libjxl

fields.cc (21029B)

---

 // Copyright (c) the JPEG XL Project Authors. All rights reserved.
 //
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
 #include "lib/jxl/fields.h"
 
 #include <algorithm>
 #include <cinttypes>
 #include <cmath>
 #include <cstddef>
 #include <hwy/base.h>
 
 #include "lib/jxl/base/bits.h"
 #include "lib/jxl/base/printf_macros.h"
 
 namespace jxl {
 
 namespace {
 
 using ::jxl::fields_internal::VisitorBase;
 
 struct InitVisitor : public VisitorBase {
   Status Bits(const size_t /*unused*/, const uint32_t default_value,
               uint32_t* JXL_RESTRICT value) override {
     *value = default_value;
     return true;
   }
 
   Status U32(const U32Enc /*unused*/, const uint32_t default_value,
              uint32_t* JXL_RESTRICT value) override {
     *value = default_value;
     return true;
   }
 
   Status U64(const uint64_t default_value,
              uint64_t* JXL_RESTRICT value) override {
     *value = default_value;
     return true;
   }
 
   Status Bool(bool default_value, bool* JXL_RESTRICT value) override {
     *value = default_value;
     return true;
   }
 
   Status F16(const float default_value, float* JXL_RESTRICT value) override {
     *value = default_value;
     return true;
   }
 
   // Always visit conditional fields to ensure they are initialized.
   Status Conditional(bool /*condition*/) override { return true; }
 
   Status AllDefault(const Fields& /*fields*/,
                     bool* JXL_RESTRICT all_default) override {
     // Just initialize this field and don't skip initializing others.
     JXL_RETURN_IF_ERROR(Bool(true, all_default));
     return false;
   }
 
   Status VisitNested(Fields* /*fields*/) override {
     // Avoid re-initializing nested bundles (their ctors already called
     // Bundle::Init for their fields).
     return true;
   }
 };
 
 // Similar to InitVisitor, but also initializes nested fields.
 struct SetDefaultVisitor : public VisitorBase {
   Status Bits(const size_t /*unused*/, const uint32_t default_value,
               uint32_t* JXL_RESTRICT value) override {
     *value = default_value;
     return true;
   }
 
   Status U32(const U32Enc /*unused*/, const uint32_t default_value,
              uint32_t* JXL_RESTRICT value) override {
     *value = default_value;
     return true;
   }
 
   Status U64(const uint64_t default_value,
              uint64_t* JXL_RESTRICT value) override {
     *value = default_value;
     return true;
   }
 
   Status Bool(bool default_value, bool* JXL_RESTRICT value) override {
     *value = default_value;
     return true;
   }
 
   Status F16(const float default_value, float* JXL_RESTRICT value) override {
     *value = default_value;
     return true;
   }
 
   // Always visit conditional fields to ensure they are initialized.
   Status Conditional(bool /*condition*/) override { return true; }
 
   Status AllDefault(const Fields& /*fields*/,
                     bool* JXL_RESTRICT all_default) override {
     // Just initialize this field and don't skip initializing others.
     JXL_RETURN_IF_ERROR(Bool(true, all_default));
     return false;
   }
 };
 
 class AllDefaultVisitor : public VisitorBase {
  public:
   explicit AllDefaultVisitor() = default;
 
   Status Bits(const size_t bits, const uint32_t default_value,
               uint32_t* JXL_RESTRICT value) override {
     all_default_ &= *value == default_value;
     return true;
   }
 
   Status U32(const U32Enc /*unused*/, const uint32_t default_value,
              uint32_t* JXL_RESTRICT value) override {
     all_default_ &= *value == default_value;
     return true;
   }
 
   Status U64(const uint64_t default_value,
              uint64_t* JXL_RESTRICT value) override {
     all_default_ &= *value == default_value;
     return true;
   }
 
   Status F16(const float default_value, float* JXL_RESTRICT value) override {
     all_default_ &= std::abs(*value - default_value) < 1E-6f;
     return true;
   }
 
