First commit

Signed-off-by: Mattias Andrée <m@maandree.se>

1 files changed, 177 insertions, 0 deletions

diff --git a/librecrypt_encode.c b/librecrypt_encode.c
new file mode 100644
index 0000000..2199ac1
--- /dev/null
+++ b/librecrypt_encode.c
@@ -0,0 +1,177 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+#ifndef TEST
+
+
+#if defined(__GNUC__)
+# pragma GCC diagnostic ignored "-Wimplicit-fallthrough"
+#endif
+
+
+#define O1(I1, I2, I3) ((I1) >> 2)
+#define O2(I1, I2, I3) (((I1) << 4) | ((I2) >> 4))
+#define O3(I1, I2, I3) (((I2) << 2) | ((I3) >> 6))
+#define O4(I1, I2, I3) (I3)
+
+
+size_t
+librecrypt_encode(char *out_buffer, size_t size, const void *binary, size_t len,
+                  const char lut[restrict static 256], char pad)
+{
+	const unsigned char *data = binary;
+	unsigned char a, b, c;
+	size_t q, r, i, j, n;
+
+	q = len / 3u;
+	r = len % 3u;
+	n = q * 4u + (!r ? 0u : pad ? 4u : r + 1u);
+
+	if (!size)
+		return n;
+
+	size -= 1u;
+	out_buffer[n < size ? n : size] = '\0';
+
+	if (r == 1u) {
+		a = data[q * 3u + 0u];
+		switch (size > q * 4u ? size - q * 4u : 0u) { /* fall-through */
+		default:
+			if (pad)
+				out_buffer[q * 4u + 3u] = pad;
+		case 3u:
+			if (pad)
+				out_buffer[q * 4u + 2u] = pad;
+		case 2u:
+			out_buffer[q * 4u + 1u] = lut[O2(a, 0, 0) & 255];
+		case 1u:
+			out_buffer[q * 4u + 0u] = lut[O1(a, 0, 0) & 255];
+		case 0u:
+			break;
+		}
+	} else if (r == 2u) {
+		a = data[q * 3u + 0u];
+		b = data[q * 3u + 1u];
+		switch (size > q * 4u ? size - q * 4u : 0u) { /* fall-through */
+		default:
+			if (pad)
+				out_buffer[q * 4u + 3u] = pad;
+		case 3u:
+			out_buffer[q * 4u + 2u] = lut[O3(a, b, 0) & 255];
+		case 2u:
+			out_buffer[q * 4u + 1u] = lut[O2(a, b, 0) & 255];
+		case 1u:
+			out_buffer[q * 4u + 0u] = lut[O1(a, b, 0) & 255];
+		case 0u:
+			break;
+		}
+	}
+
+	i = q * 4u;
+	j = q * 3u;
+	if (i > size) {
+		q = size / 4u;
+		r = size % 4u;
+		i = q * 4u;
+		j = q * 3u;
+		c = data[j + 2u];
+		b = data[j + 1u];
+		a = data[j + 0u];
+		switch (r) { /* fall-through */
+		case 3u:
+			out_buffer[i + 2u] = lut[O3(a, b, c) & 255];
+		case 2u:
+			out_buffer[i + 1u] = lut[O2(a, b, c) & 255];
+		case 1u:
+			out_buffer[i + 0u] = lut[O1(a, b, c) & 255];
+		default:
+			break;
+		}
+	}
+	while (i) {
+		i -= 4u;
+		j -= 3u;
+		c = data[j + 2u];
+		b = data[j + 1u];
+		a = data[j + 0u];
+		out_buffer[i + 3u] = lut[O4(a, b, c) & 255];
+		out_buffer[i + 2u] = lut[O3(a, b, c) & 255];
+		out_buffer[i + 1u] = lut[O2(a, b, c) & 255];
+		out_buffer[i + 0u] = lut[O1(a, b, c) & 255];
+	}
+
+	return n;
+}
+
+
+#else
+
+
+NONSTRING static const char lut[256u] = MAKE_ENCODING_LUT("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/");
+
+
+#define CHECK(BINARY, ASCII)\
+	check((BINARY), sizeof(BINARY) - 1u, (ASCII), sizeof(ASCII) - 1u)
+
+
+static void
+check(const char *binary, size_t binary_len, const char *ascii, size_t ascii_len)
+{
+	size_t padded_ascii_len = ascii_len;
+	char buf[256u];
+	size_t i, j, n;
+
+	if (padded_ascii_len & 3u) {
+		padded_ascii_len |= 3u;
+		padded_ascii_len += 1u;
+	}
+	assert(padded_ascii_len % 4u == 0u);
+	assert(padded_ascii_len / 4u == (ascii_len + 3u) / 4u);
+	assert(padded_ascii_len >= ascii_len);
+
+	EXPECT(librecrypt_encode(NULL, 0u, binary, binary_len, lut, '\0') == ascii_len);
+	EXPECT(librecrypt_encode(buf, 0u, binary, binary_len, lut, '\0') == ascii_len);
+
+	EXPECT(librecrypt_encode(NULL, 0u, binary, binary_len, lut, '=') == padded_ascii_len);
+	EXPECT(librecrypt_encode(buf, 0u, binary, binary_len, lut, '=') == padded_ascii_len);
+
+	for (i = 0u; i <= ascii_len; i++) {
+		memset(buf, 99, sizeof(buf));
+		EXPECT(librecrypt_encode(buf, i + 1u, binary, binary_len, lut, '\0') == ascii_len);
+		EXPECT(!memcmp(buf, ascii, i));
+		EXPECT(buf[i] == '\0');
+		for (j = i + 1u; j < sizeof(buf); j++)
+			EXPECT(buf[j] == 99);
+	}
+
+	for (i = 0u; i <= padded_ascii_len; i++) {
+		memset(buf, 99, sizeof(buf));
+		EXPECT(librecrypt_encode(buf, i + 1u, binary, binary_len, lut, '=') == padded_ascii_len);
+		j = i < ascii_len ? i : ascii_len;
+		n = i < padded_ascii_len ? i : padded_ascii_len;
+		EXPECT(!memcmp(buf, ascii, j));
+		for (; j < n; j++)
+			EXPECT(buf[j] == '=');
+		EXPECT(buf[j++] == '\0');
+		for (; j < sizeof(buf); j++)
+			EXPECT(buf[j] == 99);
+	}
+}
+
+
+int
+main(void)
+{
+	SET_UP_ALARM();
+	CHECK("", "");
+	CHECK("\x00", "AA");
+	CHECK("\x00\x00", "AAA");
+	CHECK("\x00\x00\x00", "AAAA");
+	CHECK("12345678", "MTIzNDU2Nzg");
+	CHECK("testtest", "dGVzdHRlc3Q");
+	CHECK("zy[]y21 !", "enlbXXkyMSAh");
+	CHECK("{~|~}~~~\x7f\x7f", "e358fn1+fn5/fw");
+	return 0;
+}
+
+
+#endif