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Ability to customize regular expression engine #192

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merged 1 commit into from
May 16, 2024
Merged

Ability to customize regular expression engine #192

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1 change: 1 addition & 0 deletions CMakeLists.txt
View file
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Original file line number Diff line number Diff line change
Expand Up @@ -124,6 +124,7 @@ if(valijson_BUILD_TESTS)
tests/test_poly_constraint.cpp
tests/test_validation_errors.cpp
tests/test_validator.cpp
tests/test_validator_with_custom_regular_expression_engine.cpp
tests/test_yaml_cpp_adapter.cpp
)

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28 changes: 28 additions & 0 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -87,6 +87,34 @@ Validator validator(Validator::kWeakTypes);

This will create a validator that will attempt to cast values to satisfy a schema. The original motivation for this was to support the Boost Property Tree library, which can parse JSON, but stores values as strings.

## Regular Expression Engine

When enforcing a 'pattern' property, a regular expression engine is in used. By default, the DefaultRegexEngine use std::regex.
std::regex has no protection against catastrophic backtracking and implementation with gcc is so suboptimal that it can easily leads to segmentation fault.
One can customise the regular expression engine by implementing it's own wrapper to it and using a ValidatorT with the custom type.

The regular expression engine wrapper must implement the following interface
```cpp
struct MyRegexpEngine
{
MyRegexpEngine(const std::string& pattern)
{
//implementation specific
}

static bool search(const std::string& s, const MyRegexpEngine& r)
{
//implementation specific
}
};

```

Then to use it
```cpp
using MyValidator = ValidatorT<MyRegexpEngine>;
```

## Memory Management

Valijson has been designed to safely manage, and eventually free, the memory that is allocated while parsing a schema or validating a document. When working with an externally loaded schema (i.e. one that is populated using the `SchemaParser` class) you can rely on RAII semantics.
Expand Down
38 changes: 19 additions & 19 deletions include/valijson/validation_visitor.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -28,7 +28,7 @@ class ValidationResults;
*
* @tparam AdapterType Adapter type for the target document.
*/
template<typename AdapterType>
template<typename AdapterType, typename RegexEngine>
class ValidationVisitor: public constraints::ConstraintVisitor
{
public:
Expand All @@ -44,14 +44,14 @@ class ValidationVisitor: public constraints::ConstraintVisitor
* recording error descriptions. If this pointer is set
* to nullptr, validation errors will caused validation to
* stop immediately.
* @param regexesCache Cache of already created std::regex objects for pattern
* @param regexesCache Cache of already created RegexEngine objects for pattern
* constraints.
*/
ValidationVisitor(const AdapterType &target,
std::vector<std::string> context,
const bool strictTypes,
ValidationResults *results,
std::unordered_map<std::string, std::regex>& regexesCache)
std::unordered_map<std::string, RegexEngine>& regexesCache)
: m_target(target),
m_context(std::move(context)),
m_results(results),
Expand Down Expand Up @@ -155,7 +155,7 @@ class ValidationVisitor: public constraints::ConstraintVisitor
ValidationResults newResults;
ValidationResults *childResults = (m_results) ? &newResults : nullptr;

ValidationVisitor<AdapterType> v(m_target, m_context, m_strictTypes, childResults, m_regexesCache);
ValidationVisitor<AdapterType, RegexEngine> v(m_target, m_context, m_strictTypes, childResults, m_regexesCache);
constraint.applyToSubschemas(
ValidateSubschemas(m_target, m_context, false, true, v, childResults, &numValidated, nullptr));

Expand Down Expand Up @@ -498,7 +498,7 @@ class ValidationVisitor: public constraints::ConstraintVisitor
std::vector<std::string> newContext = m_context;
newContext.push_back("[" + std::to_string(index) + "]");

ValidationVisitor<AdapterType> validator(*itr, newContext, m_strictTypes, m_results, m_regexesCache);
ValidationVisitor<AdapterType, RegexEngine> validator(*itr, newContext, m_strictTypes, m_results, m_regexesCache);

if (!validator.validateSchema(*additionalItemsSubschema)) {
if (m_results) {
Expand Down Expand Up @@ -874,7 +874,7 @@ class ValidationVisitor: public constraints::ConstraintVisitor
return false;
}

