make url-related functions reusable

The is_url function and url percent-decoding functions were
static, but are generally useful. Let's make them available
to other parts of the code.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 118 insertions, 0 deletions

diff --git a/url.c b/url.c
new file mode 100644
index 0000000000..cd32b927a4
--- /dev/null
+++ b/url.c
@@ -0,0 +1,118 @@
+#include "cache.h"
+
+int is_urlschemechar(int first_flag, int ch)
+{
+	/*
+	 * The set of valid URL schemes, as per STD66 (RFC3986) is
+	 * '[A-Za-z][A-Za-z0-9+.-]*'. But use sightly looser check
+	 * of '[A-Za-z0-9][A-Za-z0-9+.-]*' because earlier version
+	 * of check used '[A-Za-z0-9]+' so not to break any remote
+	 * helpers.
+	 */
+	int alphanumeric, special;
+	alphanumeric = ch > 0 && isalnum(ch);
+	special = ch == '+' || ch == '-' || ch == '.';
+	return alphanumeric || (!first_flag && special);
+}
+
+int is_url(const char *url)
+{
+	const char *url2, *first_slash;
+
+	if (!url)
+		return 0;
+	url2 = url;
+	first_slash = strchr(url, '/');
+
+	/* Input with no slash at all or slash first can't be URL. */
+	if (!first_slash || first_slash == url)
+		return 0;
+	/* Character before must be : and next must be /. */
+	if (first_slash[-1] != ':' || first_slash[1] != '/')
+		return 0;
+	/* There must be something before the :// */
+	if (first_slash == url + 1)
+		return 0;
+	/*
+	 * Check all characters up to first slash - 1. Only alphanum
+	 * is allowed.
+	 */
+	url2 = url;
+	while (url2 < first_slash - 1) {
+		if (!is_urlschemechar(url2 == url, (unsigned char)*url2))
+			return 0;
+		url2++;
+	}
+
+	/* Valid enough. */
+	return 1;
+}
+
+static int url_decode_char(const char *q)
+{
+	int i;
+	unsigned char val = 0;
+	for (i = 0; i < 2; i++) {
+		unsigned char c = *q++;
+		val <<= 4;
+		if (c >= '0' && c <= '9')
+			val += c - '0';
+		else if (c >= 'a' && c <= 'f')
+			val += c - 'a' + 10;
+		else if (c >= 'A' && c <= 'F')
+			val += c - 'A' + 10;
+		else
+			return -1;
+	}
+	return val;
+}
+
+static char *url_decode_internal(const char **query, const char *stop_at)
+{
+	const char *q = *query;
+	struct strbuf out;
+
+	strbuf_init(&out, 16);
+	do {
+		unsigned char c = *q;
+
+		if (!c)
+			break;
+		if (stop_at && strchr(stop_at, c)) {
+			q++;
+			break;
+		}
+
+		if (c == '%') {
+			int val = url_decode_char(q + 1);
+			if (0 <= val) {
+				strbuf_addch(&out, val);
+				q += 3;
+				continue;
+			}
+		}
+
+		if (c == '+')
+			strbuf_addch(&out, ' ');
+		else
+			strbuf_addch(&out, c);
+		q++;
+	} while (1);
+	*query = q;
+	return strbuf_detach(&out, NULL);
+}
+
+char *url_decode(const char *url)
+{
+	return url_decode_internal(&url, NULL);
+}
+
+char *url_decode_parameter_name(const char **query)
+{
+	return url_decode_internal(query, "&=");
+}
+
+char *url_decode_parameter_value(const char **query)
+{
+	return url_decode_internal(query, "&");
+}