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API Reference

Complete API reference for all Echo Kernel components and subsystems.

Table of Contents​

Kernel Core​

Namespace: kernel​

Core kernel functionality and system control.

Functions​

void main(void)

Kernel entry point. Initializes system and starts the shell.

void shutdown(void)

Safely shuts down the system using multiple methods:

  1. QEMU ACPI shutdown
  2. APM shutdown
  3. Standard ACPI shutdown
  4. Keyboard controller reset
  5. CPU halt as fallback
void sleep(int ms)

Delays execution for specified milliseconds using CPU busy-wait.

  • Parameters:
    • ms: Milliseconds to sleep

Namespace: kernel::eshell​

Shell interface implementation.

Functions​

void start_eshell(void)

Initializes and starts the shell interface.

void loop(void)

Main shell loop that processes user input and executes commands.

Hardware I/O​

Namespace: ports​

Port-based hardware I/O operations.

Constants​

static constexpr uint16_t QEMU_SHUTDOWN_PORT = 0xB004

QEMU-specific ACPI shutdown port.

static constexpr uint16_t APM_SHUTDOWN_PORT = 0x604

Advanced Power Management port.

static constexpr uint16_t ACPI_SHUTDOWN_PORT = 0x4004

Standard ACPI shutdown port.

static constexpr uint16_t KBC_RESET_PORT = 0x64

Keyboard controller reset port.

Functions​

static inline void outb(uint16_t port, uint8_t value)

Writes an 8-bit value to a port.

  • Parameters:
    • port: Port address
    • value: 8-bit value to write
static inline uint8_t inb(uint16_t port)

Reads an 8-bit value from a port.

  • Parameters:
    • port: Port address
  • Returns: Value read from port
static inline void outw(uint16_t port, uint16_t value)

Writes a 16-bit value to a port.

  • Parameters:
    • port: Port address
    • value: 16-bit value to write
static inline uint16_t inw(uint16_t port)

Reads a 16-bit value from a port.

  • Parameters:
    • port: Port address
  • Returns: Value read from port

Display System​

Namespace: display​

Screen output and text display functionality.

Constants​

// Color Constants
const uint8_t CL_BLACK = 0
const uint8_t CL_BLUE = 1
const uint8_t CL_GREEN = 2
const uint8_t CL_CYAN = 3
const uint8_t CL_RED = 4
const uint8_t CL_MAGENTA = 5
const uint8_t CL_BROWN = 6
const uint8_t CL_LIGHT_GREY = 7
const uint8_t CL_DARK_GREY = 8
const uint8_t CL_LIGHT_BLUE = 9
const uint8_t CL_LIGHT_GREEN = 10
const uint8_t CL_LIGHT_CYAN = 11
const uint8_t CL_LIGHT_RED = 12
const uint8_t CL_LIGHT_MAGENTA = 13
const uint8_t CL_LIGHT_BROWN = 14
const uint8_t CL_WHITE = 15

Functions​

void clear_screen(void)

Clears the screen and resets cursor position.

void print(const char* str)

Prints a string to the screen.

  • Parameters:
    • str: String to print
void printc(const char* str, uint8_t color)

Prints a colored string to the screen.

  • Parameters:
    • str: String to print
    • color: Color value from constants
void print_newline(void)

Moves cursor to the next line.

Keyboard System​

Namespace: keyboard​

Keyboard input handling.

Functions​

char* get_input(const char* prefix)

Gets a line of input from the keyboard.

  • Parameters:
    • prefix: String to display before input
  • Returns: Input string

Library Functions​

Namespace: lib​

Common utility functions.

Functions​

int strlen(const char* str)

Returns the length of a string.

  • Parameters:
    • str: Input string
  • Returns: String length
int strcmp(const char* str1, const char* str2)

Compares two strings.

  • Parameters:
    • str1: First string
    • str2: Second string
  • Returns: 0 if equal, non-zero if different
void memcpy(void* dest, const void* src, int count)

Copies memory from source to destination.

  • Parameters:
    • dest: Destination pointer
    • src: Source pointer
    • count: Number of bytes to copy
void memset(void* dest, char val, int count)

Sets memory to a specific value.

  • Parameters:
    • dest: Destination pointer
    • val: Value to set
    • count: Number of bytes to set

Bootloader​

Functions​

void boot(void)​

Main boot sequence function.

  • Initializes IDT
  • Sets up display
  • Launches kernel

Standard Library​

String Functions​

size_t strlen(const char* str)​

Returns string length.

  • Parameters: str - Input string
  • Returns: Number of characters before null terminator

int strcmp(const char* str1, const char* str2)​

Compares two strings.

  • Returns:
    • 0 if equal
    • Negative value if str1 is less than str2
    • Positive value if str1 is greater than str2

char* strcpy(char* dest, const char* src)​

Copies string including null terminator.

  • Returns: Pointer to dest

char* strncpy(char* dest, const char* src, size_t n)​

Copies up to n characters.

  • Returns: Pointer to dest

char* strcat(char* dest, const char* src)​

Concatenates strings.

  • Returns: Pointer to dest

char* strncat(char* dest, const char* src, size_t n)​

Concatenates up to n characters.

  • Returns: Pointer to dest

const char* strchr(const char* str, int ch)​

Finds first occurrence of character.

  • Returns: Pointer to character or nullptr

Memory Functions​

void* memcpy(void* dest, const void* src, size_t n)​

Copies n bytes between memory regions.

  • Returns: Pointer to dest

void* memset(void* ptr, int value, size_t n)​

Fills memory with specified value.

  • Returns: Pointer to ptr

int memcmp(const void* ptr1, const void* ptr2, size_t n)​

Compares memory regions.

  • Returns: 0 if equal, difference otherwise

Character Functions​

bool isdigit(char c)​

Checks if character is digit (0-9).

bool isalpha(char c)​

Checks if character is letter (a-z, A-Z).

bool isalnum(char c)​

Checks if character is alphanumeric.

bool islower(char c)​

Checks if character is lowercase.

bool isupper(char c)​

Checks if character is uppercase.

char tolower(char c)​

Converts to lowercase.

char toupper(char c)​

Converts to uppercase.

Time Functions​

void sleep(uint32_t milliseconds)​

Delays execution.

  • Parameters: milliseconds - Delay duration

Conversion Functions​

int atoi(const char* str)​

Converts string to integer.

  • Parameters: str - Number string
  • Returns: Integer value

char* itoa(int value, char* str, int base)​

Converts integer to string.

  • Parameters:
    • value - Number to convert
    • str - Output buffer
    • base - Number base (2-36)
  • Returns: Pointer to str

Hardware Ports​

PortDescription
0x60Keyboard Data Port
0x64Keyboard Status Port
0xb8000Video Memory Base

Memory Map​

AddressUsage
0xb8000Video Memory Start
0xb8000 + SCREENSIZEVideo Memory End

Error Codes​

Most functions return one of these types:

  • Boolean: true for success, false for failure
  • Pointers: nullptr for failure
  • Integers: 0 for success, non-zero for specific errors

Usage Notes​

  1. Display Functions

    • Always check screen boundaries
    • Handle scrolling automatically
    • Color attributes combine foreground and background (using bit shift)

  2. Keyboard Functions

    • Initialize IDT before using keyboard
    • Check input buffer limits
    • Handle input termination (Enter key)

  3. Memory Functions

    • Verify buffer sizes
    • Check for overlap in memcpy
    • Ensure proper alignment

  4. String Functions

    • Ensure destination buffers are large enough
    • Always check for null terminators
    • Use n-variants for better safety