path: root/libsolidity/codegen/CompilerUtils.h

/*
    This file is part of solidity.

    solidity is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    solidity is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with solidity.  If not, see <http://www.gnu.org/licenses/>.
*/
/**
 * @author Christian <c@ethdev.com>
 * @date 2014
 * Routines used by both the compiler and the expression compiler.
 */

#pragma once

#include <libsolidity/codegen/CompilerContext.h>
#include <libsolidity/ast/ASTForward.h>

namespace dev {
namespace solidity {

class Type; // forward

class CompilerUtils
{
public:
    explicit CompilerUtils(CompilerContext& _context): m_context(_context) {}

    /// Stores the initial value of the free-memory-pointer at its position;
    void initialiseFreeMemoryPointer();
    /// Copies the free memory pointer to the stack.
    /// Stack pre:
    /// Stack post: <mem_start>
    void fetchFreeMemoryPointer();
    /// Stores the free memory pointer from the stack.
    /// Stack pre: <mem_end>
    /// Stack post:
    void storeFreeMemoryPointer();
    /// Allocates a number of bytes in memory as given on the stack.
    /// Stack pre: <size>
    /// Stack post: <mem_start>
    void allocateMemory();
    /// Appends code that transforms memptr to (memptr - free_memptr) memptr
    /// Stack pre: <mem_end>
    /// Stack post: <size> <mem_start>
    void toSizeAfterFreeMemoryPointer();

    /// Appends code that performs a revert, providing the given string data.
    /// Will also append an error signature corresponding to Error(string).
    /// @param _argumentType the type of the string argument, will be converted to memory string.
    /// Stack pre: string data
    /// Stack post:
    void revertWithStringData(Type const& _argumentType);

    /// Loads data from memory to the stack.
    /// @param _offset offset in memory (or calldata)
    /// @param _type data type to load
    /// @param _fromCalldata if true, load from calldata, not from memory
    /// @param _padToWords if true, assume the data is padded to full words (32 bytes)
    /// @returns the number of bytes consumed in memory.
    unsigned loadFromMemory(
        unsigned _offset,
        Type const& _type = IntegerType(256),
        bool _fromCalldata = false,
        bool _padToWords = false
    );
    /// Dynamic version of @see loadFromMemory, expects the memory offset on the stack.
    /// Stack pre: memory_offset
    /// Stack post: value... (memory_offset+length)
    void loadFromMemoryDynamic(
        Type const& _type,
        bool _fromCalldata = false,
        bool _padToWords = true,
        bool _keepUpdatedMemoryOffset = true
    );
    /// Stores a 256 bit integer from stack in memory.
    /// @param _offset offset in memory
    /// @param _type type of the data on the stack
    void storeInMemory(unsigned _offset);
    /// Dynamic version of @see storeInMemory, expects the memory offset below the value on the stack
    /// and also updates that. For reference types, only copies the data pointer. Fails for
    /// non-memory-references.
    /// @param _padToWords if true, adds zeros to pad to multiple of 32 bytes. Array elements
    /// are always padded (except for byte arrays), regardless of this parameter.
    /// Stack pre: memory_offset value...
    /// Stack post: (memory_offset+length)
    void storeInMemoryDynamic(Type const& _type, bool _padToWords = true);

    /// Creates code that unpacks the arguments according to their types specified by a vector of TypePointers.
    /// From memory if @a _fromMemory is true, otherwise from call data.
    /// Calls revert if @a _revertOnOutOfBounds is true and the supplied size is shorter
    /// than the static data requirements or if dynamic data pointers reach outside of the
    /// area. Also has a hard cap of 0x100000000 for any given length/offset field.
    /// Stack pre: <source_offset> <length>
    /// Stack post: <value0> <value1> ... <valuen>
    void abiDecode(TypePointers const& _typeParameters, bool _fromMemory = false, bool _revertOnOutOfBounds = false);

