dom_parser_implementation.cpp

#include "arm64/begin_implementation.h"
#include "arm64/dom_parser_implementation.h"
#include "generic/stage2/jsoncharutils.h"

//
// Stage 1
//
namespace {
namespace SIMDJSON_IMPLEMENTATION {

using namespace simd;

struct json_character_block {
  static really_inline json_character_block classify(const simd::simd8x64<uint8_t>& in);

  really_inline uint64_t whitespace() const { return _whitespace; }
  really_inline uint64_t op() const { return _op; }
  really_inline uint64_t scalar() { return ~(op() | whitespace()); }

  uint64_t _whitespace;
  uint64_t _op;
};

really_inline json_character_block json_character_block::classify(const simd::simd8x64<uint8_t>& in) {
  // Functional programming causes trouble with Visual Studio.
  // Keeping this version in comments since it is much nicer:
  // auto v = in.map<uint8_t>([&](simd8<uint8_t> chunk) {
  //  auto nib_lo = chunk & 0xf;
  //  auto nib_hi = chunk.shr<4>();
  //  auto shuf_lo = nib_lo.lookup_16<uint8_t>(16, 0, 0, 0, 0, 0, 0, 0, 0, 8, 12, 1, 2, 9, 0, 0);
  //  auto shuf_hi = nib_hi.lookup_16<uint8_t>(8, 0, 18, 4, 0, 1, 0, 1, 0, 0, 0, 3, 2, 1, 0, 0);
  //  return shuf_lo & shuf_hi;
  // });
  const simd8<uint8_t> table1(16, 0, 0, 0, 0, 0, 0, 0, 0, 8, 12, 1, 2, 9, 0, 0);
  const simd8<uint8_t> table2(8, 0, 18, 4, 0, 1, 0, 1, 0, 0, 0, 3, 2, 1, 0, 0);

  simd8x64<uint8_t> v(
     (in.chunks[0] & 0xf).lookup_16(table1) & (in.chunks[0].shr<4>()).lookup_16(table2),
     (in.chunks[1] & 0xf).lookup_16(table1) & (in.chunks[1].shr<4>()).lookup_16(table2),
     (in.chunks[2] & 0xf).lookup_16(table1) & (in.chunks[2].shr<4>()).lookup_16(table2),
     (in.chunks[3] & 0xf).lookup_16(table1) & (in.chunks[3].shr<4>()).lookup_16(table2)
  );


  // We compute whitespace and op separately. If the code later only use one or the
  // other, given the fact that all functions are aggressively inlined, we can
  // hope that useless computations will be omitted. This is namely case when
  // minifying (we only need whitespace). *However* if we only need spaces,
  // it is likely that we will still compute 'v' above with two lookup_16: one
  // could do it a bit cheaper. This is in contrast with the x64 implementations
  // where we can, efficiently, do the white space and structural matching
  // separately. One reason for this difference is that on ARM NEON, the table
  // lookups either zero or leave unchanged the characters exceeding 0xF whereas
  // on x64, the equivalent instruction (pshufb) automatically applies a mask,
  // ignoring the 4 most significant bits. Thus the x64 implementation is
  // optimized differently. This being said, if you use this code strictly
  // just for minification (or just to identify the structural characters),
  // there is a small untaken optimization opportunity here. We deliberately
  // do not pick it up.

  uint64_t op = simd8x64<bool>(
        v.chunks[0].any_bits_set(0x7),
        v.chunks[1].any_bits_set(0x7),
        v.chunks[2].any_bits_set(0x7),
        v.chunks[3].any_bits_set(0x7)
  ).to_bitmask();

  uint64_t whitespace = simd8x64<bool>(
        v.chunks[0].any_bits_set(0x18),
        v.chunks[1].any_bits_set(0x18),
        v.chunks[2].any_bits_set(0x18),
        v.chunks[3].any_bits_set(0x18)
  ).to_bitmask();

  return { whitespace, op };
}

really_inline bool is_ascii(const simd8x64<uint8_t>& input) {
    simd8<uint8_t> bits = input.reduce_or();
    return bits.max() < 0b10000000u;
}

