Re: [Boost-users] Can boost help me organize/parse lots of binary data?

On 02/20/13 19:21, Chris Stankevitz wrote:

On Wed, Feb 20, 2013 at 3:27 PM, Richard wrote:

...

Boost.Spirit.Qi to parse the stream into data structures Boost.Spirit.Karma to emit the necessary output from the data structures

Richard,

Thank you. I am unfamiliar with Spirit and Karma. Your comment not only introduced me to them but highlighted just how vague my question was. I was thinking less about the actual decoding (who would have known based on what I wrote) and more on how I would "generically" and "extensibly" handle the many fields I am about to receive.

For example, consider the following horrible code. Is there a "boost" way to do this kind of thing... (perhaps Spirit/Karma is the answer and I am just more out of touch than I imagine):

Good things about the classes below: It is easy to add a new parameter. Just push one onto the back of EmployeePacket::Items The class EmployeePacket doesn't have hundreds of data members such as "string name_, int age_"

Bad things about the classes below: Extracting data from the EmployeePacket requires hideous dynamic_casts and hard-coded vector indices

Thank you again for your comments/criticisms/suggestions,

Chris

===

class EmployeePacket { std::vector Items;

EmployeePacket() { Items.push_back(new String("name", "John Doe")); Items.push_back(new Double("salary", "USD", 1, 1)); }

void Decode(istream& Stream) { for (auto pItem : Items) pItem->Decode(Stream) }

double GetSalary() { return dynamic_cast(Items[1])->value; } }

class Item { virtual void Decode(istream& Stream) = 0; }

class Double : public Item { string name; string units; // double decode_conversion_scale; // double decode_conversion_translate; // unsigned number_of_bits_used_to_encode // double scale_factor double value; void Decode(istream& Stream) { Stream.read(&value, 8); value = value * decode_conversion_scale + decode_conversion_translate; }

class String : public Item { string name; string value; void Decode(istream& Stream); } Hi Chris,

How do you decide whether the Stream argument to Decode contains a String or a Double? Is that already known? IOW, if you open the istream, do you *know* what types it contains already and only need to fill in the values? -regards, Larry