WebAssembly - Examples


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The chapter discusses the examples with regards to WebAssembly.

Example 1

Following is the example of C Program to get the max Element −

void displaylog(int n);
/* function returning the max between two numbers */ 
int max(int num1, int num2) {
   /* local variable declaration */ int result; 
   if (num1 > num2) 
      result = num1; 
   else result = num2;
      displaylog(result);
   return result; 
}

Compile the code in wasm fiddle and download the .wasm and .wat code.

WASM Fiddle

Wat code

The Wat code is as follows −

(module 
   (type $FUNCSIG$vi (func (param i32))) 
   (import "env" "displaylog" (func $displaylog (param i32))) 
   (table 0 anyfunc) 
   (memory $0 1) 
   (export "memory" (memory $0)) 
   (export "max" (func $max)) 
   (func $max (; 1 ;) (param $0 i32) (param $1 i32) (result i32) 
      (call $displaylog       
         (tee_local $0 
            (select 
               (get_local $0) 
               (get_local $1) 
               (i32.gt_s (get_local $0) (get_local $1)) 
            )
         )
      )
      (get_local $0) 
   )
)

Download .wasm code and let us use in the .html file as shown below −

<!DOCTYPE html> 
<html>
   <head>
      <meta charset="UTF-8">
   </head>
   <body>
      <script>
         const importObj = {
            env: { 
               displaylog: n => alert("The max of (400, 130) is " +n) 
            } 
         };
         fetch("testmax.wasm") .then(bytes => bytes.arrayBuffer()) 
            .then(module => WebAssembly.instantiate(module, importObj)) 
            .then(finalcode => { 
            console.log(finalcode); 
            console.log(finalcode.instance.exports.max(400,130)); 
         }); 
      </script> 
   </body>
</html>

Output

The output is as follows −

Html File

Example 2

Following is the C++ code to get the fibonacci series of given number.

#include <iostream>>
void displaylog(int n); 
int fibonacciSeries(int number) {
   int n1=0,n2=1,n3,i; 
   for(i=2;i<number;++i) { 
      n3=n1+n2; displaylog(n); n1=n2; n2=n3;
   }
   return 0; 
}

I am using wasm explorer to compile the code. Download Wat and Wasm and test the same in the browser.

Compile the Code

You can use the below mentioned code −

<!DOCTYPE html> 
<html>
   <head> 
      <meta charset="UTF-8">
   </head>
   <body>
      <script> 
         const importObj = { 
            env: { _Z10displaylogi: n => console.log(n) } 
         };
         fetch("fib.wasm") 
            .then(bytes => bytes.arrayBuffer()) 
            .then(module => WebAssembly.instantiate(module, importObj)) 
            .then(finalcode => { 
            console.log(finalcode); 
            console.log(finalcode.instance.exports._Z15fibonacciSeriesi(10)); 
         });
      </script> 
   </body>
</html>

Output

The output is as follows −

Rust Code

Example 3

Following is the Rust code to add elements in a given array.

fn add_array(x: i32) -> i32 { 
   let mut sum = 0; 
   let mut numbers = [10,20,30]; for i in 0..3 { 
      sum += numbers[i]; 
   } 
   sum 
}

We are going to make use of WebAssembly Studio to compile RUST to wasm.

Download WASM file

Build the code and download the wasm file and execute the same in the browser.

<!DOCTYPE html> 
<html>
   <head> 
      <meta charset="UTF-8">
   </head>
      <body>
      <script> 
         const importObj = { 
            env: {
            } 
         };
         fetch("add_array.wasm") .then(bytes => bytes.arrayBuffer())
            .then(module => WebAssembly.instantiate(module, importObj)) 
            .then(finalcode => { 
            console.log(finalcode); 
            console.log(finalcode.instance.exports.add_array());
         }); 
      </script> 
   </body> 
</html>

Output

The output will be as given below −

Browser
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