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/* 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;
/* 1 byte (8 bits) requires 2 base-64 characters (12 bits),
* 2 bytes (16 bits) requires 3 base-64 characters (18 bits), and
* 3 bytes (24 bits) requires 4 base-64 characters (24 bits) exactly */
q = len / 3u;
r = len % 3u;
n = !r ? 0u : pad ? 4u : r + 1u;
if (q > (SIZE_MAX - n) / 4u) {
errno = EOVERFLOW;
return SIZE_MAX;
}
n += q * 4u;
/* Just return the encoding length if no output is requested */
if (!size)
return n;
/* We right backwards to ensure `out_buffer` and `binary` may alias each other
* (the output is at least as long as the input (actually always longer
* unless `len` is 0)) */
/* NUL-terminate output */
size -= 1u;
out_buffer[MIN(n, size)] = '\0';
/* Deal with situation where number of bytes is not divisible
* byte there, and set excess bits to 0; padding characters are
* appended if required (they are probably optional since padding
* is only useful to allow base-64 strings to be concatenated) */
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;
}
}
/* Encode multiples of 3 bytes as multiples of 4 ASCII characters, */
i = q * 4u;
j = q * 3u;
/* however, first we may have to truncate the output to a non-multiple
* of 4 ASCII characters the output buffer is too small, */
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;
}
}
/* then we can efficiently write the multiple of 4 characters */
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 phony librecrypt_test_phony__
extern void *volatile librecrypt_test_phony__;
void *volatile librecrypt_test_phony__ = (void *)(uintptr_t)4096u;
#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;
/* Check internal test correctness */
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);
/* Check length-only request without padding */
EXPECT(librecrypt_encode(NULL, 0u, binary, binary_len, lut, '\0') == ascii_len);
EXPECT(librecrypt_encode(buf, 0u, binary, binary_len, lut, '\0') == ascii_len);
/* Check length-only request with padding */
EXPECT(librecrypt_encode(NULL, 0u, binary, binary_len, lut, '=') == padded_ascii_len);
EXPECT(librecrypt_encode(buf, 0u, binary, binary_len, lut, '=') == padded_ascii_len);
/* Check encoding requests, with and without truncation, without padding */
for (i = 0u; i <= ascii_len; i++) {
CANARY_FILL(buf);
EXPECT(librecrypt_encode(buf, i + 1u, binary, binary_len, lut, '\0') == ascii_len);
EXPECT(!memcmp(buf, ascii, i));
EXPECT(buf[i] == '\0');
CANARY_CHECK(buf, i + 1u);
}
/* Check encoding requests, with and without truncation, with padding */
for (i = 0u; i <= padded_ascii_len; i++) {
CANARY_FILL(buf);
EXPECT(librecrypt_encode(buf, i + 1u, binary, binary_len, lut, '=') == padded_ascii_len);
j = MIN(i, ascii_len);
n = MIN(i, padded_ascii_len);
EXPECT(!memcmp(buf, ascii, j));
for (; j < n; j++)
EXPECT(buf[j] == '=');
EXPECT(buf[j++] == '\0');
CANARY_CHECK(buf, j);
}
}
int
main(void)
{
SET_UP_ALARM();
INIT_RESOURCE_TEST();
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");
#if defined(__GNUC__)
# pragma GCC diagnostic push
# pragma GCC diagnostic ignored "-Wstringop-overflow="
#endif
EXPECT(librecrypt_encode(NULL, 0u, phony, (SIZE_MAX - 3u) / 4u * 3u + 1u, lut, '\0') == SIZE_MAX - 1u);
errno = 0;
EXPECT(librecrypt_encode(NULL, 0u, phony, (SIZE_MAX - 3u) / 4u * 3u + 2u, lut, '\0') == SIZE_MAX);
EXPECT(errno == 0);
errno = 0;
EXPECT(librecrypt_encode(NULL, 0u, phony, (SIZE_MAX - 3u) / 4u * 3u + 3u, lut, '\0') == SIZE_MAX);
EXPECT(errno == EOVERFLOW);
#if defined(__GNUC__)
# pragma GCC diagnostic pop
#endif
STOP_RESOURCE_TEST();
return 0;
}
#endif
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