json_tok_streq(…) and json_get_member(…) are convenience wrappers for
json_tok_strneq(…) and json_get_membern(…) respectively. Unfortunately, using
them incurs a performance penalty in the common case where they are called with
a string literal argument because the compiler is unable to substitute a
compile-time constant in place of the buried call to strlen(…).
For example,
json_get_member(buf, tok, "example");
…will have worse performance than…
json_get_membern(buf, tok, "example", strlen("example"));
…because the former is forced to scan over "example" at run-time to count its
length whereas the latter is able to elide the strlen(…) call at compile time.
Hoist these convenience functions up into common/json_parse_simple.h and mark
them as inline so that the compiler can elide the strlen(…) call in the common
case of calling these functions with a string literal argument.
Changelog-None
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