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-rw-r--r--libkeccak_degeneralise_spec.c111
1 files changed, 111 insertions, 0 deletions
diff --git a/libkeccak_degeneralise_spec.c b/libkeccak_degeneralise_spec.c
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--- /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