Add from_int_btc group of functions

Add/update the from_int group of functions to provide one that errors
and one that is const and panics (errors in const context are not useful
because one cannot call `unwrap` in const context).

bitcoin/examples/taproot-psbt.rs

@@ -49,7 +49,7 @@ const UTXO_1: P2trUtxo = P2trUtxo {
     script_pubkey: UTXO_SCRIPT_PUBKEY,
     pubkey: UTXO_PUBKEY,
     master_fingerprint: UTXO_MASTER_FINGERPRINT,
-    amount_in_sats: Amount::from_int_btc(50),
+    amount_in_sats: Amount::from_int_btc_const(50),
     derivation_path: BIP86_DERIVATION_PATH,
 };
 
@@ -60,7 +60,7 @@ const UTXO_2: P2trUtxo = P2trUtxo {
     script_pubkey: UTXO_SCRIPT_PUBKEY,
     pubkey: UTXO_PUBKEY,
     master_fingerprint: UTXO_MASTER_FINGERPRINT,
-    amount_in_sats: Amount::from_int_btc(50),
+    amount_in_sats: Amount::from_int_btc_const(50),
     derivation_path: BIP86_DERIVATION_PATH,
 };
 
@@ -71,7 +71,7 @@ const UTXO_3: P2trUtxo = P2trUtxo {
     script_pubkey: UTXO_SCRIPT_PUBKEY,
     pubkey: UTXO_PUBKEY,
     master_fingerprint: UTXO_MASTER_FINGERPRINT,
-    amount_in_sats: Amount::from_int_btc(50),
+    amount_in_sats: Amount::from_int_btc_const(50),
     derivation_path: BIP86_DERIVATION_PATH,
 };
 

units/src/amount/signed.rs

@@ -52,12 +52,42 @@ impl SignedAmount {
     /// Gets the number of satoshis in this [`SignedAmount`].
     pub const fn to_sat(self) -> i64 { self.0 }
 
-    /// Convert from a value expressing bitcoins to an [`SignedAmount`].
+    /// Convert from a value expressing bitcoins to a [`SignedAmount`].
     #[cfg(feature = "alloc")]
     pub fn from_btc(btc: f64) -> Result<SignedAmount, ParseAmountError> {
         SignedAmount::from_float_in(btc, Denomination::Bitcoin)
     }
 
+    /// Converts from a value expressing a whole number of bitcoin to a [`SignedAmount`].
+    ///
+    /// # Errors
+    ///
+    /// The function errors if the argument multiplied by the number of sats
+    /// per bitcoin overflows an `i64` type.
+    pub fn from_int_btc(btc: i64) -> Result<SignedAmount, OutOfRangeError> {
+        match btc.checked_mul(100_000_000) {
+            Some(amount) => Ok(SignedAmount::from_sat(amount)),
+            None => Err(OutOfRangeError {
+                is_signed: true,
+                is_greater_than_max: true,
+            })
+        }
+    }
+
+    /// Converts from a value expressing a whole number of bitcoin to a [`SignedAmount`]
+    /// in const context.
+    ///
+    /// # Panics
+    ///
+    /// The function panics if the argument multiplied by the number of sats
+    /// per bitcoin overflows an `i64` type.
+    pub const fn from_int_btc_const(btc: i64) -> SignedAmount {
+        match btc.checked_mul(100_000_000) {
+            Some(amount) => SignedAmount::from_sat(amount),
+            None => panic!("checked_mul overflowed"),
+        }
+    }
+
     /// Parse a decimal string as a value in the given denomination.
     ///
     /// Note: This only parses the value string.  If you want to parse a value

units/src/amount/tests.rs

@@ -65,13 +65,13 @@ fn from_str_zero_without_denomination() {
 
 #[test]
 fn from_int_btc() {
-    let amt = Amount::from_int_btc(2);
+    let amt = Amount::from_int_btc_const(2);
     assert_eq!(Amount::from_sat(200_000_000), amt);
 }
 
 #[should_panic]
 #[test]
-fn from_int_btc_panic() { Amount::from_int_btc(u64::MAX); }
+fn from_int_btc_panic() { Amount::from_int_btc_const(u64::MAX); }
 
 #[test]
 fn test_signed_amount_try_from_amount() {

units/src/amount/unsigned.rs

@@ -46,9 +46,9 @@ impl Amount {
     /// Exactly one satoshi.
     pub const ONE_SAT: Amount = Amount(1);
     /// Exactly one bitcoin.
-    pub const ONE_BTC: Amount = Self::from_int_btc(1);
+    pub const ONE_BTC: Amount = Self::from_int_btc_const(1);
     /// The maximum value allowed as an amount. Useful for sanity checking.
-    pub const MAX_MONEY: Amount = Self::from_int_btc(21_000_000);
+    pub const MAX_MONEY: Amount = Self::from_int_btc_const(21_000_000);
     /// The minimum value of an amount.
     pub const MIN: Amount = Amount::ZERO;
     /// The maximum value of an amount.
@@ -68,14 +68,30 @@ impl Amount {
         Amount::from_float_in(btc, Denomination::Bitcoin)
     }
 
-    /// Converts from a value expressing integer values of bitcoins to an [`Amount`]
+    /// Converts from a value expressing a whole number of bitcoin to an [`Amount`].
+    ///
+    /// # Errors
+    ///
+    /// The function errors if the argument multiplied by the number of sats
+    /// per bitcoin overflows a `u64` type.
+    pub fn from_int_btc(btc: u64) -> Result<Amount, OutOfRangeError> {
+        match btc.checked_mul(100_000_000) {
+            Some(amount) => Ok(Amount::from_sat(amount)),
+            None => Err(OutOfRangeError {
+                is_signed: false,
+                is_greater_than_max: true,
+            })
+        }
+    }
+
+    /// Converts from a value expressing a whole number of bitcoin to an [`Amount`]
     /// in const context.
     ///
     /// # Panics
     ///
     /// The function panics if the argument multiplied by the number of sats
-    /// per bitcoin overflows a u64 type.
-    pub const fn from_int_btc(btc: u64) -> Amount {
+    /// per bitcoin overflows a `u64` type.
+    pub const fn from_int_btc_const(btc: u64) -> Amount {
         match btc.checked_mul(100_000_000) {
             Some(amount) => Amount::from_sat(amount),
             None => panic!("checked_mul overflowed"),