   Status AllDefault(const Fields& /*fields*/,
                     bool* JXL_RESTRICT /*all_default*/) override {
     // Visit all fields so we can compute the actual all_default_ value.
     return false;
   }
 
   bool AllDefault() const { return all_default_; }
 
  private:
   bool all_default_ = true;
 };
 
 class ReadVisitor : public VisitorBase {
  public:
   explicit ReadVisitor(BitReader* reader) : reader_(reader) {}
 
   Status Bits(const size_t bits, const uint32_t /*default_value*/,
               uint32_t* JXL_RESTRICT value) override {
     *value = BitsCoder::Read(bits, reader_);
     if (!reader_->AllReadsWithinBounds()) {
       return JXL_STATUS(StatusCode::kNotEnoughBytes,
                         "Not enough bytes for header");
     }
     return true;
   }
 
   Status U32(const U32Enc dist, const uint32_t /*default_value*/,
              uint32_t* JXL_RESTRICT value) override {
     *value = U32Coder::Read(dist, reader_);
     if (!reader_->AllReadsWithinBounds()) {
       return JXL_STATUS(StatusCode::kNotEnoughBytes,
                         "Not enough bytes for header");
     }
     return true;
   }
 
   Status U64(const uint64_t /*default_value*/,
              uint64_t* JXL_RESTRICT value) override {
     *value = U64Coder::Read(reader_);
     if (!reader_->AllReadsWithinBounds()) {
       return JXL_STATUS(StatusCode::kNotEnoughBytes,
                         "Not enough bytes for header");
     }
     return true;
   }
 
   Status F16(const float /*default_value*/,
              float* JXL_RESTRICT value) override {
     ok_ &= F16Coder::Read(reader_, value);
     if (!reader_->AllReadsWithinBounds()) {
       return JXL_STATUS(StatusCode::kNotEnoughBytes,
                         "Not enough bytes for header");
     }
     return true;
   }
 
   void SetDefault(Fields* fields) override { Bundle::SetDefault(fields); }
 
   bool IsReading() const override { return true; }
 
   // This never fails because visitors are expected to keep reading until
   // EndExtensions, see comment there.
   Status BeginExtensions(uint64_t* JXL_RESTRICT extensions) override {
     JXL_QUIET_RETURN_IF_ERROR(VisitorBase::BeginExtensions(extensions));
     if (*extensions == 0) return true;
 
     // For each nonzero bit, i.e. extension that is present:
     for (uint64_t remaining_extensions = *extensions; remaining_extensions != 0;
          remaining_extensions &= remaining_extensions - 1) {
       const size_t idx_extension =
           Num0BitsBelowLS1Bit_Nonzero(remaining_extensions);
       // Read additional U64 (one per extension) indicating the number of bits
       // (allows skipping individual extensions).
       JXL_RETURN_IF_ERROR(U64(0, &extension_bits_[idx_extension]));
       if (!SafeAdd(total_extension_bits_, extension_bits_[idx_extension],
                    total_extension_bits_)) {
         return JXL_FAILURE("Extension bits overflowed, invalid codestream");
       }
     }
     // Used by EndExtensions to skip past any _remaining_ extensions.
     pos_after_ext_size_ = reader_->TotalBitsConsumed();
     JXL_ASSERT(pos_after_ext_size_ != 0);
     return true;
   }
 
   Status EndExtensions() override {
     JXL_QUIET_RETURN_IF_ERROR(VisitorBase::EndExtensions());
     // Happens if extensions == 0: don't read size, done.
     if (pos_after_ext_size_ == 0) return true;
 
     // Not enough bytes as set by BeginExtensions or earlier. Do not return
     // this as a JXL_FAILURE or false (which can also propagate to error
     // through e.g. JXL_RETURN_IF_ERROR), since this may be used while
     // silently checking whether there are enough bytes. If this case must be
     // treated as an error, reader_>Close() will do this, just like is already
     // done for non-extension fields.
     if (!enough_bytes_) return true;
 
