From b4df409614ab94f14ffc8d3fc9900e2b30910db7 Mon Sep 17 00:00:00 2001
From: Ben Edgington <ben@benjaminion.xyz>
Date: Fri, 5 Feb 2021 08:10:08 +0000
Subject: [PATCH] Pass polys when calculating quotient size

---
 src/kzg_single_proofs.c | 2 +-
 src/poly.c              | 4 ++--
 src/poly.h              | 2 +-
 src/poly_test.c         | 8 +++++++-
 4 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/src/kzg_single_proofs.c b/src/kzg_single_proofs.c
index f4da450..a6cad77 100644
--- a/src/kzg_single_proofs.c
+++ b/src/kzg_single_proofs.c
@@ -32,7 +32,7 @@ void compute_proof_single(blst_p1 *out, const KZGSettings *ks, poly *p, const ui
     divisor.coeffs[1] = one;
 
     // Calculate q = p / (x - x0)
-    init_poly(&q, poly_long_div_length(p->length, 2));
+    init_poly(&q, poly_quotient_length(p, &divisor));
     poly_long_div(&q, p, &divisor);
 
     linear_combination_g1(out, ks->secret_g1, q.coeffs, q.length);
diff --git a/src/poly.c b/src/poly.c
index 5cacc37..986c849 100644
--- a/src/poly.c
+++ b/src/poly.c
@@ -47,8 +47,8 @@ void eval_poly_at(blst_fr *out, const poly *p, const blst_fr *x) {
 }
 
 // Call this to find out how much space to allocate for the result
-uint64_t poly_long_div_length(const uint64_t len_dividend, const uint64_t len_divisor) {
-    return len_dividend - len_divisor + 1;
+uint64_t poly_quotient_length(const poly *dividend, const poly *divisor) {
+    return dividend->length - divisor->length + 1;
 }
 
 // `out` must have been pre-allocated to the correct size, and the length is provided
diff --git a/src/poly.h b/src/poly.h
index 5a755c8..3e8edfb 100644
--- a/src/poly.h
+++ b/src/poly.h
@@ -26,5 +26,5 @@ typedef struct {
 void init_poly(poly *out, const uint64_t length);
 void free_poly(poly p);
 void eval_poly_at(blst_fr *out, const poly *p, const blst_fr *x);
-uint64_t poly_long_div_length(const uint64_t len_dividend, const uint64_t len_divisor);
+uint64_t poly_quotient_length(const poly *dividend, const poly *divisor);
 C_KZG_RET poly_long_div(poly *out, const poly *dividend, const poly *divisor);
diff --git a/src/poly_test.c b/src/poly_test.c
index 6bb43cf..bcc7f07 100644
--- a/src/poly_test.c
+++ b/src/poly_test.c
@@ -18,8 +18,13 @@
 #include "debug_util.h"
 #include "poly.h"
 
+void title(void) {;}
+
 void poly_div_length(void) {
-    TEST_CHECK(3 == poly_long_div_length(4, 2));
+    poly a, b;
+    init_poly(&a, 17);
+    init_poly(&b, 5);
+    TEST_CHECK(13 == poly_quotient_length(&a, &b));
 }
 
 void poly_div_0(void) {
@@ -113,6 +118,7 @@ void eval_poly(void) {
 
 TEST_LIST =
     {
+     {"POLY_TEST", title},
      {"poly_div_length", poly_div_length},
      {"poly_div_0", poly_div_0},
      {"poly_div_1", poly_div_1},