CODEWITHSUNDEEP
gosystem-callsmmap
Cubey Mew
Cubey Mew

Reputation: 653

Read a growing mmap file in Go

I want to read a mmap file in golang.

Another process is writing things into it so its size is growing while reading.

I am using

syscall.Mmap(fd int, offset int64, length int, prot int, flags int)

which will return a byte array.

Do I need to keep doing syscall.Mmap to read the updated mmap? Any better way?

Upvotes: 0

Views: 848

Answers (1)

Michael Hampton
Michael Hampton

Reputation: 10000

syscall.Mmap() is just a thin wrapper over C mmap(2) so it will behave the same. The memory region you get back can be updated by other processes if you've used the syscall.MAP_SHARED flag (and the other process did too). You don't have to do anything else except remember to call syscall.Munmap() when you're finished. It's probably a good candidate for defering, depending on what you're doing.

But, if someone is writing to the shared space and growing it beyond the region you mapped, then you'll have to map it again. It doesn't resize itself automatically.

Upvotes: 2

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