     // Skip new fields this (old?) decoder didn't know about, if any.
     const size_t bits_read = reader_->TotalBitsConsumed();
     uint64_t end;
     if (!SafeAdd(pos_after_ext_size_, total_extension_bits_, end)) {
       return JXL_FAILURE("Invalid extension size, caused overflow");
     }
     if (bits_read > end) {
       return JXL_FAILURE("Read more extension bits than budgeted");
     }
     const size_t remaining_bits = end - bits_read;
     if (remaining_bits != 0) {
       JXL_WARNING("Skipping %" PRIuS "-bit extension(s)", remaining_bits);
       reader_->SkipBits(remaining_bits);
       if (!reader_->AllReadsWithinBounds()) {
         return JXL_STATUS(StatusCode::kNotEnoughBytes,
                           "Not enough bytes for header");
       }
     }
     return true;
   }
 
   Status OK() const { return ok_; }
 
  private:
   // Whether any error other than not enough bytes occurred.
   bool ok_ = true;
 
   // Whether there are enough input bytes to read from.
   bool enough_bytes_ = true;
   BitReader* const reader_;
   // May be 0 even if the corresponding extension is present.
   uint64_t extension_bits_[Bundle::kMaxExtensions] = {0};
   uint64_t total_extension_bits_ = 0;
   size_t pos_after_ext_size_ = 0;  // 0 iff extensions == 0.
 
   friend Status jxl::CheckHasEnoughBits(Visitor* /* visitor */,
                                         size_t /* bits */);
 };
 
 class MaxBitsVisitor : public VisitorBase {
  public:
   Status Bits(const size_t bits, const uint32_t /*default_value*/,
               uint32_t* JXL_RESTRICT /*value*/) override {
     max_bits_ += BitsCoder::MaxEncodedBits(bits);
     return true;
   }
 
   Status U32(const U32Enc enc, const uint32_t /*default_value*/,
              uint32_t* JXL_RESTRICT /*value*/) override {
     max_bits_ += U32Coder::MaxEncodedBits(enc);
     return true;
   }
 
   Status U64(const uint64_t /*default_value*/,
              uint64_t* JXL_RESTRICT /*value*/) override {
     max_bits_ += U64Coder::MaxEncodedBits();
     return true;
   }
 
   Status F16(const float /*default_value*/,
              float* JXL_RESTRICT /*value*/) override {
     max_bits_ += F16Coder::MaxEncodedBits();
     return true;
   }
 
   Status AllDefault(const Fields& /*fields*/,
                     bool* JXL_RESTRICT all_default) override {
     JXL_RETURN_IF_ERROR(Bool(true, all_default));
     return false;  // For max bits, assume nothing is default
   }
 
   // Always visit conditional fields to get a (loose) upper bound.
   Status Conditional(bool /*condition*/) override { return true; }
 
   Status BeginExtensions(uint64_t* JXL_RESTRICT /*extensions*/) override {
     // Skip - extensions are not included in "MaxBits" because their length
     // is potentially unbounded.
     return true;
   }
 
   Status EndExtensions() override { return true; }
 
   size_t MaxBits() const { return max_bits_; }
 
  private:
   size_t max_bits_ = 0;
 };
 
 class CanEncodeVisitor : public VisitorBase {
  public:
   explicit CanEncodeVisitor() = default;
 
   Status Bits(const size_t bits, const uint32_t /*default_value*/,
               uint32_t* JXL_RESTRICT value) override {
     size_t encoded_bits = 0;
     ok_ &= BitsCoder::CanEncode(bits, *value, &encoded_bits);
     encoded_bits_ += encoded_bits;
     return true;
   }
 
   Status U32(const U32Enc enc, const uint32_t /*default_value*/,
              uint32_t* JXL_RESTRICT value) override {
     size_t encoded_bits = 0;
     ok_ &= U32Coder::CanEncode(enc, *value, &encoded_bits);
     encoded_bits_ += encoded_bits;
     return true;
   }
 
   Status U64(const uint64_t /*default_value*/,
              uint64_t* JXL_RESTRICT value) override {
     size_t encoded_bits = 0;
     ok_ &= U64Coder::CanEncode(*value, &encoded_bits);
     encoded_bits_ += encoded_bits;
     return true;
   }
 
