bool bailin::MemBuffer::PopLeft( MemBuffer* pBuffer, int nLen )
{
if (pBuffer == NULL || m_nCurLen < nLen)
{
return false;
}
// 拷贝数据
pBuffer->Append(m_pBuffer, nLen);
RemoveLeft(nLen);
return true;
}
TExpressionPtr ExpressionParser::ParseOperationExpression(StringPtrLen str) const
{
BracketsBalancer balancer;
auto max_operation = OperationType::None;
auto max_operation_amount = -1L;
auto tail = str;
// Find operation with zero bracket balance and with maximum value.
// Maximum value means minimal arithmetic priority.
for (; tail.Len() > 0; tail.RemoveLeft(1))
{
if (!balancer.ProcessChar(tail.At(0)) && balancer.GetBalance() == 0)
{
OperationType operation = StartsWithOperation(tail);
// TODO: Skip the whole operation symbols
if (operation != OperationType::None)
{
if (operation > max_operation)
{
max_operation = operation;
max_operation_amount = 1;
}
else if (operation == max_operation)
{
++max_operation_amount;
}
}
}
}
if (OperationType::None == max_operation)
{
// No operations with zero balance
return TExpressionPtr();
}
assert(balancer.GetBalance() == 0);
auto max_operation_str = OperationTypeToString(max_operation);
auto max_operation_str_len = std::strlen(max_operation_str);
if (OperationType::Negation == max_operation)
{
if (!str.StartsWith(max_operation_str))
{
Error("Incorrect usage of unary operation '", max_operation_str, "'.");
}
str.RemoveLeft(max_operation_str_len);
auto child_expression = ParseExpression(str);
return std::make_unique<OperationExpression>(std::move(child_expression));
}
TExpressionPtrVector children_expressions;
children_expressions.reserve(max_operation_amount + 1);
tail = str;
while (tail.Len() > 0)
{
if (!balancer.ProcessChar(tail.At(0)) && balancer.GetBalance() == 0)
{
if (tail.StartsWith(max_operation_str))
{
auto child_expression = ParseExpression(str.Left(tail.Ptr()));
children_expressions.push_back(std::move(child_expression));
tail.RemoveLeft(max_operation_str_len);
str = tail;
continue;
}
}
tail.RemoveLeft(1);
}
auto child_expression = ParseExpression(str);
children_expressions.push_back(std::move(child_expression));
return std::make_unique<OperationExpression>(max_operation, std::move(children_expressions));
}
