1 files changed, 74 insertions, 0 deletions
diff --git a/string.c b/string.c
new file mode 100644
index 0000000..4a6d9d8
--- /dev/null
+++ b/string.c
@@ -0,0 +1,74 @@
+/* Copyright (C) 2018  C. McEnroe <june@causal.agency>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <err.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sysexits.h>
+
+#include "chat.h"
+
+static const char Base64[64] = {
+	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
+};
+
+size_t base64Size(size_t len) {
+	return 1 + (len + 2) / 3 * 4;
+}
+
+void base64(char *dst, const byte *src, size_t len) {
+	size_t i = 0;
+	while (len > 2) {
+		dst[i++] = Base64[0x3F & (src[0] >> 2)];
+		dst[i++] = Base64[0x3F & (src[0] << 4 | src[1] >> 4)];
+		dst[i++] = Base64[0x3F & (src[1] << 2 | src[2] >> 6)];
+		dst[i++] = Base64[0x3F & src[2]];
+		src += 3;
+		len -= 3;
+	}
+	if (len) {
+		dst[i++] = Base64[0x3F & (src[0] >> 2)];
+		if (len > 1) {
+			dst[i++] = Base64[0x3F & (src[0] << 4 | src[1] >> 4)];
+			dst[i++] = Base64[0x3F & (src[1] << 2)];
+		} else {
+			dst[i++] = Base64[0x3F & (src[0] << 4)];
+			dst[i++] = '=';
+		}
+		dst[i++] = '=';
+	}
+	dst[i] = '\0';
+}
+
+#ifdef TEST
+#include <assert.h>
+
+int main() {
+	assert(5 == base64Size(1));
+	assert(5 == base64Size(2));
+	assert(5 == base64Size(3));
+	assert(9 == base64Size(4));
+
+	char b64[base64Size(3)];
+	assert((base64(b64, (byte *)"cat", 3), !strcmp("Y2F0", b64)));
+	assert((base64(b64, (byte *)"ca", 2), !strcmp("Y2E=", b64)));
+	assert((base64(b64, (byte *)"c", 1), !strcmp("Yw==", b64)));
+
+	assert((base64(b64, (byte *)"\xFF\x00\xFF", 3), !strcmp("/wD/", b64)));
+	assert((base64(b64, (byte *)"\x00\xFF\x00", 3), !strcmp("AP8A", b64)));
+}
+
+#endif