File Information
Library: Foundation
Package: Core
Header: Poco/NestedDiagnosticContext.h
Description
This class implements a Nested Diagnostic Context (NDC), as described in Neil Harrison's article "Patterns for Logging Diagnostic Messages" in "Pattern Languages of Program Design 3" (Addison-Wesley).
A NDC maintains a stack of context information, consisting of an informational string (e.g., a method name), as well as an optional source code line number and file name. NDCs are especially useful for tagging log messages with context information which is very helpful in a multithreaded server scenario. Every thread has its own private NDC, which is automatically created when needed and destroyed when the thread terminates.
The NDCScope (or NDC::Scope) class can be used to automatically push information at the beginning of a scope, and to pop it at the end. The poco_ndc(info) macro augments the information with a source code line number and file name.
Member Summary
Member Functions: clear, current, depth, dump, operator =, pop, push, toString
Types
Scope
Constructors
NestedDiagnosticContext
Creates the NestedDiagnosticContext.
NestedDiagnosticContext
NestedDiagnosticContext(
const NestedDiagnosticContext & ctx
);
Copy constructor.
Destructor
~NestedDiagnosticContext
Destroys the NestedDiagnosticContext.
Member Functions
clear
void clear();
Clears the NDC stack.
current 
static NestedDiagnosticContext & current();
Returns the current thread's NDC.
depth
int depth() const;
Returns the depth (number of contexts) of the stack.
dump
void dump(
std::ostream & ostr
) const;
Dumps the stack (including line number and filenames) to the given stream. The entries are delimited by a newline.
dump
void dump(
std::ostream & ostr,
const std::string & delimiter
) const;
Dumps the stack (including line number and filenames) to the given stream.
operator =
NestedDiagnosticContext & operator = (
const NestedDiagnosticContext & ctx
);
Assignment operator.
pop
void pop();
Pops the top-most context off the stack.
push
void push(
const std::string & info
);
Pushes a context (without line number and filename) onto the stack.
push
void push(
const std::string & info,
int line,
const char * filename
);
Pushes a context (including line number and filename) onto the stack. Filename must be a static string, such as the one produced by the __FILE__ preprocessor macro.
toString
std::string toString() const;
Returns the stack as a string with entries delimited by colons. The string does not contain line numbers and filenames.