osc7: initial patch implementation (#154)

* osc7: initial patch implementation

Closes #153

* osc7: avoid redundant use of realpath()

* osc7: fix styling

* Changing position of the OSC7_PATCH toggle in patches.def.h

---------

Co-authored-by: Bakkeby <bakkeby@gmail.com>

patch/osc7.c

@@ -0,0 +1,74 @@
+static int
+hex2int(char c)
+{
+	if (c >= '0' && c <= '9')
+		return c - '0';
+	else if (c >= 'a' && c <= 'f')
+		return c - 'a' + 10;
+	else if (c >= 'A' && c <= 'F')
+		return c - 'A' + 10;
+	else
+		return -1;
+}
+
+int
+osc7parsecwd(const char *uri)
+{
+	const char *auth, *host, *hostend;
+	char *path, decoded[PATH_MAX], thishost[_POSIX_HOST_NAME_MAX];
+	size_t i, decodedlen, hostlen, urilen;
+	int h1, h2;
+	if (!term.cwd) {
+		term.cwd = xmalloc(sizeof(decoded));
+		term.cwd[0] = '\0';
+	}
+	/* reset cwd if uri is empty */
+	if ((urilen = strlen(uri)) == 0) {
+		term.cwd[0] = '\0';
+		return 1;
+	}
+	/* decode uri */
+	for (decodedlen = 0, i = 0; i < urilen; i++) {
+		if (uri[i] == '%' && i <= urilen-3 &&
+		    (h1 = hex2int(uri[i+1])) >= 0 && (h2 = hex2int(uri[i+2])) >= 0) {
+			decoded[decodedlen++] = (h1 << 4) | h2;
+			i += 2;
+		} else {
+			decoded[decodedlen++] = uri[i];
+		}
+		if (decodedlen == sizeof(decoded)) {
+			fprintf(stderr, "erresc (OSC 7): uri is too long\n");
+			return 0;
+		}
+	}
+	decoded[decodedlen] = '\0';
+	/* check scheme */
+	if (decodedlen < 5 || strncmp("file:", decoded, 5) != 0) {
+		fprintf(stderr, "erresc (OSC 7): scheme is not supported: '%s'\n", uri);
+		return 0;
+	}
+	/* find start of authority */
+	if (decodedlen < 7 || decoded[5] != '/' || decoded[6] != '/') {
+		fprintf(stderr, "erresc (OSC 7): invalid uri: '%s'\n", uri);
+		return 0;
+	}
+	auth = decoded + 7;
+	/* find start of path and reset cwd if path is missing */
+	if ((path = strchr(auth, '/')) == NULL) {
+		term.cwd[0] = '\0';
+		return 1;
+	}
+	/* ignore path if host is not localhost */
+	host = ((host = memchr(auth, '@', path - auth)) != NULL) ? host+1 : auth;
+	hostend = ((hostend = memchr(host, ':', path - host)) != NULL) ? hostend : path;
+	hostlen = hostend - host;
+	if (gethostname(thishost, sizeof(thishost)) < 0)
+		thishost[0] = '\0';
+	if (hostlen > 0 &&
+	    !(hostlen == 9 && strncmp("localhost", host, hostlen) == 0) &&
+	    !(hostlen == strlen(thishost) && strncmp(host, thishost, hostlen) == 0)) {
+		return 0;
+	}
+	memcpy(term.cwd, path, decodedlen - (path - decoded) + 1);
+	return 1;
+}