   Status F16(const float /*default_value*/,
              float* JXL_RESTRICT value) override {
     size_t encoded_bits = 0;
     ok_ &= F16Coder::CanEncode(*value, &encoded_bits);
     encoded_bits_ += encoded_bits;
     return true;
   }
 
   Status AllDefault(const Fields& fields,
                     bool* JXL_RESTRICT all_default) override {
     *all_default = Bundle::AllDefault(fields);
     JXL_RETURN_IF_ERROR(Bool(true, all_default));
     return *all_default;
   }
 
   Status BeginExtensions(uint64_t* JXL_RESTRICT extensions) override {
     JXL_QUIET_RETURN_IF_ERROR(VisitorBase::BeginExtensions(extensions));
     extensions_ = *extensions;
     if (*extensions != 0) {
       JXL_ASSERT(pos_after_ext_ == 0);
       pos_after_ext_ = encoded_bits_;
       JXL_ASSERT(pos_after_ext_ != 0);  // visited "extensions"
     }
     return true;
   }
   // EndExtensions = default.
 
   Status GetSizes(size_t* JXL_RESTRICT extension_bits,
                   size_t* JXL_RESTRICT total_bits) {
     JXL_RETURN_IF_ERROR(ok_);
     *extension_bits = 0;
     *total_bits = encoded_bits_;
     // Only if extension field was nonzero will we encode their sizes.
     if (pos_after_ext_ != 0) {
       JXL_ASSERT(encoded_bits_ >= pos_after_ext_);
       *extension_bits = encoded_bits_ - pos_after_ext_;
       // Also need to encode *extension_bits and bill it to *total_bits.
       size_t encoded_bits = 0;
       ok_ &= U64Coder::CanEncode(*extension_bits, &encoded_bits);
       *total_bits += encoded_bits;
 
       // TODO(janwas): support encoding individual extension sizes. We
       // currently ascribe all bits to the first and send zeros for the
       // others.
       for (size_t i = 1; i < hwy::PopCount(extensions_); ++i) {
         encoded_bits = 0;
         ok_ &= U64Coder::CanEncode(0, &encoded_bits);
         *total_bits += encoded_bits;
       }
     }
     return true;
   }
 
  private:
   bool ok_ = true;
   size_t encoded_bits_ = 0;
   uint64_t extensions_ = 0;
   // Snapshot of encoded_bits_ after visiting the extension field, but NOT
   // including the hidden extension sizes.
   uint64_t pos_after_ext_ = 0;
 };
 }  // namespace
 
 void Bundle::Init(Fields* fields) {
   InitVisitor visitor;
   if (!visitor.Visit(fields)) {
     JXL_UNREACHABLE("Init should never fail");
   }
 }
 void Bundle::SetDefault(Fields* fields) {
   SetDefaultVisitor visitor;
   if (!visitor.Visit(fields)) {
     JXL_UNREACHABLE("SetDefault should never fail");
   }
 }
 bool Bundle::AllDefault(const Fields& fields) {
   AllDefaultVisitor visitor;
   if (!visitor.VisitConst(fields)) {
     JXL_UNREACHABLE("AllDefault should never fail");
   }
   return visitor.AllDefault();
 }
 size_t Bundle::MaxBits(const Fields& fields) {
   MaxBitsVisitor visitor;
 #if JXL_ENABLE_ASSERT
   Status ret =
 #else
   (void)
 #endif  // JXL_ENABLE_ASSERT
       visitor.VisitConst(fields);
   JXL_ASSERT(ret);
   return visitor.MaxBits();
 }
 Status Bundle::CanEncode(const Fields& fields, size_t* extension_bits,
                          size_t* total_bits) {
   CanEncodeVisitor visitor;
   JXL_QUIET_RETURN_IF_ERROR(visitor.VisitConst(fields));
   JXL_QUIET_RETURN_IF_ERROR(visitor.GetSizes(extension_bits, total_bits));
   return true;
 }
 Status Bundle::Read(BitReader* reader, Fields* fields) {
   ReadVisitor visitor(reader);
   JXL_RETURN_IF_ERROR(visitor.Visit(fields));
   return visitor.OK();
 }
 bool Bundle::CanRead(BitReader* reader, Fields* fields) {
   ReadVisitor visitor(reader);
   Status status = visitor.Visit(fields);
   // We are only checking here whether there are enough bytes. We still return
   // true for other errors because it means there are enough bytes to determine
   // there's an error. Use Read() to determine which error it is.
   return status.code() != StatusCode::kNotEnoughBytes;
 }
 
