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| -rw-r--r-- | third_party/jpeg-xl/lib/jxl/fields.h | 377 |
1 files changed, 377 insertions, 0 deletions
diff --git a/third_party/jpeg-xl/lib/jxl/fields.h b/third_party/jpeg-xl/lib/jxl/fields.h new file mode 100644 index 0000000000..10d0b7aa30 --- /dev/null +++ b/third_party/jpeg-xl/lib/jxl/fields.h @@ -0,0 +1,377 @@ +// 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. + +#ifndef LIB_JXL_FIELDS_H_ +#define LIB_JXL_FIELDS_H_ + +// Forward/backward-compatible 'bundles' with auto-serialized 'fields'. + +#include <inttypes.h> +#include <stddef.h> +#include <stdint.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> + +#include <cinttypes> +#include <cmath> // abs +#include <cstdarg> + +#include "lib/jxl/base/bits.h" +#include "lib/jxl/base/compiler_specific.h" +#include "lib/jxl/base/status.h" +#include "lib/jxl/common.h" +#include "lib/jxl/dec_bit_reader.h" +#include "lib/jxl/field_encodings.h" + +namespace jxl { + +struct AuxOut; +struct BitWriter; + +// Integer coders: BitsCoder (raw), U32Coder (table), U64Coder (varint). + +// Reads/writes a given (fixed) number of bits <= 32. +namespace BitsCoder { +size_t MaxEncodedBits(size_t bits); + +Status CanEncode(size_t bits, uint32_t value, + size_t* JXL_RESTRICT encoded_bits); + +uint32_t Read(size_t bits, BitReader* JXL_RESTRICT reader); + +// Returns false if the value is too large to encode. +Status Write(size_t bits, uint32_t value, BitWriter* JXL_RESTRICT writer); +} // namespace BitsCoder + +// Encodes u32 using a lookup table and/or extra bits, governed by a per-field +// encoding `enc` which consists of four distributions `d` chosen via a 2-bit +// selector (least significant = 0). Each d may have two modes: +// - direct: if d.IsDirect(), the value is d.Direct(); +// - offset: the value is derived from d.ExtraBits() extra bits plus d.Offset(); +// This encoding is denser than Exp-Golomb or Gamma codes when both small and +// large values occur. +// +// Examples: +// Direct: U32Enc(Val(8), Val(16), Val(32), Bits(6)), value 32 => 10b. +// Offset: U32Enc(Val(0), BitsOffset(1, 1), BitsOffset(2, 3), BitsOffset(8, 8)) +// defines the following prefix code: +// 00 -> 0 +// 01x -> 1..2 +// 10xx -> 3..7 +// 11xxxxxxxx -> 8..263 +namespace U32Coder { +size_t MaxEncodedBits(U32Enc enc); +Status CanEncode(U32Enc enc, uint32_t value, size_t* JXL_RESTRICT encoded_bits); +uint32_t Read(U32Enc enc, BitReader* JXL_RESTRICT reader); + +// Returns false if the value is too large to encode. +Status Write(U32Enc enc, uint32_t value, BitWriter* JXL_RESTRICT writer); + +// "private" +Status ChooseSelector(U32Enc enc, uint32_t value, + uint32_t* JXL_RESTRICT selector, + size_t* JXL_RESTRICT total_bits); +} // namespace U32Coder + +// Encodes 64-bit unsigned integers with a fixed distribution, taking 2 bits +// to encode 0, 6 bits to encode 1 to 16, 10 bits to encode 17 to 272, 15 bits +// to encode up to 4095, and on the order of log2(value) * 1.125 bits for +// larger values. +namespace U64Coder { +constexpr size_t MaxEncodedBits() { return 2 + 12 + 6 * (8 + 1) + (4 + 1); } + +uint64_t Read(BitReader* JXL_RESTRICT reader); + +// Returns false if the value is too large to encode. +Status Write(uint64_t value, BitWriter* JXL_RESTRICT writer); + +// Can always encode, but useful because it also returns bit size. +Status CanEncode(uint64_t value, size_t* JXL_RESTRICT encoded_bits); +} // namespace U64Coder + +// IEEE 754 half-precision (binary16). Refuses to read/write NaN/Inf. +namespace F16Coder { +constexpr size_t MaxEncodedBits() { return 16; } + +// Returns false if the bit representation is NaN or infinity +Status Read(BitReader* JXL_RESTRICT reader, float* JXL_RESTRICT value); + +// Returns false if the value is too large to encode. +Status Write(float value, BitWriter* JXL_RESTRICT writer); +Status CanEncode(float value, size_t* JXL_RESTRICT encoded_bits); +} // namespace F16Coder + +// A "bundle" is a forward- and backward compatible collection of fields. +// They are used for SizeHeader/FrameHeader/GroupHeader. Bundles can be +// extended by appending(!) fields. Optional fields may be omitted from the +// bitstream by conditionally visiting them. When reading new