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Stringozzi

Serving efficiently, Served with 💖

License: MIT Build Status codecov Language grade: C/C++

C++ Parsing Expression grammar library for parsing/searching/validating strings similar to RegEx

What's new

the version 2.0.0 comes with totally revamped and rewritten core to provide the balance between flexibility and performance

Motivation

The idea of this project comes from the need to a library that the user can build his ABNF like messages to parse text based network messages easily and efficiently (i.e.. HTTP/SIP) which has so complex string patterns and structures ...

Philosophy

  1. To be open source and friendly available for commercial product
  2. To be efficient specially in parsing without loosing flexibility
  3. To be cross platform (Windows and Linux for now !!)
  4. To support wide C++ standards choices as much as possible

Why Stringozzi ?

  1. Wide cross C++ standard compliance (this version is compliant to C++97 and upward)
  2. 3x-10x* faster than std::regex VS/GCC
  3. Lean and mean.. use only feature that you need to ( Validate / Search distinction and disable matching results )
  4. the grammar is checked by C++ compiler rather than the engine
  5. new features not in Regex like Support for recursive expressions, character chains detection , conditional parsing and (A)BNF like rules
  6. Seamless support for UTF and Unicode string with mix and match
  7. support for long expressions and text ( which is not the case in Regex for some reason)
  8. Packed with useful built-in expressions (IPv4,URI, ServerName)

Why not ?

  1. You don't like pasta or Italian cuisine 😄
  2. The expressions you use are too short
  3. The program loads validation expressions from remote source(like DB or text files)

The magic you can do

Expression like that

^([XYZ]{5}X?\s+\<(AB){3}\>)*$

Is equivalent to

Rule z = *(5 * (In("XYZ")) > ~Is('X') > +WhiteSpace() > Enclosed(3 * (Is("AB")), "<", ">")) > End();
...
StringozziA(z).Test("ZXYZZ <ABABAB>")

Or structured ones like these

const Rule Verb = (Is("GET") | Is("POST"));
const Rule URI = Is("http://") > *(Any() & !WhiteSpace());
const Rule RequestLine = Verb > URI > Is("HTTP/2.0") > EndOfLine();
const Rule Header =  *(Any() & !WhiteSpaces()) >  Is(":") > *(Any() & !WhiteSpaces())
const Rule Request = RequestLine > *(Headers) > EndOfLine() > Content;
...

Getting Started

Cloning the repository

cd stringozzi
git.exe clone "https://github.com/osamasalem/stringozzi.git ."

Building

For Windows

build.bat

For Linux

./build.sh

First Steps

#include <Stringozzi.h>
int main(int argc, char** argv) 
{
  const Rule r = Is("Student No#:") > (Range(1,3) * Digit());

  Actions::Test(r, "Student No#: 434");
}

Rules and Operators

Rule Description
Any() Any character
Digit() Any numeric character between '0' and '9'
Alphabet() Any character between 'A' and 'Z'
Alphanumeric() Digit or Alphabet
Whitespace() Any space character
Beginning() Matches the beginning of text
End() Matches the end of text (i.e. '\0')
a>b Parsing sequentially using rule a first then rule b
!a Negate parsing rule a, this action does not move parsing pointer
a&b Boolean "And" operation: Rule a and Rule b must be matched, the token must comply with both rules, and apply the most relevant one
a|b Boolean "Or" operation: Rule a or Rule b, the token may comply with one of the rules, short circuit applies here, the first rule matched.. the pointer will move accordingly to the end of that match... so start always with most specific rule to more general ones OR use Greedy OR operator
a||b Rule a or Rule b, the token may comply with either rules, it always checks all rules and takes the most relevant (matching) one in expense of performance
*a Zero Or More: succeed if whether does not match or matches multiple instances Take care when using this rule it can match any thing
[num]*a exact num of matches
[num]+a One Or More (optional maximum num) (at least rule), Matches a single instance or multiple instances
~a Optional rule a . it parses the token whenever possible
Between(a,b) a and b are chars, this matches any character in the specified range
In(str) str is string pointer,Belongs to rule: matches the character with a set of characters
Out(str) Any character out of set str
Is(tok) Equal operator,tok is either a char or string pointer .. it matches the token with a single character or a set of consecutive characters
rule >> str put the matched by rule rule string in matches table with the name specified in str
Skip(rule) Skip the characters till it matches the rule, always return true
Until(rule) Skip the characters till it matches the rule, it requires the next token to match rule
LookAhead(rule) it peeks the next token and checks if it matches rule, it does not move parsing pointer
LookBack(rule) it peeks the previous token and checks if it matches rule, it does not move parsing pointer
CaseSensitive() this will set case sensitive mode in parsing process
CaseSensitive() this will set case insensitive mode in parsing process
SetVar([varname], [value]) this will match all the time .. this sets a flag/variable with specified value.. if no value is supplied the default will be 1
DelVar([varname]) this will match always .. removes/unset flag/variable
If(varname,[value]) checks if the stored named variable varname equals the specified value.. if no value speicified the default value will be 1

Flags definition

Flag Description
SPEG_CASEINSENSITIVE Specify if matching process is case (in)sensitive
SPEG_MATCHNAMED Match all named returns by Extract or >> operators. clearing this flag will bypass marking matches
SPEG_MATCHUNNAMED Store all successful matches , clearing this flag will bypass marking matches
SPEG_IGNORESPACES Will match all successive tokens whether there are spaces between them or not, Whitespace match pattern will not work here in this mode

