Logger Library (C / C++ Android NDK)

Lightweight, modular logging library designed for Android NDK environments (armeabi-v7a / arm64-v8a), providing both C++ and C-compatible APIs with Android logcat integration.

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📌 Overview

This library provides:

• C++ object-oriented logging API
• C ABI-compatible wrapper (stable interface)
• Log levels with priority control (Info, Error, Debug, etc.)
• Dynamic tag system
• Callback hooks for external integration
• va_list and variadic function support
• Native Android logging via __android_log_write
• Formatting via stb_sprintf (required)

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🧱 Structure

logger.hpp / logger.cpp     → Core C++ implementation
logger_c.h / logger_c.cpp   → C ABI wrapper layer
stb_sprintf.h               → Required formatter backend

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⚙️ Requirements

Mandatory dependency

• stb_sprintf.h (formatting backend)

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🚀 Usage (C++ API)

#include "logger.hpp"

Logger* log = Logger::GetLogger();

log->Info("Hello %s", "world");
log->Error("Error code: %d", 404);

log->SetTag("GameCore");
log->Print(LogP_Debug, "Debug value: %d", 123);

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🚀 Usage (C API)

#include "logger_c.h"

LoggerC* log = logger_get_global();

logger_info(log, "Hello %s", "world");
logger_error(log, "Fatal error: %d", -1);

logger_set_tag(log, "Engine");
logger_print(log, LogP_Debug, "Value: %f", 3.14f);

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🔗 Callback System

C++

logger->SetMessageCB(myCallback);
logger->SetTagCB(tagCallback);
logger->SetToggleCB(toggleCallback);

C

logger_set_message_cb(log, myCallback);
logger_set_tag_cb(log, tagCallback);
logger_set_toggle_cb(log, toggleCallback);

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📱 Android Integration

The logger writes directly to Android logcat via:

#include <android/log.h>
__android_log_write(...)

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🧠 Technical Characteristics

• Fixed stack buffer (2048 bytes)
• Formatting powered by stb_sprintf
• No STL dependency required
• Optional compile-time logging disable (NOLOGGING)
• C ABI stability via opaque pointer design
• Low overhead (no allocations in hot path)

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⚠️ Notes

• stb_sprintf.h is required for compilation
• No fallback to standard vsnprintf is provided
• Designed for performance-sensitive runtime environments

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📄 Licenses

STB_LICENSE

• File: stb_sprintf.h
• Author: Sean Barrett
• License: MIT / Public Domain

RUSJJ_LICENSE

• Files: logger.hpp, logger.cpp
• Author: Rusjj
• License: MIT

MY_LICENSE

• Files: logger_c.h, logger_c.cpp
• Author: DeviceBlack
• License: MIT

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👤 Credits

• Sean Barrett — stb_sprintf.h
• Rusjj — original C++ logger implementation
• DeviceBlack — refactoring, fixes, C API wrapper