    /// Copies values (of types @a _givenTypes) given on the stack to a location in memory given
    /// at the stack top, encoding them according to the ABI as the given types @a _targetTypes.
    /// Removes the values from the stack and leaves the updated memory pointer.
    /// Stack pre: <v1> <v2> ... <vn> <memptr>
    /// Stack post: <memptr_updated>
    /// Does not touch the memory-free pointer.
    /// @param _padToWords if false, all values are concatenated without padding.
    /// @param _copyDynamicDataInPlace if true, dynamic types is stored (without length)
    /// together with fixed-length data.
    /// @param _encodeAsLibraryTypes if true, encodes for a library function, e.g. does not
    /// convert storage pointer types to memory types.
    /// @note the locations of target reference types are ignored, because it will always be
    /// memory.
    void encodeToMemory(
        TypePointers const& _givenTypes,
        TypePointers const& _targetTypes,
        bool _padToWords,
        bool _copyDynamicDataInPlace,
        bool _encodeAsLibraryTypes = false
    );

    /// Special case of @a encodeToMemory which assumes tight packing, e.g. no zero padding
    /// and dynamic data is encoded in-place.
    /// Stack pre: <value0> <value1> ... <valueN-1> <head_start>
    /// Stack post: <mem_ptr>
    void packedEncode(
        TypePointers const& _givenTypes,
        TypePointers const& _targetTypes,
        bool _encodeAsLibraryTypes = false
    )
    {
        encodeToMemory(_givenTypes, _targetTypes, false, true, _encodeAsLibraryTypes);
    }

    /// Special case of @a encodeToMemory which assumes that everything is padded to words
    /// and dynamic data is not copied in place (i.e. a proper ABI encoding).
    /// Stack pre: <value0> <value1> ... <valueN-1> <head_start>
    /// Stack post: <mem_ptr>
    void abiEncode(
        TypePointers const& _givenTypes,
        TypePointers const& _targetTypes,
        bool _encodeAsLibraryTypes = false
    )
    {
        encodeToMemory(_givenTypes, _targetTypes, true, false, _encodeAsLibraryTypes);
    }

    /// Special case of @a encodeToMemory which assumes that everything is padded to words
    /// and dynamic data is not copied in place (i.e. a proper ABI encoding).
    /// Uses a new, less tested encoder implementation.
    /// Stack pre: <value0> <value1> ... <valueN-1> <head_start>
    /// Stack post: <mem_ptr>
    void abiEncodeV2(
        TypePointers const& _givenTypes,
        TypePointers const& _targetTypes,
        bool _encodeAsLibraryTypes = false
    );

    /// Decodes data from ABI encoding into internal encoding. If @a _fromMemory is set to true,
    /// the data is taken from memory instead of from calldata.
    /// Can allocate memory.
    /// Stack pre: <source_offset> <length>
    /// Stack post: <value0> <value1> ... <valuen>
    void abiDecodeV2(TypePointers const& _parameterTypes, bool _fromMemory = false);

    /// Zero-initialises (the data part of) an already allocated memory array.
    /// Length has to be nonzero!
    /// Stack pre: <length> <memptr>
    /// Stack post: <updated_memptr>
    void zeroInitialiseMemoryArray(ArrayType const& _type);

    /// Copies full 32 byte words in memory (regions cannot overlap), i.e. may copy more than length.
    /// Length can be zero, in this case, it copies nothing.
    /// Stack pre: <size> <target> <source>
    /// Stack post:
    void memoryCopy32();
    /// Copies data in memory (regions cannot overlap).
    /// Length can be zero, in this case, it copies nothing.
    /// Stack pre: <size> <target> <source>
    /// Stack post:
    void memoryCopy();

    /// Converts the combined and left-aligned (right-aligned if @a _rightAligned is true)
    /// external function type <address><function identifier> into two stack slots:
    /// address (right aligned), function identifier (right aligned)
    void splitExternalFunctionType(bool _rightAligned);
    /// Performs the opposite operation of splitExternalFunctionType(_rightAligned)
    void combineExternalFunctionType(bool _rightAligned);
    /// Appends code that combines the construction-time (if available) and runtime function
    /// entry label of the given function into a single stack slot.
    /// Note: This might cause the compilation queue of the runtime context to be extended.
    /// If @a _runtimeOnly, the entry label will include the runtime assembly tag.
    void pushCombinedFunctionEntryLabel(Declaration const& _function, bool _runtimeOnly = true);

