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Make JSON.generate 1.75x as fast #562

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Make JSON.generate 1.75x as fast #562

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Commits on Dec 27, 2023

  1. Stop prebuilding array_delim 

    The purpose of this change is to exploit `fbuffer_append_char` that is
faster than `fbuffer_append`.

`array_delim` was a buffer that concatenated a single comma with
`array_nl`. However, in the typical use case (`JSON.generate(data)`),
`array_nl` is empty. This means that `array_delim` was a
single-character buffer in many cases.

`fbuffer_append(buffer, array_delim)` used `memcpy` to copy one byte,
which was not so efficient.
Rather, this change uses `fbuffer_append_char(buffer, ',')` and then
`fbuffer_append(buffer, array_nl)` only when `array_nl` is not NULL.

This speeds up `JSON.generate` by about 9% in a benchmark.
    @mame
    mame committed Dec 27, 2023
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  2. Stop prebuilding object_delim 

    This speeds up `JSON.generate` by about 4% in a benchmark
    @mame
    mame committed Dec 27, 2023
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  3. Stop prebuilding object_delim2 

    Also, remove static functions that are no longer used.

This speeds up `JSON.generate` by about 5% in a benchmark.
    @mame
    mame committed Dec 27, 2023
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  4. Apply RB_UNLIKELY for less frequently used options 

    This speeds up `JSON.generate` by about 4% in a benchmark.
    @mame
    mame committed Dec 27, 2023
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  5. Use RB_ENCODING_GET instead of rb_enc_get to improve performance 

    This speeds up `JSON.generate` by about 12% in a benchmark.
    @mame
    mame committed Dec 27, 2023
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  6. Pre-check that escaping is not required for string dump 

    ... instead of `rb_enc_str_asciionly_p`.
If escaping is not needed, we can use `fbuffer_append` directly, which
is much faster.

This speeds up `JSON.generate` by about 16% in a benchmark.
    @mame
    mame committed Dec 27, 2023
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  7. Use efficient object-type dispatching 

    Dispatching based on Ruby's VALUE structure is more efficient than
simply cascaded "if ... else if ..." checks.

This speeds up `JSON.generate` by about 5% in a benchmark.
    @mame
    mame committed Dec 27, 2023
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  8. Directly use generate_json_string for object keys 

    ... instead of `generate_json`.

Since the object key is already confirmed to be a string, using a
generic dispatch function brings an unnecessary overhead.

This speeds up `JSON.generate` by about 3% in a benchmark.
    @mame
    mame committed Dec 27, 2023
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  9. Use RARRAY_AREF instead of rb_ary_entry to improve performance 

    It is safe to use `RARRAY_AREF` here because no Ruby code is executed
between `RARRAY_LEN` and `RARRAY_AREF`.

This speeds up `JSON.generate` by about 4% in a benchmark.
    @mame
    mame committed Dec 27, 2023
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  10. Define dummy RB_UNLIKELY for old ruby versions

    @mame
    mame committed Dec 27, 2023
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