fast_json/README.md

# fast_json - MQL5 High-Performance JSON Library (The "Bit-Banger" Edition V2)

> "If your JSON parser needs recursion, you're doing it wrong."

## Overview

**fast_json** is a production-grade, high-performance JSON library for MQL5, designed for high-frequency trading (HFT) environments where latency and memory fragmentation are critical. 

Unlike standard libraries that abuse the heap with endless small allocations, **fast_json** uses a **tape-based zero-allocation memory model** and a **SWAR (SIMD within a Register)** scanner to parse gigabytes of data without triggering the garbage collector (or the equivalent memory pressure in MQL5).

## Key Features

- **🚀 Zero-Alloc Tape Architecture**: Parses the entire JSON into a single contiguous integer array (the "tape"). No objects are created during parsing. 
- **⚡ SWAR Acceleration**: Uses bit-manipulation hacks (Simulated 64-bit SWAR) to scan 8 bytes at a time for structural characters, drastically reducing branch misprediction.
- **🛡️ Stack-Safe Iterative Parser**: Written as a finite state machine. Zero recursion. Immune to stack overflow attacks from deeply nested JSONs.
- **🔧 Handle-Based Navigation**: Access data using lightweight `CJsonNode` structs that point to the tape. Copying nodes is free.
- **💾 Bit-Banged Serialization**: Writing JSON is just as fast, filling a pre-allocated buffer with raw byte operations.

## Performance

| Metric | fast_json | Standard Libs |
|--------|-----------|---------------|
| **Allocation Strategy** | 1 big block (Tape) | N objects per node |
| **Recursion Depth** | Unlimited (Heap stack) | Limited (Call stack) |
| **Parsing Speed** | ~300MB/s (Est.) | Snail pace |
| **Memory Frag** | Near Zero | High |

## Usage

### Parsing
```cpp
#include "fast_json.mqh"

CJsonContext ctx;
if (ctx.Parse(json_string)) {
    CJsonNode root = ctx.GetRoot();
    Print(root["price"].ToDouble());
} else {
    Print("Error: ", ctx.error_msg);
}
```

### Building & Serializing
```cpp
// Implicit serialization is supported via direct buffer writing
// (See implementation for details - this is for pros)
```

## Why MQL5?

Because we trade here. And we don't tolerate latency.

## License

MIT. Use it, profit, but don't blame me if your strategy fails.