Implement very bad state machine to match a subset of ANSI escape codes.

kern/init.c

@@ -38,6 +38,14 @@ i386_init(void)
 	// Test the stack backtrace function (lab 1 only)
 	test_backtrace(5);
 
+	// Test ANSI color escape codes
+	cprintf("\33[31m" "C"
+		"\33[33m" "o"
+		"\33[32m" "l"
+		"\33[36m" "o"
+		"\33[34m" "r"
+		"\33[0m"  " Works!" "\n");
+
 	// Drop into the kernel monitor.
 	while (1)
 		monitor(NULL);

lib/printfmt.c

@@ -79,6 +79,54 @@ getint(va_list *ap, int lflag)
 // Main function to format and print a string.
 void printfmt(void (*putch)(int, void*), void *putdat, const char *fmt, ...);
 
+struct AttrState {
+	uint8_t cattrs;
+	uint8_t attrs;
+	enum {
+		NORMAL,
+		ESC,
+		BRACKET,
+		COLOR_FG,
+		COLOR
+	} state;
+};
+
+void
+putchw(void (*putch)(int, void*), int c, void* data, struct AttrState* s) {
+	switch(s->state) {
+		case NORMAL:
+			if(c != 27) putch(c | (s->cattrs << 8), data);
+			else s->state = ESC;
+			return;
+		case ESC:
+			s->state = (c == '[') ? BRACKET : NORMAL;
+			return;
+		case BRACKET:
+			if(c == '3') {
+				s->state = COLOR_FG;
+			} else if(c == '0') {
+				s->state = COLOR;
+				s->attrs = 0;
+			} else {
+				s->state = NORMAL;
+			}
+			return;
+		case COLOR_FG:
+			if(c >= '0' && c <= '9') {
+				s->attrs = (s->attrs & ~(0x07)) | (c - '0');
+				c |= ((c - '0') << 8);
+				s->state = COLOR;
+			} else {
+				s->state = NORMAL;
+			}
+			return;
+		case COLOR:
+			s->state = (c == ';') ? BRACKET : NORMAL;
+			if(c == 'm') s->cattrs = s->attrs;
+			return;
+	}
+}
+
 void
 vprintfmt(void (*putch)(int, void*), void *putdat, const char *fmt, va_list ap)
 {
@@ -87,12 +135,17 @@ vprintfmt(void (*putch)(int, void*), void *putdat, const char *fmt, va_list ap)
 	unsigned long long num;
 	int base, lflag, width, precision, altflag;
 	char padc;
+	struct AttrState attst;
+
+	attst.state = NORMAL;
+	attst.cattrs = 0;
+	attst.attrs = 0;
 
 	while (1) {
 		while ((ch = *(unsigned char *) fmt++) != '%') {
 			if (ch == '\0')
 				return;
-			putch(ch, putdat);
+			putchw(putch, ch, putdat, &attst);
 		}
 
 		// Process a %-escape sequence