How do I include extremely long literals in C++ so

问题:

I've got a bit of a problem. Essentially, I need to store a large list of whitelisted entries inside my program, and I'd like to include such a list directly -- I don't want to have to distribute other libraries and such, and I don't want to embed the strings into a Win32 resource, for a bunch of reasons I don't want to go into right now.

I simply included my big whitelist in my .cpp file, and was presented with this error:

1>ServicesWhitelist.cpp(2807): fatal error C1091: compiler limit: string exceeds 65535 bytes in length

The string itself is about twice this allowed limit by VC++. What's the best way to include such a large literal in a program?

EDIT:

I'm storing the string like this:

const std::wstring servicesWhitelist
(
 L".NETFRAMEWORK|"
 L"_IOMEGA_ACTIVE_DISK_SERVICE_|"
 L"{6080A529-897E-4629-A488-ABA0C29B635E}|"
 L"{834170A7-AF3B-4D34-A757-E05EB29EE96D}|"
 L"{85CCB53B-23D8-4E73-B1B7-9DDB71827D9B}|"
 L"{95808DC4-FA4A-4C74-92FE-5B863F82066B}|"
 L"{A7447300-8075-4B0D-83F1-3D75C8EBC623}|"
 L"{D31A0762-0CEB-444E-ACFF-B049A1F6FE91}|"
 L"{E2B953A6-195A-44F9-9BA3-3D5F4E32BB55}|"
 L"{EDA5F5D3-9E0F-4F4D-8A13-1D1CF469C9CC}|"
 L"2WIREPCP|"
//About 3800 more lines
);

EDIT2 It's used at runtime in a way similar to this:

static const boost::wregex servicesWhitelistRegex(servicesWhitelist);
std::wstring service;
//code to populate service
if (!boost::regex_match(service, servicesWhitelistRegex))
 //Do something to print service

回答1:

How about an array? (you would put the commas only after the legal limit for every element)

const std::wstring servicesWhitelist[] = {
 L".NETFRAMEWORK|",
 L"_IOMEGA_ACTIVE_DISK_SERVICE_|",
 L"{6080A529-897E-4629-A488-ABA0C29B635E}|",
 L"{834170A7-AF3B-4D34-A757-E05EB29EE96D}|",
 L"{85CCB53B-23D8-4E73-B1B7-9DDB71827D9B}|",
 L"{95808DC4-FA4A-4C74-92FE-5B863F82066B}|",
 L"{A7447300-8075-4B0D-83F1-3D75C8EBC623}|",
 L"{D31A0762-0CEB-444E-ACFF-B049A1F6FE91}|",
 L"{E2B953A6-195A-44F9-9BA3-3D5F4E32BB55}|",
 L"{EDA5F5D3-9E0F-4F4D-8A13-1D1CF469C9CC}|",
 L"2WIREPCP|",
...
};

You could use the below statement to get the combined string.

accumulate(servicesWhitelist, servicesWhitelist+sizeof(servicesWhitelist)/sizeof(servicesWhitelist[0]), "")

回答2:

Let's assume you actually need to store a string >64k characters (i.e. all of the above "just don't do that" solutions don't apply.)

To make MSVC happy, instead of saying:

const char *foo = "abcd...";

You can convert your >64k character string to individual characters represented as integers:

const char foo[] = { 97, 98, 99, 100, ..., 0 };

Where each letter has been converted to its ascii equivalent (97 == 'a', etc.), and a NUL terminator has been added at the end.

MSVC2010 at least is happy with this.

回答3:

If it's only about twice the limit the obvious solution would seem to be to store 2 (or 3) such strings. :) I'm sure your code that reads them at runtime can deal with that easily enough.

EDIT: Do you need to use a regex for some reason? Could you break up the big strings into a list of individual tokens and do a simple string comparison?

回答4:

I claim no credit for this one:

https://social.msdn.microsoft.com/Forums/vstudio/en-US/c573db8b-c9cd-43d7-9f89-202ba9417296/fatal-error-c1091

Use the STL instead.

Code Snippet

#include <sstream>

std::ostringstream oss;

oss << myString1 << myString2 << myString3 << myString4;

oss.str() would now return an instance of the STL's std:: string class, and oss.str().c_str() would return a const char*

回答5:

You problem could be stripped down to (in Python):

whitelist_services = { ".NETFRAMEWORK", "_IOMEGA_ACTIVE_DISK_SERVICE_" }
if service in whitelist_services:
   print service, "is a whitelisted service"

A direct translation to C++ would be:

// g++ *.cc -std=c++0x && ./a.out
#include <iostream>
#include <unordered_set>

namespace {
  typedef const wchar_t* str_t;
  // or
  ////typedef std::wstring str_t;
  str_t servicesWhitelist[] = {
    L".NETFRAMEWORK",
    L"_IOMEGA_ACTIVE_DISK_SERVICE_",
  };
  const size_t N = sizeof(servicesWhitelist) / sizeof(*servicesWhitelist);

  // if you need to search for multiple services then a hash table
  // could speed searches up O(1). Otherwise std::find() on the array
  // might be sufficient O(N), or std::binary_search() on sorted array
  // O(log N) 
  const std::unordered_set<str_t> services
    (servicesWhitelist, servicesWhitelist + N);
}

int main() {
  str_t service = L".NETFRAMEWORK";
  if (services.find(service) != services.end())
    std::wcout << service << " is a whitelisted service" << std::endl;
}