ValidationVisitor<AdapterType> v(m_target, m_context, m_strictTypes, nullptr, m_regexesCache);
ValidationVisitor<AdapterType, RegexEngine> v(m_target, m_context, m_strictTypes, nullptr, m_regexesCache);
if (v.validateSchema(*subschema)) {
if (m_results) {
m_results->pushError(m_context,
Expand All @@ -901,7 +901,7 @@ class ValidationVisitor: public constraints::ConstraintVisitor
ValidationResults newResults;
ValidationResults *childResults = (m_results) ? &newResults : nullptr;

ValidationVisitor<AdapterType> v(m_target, m_context, m_strictTypes, childResults, m_regexesCache);
ValidationVisitor<AdapterType, RegexEngine> v(m_target, m_context, m_strictTypes, childResults, m_regexesCache);
constraint.applyToSubschemas(
ValidateSubschemas(m_target, m_context, true, true, v, childResults, &numValidated, nullptr));

Expand Down Expand Up @@ -943,10 +943,10 @@ class ValidationVisitor: public constraints::ConstraintVisitor
std::string pattern(constraint.getPattern<std::string::allocator_type>());
auto it = m_regexesCache.find(pattern);
if (it == m_regexesCache.end()) {
it = m_regexesCache.emplace(pattern, std::regex(pattern)).first;
it = m_regexesCache.emplace(pattern, RegexEngine(pattern)).first;
}

if (!std::regex_search(m_target.asString(), it->second)) {
if (!RegexEngine::search(m_target.asString(), it->second)) {
if (m_results) {
m_results->pushError(m_context, "Failed to match regex specified by 'pattern' constraint.");
}
Expand Down Expand Up @@ -1086,7 +1086,7 @@ class ValidationVisitor: public constraints::ConstraintVisitor

for (const typename AdapterType::ObjectMember m : m_target.asObject()) {
adapters::StdStringAdapter stringAdapter(m.first);
ValidationVisitor<adapters::StdStringAdapter> validator(stringAdapter, m_context, m_strictTypes, nullptr, m_regexesCache);
ValidationVisitor<adapters::StdStringAdapter, RegexEngine> validator(stringAdapter, m_context, m_strictTypes, nullptr, m_regexesCache);
if (!validator.validateSchema(*constraint.getSubschema())) {
return false;
}
Expand Down Expand Up @@ -1155,7 +1155,7 @@ class ValidationVisitor: public constraints::ConstraintVisitor
newContext.push_back("[" + std::to_string(index) + "]");

// Create a validator for the current array item
ValidationVisitor<AdapterType> validationVisitor(item, newContext, m_strictTypes, m_results, m_regexesCache);
ValidationVisitor<AdapterType, RegexEngine> validationVisitor(item, newContext, m_strictTypes, m_results, m_regexesCache);

// Perform validation
if (!validationVisitor.validateSchema(*itemsSubschema)) {
Expand Down Expand Up @@ -1420,7 +1420,7 @@ class ValidationVisitor: public constraints::ConstraintVisitor
ValidationResults *results,
unsigned int *numValidated,
bool *validated,
std::unordered_map<std::string, std::regex>& regexesCache)
std::unordered_map<std::string, RegexEngine>& regexesCache)
: m_arr(arr),
m_context(context),
m_continueOnSuccess(continueOnSuccess),
Expand Down Expand Up @@ -1477,7 +1477,7 @@ class ValidationVisitor: public constraints::ConstraintVisitor
ValidationResults * const m_results;
unsigned int * const m_numValidated;
bool * const m_validated;
std::unordered_map<std::string, std::regex>& m_regexesCache;
std::unordered_map<std::string, RegexEngine>& m_regexesCache;
};

/**
Expand Down Expand Up @@ -1563,7 +1563,7 @@ class ValidationVisitor: public constraints::ConstraintVisitor
ValidationResults *results,
std::set<std::string> *propertiesMatched,
bool *validated,
std::unordered_map<std::string, std::regex>& regexesCache)
std::unordered_map<std::string, RegexEngine>& regexesCache)
: m_object(object),
m_context(context),
m_continueOnSuccess(continueOnSuccess),
Expand Down Expand Up @@ -1640,7 +1640,7 @@ class ValidationVisitor: public constraints::ConstraintVisitor
ValidationResults * const m_results;
std::set<std::string> * const m_propertiesMatched;
bool * const m_validated;
std::unordered_map<std::string, std::regex>& m_regexesCache;
std::unordered_map<std::string, RegexEngine>& m_regexesCache;
};

