feat!: optimize and rework send() function

docs/src/content/docs/ref/core-advanced.mdx

@@ -163,7 +163,7 @@ extends fun readForwardFee(self: Context): Int;
 
 Extension function for the [`Context{:tact}`](/ref/core-common#context).
 
-Reads [forward fee](https://docs.ton.org/develop/smart-contracts/guidelines/processing) and returns it as [`Int{:tact}`][int] amount of [nanoToncoins][nanotoncoin].
+Reads [forward fee][forward-fee] and returns it as [`Int{:tact}`][int] amount of [nanoToncoins][nanotoncoin].
 
 Usage example:
 

src/stdlib/stdlib.ts

@@ -232,9 +232,26 @@ files["std/config.tact"] =
 files["std/context.tact"] =
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     "ZShfX3RhY3RfY29udGV4dF9nZXQpCm5hdGl2ZSBjb250ZXh0KCk6IENvbnRleHQ7CgpAbmFtZShfX3RhY3RfY29udGV4dF9nZXRfc2VuZGVyKQpuYXRpdmUgc2VuZGVy" +
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 files["std/contract.tact"] =
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@@ -400,29 +417,50 @@ files["std/send.tact"] =
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+    "LyBzMjogYGJvZHlgCiAgICAvLyBzMzogYG1vZGVgCgogICAgLy8gR3JvdXAgNTogRmluYWxpemluZyB0aGUgbWVzc2FnZQogICAgU1RESUNUIC8vIHN0b3JlIFN0YXRl" +
+    "SW5pdAogICAgU1RESUNUIC8vIHN0b3JlIGBib2R5YCBhcyByZWYgd2l0aCBhbiBleHRyYSBNYXliZSBiaXQsIHNpbmNlIGBib2R5YCBtaWdodCBiZSBudWxsCiAgICBF" +
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+    "ZSwgd2l0aCBgbW9kZWAgb24gdG9wCiAgICBTV0FQCiAgICBTRU5EUkFXTVNHIC8vIGh0dHBzOi8vZ2l0aHViLmNvbS90YWN0LWxhbmcvdGFjdC9pc3N1ZXMvMTU1OAp9" +
+    "CgppbmxpbmUgZnVuIGVtaXQoYm9keTogQ2VsbCkgewogICAgLy8gZXh0X291dF9tc2dfaW5mbyQxMSBzcmM6TXNnQWRkcmVzc0ludCBkZXN0Ok1zZ0FkZHJlc3NFeHQg" +
+    "Y3JlYXRlZF9sdDp1aW50NjQgY3JlYXRlZF9hdDp1aW50MzIKICAgIC8vICAgICAgICAgICAgICAgICAgICAgbWF5YmU6IHN0YXRlSW5pdCAoZmFsc2UpIGJvZHlSZWY6" +
+    "IGJvb2wgKHRydWUpCiAgICBsZXQgYzogQ2VsbCA9IGJlZ2luQ2VsbCgpCiAgICAgICAgLnN0b3JlVWludCgxNTIxMTgwNzIwMjczODc1MjgxNzk2MDQzODQ2NDUxMywg" +
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+    "ZXNzYWdlKCkgeyBBQ0NFUFQgfQoKYXNtIGZ1biBjb21taXQoKSB7IENPTU1JVCB9Cg==";
 files["std/text.tact"] =
     "Ly8KLy8gU3RyaW5nIGJ1aWxkZXIKLy8KCkBuYW1lKF9fdGFjdF9zdHJpbmdfYnVpbGRlcl9zdGFydF9zdHJpbmcpCm5hdGl2ZSBiZWdpblN0cmluZygpOiBTdHJpbmdC" +
     "dWlsZGVyOwoKQG5hbWUoX190YWN0X3N0cmluZ19idWlsZGVyX3N0YXJ0X2NvbW1lbnQpCm5hdGl2ZSBiZWdpbkNvbW1lbnQoKTogU3RyaW5nQnVpbGRlcjsKCkBuYW1l" +

src/stdlib/stdlib/std/context.tact

@@ -11,15 +11,52 @@ native context(): Context;
 @name(__tact_context_get_sender)
 native sender(): Address;
 
+/// Extension function for the `Context` structure.
+///
+/// Reads forward fee and returns it as `Int` amount of nanoToncoins.
+///
+/// ```tact
+/// fun example() {
+///     let fwdFee: Int = context().readForwardFee();
+/// }
+/// ```
+///
+/// See:
+/// * https://docs.tact-lang.org/ref/core-advanced#contextreadforwardfee
+/// * https://docs.tact-lang.org/ref/core-advanced#getoriginalfwdfee
+///
 asm extends fun readForwardFee(self: Context): Int {
-    LDMSGADDR
-    LDGRAMS
+    // Only the self.raw (Context.raw) is important,
+    // so all the other fields and loaded values will be dropped by `BLKDROP2`
+    //
+    // Context.raw starts at the dest:MsgAddressInt, following this TL-B scheme:
+    // int_msg_info$0
+    //   ihr_disabled:Bool
+    //   bounce:Bool
+    //   bounced:Bool
+    //   src:MsgAddress
+    //   dest:MsgAddressInt ← here is the start
+    //   value:CurrencyCollection
+    //   ihr_fee:Grams
+    //   fwd_fee:Grams
+    //   created_lt:uint64
+    //   created_at:uint32
+    // = CommonMsgInfoRelaxed;
+
+    LDMSGADDR   // load dest:MsgAddressInt
+    LDGRAMS     // load value:CurrencyCollection
     ONE
-    SDSKIPFIRST
-    LDGRAMS
-    LDGRAMS
-    DROP
-    6 1 BLKDROP2
-    ZERO
-    GETORIGINALFWDFEE
-}
+    SDSKIPFIRST // skip extra currency collection
+    LDGRAMS     // load ihr_fee
+    LDGRAMS     // load fwd_fee, we'll be using this!
+    DROP        // drop remaining Slice (with created_lt and created_at)
+
+    // There are 7 entries on the stack — first 3 fields of Context plus 4 loaded ones.
+    // The topmost is fwd_fee, which is the only one we're after, so let's drop 6 entries below:
+    6 1 BLKDROP2 // drop the loaded values as well as the first 3 fields of Context
+
+    ZERO              // not masterchain
+    GETORIGINALFWDFEE // (fwd_fee * 2^16) / first_frac, where
+                      // first_frac is a value listed in config param 25
+                      // of the blockchain: https://tonscan.org/config#25
+}