1 files changed, 111 insertions, 0 deletions
diff --git a/libkeccak_degeneralise_spec.c b/libkeccak_degeneralise_spec.c
new file mode 100644
index 0000000..13963f8
--- /dev/null
+++ b/libkeccak_degeneralise_spec.c
@@ -0,0 +1,111 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+
+
+#ifdef __GNUC__
+# pragma GCC diagnostic push
+# pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
+#endif
+
+#define have(v)     (spec->v != LIBKECCAK_GENERALISED_SPEC_AUTOMATIC)
+#define copy(v)     (v = spec->v)
+#define deft(v, dv) (have_##v ? v : (dv))
+
+
+/**
+ * Convert a `libkeccak_generalised_spec_t` to a `libkeccak_spec_t`
+ *
+ * If you are interrested in finding errors, you should call
+ * `libkeccak_spec_check(output)` if this function returns zero
+ * 
+ * @param   spec         The generalised input specifications, will be update with resolved automatic values
+ * @param   output_spec  The specification datastructure to fill in
+ * @return               Zero if `spec` is valid, a `LIBKECCAK_GENERALISED_SPEC_ERROR_*` if an error was found
+ */
+int
+libkeccak_degeneralise_spec(libkeccak_generalised_spec_t *restrict spec,
+                            libkeccak_spec_t *restrict output_spec)
+{
+	long int state_size, word_size, capacity, bitrate, output;
+	const int have_state_size = have(state_size);
+	const int have_word_size  = have(word_size);
+	const int have_capacity   = have(capacity);
+	const int have_bitrate    = have(bitrate);
+	const int have_output     = have(output);
+
+
+	if (have_state_size) {
+		copy(state_size);
+		if (state_size <= 0)   return LIBKECCAK_GENERALISED_SPEC_ERROR_STATE_NONPOSITIVE;
+		if (state_size > 1600) return LIBKECCAK_GENERALISED_SPEC_ERROR_STATE_TOO_LARGE;
+		if (state_size % 25)   return LIBKECCAK_GENERALISED_SPEC_ERROR_STATE_MOD_25;
+	}
+
+	if (have_word_size) {
+		copy(word_size);
+		if (word_size <= 0) return LIBKECCAK_GENERALISED_SPEC_ERROR_WORD_NONPOSITIVE;
+		if (word_size > 64) return LIBKECCAK_GENERALISED_SPEC_ERROR_WORD_TOO_LARGE;
+		if (have_state_size && state_size != word_size * 25)
+			return LIBKECCAK_GENERALISED_SPEC_ERROR_STATE_WORD_INCOHERENCY;
+		else if (!have_state_size)
+			spec->state_size = 1, state_size = word_size * 25;
+	}
+
+	if (have_capacity) {
+		copy(capacity);
+		if (capacity <= 0) return LIBKECCAK_GENERALISED_SPEC_ERROR_CAPACITY_NONPOSITIVE;
+		if (capacity & 7)  return LIBKECCAK_GENERALISED_SPEC_ERROR_CAPACITY_MOD_8;
+	}
+
+	if (have_bitrate) {
+		copy(bitrate);
+		if (bitrate <= 0) return LIBKECCAK_GENERALISED_SPEC_ERROR_BITRATE_NONPOSITIVE;
+		if (bitrate & 7)  return LIBKECCAK_GENERALISED_SPEC_ERROR_BITRATE_MOD_8;
+	}
+
+	if (have_output) {
+		copy(output);
+		if (output <= 0) return LIBKECCAK_GENERALISED_SPEC_ERROR_OUTPUT_NONPOSITIVE;
+	}
+
+
+	if (!have_bitrate && !have_capacity && !have_output) {
+		state_size = deft(state_size, 1600L);
+		output = ((state_size << 5) / 100L + 7L) & ~0x07L;
+		bitrate = output << 1;
+		capacity = state_size - bitrate;
+		output = output >= 8 ? output : 8;
+	} else if (!have_bitrate && !have_capacity) {
+		bitrate = 1024;
+		capacity = 1600 - 1024;
+		state_size = deft(state_size, bitrate + capacity);
+	} else if (!have_bitrate) {
+		state_size = deft(state_size, 1600L);
+		bitrate = state_size - capacity;
+		output = deft(output, capacity == 8 ? 8 : (capacity << 1));
+	} else if (!have_capacity) {
+		state_size = deft(state_size, 1600L);
+		capacity = state_size - bitrate;
+		output = deft(output, capacity == 8 ? 8 : (capacity << 1));
+	} else {
+		state_size = deft(state_size, bitrate + capacity);
+		output = deft(output, capacity == 8 ? 8 : (capacity << 1));
+	}
+
+	spec->capacity   = output_spec->capacity = capacity;
+	spec->bitrate    = output_spec->bitrate  = bitrate;
+	spec->output     = output_spec->output   = output;
+	spec->state_size = state_size;
+	spec->word_size  = state_size / 25;
+
+	return 0;
+}
+
+
+#undef deft
+#undef copy
+#undef have
+
+#ifdef __GNUC__
+# pragma GCC diagnostic pop
+#endif