Guides and Use Cases

Use structured Rules

It is possible to use the Rules inside each other like this

const Rule Digit = Between('0','9');

const Rule SmallAlphabet = Between('a','z');

const Rule CapitalAlphabet = Between('A','Z');

const Rule Alphabet = CapitalAlphabet | SmallAlphabet;

const Rule Alphanumeric = Digit | Alphabet;

Basic operations

the basic operation you can do with Stringozzi

  1. Test: It validate the input string against the set rule
Actions::Test(In("ABC"), "A")
  1. FastMatch: like Test but returns the related matches
MatchesA m;
Actions::FastMatch(In("ABC") >> "Match" , "A", m)
  1. Search: it searches the string till the rule applies
bool b = Actions::Search(Is('b'), "abc"); // true
char* ptr = Actions::SearchAndGetPtr(Is('b'), "abc"); // "bc"
int idx = Actions::SearchAndGetIndex(Is('b'), "abc"); // 1
  1. Match: it is the combined operations of Search + FastMatch ... it searches the string till the rule applies then extract matches
  MatchesA m;
  Actions::Match(In("ABC") >> "Match" , "-----A", m)
  1. Replace: searches the string till the rule applies and then replace the string match with the specified text
  Actions::Replace(Is("ABC"), "1234567ABC890ABC", "X", 0, 1) // "1234567X890ABC";
  1. Split: searches the string till the rule applies and then replace the string match with the specified text
  vector<string> vec;
  Actions::Split(Is("<=>"), "1234567<=>ABC", vec, 0, true, 1); // ["1234567","ABC"]

Using Matches.. (Not 🔥 ones 😉)

There are two types of expression matches

  1. Named : where you set the name of the match in the rule
  2. Anonymous : Any other tokens matched by expression elements

you can use extract that way and get the resulting Matches

MatchesA m;
StringozziA str(Is('K') >> "MYMATCH"); //a rule to match letter K and store it as "MYMATCH"
str.Match("K", m); // Match against string "K"

//number of total matches entries 
m.NumberOfMatches(); // == 2 => "K" and "<UNNAMED>" 

// number of MYATCH entries
m.NumberOfMatches("MYMATCH"); // == 1
m.NumberOfMatches("NOTFOUND"); // == 0
m.NumberOfMatches("<UNNAMED>"); //  == 1

m.Get("MYMATCH",0); // "K"
m.Get("MYMATCH",1); // <NULL>

Case sensitivity

The default mode for Stringozzi is case sensitive You can specify the case insensitivity in two ways either you can specify SPEG_CASEINSENSITIVE in the operation

Actions::Test(In("ABC"), "a", SPEG_CASEINSENSITIVE);

Or you can use mode change in the rule it self

Actions::Test(CaseInsensitive > In("ABC") > CaseSensitive, "a")

- Or Vs. Greedy Or

Consider this example

Rule r = (Is("V") | Is("Via")) > Is(':') ; // will not work for Via

This will work with V: but not for Via: because it will always match the first letter and in the other hand ia: and : will not match due to the fact that OR operator will be short circuited to the first option and will not check the other routes

So the expression should be written like that

Rule r = (Is("Via") | Is("V")) > Is(':') ; // Works !!

or using Greedy OR which seek the most beneficial match in a set of OR

Rule r = (Is("Via") || Is("V")) > Is(':') ; // Works too !!

Recursive rules

Sometimes we want to use the rule inside itself to check some recursive behavior

For instance .. we want to have some sort of brackets structured data like this

( Data ( String ( ABC ) ) Count ( Max( 1 ) ))

we will face matching the parentheses properly.. the problem in such situations is we have to use an expression which is not even initialized

⚠️ WARNING: Generally take care to adjust the stopping condition in recursive rules to avoid stack overflow situation

1- Ref operator

this is a better way .. Ref operator receives rule reference and wait for parsing to evaluate it .. the down side here is that the developer must maintain the lifetime of the reference while parsing takes place

Rule r = Is('(') > (*Any() | Ref(r) ) Is(')');

2- Better: Ref operator with PlaceHolder

Placeholder is a special object that fill the reference gap in expression .. and then we redirect this holder to the right object after initialization phase

Take a look

Placeholder ph;
Rule r = Is('(') > (*Any() | Ref(ph) ) Is(')');
ph.Inject(r);

Inject() will adjust itself to point to the rule's internal object pointer which is independent of Rule lifetime

🖊️ NOTE: PlaceHolder object does not touch reference counting of internal objects, so avoid using it with other rules objects.. this may leave a dangling pointer.. instead you can directly reference it in the rule

Q&A

Q. Is the library thread-safe ? A. Ammm..Yes and no ... the parsing expression tree is relying on reference counting which is atomic operation .. so most probably using the same rule in multiple threads is Ok.. However.. the parsing process is somehow dependent on each other so the internal context and matches table are not thread safe (and it should not be )..this is a design choice to not impact the speed of parsing The rule of the thumb here ... keep the whole parsing cycle in the same thread..

Q. why case insensitivity is not working on European languages A. Yes the internal 'to lower' function is ASCII only for now it is probable to add ICU lib to support such a function in near future ... ( just I don't like to overcomplicate things)

Contribution

if there is any problem or bug .. take a look on the issues first and check if it is already reported and follow up with this ticket .. if not, it will be a pleasure to file a new issue here

Sure you can fork the clone and fork the source code and create a pull request

License

This software is licensed under MIT