also convert from confidential to satoshi

Author: glslang

include/wally_transaction.h

@@ -844,7 +844,7 @@ WALLY_CORE_API int wally_tx_is_elements(
     size_t *written);
 
 /**
- * Convert satoshi to an (explicit) confidential value representation.
+ * Convert satoshi to an explicit confidential value representation.
  *
  * :param satoshi: The value in satoshi to convert.
  * :param bytes_out: Destination for the confidential value bytes.
@@ -855,6 +855,18 @@ WALLY_CORE_API int wally_tx_confidential_value_from_satoshi(
     unsigned char *bytes_out,
     size_t len);
 
+/**
+ * Convert an explicit confidential value representation to satoshi.
+ *
+ * :param value: The confidential value bytes.
+ * :param value_len: Size of ``value`` in bytes. Must be ``WALLY_TX_ASSET_CT_VALUE_UNBLIND_LEN``.
+ * :param value_out: The converted value in satoshi.
+ */
+WALLY_CORE_API int wally_tx_confidential_value_to_satoshi(
+    const unsigned char *value,
+    size_t value_len,
+    uint64_t* value_out);
+
 /**
  * Create a Elements transaction for signing and return its hash.
  *

src/swig_java/swig.i

@@ -448,6 +448,7 @@ static jbyteArray create_array(JNIEnv *jenv, const unsigned char* p, size_t len)
 %returns_void__(wally_tx_add_output);
 %returns_void__(wally_tx_add_raw_output);
 %returns_array_(wally_tx_confidential_value_from_satoshi, 2, 3, WALLY_TX_ASSET_CT_VALUE_UNBLIND_LEN);
+%returns_uint64(wally_tx_confidential_value_to_satoshi);
 %returns_struct(wally_tx_elements_input_init_alloc, wally_tx_input);
 %rename("_tx_elements_input_is_pegin") wally_tx_elements_input_is_pegin;
 %returns_size_t(_tx_elements_input_is_pegin);

src/transaction.c

@@ -2720,7 +2720,7 @@ int wally_tx_confidential_value_from_satoshi(uint64_t satoshi,
                                              unsigned char *bytes_out,
                                              size_t len)
 {
-    if (!bytes_out || len < WALLY_TX_ASSET_CT_VALUE_UNBLIND_LEN)
+    if (!bytes_out || len != WALLY_TX_ASSET_CT_VALUE_UNBLIND_LEN)
         return WALLY_EINVAL;
 
     *bytes_out = 0x1;
@@ -2729,6 +2729,18 @@ int wally_tx_confidential_value_from_satoshi(uint64_t satoshi,
     return WALLY_OK;
 }
 
+int wally_tx_confidential_value_to_satoshi(const unsigned char *value,
+                                           size_t value_len,
+                                           uint64_t* value_out)
+{
+    if (!value || value_len != WALLY_TX_ASSET_CT_VALUE_UNBLIND_LEN || !value_out || value[0] != 0x1)
+        return WALLY_EINVAL;
+
+    uint64_from_be_bytes(&value[1], value_out);
+
+    return WALLY_OK;
+}
+
 int wally_tx_elements_issuance_generate_entropy(const unsigned char *txhash,
                                                 size_t txhash_len,
                                                 uint32_t index,