The Standard Library #

The standard library of HalideOS is a set of a few abstractions for some common data structures and utility functions that we used to again and again for the kernel as well as the shell programs.

All the classes and the functions are encapsulated in the hldstd namespace for clarity.

• Files: include/halidestdlib.h and src/halidestdlib.cpp
• Namespaces: hldstd, hldstd::math

Classes #

hldstd::string #

A regular string class to maintain a character array and it’s size, with some conversion functions.

Functions

• string(int x); - Contructor to convert int to string
• string(double x, int digits_after_point); - Constructor to convert double to string
• string(char *str); - Constructor to convert a raw char* to string
• string(bool val); - Constructor to convert bool to string
• string(string &other); - Copy Constructor
• int size(); - Returns size of the string
• char at(int i); - Returns the character at index i of the string
• char *c_ptr(); - Returns a raw char * to the string
• int to_int(); - Converts the string to int
• double to_double(); - Converts the string to double

#include <halidestdlib.h>

// Various ways to construct a hldstd::string
hldstd::string a = "From char *";
hldstd::string b = 10; 
hldstd::string c = false;
hldstd::string d(10.21343, 3);
hldstd::string e = a;

// Utility Functions
hldstd::string s = "FooBarBaz";

int s_size = s.size() // returns 9
char s_char = a.at(3) // returns 'B'
char* s_ptr = s.c_ptr() // returns a pointer to 
						// the char array stored in the class

// Conversion
hldstd::string i = "1201032";
hldstd::srting j = "1213.21434"

int i_int = i.to_int(); // return 1201032
double j_double = j.to_double(); // returns 1213.21434

hldstd::stack<T> #

A standard stack or LIFO list with the standard operations. This is a template class, the stack can hold any data-type T

Functions

All functions are template functions with <typename T>

• stack(int size, T x); - Constructor to initialise the stack with size and the first element;
• bool pop(); - false for underflow, true for successful pop
• bool push(T x); - false for overflow, true for successful push
• T top(); - Returns the top element of the stack
• bool isEmpty(); - Check if stack is empty or not.

#include <halidestdlib.h>

hldstd::stack<int> st(20, 0);

st.push(1);
st.push(2);
st.push(3);

st.pop();

int x = st.top(); // returns true
bool e = st.isEmpty(); // returns false

Functions #

Some simple mathematical functions are declared in the math namespace.

• int hldstd::stringCompare(char *, char *) - Compare 2 strings from the char pointers
• int hldstd::stringLength(char *) - Get length of string
• double hldstd::math::pow(double x, int y) - x^y
• int hldstd::math::abs(int x) - |x|