    /// Appends code for an implicit or explicit type conversion. This includes erasing higher
    /// order bits (@see appendHighBitCleanup) when widening integer but also copy to memory
    /// if a reference type is converted from calldata or storage to memory.
    /// If @a _cleanupNeeded, high order bits cleanup is also done if no type conversion would be
    /// necessary.
    /// If @a _chopSignBits, the function resets the signed bits out of the width of the signed integer.
    /// If @a _asPartOfArgumentDecoding is true, failed conversions are flagged via REVERT,
    /// otherwise they are flagged with INVALID.
    void convertType(
        Type const& _typeOnStack,
        Type const& _targetType,
        bool _cleanupNeeded = false,
        bool _chopSignBits = false,
        bool _asPartOfArgumentDecoding = false
    );

    /// Creates a zero-value for the given type and puts it onto the stack. This might allocate
    /// memory for memory references.
    void pushZeroValue(Type const& _type);
    /// Pushes a pointer to the stack that points to a (potentially shared) location in memory
    /// that always contains a zero. It is not allowed to write there.
    void pushZeroPointer();

    /// Moves the value that is at the top of the stack to a stack variable.
    void moveToStackVariable(VariableDeclaration const& _variable);
    /// Copies an item that occupies @a _itemSize stack slots from a stack depth of @a _stackDepth
    /// to the top of the stack.
    void copyToStackTop(unsigned _stackDepth, unsigned _itemSize);
    /// Moves an item that occupies @a _itemSize stack slots and has items occupying @a _stackDepth
    /// slots above it to the top of the stack.
    void moveToStackTop(unsigned _stackDepth, unsigned _itemSize = 1);
    /// Moves @a _itemSize elements past @a _stackDepth other stack elements
    void moveIntoStack(unsigned _stackDepth, unsigned _itemSize = 1);
    /// Rotates the topmost @a _items items on the stack, such that the previously topmost element
    /// is bottom-most.
    void rotateStackUp(unsigned _items);
    /// Rotates the topmost @a _items items on the stack, such that the previously bottom-most element
    /// is now topmost.
    void rotateStackDown(unsigned _items);
    /// Removes the current value from the top of the stack.
    void popStackElement(Type const& _type);
    /// Removes element from the top of the stack _amount times.
    void popStackSlots(size_t _amount);

    template <class T>
    static unsigned sizeOnStack(std::vector<T> const& _variables);
    static unsigned sizeOnStack(std::vector<std::shared_ptr<Type const>> const& _variableTypes);

    /// Helper function to shift top value on the stack to the left.
    /// Stack pre: <value> <shift_by_bits>
    /// Stack post: <shifted_value>
    void leftShiftNumberOnStack(unsigned _bits);

    /// Helper function to shift top value on the stack to the right.
    /// Stack pre: <value> <shift_by_bits>
    /// Stack post: <shifted_value>
    void rightShiftNumberOnStack(unsigned _bits);

    /// Appends code that computes tha Keccak-256 hash of the topmost stack element of 32 byte type.
    void computeHashStatic();

    /// Bytes we need to the start of call data.
    ///  - The size in bytes of the function (hash) identifier.
    static const unsigned dataStartOffset;

    /// Position of the free-memory-pointer in memory;
    static const size_t freeMemoryPointer;
    /// Position of the memory slot that is always zero.
    static const size_t zeroPointer;
    /// Starting offset for memory available to the user (aka the contract).
    static const size_t generalPurposeMemoryStart;

private:
    /// Address of the precompiled identity contract.
    static const unsigned identityContractAddress;

    /// Stores the given string in memory.
    /// Stack pre: mempos
    /// Stack post:
    void storeStringData(bytesConstRef _data);

    /// Appends code that cleans higher-order bits for integer types.
    void cleanHigherOrderBits(IntegerType const& _typeOnStack);

    /// Prepares the given type for storing in memory by shifting it if necessary.
    unsigned prepareMemoryStore(Type const& _type, bool _padToWords);
    /// Loads type from memory assuming memory offset is on stack top.
    unsigned loadFromMemoryHelper(Type const& _type, bool _fromCalldata, bool _padToWords);

    CompilerContext& m_context;
};


template <class T>
unsigned CompilerUtils::sizeOnStack(std::vector<T> const& _variables)
{
    unsigned size = 0;
    for (T const& variable: _variables)
        size += variable->annotation().type->sizeOnStack();
    return size;
}

}
}