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Regular Expression Component Library for BCB6 — Complete Toolkit

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Overview

BCB6 ships with limited built-in regular expression support. A dedicated Regular Expression Component Library provides reusable VCL components that integrate regex functionality into visual forms and non-visual classes, exposing design-time properties, events, and methods familiar to BCB developers. Such a library usually wraps a mature regex engine (PCRE, Oniguruma, or a custom engine) and adapts it to BCB6’s component model.

Typical Library Structure

A well-structured BCB6 regex component library often includes:

  • Core engine unit(s) — wrapper around the chosen regex engine (matching, searching, replacing).
  • Component units — TRegex, TRegexEdit, TRegexLabel, TRegexTester, TRegexManager (examples).
  • Design-time package — components palette integration, property editors, and component registration.
  • Run-time package — compiled component units for distribution.
  • Demo projects — sample forms and usage scenarios.
  • Documentation — API reference, installation steps, and examples.

Installation

  1. Backup your projects and BCB6 configuration.
  2. Obtain the library source or precompiled packages compatible with BCB6.
  3. If source is provided, open the package project (.bpk) in BCB6.
  4. Compile the runtime package first (contains component units).
  5. Compile and install the design-time package (registers components on the IDE palette).
  6. If provided, run demo projects to verify correct behavior.

Common issues and fixes:

  • Missing library paths: Add library directories (Project → Options → Directories/Conditionals) so BCB6 can find units.
  • Compiler version mismatches: Ensure the package was built with the same compiler settings or rebuild from source.
  • DLL dependencies: Place any required DLLs in the application folder or system path.

Core Components & Their Roles

  • TRegex — non-visual component encapsulating a compiled pattern, expose methods Match, Replace, Split, CaptureGroups, Options (case-insensitive, multiline), and events OnMatch, OnError.
  • TRegexEdit — a TEdit descendant that validates input against a pattern in real time; properties: Pattern, ValidBackgroundColor, InvalidBackgroundColor.
  • TRegexLabel — displays match results or validation messages; optionally supports highlighting matched substrings.
  • TRegexTester — a demo/testing form that allows entering patterns and test strings, showing matches, captures, and replacement previews.
  • TRegexManager — centralizes compiled patterns for reuse and caching to improve performance.

Example: Using TRegex (code)

// Example C++ Builder 6 usage with a hypothetical TRegex component #include <vcl.h> #pragma hdrstop #include "Unit1.h" #pragma package(smart_init) #pragma resource "*.dfm" TForm1 *Form1; void __fastcall TForm1::ButtonMatchClick(TObject *Sender) {     try {         TRegex *r = new TRegex(this);         r->Pattern = "\b(\w+)@(\w+\.\w+)\b";         r->Options = r->Options | roIgnoreCase; // example option flag         TStringList *captures = new TStringList();         bool matched = r->Match(EditInput->Text, captures);         if (matched) {             MemoResults->Lines->Add("Matched: " + captures->Strings[0]);             for (int i = 1; i < captures->Count; ++i)                 MemoResults->Lines->Add("Group " + IntToStr(i) + ": " + captures->Strings[i]);         } else {             MemoResults->Lines->Add("No match found");         }         delete captures;         delete r;     }     catch (Exception &e) {         ShowMessage("Regex error: " + e.Message);     } }

Design-Time Integration

  • Register property editors for Pattern (provide syntax highlighting in the editor) and Options (enum flags editor).
  • Add a component icon and descriptive help text in the palette.
  • Implement streaming methods (DefineProperties, ReadState) if components maintain complex state.

Performance Considerations

  • Precompile patterns when used repeatedly (store compiled objects in TRegexManager).
  • Avoid catastrophic backtracking by preferring non-greedy quantifiers or atomic grouping when supported.
  • Use anchored patterns when possible.
  • For large texts, use streaming matches or process in chunks to reduce memory spikes.

Debugging Tips

  • Provide an integrated tester (TRegexTester) to iterate on patterns before embedding them.
  • Catch and display engine exceptions with context (pattern and sample text).
  • Log pattern compilation times and match counts during profiling.
  • If behavior differs from PCRE or other engines, consult the library’s engine documentation—some features (lookbehind, recursion) may be unsupported.

Extending the Library

  • Add language-specific components (e.g., file validators, CSV parsers).
  • Build additional UI helpers: highlighted search results in TMemo/TListView, replace previews, and batch processors.
  • Implement localization for messages and designer integration.
  • Expose lower-level engine options (callouts, JIT flags) if engine supports them.

Security and Safety

  • Treat user-supplied patterns as untrusted input in applications that accept them from external sources; limit pattern complexity or execution time to prevent Denial-of-Service via regex (ReDoS).
  • Run pattern compilation and matching in worker threads with timeouts for untrusted input.
  • Validate and sanitize patterns where feasible (restrict excessive backtracking constructs).

Example Use Cases

  • Form input validation (email, phone, postal codes) using TRegexEdit for immediate feedback.
  • Log file parsing and extraction tools with TRegexManager caching common patterns.
  • Search-and-replace utilities integrated into editors, with preview and undo support.
  • Data import pipelines (CSV/TSV) that need flexible, pattern-driven parsing.

Packaging & Distribution

  • Build runtime packages for deployment with your applications.
  • Provide redistributable DLLs or static libraries required by the regex engine.
  • Include license information (especially if wrapping GPL/LGPL code) and clear installation instructions for end users.

Troubleshooting Checklist

  • Component palette missing: verify design-time package compiled and installed.
  • Linker errors: check for duplicate symbol definitions or mismatched runtime packages.
  • Different behavior between demo and deployed app: ensure runtime package and DLL versions match.
  • Crashes on pattern compilation: validate input and catch exceptions; test under debugger.
  • Ship precompiled commonly used patterns to speed startup.
  • Provide a well-documented sample set of patterns for common validation tasks.
  • Offer clear error messages and pattern help in the designer to reduce developer friction.
  • Keep the API small and idiomatic to VCL conventions (properties, events, methods).

Further Reading & Resources

  • Regular expression engine manuals (PCRE, Oniguruma) for advanced pattern features.
  • Borland C++ Builder 6 VCL component development guides — packaging and design-time integration.
  • Articles on ReDoS and safe regex practices.

This guide gives a practical roadmap for integrating and using a Regular Expression Component Library in BCB6 projects: install cleanly, prefer compiled patterns, include design-time helpers, guard against ReDoS, and provide demos and documentation for users.

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