Closing Channels in Assembly Language

; Closing Channels Example

section .data
    jobs    dd 0, 0, 0, 0, 0  ; Array to simulate channel
    jobsEnd dd 0              ; End of jobs array
    done    dd 0              ; Done flag
    fmt1    db 'received job %d', 10, 0
    fmt2    db 'received all jobs', 10, 0
    fmt3    db 'sent job %d', 10, 0
    fmt4    db 'sent all jobs', 10, 0
    fmt5    db 'received more jobs: %d', 10, 0

section .text
    global _start
    extern printf

_start:
    ; Initialize jobs array
    mov dword [jobsEnd], jobs

    ; Start worker function
    call worker

    ; Send jobs
    mov ecx, 1
.send_loop:
    push ecx
    call send_job
    pop ecx
    inc ecx
    cmp ecx, 4
    jl .send_loop

    ; Close jobs (set end of array)
    mov eax, [jobsEnd]
    mov dword [eax], -1
    push fmt4
    call printf
    add esp, 4

    ; Wait for worker to finish
    mov eax, [done]
    test eax, eax
    jz $-6

    ; Try to receive more jobs
    call receive_job
    push eax
    push fmt5
    call printf
    add esp, 8

    ; Exit program
    mov eax, 1
    xor ebx, ebx
    int 0x80

worker:
    push ebp
    mov ebp, esp
.loop:
    call receive_job
    cmp eax, -1
    je .done
    push eax
    push fmt1
    call printf
    add esp, 8
    jmp .loop
.done:
    push fmt2
    call printf
    add esp, 4
    mov dword [done], 1
    mov esp, ebp
    pop ebp
    ret

send_job:
    mov eax, [jobsEnd]
    mov [eax], ecx
    add dword [jobsEnd], 4
    push ecx
    push fmt3
    call printf
    add esp, 8
    ret

receive_job:
    mov eax, [jobs]
    cmp eax, -1
    je .closed
    push dword [jobs]
    mov ecx, jobs
    add ecx, 4
    mov edx, [jobsEnd]
    sub edx, 4
    cld
    rep movsd
    sub dword [jobsEnd], 4
    pop eax
    ret
.closed:
    mov eax, 0
    ret

This Assembly Language code simulates the concept of channels and closing channels from the original example. Here’s an explanation of the key parts:

We use an array jobs to simulate a channel. The jobsEnd variable points to the end of the array, simulating the channel’s buffer.
The worker function continuously receives jobs until it gets a special value (-1) indicating the channel is closed.
The send_job function adds a job to the jobs array and prints a message.
The receive_job function removes a job from the jobs array and returns it. If the array is empty and closed (contains -1), it returns 0.
In the main program (_start), we send three jobs, close the channel (by setting -1 at the end of the array), and wait for the worker to finish.
After the worker is done, we try to receive more jobs to demonstrate that reading from a closed channel returns 0.

This Assembly code provides a low-level implementation of the channel closing concept. It uses a simple array and some helper functions to mimic the behavior of channels in higher-level languages.

Note that this is a simplified simulation and doesn’t include features like true concurrency or the ability to block on channel operations. In real Assembly programming, you would typically use system calls or libraries for more complex concurrency patterns.

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Closing Channels in Assembly Language