UNUSED really_inline simd8<bool> must_be_continuation(const simd8<uint8_t> prev1, const simd8<uint8_t> prev2, const simd8<uint8_t> prev3) {
    simd8<bool> is_second_byte = prev1 >= uint8_t(0b11000000u);
    simd8<bool> is_third_byte  = prev2 >= uint8_t(0b11100000u);
    simd8<bool> is_fourth_byte = prev3 >= uint8_t(0b11110000u);
    // Use ^ instead of | for is_*_byte, because ^ is commutative, and the caller is using ^ as well.
    // This will work fine because we only have to report errors for cases with 0-1 lead bytes.
    // Multiple lead bytes implies 2 overlapping multibyte characters, and if that happens, there is
    // guaranteed to be at least *one* lead byte that is part of only 1 other multibyte character.
    // The error will be detected there.
    return is_second_byte ^ is_third_byte ^ is_fourth_byte;
}

really_inline simd8<bool> must_be_2_3_continuation(const simd8<uint8_t> prev2, const simd8<uint8_t> prev3) {
    simd8<bool> is_third_byte  = prev2 >= uint8_t(0b11100000u);
    simd8<bool> is_fourth_byte = prev3 >= uint8_t(0b11110000u);
    return is_third_byte ^ is_fourth_byte;
}

} // namespace SIMDJSON_IMPLEMENTATION
} // unnamed namespace

#include "generic/stage1/utf8_lookup4_algorithm.h"
#include "generic/stage1/json_structural_indexer.h"
#include "generic/stage1/utf8_validator.h"

//
// Stage 2
//

#include "arm64/stringparsing.h"
#include "arm64/numberparsing.h"
#include "generic/stage2/structural_parser.h"
#include "generic/stage2/tape_builder.h"

//
// Implementation-specific overrides
//
namespace {
namespace SIMDJSON_IMPLEMENTATION {
namespace stage1 {

really_inline uint64_t json_string_scanner::find_escaped(uint64_t backslash) {
  // On ARM, we don't short-circuit this if there are no backslashes, because the branch gives us no
  // benefit and therefore makes things worse.
  // if (!backslash) { uint64_t escaped = prev_escaped; prev_escaped = 0; return escaped; }
  return find_escaped_branchless(backslash);
}

} // namespace stage1

WARN_UNUSED error_code implementation::minify(const uint8_t *buf, size_t len, uint8_t *dst, size_t &dst_len) const noexcept {
  return arm64::stage1::json_minifier::minify<64>(buf, len, dst, dst_len);
}

WARN_UNUSED error_code dom_parser_implementation::stage1(const uint8_t *_buf, size_t _len, bool streaming) noexcept {
  this->buf = _buf;
  this->len = _len;
  return arm64::stage1::json_structural_indexer::index<64>(buf, len, *this, streaming);
}

WARN_UNUSED bool implementation::validate_utf8(const char *buf, size_t len) const noexcept {
  return arm64::stage1::generic_validate_utf8(buf,len);
}

WARN_UNUSED error_code dom_parser_implementation::stage2(dom::document &_doc) noexcept {
  doc = &_doc;
  stage2::tape_builder builder(*doc);
  return stage2::structural_parser::parse<false>(*this, builder);
}

WARN_UNUSED error_code dom_parser_implementation::stage2_next(dom::document &_doc) noexcept {
  doc = &_doc;
  stage2::tape_builder builder(_doc);
  return stage2::structural_parser::parse<true>(*this, builder);
}

WARN_UNUSED error_code dom_parser_implementation::parse(const uint8_t *_buf, size_t _len, dom::document &_doc) noexcept {
  auto error = stage1(_buf, _len, false);
  if (error) { return error; }
  return stage2(_doc);
}

} // namespace SIMDJSON_IMPLEMENTATION
} // unnamed namespace

#include "arm64/end_implementation.h"