Types Module - User Guide

What is Types?

Types module defines fixed-width integer types for safety-critical systems. All framework code uses uint32_t, int16_t, etc. instead of bare int or long. This ensures consistent behavior across platforms (8-bit MCU, 32-bit ARM, 64-bit x86).

Key principle: Platform-independent sizing guarantees.

Available Types

// Unsigned integers
uint8_t   uint16_t   uint32_t   uint64_t
 
// Signed integers  
int8_t    int16_t    int32_t    int64_t
 
// Boolean
bool      (C11 standard, true/false)
 
// Standard types
size_t    (pointer-sized)

Quick Start

1. Include Header

#include "rte/types/rte_types.h"

2. Use Fixed-Width Types

// BAD: Platform-dependent
int counter;          // Could be 16, 32, or 64 bits!
unsigned long value;  // Size varies
 
// GOOD: Platform-independent
uint32_t counter;     // Always 32 bits
uint64_t value;       // Always 64 bits

Type Ranges

uint8_t:   0 to 255
uint16_t:  0 to 65,535
uint32_t:  0 to 4,294,967,295
uint64_t:  0 to (2^64 - 1)

int8_t:    -128 to 127
int16_t:   -32,768 to 32,767
int32_t:   -2,147,483,648 to 2,147,483,647
int64_t:   -(2^63) to +(2^63 - 1)

Practical Examples

Example 1: Type-Safe Structure

// For wire protocol (network or storage)
typedef struct {
    uint32_t message_id;      // Always 4 bytes
    uint16_t length;          // Always 2 bytes
    int16_t temperature;      // -50°C to +50°C
    uint8_t flags;            // Bit flags
} train_msg_t;
 
// Size is predictable on ALL platforms
STATIC_ASSERT(sizeof(train_msg_t) == 9);

Example 2: Sized Counters

uint16_t packet_count;   // 0-65535 packets
uint32_t byte_count;     // 0-4B packets
uint64_t total_uptime_ms; // Milliseconds since boot

Best Practices

1. Never use bare int, long, char
   • Always explicit type: int32_t, uint8_t, etc.
   • Makes size guarantees visible
2. Match type to purpose
   • 16-bit counters: values 0-65535?
   • 32-bit time: milliseconds for ~49 days?
   • Don't over-allocate
3. Use uint8_t for bytes
   • Not unsigned char (confusing)
   • Not int (wrong size)
   • Always uint8_t for byte arrays
4. Use bool for single flags
   • bool enabled = true;
   • For multiple flags: uint32_t flags; with bit manipulation
5. Watch for overflow
   • uint8_t max = 255; max++; // Wraps to 0
   • int32_t sum = MAX + 1; // Undefined behavior!
   • Use next size up if needed

See Also

• Types Module - Architecture for implementation details
• Cast Module - User Guide for safe type conversions