 size_t BitsCoder::MaxEncodedBits(const size_t bits) { return bits; }
 
 Status BitsCoder::CanEncode(const size_t bits, const uint32_t value,
                             size_t* JXL_RESTRICT encoded_bits) {
   *encoded_bits = bits;
   if (value >= (1ULL << bits)) {
     return JXL_FAILURE("Value %u too large for %" PRIu64 " bits", value,
                        static_cast<uint64_t>(bits));
   }
   return true;
 }
 
 uint32_t BitsCoder::Read(const size_t bits, BitReader* JXL_RESTRICT reader) {
   return reader->ReadBits(bits);
 }
 
 size_t U32Coder::MaxEncodedBits(const U32Enc enc) {
   size_t extra_bits = 0;
   for (uint32_t selector = 0; selector < 4; ++selector) {
     const U32Distr d = enc.GetDistr(selector);
     if (d.IsDirect()) {
       continue;
     } else {
       extra_bits = std::max<size_t>(extra_bits, d.ExtraBits());
     }
   }
   return 2 + extra_bits;
 }
 
 Status U32Coder::CanEncode(const U32Enc enc, const uint32_t value,
                            size_t* JXL_RESTRICT encoded_bits) {
   uint32_t selector;
   size_t total_bits;
   const Status ok = ChooseSelector(enc, value, &selector, &total_bits);
   *encoded_bits = ok ? total_bits : 0;
   return ok;
 }
 
 uint32_t U32Coder::Read(const U32Enc enc, BitReader* JXL_RESTRICT reader) {
   const uint32_t selector = reader->ReadFixedBits<2>();
   const U32Distr d = enc.GetDistr(selector);
   if (d.IsDirect()) {
     return d.Direct();
   } else {
     return reader->ReadBits(d.ExtraBits()) + d.Offset();
   }
 }
 
 Status U32Coder::ChooseSelector(const U32Enc enc, const uint32_t value,
                                 uint32_t* JXL_RESTRICT selector,
                                 size_t* JXL_RESTRICT total_bits) {
 #if JXL_ENABLE_ASSERT
   const size_t bits_required = 32 - Num0BitsAboveMS1Bit(value);
 #endif  // JXL_ENABLE_ASSERT
   JXL_ASSERT(bits_required <= 32);
 
   *selector = 0;
   *total_bits = 0;
 
   // It is difficult to verify whether Dist32Byte are sorted, so check all
   // selectors and keep the one with the fewest total_bits.
   *total_bits = 64;  // more than any valid encoding
   for (uint32_t s = 0; s < 4; ++s) {
     const U32Distr d = enc.GetDistr(s);
     if (d.IsDirect()) {
       if (d.Direct() == value) {
         *selector = s;
         *total_bits = 2;
         return true;  // Done, direct is always the best possible.
       }
       continue;
     }
     const size_t extra_bits = d.ExtraBits();
     const uint32_t offset = d.Offset();
     if (value < offset || value >= offset + (1ULL << extra_bits)) continue;
 
     // Better than prior encoding, remember it:
     if (2 + extra_bits < *total_bits) {
       *selector = s;
       *total_bits = 2 + extra_bits;
     }
   }
 
   if (*total_bits == 64) {
     return JXL_FAILURE("No feasible selector for %u", value);
   }
 
   return true;
 }
 
 uint64_t U64Coder::Read(BitReader* JXL_RESTRICT reader) {
   uint64_t selector = reader->ReadFixedBits<2>();
   if (selector == 0) {
     return 0;
   }
   if (selector == 1) {
     return 1 + reader->ReadFixedBits<4>();
   }
   if (selector == 2) {
     return 17 + reader->ReadFixedBits<8>();
   }
 
