thodg/libgit2

diff --git a/src/buffer.c b/src/buffer.c
index 61cfaf9..ee2dd28 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -186,6 +186,46 @@ int git_buf_puts_escaped(
 	return 0;
 }
 
+static const char b64str[64] =
+	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+
+int git_buf_put_base64(git_buf *buf, const char *data, size_t len)
+{
+	size_t extra = len % 3;
+	uint8_t *write, a, b, c;
+	const uint8_t *read = (const uint8_t *)data;
+
+	ENSURE_SIZE(buf, buf->size + ((len * 4 + 3) / 3) + 1);
+	write = (uint8_t *)&buf->ptr[buf->size];
+
+	/* convert each run of 3 bytes into 4 output bytes */
+	for (len -= extra; len > 0; len -= 3) {
+		a = *read++;
+		b = *read++;
+		c = *read++;
+
+		*write++ = b64str[a >> 2];
+		*write++ = b64str[(a & 0x03) << 4 | b >> 4];
+		*write++ = b64str[(b & 0x0f) << 2 | c >> 6];
+		*write++ = b64str[c & 0x3f];
+	}
+
+	if (extra > 0) {
+		a = *read++;
+		b = (extra > 1) ? *read++ : 0;
+
+		*write++ = b64str[a >> 2];
+		*write++ = b64str[(a & 0x03) << 4 | b >> 4];
+		*write++ = (extra > 1) ? b64str[(b & 0x0f) << 2] : '=';
+		*write++ = '=';
+	}
+
+	buf->size = ((char *)write) - buf->ptr;
+	buf->ptr[buf->size] = '\0';
+
+	return 0;
+}
+
 int git_buf_vprintf(git_buf *buf, const char *format, va_list ap)
 {
 	int len;
diff --git a/src/buffer.h b/src/buffer.h
index 17922e4..94b7e0e 100644
--- a/src/buffer.h
+++ b/src/buffer.h
@@ -154,4 +154,7 @@ bool git_buf_is_binary(const git_buf *buf);
 /* Unescape all characters in a buffer */
 void git_buf_unescape(git_buf *buf);
 
+/* Write data as base64 encoded in buffer */
+int git_buf_put_base64(git_buf *buf, const char *data, size_t len);
+
 #endif
diff --git a/tests-clar/core/buffer.c b/tests-clar/core/buffer.c
index 972567e..236bf39 100644
--- a/tests-clar/core/buffer.c
+++ b/tests-clar/core/buffer.c
@@ -678,3 +678,28 @@ void test_core_buffer__unescape(void)
 	assert_unescape("\\", "\\\\");
 	assert_unescape("", "");
 }
+
+void test_core_buffer__base64(void)
+{
+	git_buf buf = GIT_BUF_INIT;
+
+	/*     t  h  i  s
+	 * 0x 74 68 69 73
+     * 0b 01110100 01101000 01101001 01110011
+	 * 0b 011101 000110 100001 101001 011100 110000
+	 * 0x 1d 06 21 29 1c 30
+	 *     d  G  h  p  c  w
+	 */
+	cl_git_pass(git_buf_put_base64(&buf, "this", 4));
+	cl_assert_equal_s("dGhpcw==", buf.ptr);
+
+	git_buf_clear(&buf);
+	cl_git_pass(git_buf_put_base64(&buf, "this!", 5));
+	cl_assert_equal_s("dGhpcyE=", buf.ptr);
+
+	git_buf_clear(&buf);
+	cl_git_pass(git_buf_put_base64(&buf, "this!\n", 6));
+	cl_assert_equal_s("dGhpcyEK", buf.ptr);
+
+	git_buf_free(&buf);
+}