cancellation file support for bluebox (#212)

* cancellation file support for bluebox
* filter out EINTR thanks arvid

src/c_bindings/c_wrapper.cpp

@@ -22,7 +22,7 @@ extern "C" {
             std::vector<uint8_t> challenge_hash_bytes(challenge_hash, challenge_hash + challenge_size);
             integer discriminant = CreateDiscriminant(challenge_hash_bytes, discriminant_size_bits);
             form x = DeserializeForm(discriminant, x_s, x_s_size);
-            std::vector<uint8_t> result = ProveSlow(discriminant, x, num_iterations);
+            std::vector<uint8_t> result = ProveSlow(discriminant, x, num_iterations, "");
 
             // Allocate memory for the result and copy data
             uint8_t* resultData = new uint8_t[result.size()];

src/prover_slow.h

@@ -5,6 +5,7 @@
 #include "nucomp.h"
 #include "picosha2.h"
 #include "proof_common.h"
+#include <sys/stat.h>
 
 
 // TODO: Refactor to use 'Prover' class once new_vdf is merged in.
@@ -78,7 +79,7 @@ form GenerateWesolowski(form &y, form &x_init,
     return x;
 }
 
-std::vector<uint8_t> ProveSlow(integer& D, form& x, uint64_t num_iterations) {
+std::vector<uint8_t> ProveSlow(integer& D, form& x, uint64_t num_iterations, std::string shutdown_file_path) {
     integer L = root(-D, 4);
     PulmarkReducer reducer;
     form y = form::from_abd(x.a, x.b, D);
@@ -100,6 +101,20 @@ std::vector<uint8_t> ProveSlow(integer& D, form& x, uint64_t num_iterations) {
         }
         nudupl_form(y, y, D, L);
         reducer.reduce(y);
+
+        // Check for cancellation every 65535 interations
+        if ((i&0xffff)==0) {
+            // Only if we have a shutdown path
+            if (shutdown_file_path!="") {
+                struct stat buffer;
+
+                int statrst = stat(shutdown_file_path.c_str(), &buffer);
+                if ((statrst != 0) && (errno != EINTR)) {
+                    // shutdown file doesn't exist, abort out
+                    return {};
+                }
+            }
+        }
     }
 
     form proof = GenerateWesolowski(y, x, D, reducer, intermediates, num_iterations, k, l);

src/python_bindings/fastvdf.cpp

@@ -54,7 +54,7 @@ PYBIND11_MODULE(chiavdf, m) {
         return CheckProofOfTimeNWesolowski(integer(discriminant_copy), (const uint8_t *)x_s_copy.data(), proof_blob_ptr, proof_blob_size, num_iterations, disc_size_bits, recursion);
     });
 
-    m.def("prove", [] (const py::bytes& challenge_hash, const string& x_s, int discriminant_size_bits, uint64_t num_iterations) {
+    m.def("prove", [] (const py::bytes& challenge_hash, const string& x_s, int discriminant_size_bits, uint64_t num_iterations, const string& shutdown_file_path) {
         std::string challenge_hash_str(challenge_hash);
         std::string x_s_copy(x_s);
         std::vector<uint8_t> result;
@@ -66,7 +66,7 @@ PYBIND11_MODULE(chiavdf, m) {
                     discriminant_size_bits
             );
             form x = DeserializeForm(D, (const uint8_t *) x_s_copy.data(), x_s_copy.size());
-            result = ProveSlow(D, x, num_iterations);
+            result = ProveSlow(D, x, num_iterations, shutdown_file_path);
         }
         py::bytes ret = py::bytes(reinterpret_cast<char*>(result.data()), result.size());
         return ret;

tests/test_n_weso_verifier.py

@@ -15,13 +15,13 @@ def prove_n_weso(discriminant_challenge, x, discriminant_size, form_size, iters,
     partials = []
     discriminant = create_discriminant(discriminant_challenge, discriminant_size)
     for _ in range(witness):
-        result = prove(discriminant_challenge, x, discriminant_size, iters_chunk)
+        result = prove(discriminant_challenge, x, discriminant_size, iters_chunk, "")
         y = result[:form_size]
         proof = result[form_size : 2 * form_size]
         partials.append((x, y, proof))
         x = y
     iters -= iters_chunk * witness
-    result = prove(discriminant_challenge, x, discriminant_size, iters)
+    result = prove(discriminant_challenge, x, discriminant_size, iters, "")
     y_result = result[:form_size]
     y_proof = result[form_size : 2 * form_size]
     assert verify_wesolowski(discriminant, x, y_result, y_proof, iters)

tests/test_verifier.py

@@ -13,7 +13,7 @@ def test_prove_and_verify():
 
     iters = 1000000
     t1 = time.time()
-    result = prove(discriminant_challenge, initial_el, discriminant_size, iters)
+    result = prove(discriminant_challenge, initial_el, discriminant_size, iters, "")
     t2 = time.time()
     print(f"IPS: {iters / (t2 - t1)}")
     result_y = result[:form_size]
@@ -36,6 +36,7 @@ def test_prove_and_verify():
         result_y,
         discriminant_size,
         iters_2,
+        ""
     )
     t2 = time.time()
     print(f"IPS: {iters_2 / (t2 - t1)}")