tor-browser

fields.cc (20931B)

---

// 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>  // PRIu64
#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_ENSURE(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_ENSURE(pos_after_ext_ == 0);
     pos_after_ext_ = encoded_bits_;
     JXL_ENSURE(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_ENSURE(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_DEBUG_ABORT("Init should never fail");
 }
}
void Bundle::SetDefault(Fields* fields) {
 SetDefaultVisitor visitor;
 if (!visitor.Visit(fields)) {
   JXL_DEBUG_ABORT("SetDefault should never fail");
 }
}
bool Bundle::AllDefault(const Fields& fields) {
 AllDefaultVisitor visitor;
 if (!visitor.VisitConst(fields)) {
   JXL_DEBUG_ABORT("AllDefault should never fail");
 }
 return visitor.AllDefault();
}
size_t Bundle::MaxBits(const Fields& fields) {
 MaxBitsVisitor visitor;
 Status ret = visitor.VisitConst(fields);
 (void)ret;
 JXL_DASSERT(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) {
 const size_t bits_required = 32 - Num0BitsAboveMS1Bit(value);
 JXL_ENSURE(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