c++11 library to ease hashing of user-defined types
API Reference: http://en.cppreference.com/w/cpp/utility/hash
Questions tagged [stdhash]
59 questions
0
votes
2 answers
std::hash with a pointer and a byte size
I've got a variable size binary data blob that is accessible through a std::byte pointer and a byte size. Is there a way to call std::hash on it? (I can't find any example for this)
moala
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0
votes
0 answers
How to use std::hash to hash data by chunks and not all together?
I am learning about std::hash and I would like to make a program that hashes a file, even if that file is large. I don't want to load that entire file in memory, I'd rather just hash individual chunks and then somehow hash the hashes.
I understand…
Tomáš Zato
- 50,171
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- 778
0
votes
1 answer
How to pass reference type to std::hash
I am creating a Template Cache library in C++-11 where I want to hash the keys. I want to use default std::hash for primitive/pre-defined types like int, std::string, etc. and user-defined hash functions for user-defined types. My code currently…
AbhayKrSomani
- 73
- 4
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0 answers
Using union for structure hashing with std::unordered_map or std::unordered_set
I have a simple structure:
struct data
{
bool flag;
std::size_t ix;
std::size_t iy;
std::size_t d;
};
I keep all instances of this structure in container, and I need to search it as fast as possible. At the moment I use the std::set with…
one_two_three
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0
votes
1 answer
Why this code provides specialization for **ALL** enums for std::hash template?
I'm not a pro in C++ but somehow I provided a solution while porting my MSVS 2015 C++ code to MinGW 4.9.2 to specialize std::hash class to support all enums. It there's any C++ compiler developers or C++ pro programmers here, can you explain why…
Vyacheslav Napadovsky
- 887
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- 15
0
votes
1 answer
Compile error when using std::hash; does not name a template type
I am receiving the error
"hashmap.hpp:63:14: error: ‘hash’ in namespace ‘std’ does not name a
template type std::hash hash;"
I don't understand why i need to implement my own specialization when I'm passing in type T, which will probably be one…
Adele
- 39
- 2
- 9
0
votes
2 answers
Inner scoped enumeration, hash function and unordered_set data member
I've the following problem of which I cannot find a solution.
Of course, it could be that a solution does not exist at all, but I'd like to have a try on SO before to give up.
First of all, a snippet that compiles with no errors:
#include…
skypjack
- 49,335
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- 187
0
votes
3 answers
Unable to Use Specialization of std::hash for Pointer-to-Member?
I assume that std::hash's specialization for generic pointer types can be used for pointer-to-members, however I am unable to use it as such; instead, my compiler gives me an "incomplete type" error, which I assume means that is' not using the…
Shokwav
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0
votes
1 answer
c++ std::hash specilization trait compile error
hi i am tryng to implement a trait class of std::hash struct but i cannot progress from here:
#include
#include
namespace std {
template<>
struct hash< Test::AckMsgType >
{
…
Ricardo_arg
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0
votes
2 answers
Why std::Hash equal for differen strings?
Why std::Hash has equal result for different strings?
I used msvc2010sp1 and I was suprised when saw this result:
int _tmain(int argc, _TCHAR* argv[])
{
std::string sUniqId ("IndexBuf");
std::stringstream sStream;
sStream << 10;
…
angevad
- 187
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0
votes
1 answer
Clang compiling error on 'std::hash'
I am trying to compile a project on my mac, which is originally written on linux. It went smoothly on archlinux but has a lot of errors on mac. Especially, I'm very confused with this error message:
In file included from…
Nothing More
- 873
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0
votes
1 answer
My std::hash for std::tuples... Any improvements?
Some may have noticed that std::hash does not support tuples. So I added an overload which just seems "nicer" than the solution I saw up till now. Anyone got ideas to further cut down this code? Please note that this is a compiler killer! The only…
thesaint
- 1,253
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0
votes
1 answer
What is the purpose of std::hash and/or boost::hash ?
Why providing an hash function without specifing any implementation of reference and also without specifying the algorithm of reference ( md5, sha256, etc etc ) ?
Also there are similar features for data structures such as the C++ standard-compliant…
user1824407
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-1
votes
1 answer
How to find multiplier x if x * c1 = c2, but x * c1 causes overflow
I am writing a code that will find collisions for std::hash and trying to reverse some of hash calculation steps.
There is such a multiplication in std::hash implementation.
size_t hash2 = shift_mix(hash1) * mul;
I know hash2 - from…
Владимир Говорухин
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