */
const int column_colors_ansi_max = ARRAY_SIZE(column_colors_ansi) - 1;
-static int parse_color(const char *name, int len)
+/* An individual foreground or background color. */
+struct color {
+ enum {
+ COLOR_UNSPECIFIED = 0,
+ COLOR_NORMAL,
+ COLOR_ANSI, /* basic 0-7 ANSI colors */
+ COLOR_256
+ } state;
+ /* The numeric value for ANSI and 256-color modes */
+ unsigned char value;
+};
+
+/*
+ * "word" is a buffer of length "len"; does it match the NUL-terminated
+ * "match" exactly?
+ */
+static int match_word(const char *word, int len, const char *match)
{
+ return !strncasecmp(word, match, len) && !match[len];
+}
+
+static int parse_color(struct color *out, const char *name, int len)
+{
+ /* Positions in array must match ANSI color codes */
static const char * const color_names[] = {
- "normal", "black", "red", "green", "yellow",
+ "black", "red", "green", "yellow",
"blue", "magenta", "cyan", "white"
};
char *end;
int i;
+ long val;
+
+ /* First try the special word "normal"... */
+ if (match_word(name, len, "normal")) {
+ out->state = COLOR_NORMAL;
+ return 0;
+ }
+
+ /* Then pick from our human-readable color names... */
for (i = 0; i < ARRAY_SIZE(color_names); i++) {
- const char *str = color_names[i];
- if (!strncasecmp(name, str, len) && !str[len])
- return i - 1;
+ if (match_word(name, len, color_names[i])) {
+ out->state = COLOR_ANSI;
+ out->value = i;
+ return 0;
+ }
}
- i = strtol(name, &end, 10);
- if (end - name == len && i >= -1 && i <= 255)
- return i;
- return -2;
+
+ /* And finally try a literal 256-color-mode number */
+ val = strtol(name, &end, 10);
+ if (end - name == len) {
+ /*
+ * Allow "-1" as an alias for "normal", but other negative
+ * numbers are bogus.
+ */
+ if (val < -1)
+ ; /* fall through to error */
+ else if (val < 0) {
+ out->state = COLOR_NORMAL;
+ return 0;
+ /* Rewrite low numbers as more-portable standard colors. */
+ } else if (val < 8) {
+ out->state = COLOR_ANSI;
+ out->value = val;
+ } else if (val < 256) {
+ out->state = COLOR_256;
+ out->value = val;
+ return 0;
+ }
+ }
+
+ return -1;
}
static int parse_attr(const char *name, int len)
@@ -65,13 +119,43 @@ int color_parse(const char *value, char *dst)
return color_parse_mem(value, strlen(value), dst);
}
+#define COLOR_FOREGROUND '3'
+#define COLOR_BACKGROUND '4'
+
+/*
+ * Write the ANSI color codes for "c" to "out"; the string should
+ * already have the ANSI escape code in it. "out" should have enough
+ * space in it to fit any color.
+ */
+static char *color_output(char *out, const struct color *c, char type)
+{
+ switch (c->state) {
+ case COLOR_UNSPECIFIED:
+ case COLOR_NORMAL:
+ break;
+ case COLOR_ANSI:
+ *out++ = type;
+ *out++ = '0' + c->value;
+ break;
+ case COLOR_256:
+ out += sprintf(out, "%c8;5;%d", type, c->value);
+ break;
+ }
+ return out;
+}
+
+static int color_empty(const struct color *c)
+{
+ return c->state <= COLOR_NORMAL;
+}
+
int color_parse_mem(const char *value, int value_len, char *dst)
{
const char *ptr = value;
int len = value_len;
unsigned int attr = 0;
- int fg = -2;
- int bg = -2;
+ struct color fg = { COLOR_UNSPECIFIED };
+ struct color bg = { COLOR_UNSPECIFIED };
if (!strncasecmp(value, "reset", len)) {
strcpy(dst, GIT_COLOR_RESET);
@@ -81,6 +165,7 @@ int color_parse_mem(const char *value, int value_len, char *dst)
/* [fg [bg]] [attr]... */
while (len > 0) {
const char *word = ptr;
+ struct color c;
int val, wordlen = 0;
while (len > 0 && !isspace(word[wordlen])) {
@@ -94,14 +179,13 @@ int color_parse_mem(const char *value, int value_len, char *dst)
len--;
}
- val = parse_color(word, wordlen);
- if (val >= -1) {
- if (fg == -2) {
- fg = val;
+ if (!parse_color(&c, word, wordlen)) {
+ if (fg.state == COLOR_UNSPECIFIED) {
+ fg = c;
continue;
}
- if (bg == -2) {
- bg = val;
+ if (bg.state == COLOR_UNSPECIFIED) {
+ bg = c;
continue;
}
goto bad;
@@ -113,7 +197,7 @@ int color_parse_mem(const char *value, int value_len, char *dst)
goto bad;
}
- if (attr || fg >= 0 || bg >= 0) {
+ if (attr || !color_empty(&fg) || !color_empty(&bg)) {
int sep = 0;
int i;
@@ -129,25 +213,15 @@ int color_parse_mem(const char *value, int value_len, char *dst)
*dst++ = ';';
*dst++ = '0' + i;
}
- if (fg >= 0) {
+ if (!color_empty(&fg)) {
if (sep++)
*dst++ = ';';
- if (fg < 8) {
- *dst++ = '3';
- *dst++ = '0' + fg;
- } else {
- dst += sprintf(dst, "38;5;%d", fg);
- }
+ dst = color_output(dst, &fg, COLOR_FOREGROUND);
}
- if (bg >= 0) {
+ if (!color_empty(&bg)) {
if (sep++)
*dst++ = ';';
- if (bg < 8) {
- *dst++ = '4';
- *dst++ = '0' + bg;
- } else {
- dst += sprintf(dst, "48;5;%d", bg);
- }
+ dst = color_output(dst, &bg, COLOR_BACKGROUND);
}
*dst++ = 'm';
}
--
2.2.0.rc2.402.g4519813
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