   // selector 3, varint, groups have first 12, then 8, and last 4 bits.
   uint64_t result = reader->ReadFixedBits<12>();
 
   uint64_t shift = 12;
   while (reader->ReadFixedBits<1>()) {
     if (shift == 60) {
       result |= static_cast<uint64_t>(reader->ReadFixedBits<4>()) << shift;
       break;
     }
     result |= static_cast<uint64_t>(reader->ReadFixedBits<8>()) << shift;
     shift += 8;
   }
 
   return result;
 }
 
 // Can always encode, but useful because it also returns bit size.
 Status U64Coder::CanEncode(uint64_t value, size_t* JXL_RESTRICT encoded_bits) {
   if (value == 0) {
     *encoded_bits = 2;  // 2 selector bits
   } else if (value <= 16) {
     *encoded_bits = 2 + 4;  // 2 selector bits + 4 payload bits
   } else if (value <= 272) {
     *encoded_bits = 2 + 8;  // 2 selector bits + 8 payload bits
   } else {
     *encoded_bits = 2 + 12;  // 2 selector bits + 12 payload bits
     value >>= 12;
     int shift = 12;
     while (value > 0 && shift < 60) {
       *encoded_bits += 1 + 8;  // 1 continuation bit + 8 payload bits
       value >>= 8;
       shift += 8;
     }
     if (value > 0) {
       // This only could happen if shift == N - 4.
       *encoded_bits += 1 + 4;  // 1 continuation bit + 4 payload bits
     } else {
       *encoded_bits += 1;  // 1 stop bit
     }
   }
 
   return true;
 }
 
 Status F16Coder::Read(BitReader* JXL_RESTRICT reader,
                       float* JXL_RESTRICT value) {
   const uint32_t bits16 = reader->ReadFixedBits<16>();
   const uint32_t sign = bits16 >> 15;
   const uint32_t biased_exp = (bits16 >> 10) & 0x1F;
   const uint32_t mantissa = bits16 & 0x3FF;
 
   if (JXL_UNLIKELY(biased_exp == 31)) {
     return JXL_FAILURE("F16 infinity or NaN are not supported");
   }
 
   // Subnormal or zero
   if (JXL_UNLIKELY(biased_exp == 0)) {
     *value = (1.0f / 16384) * (mantissa * (1.0f / 1024));
     if (sign) *value = -*value;
     return true;
   }
 
   // Normalized: convert the representation directly (faster than ldexp/tables).
   const uint32_t biased_exp32 = biased_exp + (127 - 15);
   const uint32_t mantissa32 = mantissa << (23 - 10);
   const uint32_t bits32 = (sign << 31) | (biased_exp32 << 23) | mantissa32;
   memcpy(value, &bits32, sizeof(bits32));
   return true;
 }
 
 Status F16Coder::CanEncode(float value, size_t* JXL_RESTRICT encoded_bits) {
   *encoded_bits = MaxEncodedBits();
   if (std::isnan(value) || std::isinf(value)) {
     return JXL_FAILURE("Should not attempt to store NaN and infinity");
   }
   return std::abs(value) <= 65504.0f;
 }
 
 Status CheckHasEnoughBits(Visitor* visitor, size_t bits) {
   if (!visitor->IsReading()) return false;
   ReadVisitor* rv = static_cast<ReadVisitor*>(visitor);
   size_t have_bits = rv->reader_->TotalBytes() * kBitsPerByte;
   size_t want_bits = bits + rv->reader_->TotalBitsConsumed();
   if (have_bits < want_bits) {
     return JXL_STATUS(StatusCode::kNotEnoughBytes,
                       "Not enough bytes for header");
   }
   return true;
 }
 
 }  // namespace jxl