FujiNetWIFI/fujinet-firmware

Improve CP/M file performance.

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#917 opened on Apr 24, 2025

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enhancementhelp wanted

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Description

File I/O is slow in CP/M.

This is because for each BIOS read sector:

  • The file is opened
  • The sector is read
  • The file is closed.

A similar pattern is done for the other methods I list below, it's very atomic, but very slow.

Calls to OpenFile() in lib/runcpm/disk.h call _sys_openfile(): https://github.com/FujiNetWIFI/fujinet-firmware/blob/master/lib/runcpm/abstraction_fujinet.h#L153 and read sequential: https://github.com/FujiNetWIFI/fujinet-firmware/blob/master/lib/runcpm/abstraction_fujinet.h#L223 and write sequential: https://github.com/FujiNetWIFI/fujinet-firmware/blob/master/lib/runcpm/abstraction_fujinet.h#L263 and read random: https://github.com/FujiNetWIFI/fujinet-firmware/blob/master/lib/runcpm/abstraction_fujinet.h#L293 and write random: https://github.com/FujiNetWIFI/fujinet-firmware/blob/master/lib/runcpm/abstraction_fujinet.h#L339

This needs to be extended to hold onto the file handle, and not open the file again if it has already been opened, thus avoiding the file_open call if needed, and finding out when to best close the file when it is no longer needed (so we don't leak file descriptors! A timer?)

-Thom

Contributor guide

Research direction
Investigate the CP/M file abstraction in lib/runcpm/abstraction fujinet.h. The goal is to modify the file I/O functions (open, read, write, close) to cache the file handle, avoiding repeated open/close calls. Determine when to close the file (e.g., after a timeout or explicit close) to prevent file descriptor leaks.
Tech stack
c
Domain
backendperformance
Issue type
Performance
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
C
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65