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Small changes to yul object specification.

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chriseth 2018-11-14 17:33:02 +01:00
parent aaa50189a9
commit 5783ebb93d
1 changed files with 37 additions and 6 deletions
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docs/yul.rst
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@ -515,6 +515,16 @@ The following functions must be available:
+---------------------------------------------+-----------------------------------------------------------------+
| keccak256(p:u256, s:u256) -> v:u256 | keccak(mem[p...(p+s))) |
+---------------------------------------------+-----------------------------------------------------------------+
| *Object access* | |
+---------------------------------------------+-----------------------------------------------------------------+
| datasize(name:string) -> size:u256 | size of the data object in bytes, name has to be string literal |
+---------------------------------------------+-----------------------------------------------------------------+
| dataoffset(name:string) -> offset:u256 | offset of the data object inside the data area in bytes, |
| | name has to be string literal |
+---------------------------------------------+-----------------------------------------------------------------+
| datacopy(dst:u256, src:u256, len:u256) | copy len bytes from the data area starting at offset src bytes |
| | to memory at position dst |
+---------------------------------------------+-----------------------------------------------------------------+
Backends
--------
@ -540,12 +550,19 @@ TBD
Specification of Yul Object
===========================
Yul objects are used to group named code and data sections.
The functions ``datasize``, ``dataoffset`` and ``datacopy``
can be used to access these sections from within code.
Hex strings can be used to specify data in hex encoding,
regular strings in native encoding. For code,
``datacopy`` will access its assembled binary representation.
Grammar::
TopLevelObject = 'object' '{' Code? ( Object | Data )* '}'
Object = 'object' StringLiteral '{' Code? ( Object | Data )* '}'
Code = 'code' Block
Data = 'data' StringLiteral HexLiteral
Data = 'data' StringLiteral ( HexLiteral | StringLiteral )
HexLiteral = 'hex' ('"' ([0-9a-fA-F]{2})* '"' | '\'' ([0-9a-fA-F]{2})* '\'')
StringLiteral = '"' ([^"\r\n\\] | '\\' .)* '"'
@ -558,14 +575,28 @@ An example Yul Object is shown below:
// Code consists of a single object. A single "code" node is the code of the object.
// Every (other) named object or data section is serialized and
// made accessible to the special built-in functions datacopy / dataoffset / datasize
object {
// Access to nested objects can be performed by joining the names using ``.``.
// The current object and sub-objects and data items inside the current object
// are in scope without nested access.
object "Contract1" {
code {
let size = datasize("runtime")
// first create "runtime.Contract2"
let size = datasize("runtime.Contract2")
let offset = allocate(size)
// This will turn into a memory->memory copy for eWASM and
// a codecopy for EVM
datacopy(dataoffset("runtime"), offset, size)
// this is a constructor and the runtime code is returned
datacopy(offset, dataoffset("runtime.Contract2"), size)
// constructor parameter is a single number 0x1234
mstore(add(offset, size), 0x1234)
create(offset, add(size, 32))
// now return the runtime object (this is
// constructor code)
size := datasize("runtime")
offset := allocate(size)
// This will turn into a memory->memory copy for eWASM and
// a codecopy for EVM
datacopy(offset, dataoffset("runtime"), size)
return(offset, size)
}
@ -579,7 +610,7 @@ An example Yul Object is shown below:
let offset = allocate(size)
// This will turn into a memory->memory copy for eWASM and
// a codecopy for EVM
datacopy(dataoffset("Contract2"), offset, size)
datacopy(offset, dataoffset("Contract2"), size)
// constructor parameter is a single number 0x1234
mstore(add(offset, size), 0x1234)
create(offset, add(size, 32))