def _slice(expr, args, kwargs, context):
sub, start, length = args[0], kwargs['start'], kwargs['len']
if not are_units_compatible(start.typ, BaseType("num")):
raise TypeMismatchException("Type for slice start index must be a unitless number")
# Expression representing the length of the slice
if not are_units_compatible(length.typ, BaseType("num")):
raise TypeMismatchException("Type for slice length must be a unitless number")
# Node representing the position of the output in memory
np = context.new_placeholder(ByteArrayType(maxlen=sub.typ.maxlen + 32))
placeholder_node = LLLnode.from_list(np, typ=sub.typ, location='memory')
placeholder_plus_32_node = LLLnode.from_list(np + 32, typ=sub.typ, location='memory')
# Copies over bytearray data
if sub.location == 'storage':
adj_sub = LLLnode.from_list(
['add', ['sha3_32', sub], ['add', ['div', '_start', 32], 1]], typ=sub.typ, location=sub.location
)
else:
adj_sub = LLLnode.from_list(
['add', sub, ['add', ['sub', '_start', ['mod', '_start', 32]], 32]], typ=sub.typ, location=sub.location
)
copier = make_byte_slice_copier(placeholder_plus_32_node, adj_sub, ['add', '_length', 32], sub.typ.maxlen)
# New maximum length in the type of the result
newmaxlen = length.value if not len(length.args) else sub.typ.maxlen
out = ['with', '_start', start,
['with', '_length', length,
['with', '_opos', ['add', placeholder_node, ['mod', '_start', 32]],
['seq',
['assert', ['lt', ['add', '_start', '_length'], sub.typ.maxlen]],
copier,
['mstore', '_opos', '_length'],
'_opos']]]]
return LLLnode.from_list(out, typ=ByteArrayType(newmaxlen), location='memory', pos=getpos(expr))
def concat(expr, context):
from viper.parser.parser import parse_expr, unwrap_location
args = [parse_expr(arg, context) for arg in expr.args]
if len(args) < 2:
raise StructureException("Concat expects at least two arguments", expr)
for expr_arg, arg in zip(expr.args, args):
if not isinstance(arg.typ, ByteArrayType) and not is_base_type(arg.typ, 'bytes32') and not is_base_type(arg.typ, 'method_id'):
raise TypeMismatchException("Concat expects byte arrays or bytes32 objects", expr_arg)
# Maximum length of the output
total_maxlen = sum([arg.typ.maxlen if isinstance(arg.typ, ByteArrayType) else 32 for arg in args])
# Node representing the position of the output in memory
placeholder = context.new_placeholder(ByteArrayType(total_maxlen))
# Object representing the output
seq = []
# For each argument we are concatenating...
for arg in args:
# Start pasting into a position the starts at zero, and keeps
# incrementing as we concatenate arguments
placeholder_node = LLLnode.from_list(['add', placeholder, '_poz'], typ=ByteArrayType(total_maxlen), location='memory')
placeholder_node_plus_32 = LLLnode.from_list(['add', ['add', placeholder, '_poz'], 32], typ=ByteArrayType(total_maxlen), location='memory')
if isinstance(arg.typ, ByteArrayType):
# Ignore empty strings
if arg.typ.maxlen == 0:
continue
# Get the length of the current argument
if arg.location == "memory":
length = LLLnode.from_list(['mload', '_arg'], typ=BaseType('num'))
argstart = LLLnode.from_list(['add', '_arg', 32], typ=arg.typ, location=arg.location)
elif arg.location == "storage":
length = LLLnode.from_list(['sload', ['sha3_32', '_arg']], typ=BaseType('num'))
argstart = LLLnode.from_list(['add', ['sha3_32', '_arg'], 1], typ=arg.typ, location=arg.location)
# Make a copier to copy over data from that argyument
seq.append(['with', '_arg', arg,
['seq',
make_byte_slice_copier(placeholder_node_plus_32,
argstart,
length,
arg.typ.maxlen),
# Change the position to start at the correct
# place to paste the next value
['set', '_poz', ['add', '_poz', length]]]])
elif isinstance(arg.typ, BaseType) and arg.typ.typ == "method_id":
seq.append(['seq',
['mstore', ['add', placeholder_node, 32], arg.value * 2**224],
['set', '_poz', ['add', '_poz', 4]]])
else:
seq.append(['seq',
['mstore', ['add', placeholder_node, 32], unwrap_location(arg)],
['set', '_poz', ['add', '_poz', 32]]])
# The position, after all arguments are processing, equals the total
# length. Paste this in to make the output a proper bytearray
seq.append(['mstore', placeholder, '_poz'])
# Memory location of the output
seq.append(placeholder)
return LLLnode.from_list(
['with', '_poz', 0, ['seq'] + seq], typ=ByteArrayType(total_maxlen), location='memory', pos=getpos(expr)
)