Skip to content

Latest commit

 

History

History
137 lines (109 loc) · 3.12 KB

README.md

File metadata and controls

137 lines (109 loc) · 3.12 KB

Lab 2 Primitives and Arrays

The objective of this lab is learn about MemorySegments with C primitives and arrays. The values in memory can be manipulated off of the Java heap.

Before you begin change directory to lab2 and run the following scripts to clean up:

Linux and MacOS

bash clean.sh

Windows

clean_windows.cmd

Note: Reminder to change directory into lab2: cd lab2

Before doing the exercises run jextract against the stdio.h file the following:

Linux

bash jextract_linux.sh

MacOS

bash jextract_macos.sh

Windows

jextract_windows.cmd

The following are the exercises for Lab 2:

  • Exercise 1 - Changing values in C primitives
  • Exercise 2 - Change values in C arrays

Exercise 1 - Changing values in C primitives

The objective is to add code to change the value inside a MemorySegment to the a new value and outputting a string.

First lets run the Java file Primitive.java with the following:

Linux/MacOS

java -cp classes \
--enable-native-access=ALL-UNNAMED \
--add-modules jdk.incubator.foreign \
src/Primitive.java

Windows

java -cp classes --enable-native-access=ALL-UNNAMED --add-modules jdk.incubator.foreign \
src/Primitive.java

The output shows:

A slice of 3.141593 
New value is 3.141593

Open the file Primitive.java and look at the line that appears like the following:

// Change the cDouble to Math.PI * 4 [ADD CODE BELOW THIS LINE]

In the code the variable cDouble of typeMemorySegment

var cDouble = allocator.allocate(C_DOUBLE, Math.PI);

Change value to Math.PI * 4 contents in cDouble

Expected output:

A slice of 3.141593
New value is 12.566371

Exercise 2 - Changing values in C arrays

The objective is to add code to update the value inside the C array (MemorySegment) to the a new value and outputting the contents.

Open the file PrimitiveArray.java and locate the line as follows:

// double each value in C array [ADD CODE BELOW THIS LINE]

This is where you need to create a for loop to set the values into the C array of doubles (MemorySegment).

for (long i = 0; i < 16; i++) {
        // cDoubleArray...
}

First lets run the Java file Primitive.java to see the current output with the following:

Linux/MacOS

java -cp classes \
--enable-native-access=ALL-UNNAMED \
--add-modules jdk.incubator.foreign \
src/PrimitiveArray.java

Windows

java -cp classes --enable-native-access=ALL-UNNAMED --add-modules jdk.incubator.foreign \
src/PrimitiveArray.java

The output shows:

An array of data
1.000000  2.000000  3.000000  4.000000
1.000000  1.000000  1.000000  1.000000
3.000000  4.000000  5.000000  6.000000
5.000000  6.000000  7.000000  8.000000

In the code the variable (MemorySegment)

MemorySegment cDoubleArray = ...

Add code to iterate through the C array and set the value to (multiply by two).

Expected output:

An array of data
2.000000  4.000000  6.000000  8.000000
2.000000  2.000000  2.000000  2.000000
6.000000  8.000000  10.000000  12.000000
10.000000  12.000000  14.000000  16.000000