str: add hexadigit encoding to strings

src/str.c

@@ -217,6 +217,32 @@ int git_str_puts(git_str *buf, const char *string)
 	return git_str_put(buf, string, strlen(string));
 }
 
+static char hex_encode[] = "0123456789abcdef";
+
+int git_str_encode_hexstr(git_str *str, const char *data, size_t len)
+{
+	size_t new_size, i;
+	char *s;
+
+	GIT_ERROR_CHECK_ALLOC_MULTIPLY(&new_size, len, 2);
+	GIT_ERROR_CHECK_ALLOC_ADD(&new_size, new_size, 1);
+
+	if (git_str_grow_by(str, new_size) < 0)
+		return -1;
+
+	s = str->ptr + str->size;
+
+	for (i = 0; i < len; i++) {
+		*s++ = hex_encode[(data[i] & 0xf0) >> 4];
+		*s++ = hex_encode[(data[i] & 0x0f)];
+	}
+
+	str->size += (len * 2);
+	str->ptr[str->size] = '\0';
+
+	return 0;
+}
+
 static const char base64_encode[] =
 	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 

src/str.h

@@ -217,6 +217,9 @@ int git_str_cmp(const git_str *a, const git_str *b);
 int git_str_quote(git_str *str);
 int git_str_unquote(git_str *str);
 
+/* Write data as a hex string */
+int git_str_encode_hexstr(git_str *str, const char *data, size_t len);
+
 /* Write data as base64 encoded in string buffer */
 int git_str_encode_base64(git_str *str, const char *data, size_t len);
 /* Decode the given bas64 and write the result to the string buffer */