program: Add optional buffer to Write instruction

[febo]

Problem

Currently, the Write instruction only accepts the data to write as instruction data. This limits each write to the maximum transaction size.

Solution

Add an optional buffer account to allow passing more data for a single write. This is useful when writing to PDA accounts controlled by multisigs, since the process of writing the data to a buffer can be done by a separate keypair.

[lorisleiva]

Thanks Febo! I've done the JS side. Let me know if you're happy with it and LGTM. 💪

[febo]

Thanks Febo! I've done the JS side. Let me know if you're happy with it and LGTM. 💪

Nice! Something that just occurred to me. Perhaps the offset should be optional and only used when writing from the instruction data. If you are writing from a buffer, most likely the buffer has all the data so the offset will be always 0.

[lorisleiva]

Perhaps the offset should be optional

I think I prefer having it required to explicitly hint that you are going to override data from the provided offset. Otherwise users providing multiple write instructions using instruction data might wrongly assume it'll be appended when in actual fact, the first part of the buffer will keep being written to.

[febo]

Perhaps the offset should be optional

I think I prefer having it required to explicitly hint that you are going to override data from the provided offset. Otherwise users providing multiple write instructions using instruction data might wrongly assume it'll be appended when in actual fact, the first part of the buffer will keep being written to.

I was thinking making both offset and data optional at the same time. So if you specify the data you need to inform the offset. When you use a buffer, then there is no need specify an offset.

[febo]

Perhaps the offset should be optional

I think I prefer having it required to explicitly hint that you are going to override data from the provided offset. Otherwise users providing multiple write instructions using instruction data might wrongly assume it'll be appended when in actual fact, the first part of the buffer will keep being written to.

I was thinking making both offset and data optional at the same time. So if you specify the data you need to inform the offset. When you use a buffer, then there is no need specify an offset.

Spoke offline, better to keep the offset explicit so when overriding the whole data the offset must be 0.