From f99804de08c64531ea6fcd508e1cf32ac237d0b2 Mon Sep 17 00:00:00 2001
From: Alexandre Paillier <alexandre.paillier@ledger.fr>
Date: Mon, 6 Jun 2022 18:36:20 +0200
Subject: [PATCH] Added a signed int256 formatting function

---
 src_common/uint128.c | 39 +++++++++++++++++++++++++++++++++++++++
 src_common/uint128.h |  4 ++++
 src_common/uint256.c | 39 +++++++++++++++++++++++++++++++++++++++
 src_common/uint256.h |  5 +++++
 4 files changed, 87 insertions(+)

diff --git a/src_common/uint128.c b/src_common/uint128.c
index e286412..1962cc8 100644
--- a/src_common/uint128.c
+++ b/src_common/uint128.c
@@ -245,3 +245,42 @@ bool tostring128(const uint128_t *const number,
     reverseString(out, offset);
     return true;
 }
+
+/**
+ * Format a uint128_t into a string as a signed integer
+ *
+ * @param[in] number the number to format
+ * @param[in] base the radix used in formatting
+ * @param[out] out the output buffer
+ * @param[in] out_length the length of the output buffer
+ * @return whether the formatting was successful or not
+ */
+bool tostring128_signed(const uint128_t *const number,
+                        uint32_t base,
+                        char *const out,
+                        uint32_t out_length) {
+    uint128_t max_unsigned_val;
+    uint128_t max_signed_val;
+    uint128_t one_val;
+    uint128_t two_val;
+    uint128_t tmp;
+
+    // showing negative numbers only really makes sense in base 10
+    if (base == 10) {
+        explicit_bzero(&one_val, sizeof(one_val));
+        LOWER(one_val) = 1;
+        explicit_bzero(&two_val, sizeof(two_val));
+        LOWER(two_val) = 2;
+
+        memset(&max_unsigned_val, 0xFF, sizeof(max_unsigned_val));
+        divmod128(&max_unsigned_val, &two_val, &max_signed_val, &tmp);
+        if (gt128(number, &max_signed_val))  // negative value
+        {
+            sub128(&max_unsigned_val, number, &tmp);
+            add128(&tmp, &one_val, &tmp);
+            out[0] = '-';
+            return tostring128(&tmp, base, out + 1, out_length - 1);
+        }
+    }
+    return tostring128(number, base, out, out_length);  // positive value
+}
diff --git a/src_common/uint128.h b/src_common/uint128.h
index 8f76504..e1166c2 100644
--- a/src_common/uint128.h
+++ b/src_common/uint128.h
@@ -52,5 +52,9 @@ void divmod128(const uint128_t *const l,
                uint128_t *const div,
                uint128_t *const mod);
 bool tostring128(const uint128_t *const number, uint32_t base, char *const out, uint32_t outLength);
+bool tostring128_signed(const uint128_t *const number,
+                        uint32_t base,
+                        char *const out,
+                        uint32_t out_length);
 
 #endif  // _UINT128_H_
diff --git a/src_common/uint256.c b/src_common/uint256.c
index e8698ee..68ac0a3 100644
--- a/src_common/uint256.c
+++ b/src_common/uint256.c
@@ -248,3 +248,42 @@ bool tostring256(const uint256_t *const number,
     reverseString(out, offset);
     return true;
 }
+
+/**
+ * Format a uint256_t into a string as a signed integer
+ *
+ * @param[in] number the number to format
+ * @param[in] base the radix used in formatting
+ * @param[out] out the output buffer
+ * @param[in] out_length the length of the output buffer
+ * @return whether the formatting was successful or not
+ */
+bool tostring256_signed(const uint256_t *const number,
+                        uint32_t base,
+                        char *const out,
+                        uint32_t out_length) {
+    uint256_t max_unsigned_val;
+    uint256_t max_signed_val;
+    uint256_t one_val;
+    uint256_t two_val;
+    uint256_t tmp;
+
+    // showing negative numbers only really makes sense in base 10
+    if (base == 10) {
+        explicit_bzero(&one_val, sizeof(one_val));
+        LOWER(LOWER(one_val)) = 1;
+        explicit_bzero(&two_val, sizeof(two_val));
+        LOWER(LOWER(two_val)) = 2;
+
+        memset(&max_unsigned_val, 0xFF, sizeof(max_unsigned_val));
+        divmod256(&max_unsigned_val, &two_val, &max_signed_val, &tmp);
+        if (gt256(number, &max_signed_val))  // negative value
+        {
+            sub256(&max_unsigned_val, number, &tmp);
+            add256(&tmp, &one_val, &tmp);
+            out[0] = '-';
+            return tostring256(&tmp, base, out + 1, out_length - 1);
+        }
+    }
+    return tostring256(number, base, out, out_length);  // positive value
+}
diff --git a/src_common/uint256.h b/src_common/uint256.h
index dfc97f7..351953b 100644
--- a/src_common/uint256.h
+++ b/src_common/uint256.h
@@ -53,5 +53,10 @@ void divmod256(const uint256_t *const l,
                uint256_t *const div,
                uint256_t *const mod);
 bool tostring256(const uint256_t *const number, uint32_t base, char *const out, uint32_t outLength);
+bool tostring256_signed(const uint256_t *const number,
+                        uint32_t base,
+                        char *const out,
+                        uint32_t out_length);
+
 
 #endif  // _UINT256_H_