/**
Expand All @@ -1659,7 +1659,7 @@ class ValidationVisitor: public constraints::ConstraintVisitor
ValidationResults *results,
std::set<std::string> *propertiesMatched,
bool *validated,
std::unordered_map<std::string, std::regex>& regexesCache)
std::unordered_map<std::string, RegexEngine>& regexesCache)
: m_object(object),
m_context(context),
m_continueOnSuccess(continueOnSuccess),
Expand Down Expand Up @@ -1716,7 +1716,7 @@ class ValidationVisitor: public constraints::ConstraintVisitor
ValidationResults * const m_results;
std::set<std::string> * const m_propertiesMatched;
bool * const m_validated;
std::unordered_map<std::string, std::regex>& m_regexesCache;
std::unordered_map<std::string, RegexEngine>& m_regexesCache;
};

/**
Expand Down Expand Up @@ -1842,7 +1842,7 @@ class ValidationVisitor: public constraints::ConstraintVisitor
*
* @return true if the visitor returns successfully, false otherwise.
*/
static bool validationCallback(const constraints::Constraint &constraint, ValidationVisitor<AdapterType> &visitor)
static bool validationCallback(const constraints::Constraint &constraint, ValidationVisitor<AdapterType, RegexEngine> &visitor)
{
return constraint.accept(visitor);
}
Expand Down Expand Up @@ -1901,7 +1901,7 @@ class ValidationVisitor: public constraints::ConstraintVisitor
bool m_strictTypes;

/// Cached regex objects for pattern constraint
std::unordered_map<std::string, std::regex>& m_regexesCache;
std::unordered_map<std::string, RegexEngine>& m_regexesCache;
};

} // namespace valijson
Expand Down
35 changes: 29 additions & 6 deletions include/valijson/validator.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -8,10 +8,15 @@ namespace valijson {
class Schema;
class ValidationResults;


/**
* @brief Class that provides validation functionality.
* @brief Class that provides validation functionality.
*
* @tparam RegexEngine regular expression engine used for pattern constraint validation.

*/
class Validator
template <typename RegexEngine>
class ValidatorT
{
public:
enum TypeCheckingMode
Expand All @@ -23,15 +28,15 @@ class Validator
/**
* @brief Construct a Validator that uses strong type checking by default
*/
Validator()
ValidatorT()
: strictTypes(true) { }

/**
* @brief Construct a Validator using a specific type checking mode
*
* @param typeCheckingMode choice of strong or weak type checking
*/
Validator(TypeCheckingMode typeCheckingMode)
ValidatorT(TypeCheckingMode typeCheckingMode)
: strictTypes(typeCheckingMode == kStrongTypes) { }

/**
Expand All @@ -58,7 +63,7 @@ class Validator
ValidationResults *results)
{
// Construct a ValidationVisitor to perform validation at the root level
ValidationVisitor<AdapterType> v(target,
ValidationVisitor<AdapterType, RegexEngine> v(target,
std::vector<std::string>(1, "<root>"), strictTypes, results, regexesCache);

return v.validateSchema(schema);
Expand All @@ -70,7 +75,25 @@ class Validator
bool strictTypes;

/// Cached regex objects for pattern constraint. Key - pattern.
std::unordered_map<std::string, std::regex> regexesCache;
std::unordered_map<std::string, RegexEngine> regexesCache;
};

/**
* @brief Struct that provides a default Regular Expression Engine using std::regex
*
*/
struct DefaultRegexEngine
{
DefaultRegexEngine(const std::string& pattern)
: regex(pattern) { }

static bool search(const std::string& s, const DefaultRegexEngine& r)
{
return std::regex_search(s, r.regex);
}
std::regex regex;
};

using Validator = ValidatorT<DefaultRegexEngine>;

} // namespace valijson
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