PMEMLOG_APPENDV(3)

💖 PMEMLOG_APPEND 💖

okay bestie, welcome to pmemlog_append() and pmemlog_appendv() — two little legends from the PMDK Programmer's Manual 💅

⚠️ heads up queen: both of these are DEPRECATED. Like, they still work, but they're giving "we don't talk about that era anymore". Use with the knowledge that the universe is gently side-eyeing them.

They do one thing and they do it fabulously: append bytes to the persistent memory resident log file. periodt. ✨

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📜 SYNOPSIS

#include <libpmemlog.h>

int pmemlog_append(PMEMlogpool *plp, const void *buf, size_t count);
int pmemlog_appendv(PMEMlogpool *plp, const struct iovec *iov, int iovcnt);

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🌸 DESCRIPTION

✨ pmemlog_append()

So basically, pmemlog_append() takes count bytes from buf and appends them to the current write offset in the log memory pool plp. It's literally the same energy as appending to a file — you know the vibe.

And here's the slay part: the append is atomic and cannot be torn by a program failure or system crash. no cap. 💀🔥

✨ pmemlog_appendv()

pmemlog_appendv() appends to the log memory pool plp from the scatter/gather list iov, in a manner similar to writev(2). The entire list of buffers gets appended atomically, as if the buffers in iov were concatenated in order. 🦋

And same deal: the append is atomic and cannot be torn by a program failure or system crash. iconic behaviour fr fr 💖

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🎀 RETURN VALUE

On success, both pmemlog_append() and pmemlog_appendv() return 0. 🥳

On error, they return -1 and set errno appropriately. (yes bestie, that's the standard "something went wrong" ritual.)

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😭 ERRORS

• EINVAL — the vector count iovcnt is less than zero. ma'am. that's not a number of buffers, that's a cry for help.
• ENOSPC — there is no room for the data in the log file. the log said "full, not accepting new entries, respectfully". 🚫
• EROFS — the log file is open in read-only mode. you cannot write to it. you simply cannot. read-only means read-only, babe. 🙈

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🧚 NOTES

okay so this is important and lowkey kinda unhinged: since libpmemlog(7) is designed as a low-latency code path, many of the checks that the operating system routinely does for writev(2) are just not practical in the library's implementation of pmemlog_appendv().

💀 Not a single attempt is made to detect NULL or incorrect pointers. For example. None. Zero. It's giving "you're on your own, bestie, but with love".

So like, please double-check your own pointers. The library trusts you completely and that is both beautiful and terrifying. 🫶

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👑 SEE ALSO

writev(2), libpmemlog(7) and <https://pmem.io>

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PMDK · 2023-05-31 — that's the source, the version, and the date, mwah 💋 hope this helped, go forth and append responsibly, ily 🎀✨🦋