refactor: RPC: pass named argument value as string

stickies-v commented at 6:20 pm on November 30, 2022: contributor

Inspired by MarcoFalke’s comment. Main purpose of this PR is to minimize copying (potentially large) RPC named arguments when calling .substr() by using std::string_view instead of std::string. Furthermore, cleans up the code by removing unnecessary complexity in ParseNonRFCJSONValue() (done first to avoid refactoring required to concatenate string and string_view), updates some naming and adds a few test cases. Should not introduce any behaviour change.

Questions

Was there actually any merit to ParseNonRFCJSONValue() surrounding the value with brackets and then parsing it as an array? I don’t see it, and the new approach doesn’t fail any tests. Still a bit suspicious about it though.
- Cleared up by #26506#pullrequestreview-1211984059
- If there are no objections to 7727603e44f8f674e0fc8389e78047e2b56e6052, I think we should follow up with a PR to rename ParseNonRFCJSONValue() to a local Parse() helper function (that throws if invalid), remove it from client.h and merge the test coverage we currently have on ParseNonRFCJSONValue() with the coverage we have on UniValue::read().

DrahtBot commented at 6:20 pm on November 30, 2022: contributor

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Type	Reviewers
ACK	ryanofsky, MarcoFalke
Approach ACK	pablomartin4btc

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No conflicts as of last run.

DrahtBot added the label Needs rebase on Dec 13, 2022

in src/rpc/client.cpp:233 in d53953f990 outdated

227@@ -225,11 +228,14 @@ class CRPCConvertTable
228 public:
229     CRPCConvertTable();
230 
231-    bool convert(const std::string& method, int idx) {
232-        return (members.count(std::make_pair(method, idx)) > 0);
233+    /* Return value as UniValue, and first parse it if it is a non-string parameter */
234+    UniValue ParseIfNonString(std::string_view value, const std::string& method, int idx) {
235+        return (members.count(std::make_pair(method, idx))) > 0 ? ParseNonRFCJSONValue(value) : value;

maflcko commented at 12:22 pm on January 18, 2023:

0        return (members.count({method, idx})) > 0 ? ParseNonRFCJSONValue(value) : value;

nit

test: add cases to JSON parsing 1d02e59901

refactor: reduce unnecessary complexity in ParseNonRFCJSONValue

Since https://github.com/jgarzik/univalue/pull/31, UniValue::read() can now
parse raw literals directly, so there is no more need to wrap them into an
array first.

7727603e44

refactor: use string_view for RPC named argument values

Minimize copying RPC named argument values when calling .substr() by
using std::string_view instead of std::string.

545ff924ab

stickies-v force-pushed on Jan 18, 2023

stickies-v renamed this:
~~[WIP] refactor: RPC: pass named argument as string_view~~
refactor: RPC: pass named argument value as string_view
on Jan 18, 2023

stickies-v marked this as ready for review on Jan 18, 2023

stickies-v commented at 5:18 pm on January 18, 2023: contributor

Rebased now that #26506 is merged, ready for review!

Also added to PR description:

If there are no objections to https://github.com/bitcoin/bitcoin/commit/7727603e44f8f674e0fc8389e78047e2b56e6052, I think we should follow up with a PR to rename ParseNonRFCJSONValue() to a local Parse() function, remove it from client.h and merge the test coverage we currently have on ParseNonRFCJSONValue() with the coverage we have on UniValue::read().

DrahtBot removed the label Needs rebase on Jan 18, 2023

DrahtBot added the label Refactoring on Jan 18, 2023

ryanofsky approved

ryanofsky commented at 6:55 pm on March 2, 2023: contributor

Code review ACK 545ff924ab6303ffabd91fdfc4f0a4962daf133c

I think the followup ideas in the PR description sound very good too

pablomartin4btc commented at 7:03 pm on March 2, 2023: member

Approach ACK.

I’ve investigated why (if?) we would need to declare const std::string_view. I see that while std::string_view is already read-only by design, declaring it as const can provide additional benefits in terms of communication, const correctness, and optimization but if we expect large values as @MarcoFalke mentioned on his comment perhaps we need to consider it. This is a very interesting article on reasons to pass std::string_view by value, there are links to godbolt snippets where it compares machine code differences on using one or the other approach.

Is there any benchmark that you think I could run in order to get some stats in terms of gains in performance improvement?

maflcko approved

maflcko commented at 10:36 am on March 3, 2023: member

nice

review ACK 545ff924ab6303ffabd91fdfc4f0a4962daf133c 📻

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fanquake merged this on Mar 3, 2023

fanquake closed this on Mar 3, 2023

fanquake commented at 2:35 pm on March 3, 2023: member

I think the followup ideas in the PR description sound very good too @stickies-v will you follow up here?

stickies-v deleted the branch on Mar 3, 2023

sidhujag referenced this in commit 04dac02b35 on Mar 3, 2023

stickies-v commented at 3:00 pm on March 14, 2023: contributor

@stickies-v will you follow up here?

Done in #27256 (cc @ryanofsky)

fanquake referenced this in commit 436c185b05 on Jun 2, 2023

bitcoin locked this on Mar 13, 2024

refactor: RPC: pass named argument value as string_view #26612

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