bitstreams with +// old code, we skip unknown fields at the end of the bundle. This requires +// storing the amount of extra appended bits, and that fields are visited in +// chronological order of being added to the format, because old decoders +// cannot skip some future fields and resume reading old fields. Similarly, +// new readers query bits in an "extensions" field to skip (groups of) fields +// not present in old bitstreams. Note that each bundle must include an +// "extensions" field prior to freezing the format, otherwise it cannot be +// extended. +// +// To ensure interoperability, there will be no opaque fields. +// +// HOWTO: +// - basic usage: define a struct with member variables ("fields") and a +// VisitFields(v) member function that calls v->U32/Bool etc. for each +// field, specifying their default values. The ctor must call +// Bundle::Init(this). +// +// - print a trace of visitors: ensure each bundle has a static Name() member +// function, and change Bundle::Print* to return true. +// +// - optional fields: in VisitFields, add if (v->Conditional(your_condition)) +// { v->Bool(default, &field); }. This prevents reading/writing field +// if !your_condition, which is typically computed from a prior field. +// WARNING: to ensure all fields are initialized, do not add an else branch; +// instead add another if (v->Conditional(!your_condition)). +// +// - repeated fields: for dynamic sizes, use e.g. std::vector and in +// VisitFields, if (v->IsReading()) field.resize(size) before accessing field. +// For static or bounded sizes, use an array or std::array. In all cases, +// simply visit each array element as if it were a normal field. +// +// - nested bundles: add a bundle as a normal field and in VisitFields call +// JXL_RETURN_IF_ERROR(v->VisitNested(&nested)); +// +// - allow future extensions: define a "uint64_t extensions" field and call +// v->BeginExtensions(&extensions) after visiting all non-extension fields, +// and `return v->EndExtensions();` after the last extension field. +// +// - encode an entire bundle in one bit if ALL its fields equal their default +// values: add a "mutable bool all_default" field and as the first visitor: +// if (v->AllDefault(*this, &all_default)) { +// // Overwrite all serialized fields, but not any nonserialized_*. +// v->SetDefault(this); +// return true; +// } +// Note: if extensions are present, AllDefault() == false. + +namespace Bundle { +constexpr size_t kMaxExtensions = 64; // bits in u64 + +// Initializes fields to the default values. It is not recursive to nested +// fields, this function is intended to be called in the constructors so +// each nested field will already Init itself. +void Init(Fields* JXL_RESTRICT fields); + +// Similar to Init, but recursive to nested fields. +void SetDefault(Fields* JXL_RESTRICT fields); + +// Returns whether ALL fields (including `extensions`, if present) are equal +// to their default value. +bool AllDefault(const Fields& fields); + +// Returns max number of bits required to encode a T. +size_t MaxBits(const Fields& fields); + +// Returns whether a header's fields can all be encoded, i.e. they have a +// valid representation. If so, "*total_bits" is the exact number of bits +// required. Called by Write. +Status CanEncode(const Fields& fields, size_t* JXL_RESTRICT extension_bits, + size_t* JXL_RESTRICT total_bits); + +Status Read(BitReader* reader, Fields* JXL_RESTRICT fields); + +// Returns whether enough bits are available to fully read this bundle using +// Read. Also returns true in case of a codestream error (other than not being +// large enough): that means enough bits are available to determine there's an +// error, use Read to get such error status. +// NOTE: this advances the BitReader, a different one pointing back at the +// original bit position in the codestream must be created to use Read after +// this. +bool CanRead(BitReader* reader, Fields* JXL_RESTRICT fields); + +Status Write(const Fields& fields, BitWriter* JXL_RESTRICT writer, size_t layer, + AuxOut* aux_out); +} // namespace Bundle + +// Different subclasses of Visitor are passed to implementations of Fields +// throughout their lifetime. Templates used to be used for this but dynamic +// polymorphism produces more compact executables than template reification did. +class Visitor { + public: + virtual ~Visitor() = default; + virtual Status Visit(Fields* fields) = 0; + + virtual Status Bool(bool default_value, bool* JXL_RESTRICT value) = 0; + virtual Status U32(U32Enc, uint32_t, uint32_t*) = 0; + + // Helper to construct U32Enc from U32Distr. + Status U32(const U32Distr d0, const U32Distr d1, const U32Distr d2, + const U32Distr d3, const uint32_t default_value, + uint32_t* JXL_RESTRICT value) { + return U32(U32Enc(d0, d1, d2, d3), default_value, value); + } + + template <typename EnumT> + Status Enum(const EnumT default_value, EnumT* JXL_RESTRICT value) { + uint32_t u32 = static_cast<uint32_t>(*value); + // 00 -> 0 + // 01 -> 1 + // 10xxxx -> 2..17 + // 11yyyyyy -> 18..81 + JXL_RETURN_IF_ERROR(U32(Val(0), Val(1), BitsOffset(4, 2), BitsOffset(6, 18), + static_cast<uint32_t>(default_value), &u32)); + *value = static_cast<EnumT>(u32); + return EnumValid(*value); + } + + virtual Status Bits(size_t bits, uint32_t default_value, + uint32_t* JXL_RESTRICT value) = 0; + virtual Status U64(uint64_t default_value, uint64_t* JXL_RESTRICT value) = 0; + virtual Status F16(float default_value, float* JXL_RESTRICT value) = 0; + + // Returns whether VisitFields should visit some subsequent fields. + // "condition" is typically from prior fields, e.g. flags. + // Overridden by InitVisitor and MaxBitsVisitor. + virtual Status Conditional(bool condition) { return condition; } + + // Overridden by InitVisitor, AllDefaultVisitor and CanEncodeVisitor. + virtual Status AllDefault(const Fields& /*fields*/, + bool* JXL_RESTRICT all_default) { + JXL_RETURN_IF_ERROR(Bool(true, all_default)); + return *all_default; + } + + virtual void SetDefault(Fields* /*fields*/) { + // Do nothing by default, this is overridden by ReadVisitor. + } + + // Returns the result of visiting a nested Bundle. + // Overridden by InitVisitor. + virtual Status VisitNested(Fields* fields) { return Visit(fields); } + + // Overridden by ReadVisitor. Enables dynamically-sized fields. + virtual bool IsReading() const { return false; } + + virtual Status BeginExtensions(uint64_t* JXL_RESTRICT extensions) = 0; + virtual Status EndExtensions() = 0; +}; + +namespace fields_internal { +// A bundle can be in one of three states concerning extensions: not-begun, +// active, ended. Bundles may be nested, so we need a stack of states. +class ExtensionStates { + public: + void Push() { + // Initial state = not-begun. + begun_ <<= 1; + ended_ <<= 1; + } + + // Clears current state; caller must check IsEnded beforehand. + void Pop() { + begun_ >>= 1; + ended_ >>= 1; + } + + // Returns true if state == active || state == ended. + Status IsBegun() const { return (begun_ & 1) != 0; } + // Returns true if state != not-begun && state != active. + Status IsEnded() const { return (ended_ & 1) != 0; } + + void Begin() { + JXL_ASSERT(!IsBegun()); + JXL_ASSERT(!IsEnded()); + begun_ += 1; + } + + void End() { + JXL_ASSERT(IsBegun()); + JXL_ASSERT(!IsEnded()); + ended_ += 1; + } + + private: + // Current state := least-significant bit of begun_ and ended_. + uint64_t begun_ = 0; + uint64_t ended_ = 0; +}; + +// Visitors generate Init/AllDefault/Read/Write logic for all fields. Each +// bundle's VisitFields member function calls visitor->U32 etc. We do not +// overload operator() because a function name is easier to search for. + +class VisitorBase : public Visitor { + public: + explicit VisitorBase() {} + ~VisitorBase() override { JXL_ASSERT(depth_ == 0); } + + // This is the only call site of Fields::VisitFields. + // Ensures EndExtensions was called. + Status Visit(Fields* fields) override { + depth_ += 1; + JXL_ASSERT(depth_ <= Bundle::kMaxExtensions); + extension_states_.Push(); + + const Status ok = fields->VisitFields(this); + + if (ok) { + // If VisitFields called BeginExtensions, must also call + // EndExtensions. + JXL_ASSERT(!extension_states_.IsBegun() || extension_states_.IsEnded()); + } else { + // Failed, undefined state: don't care whether EndExtensions was + // called. + } + + extension_states_.Pop(); + JXL_ASSERT(depth_ != 0); + depth_ -= 1; + + return ok; + } + + // For visitors accepting a const Visitor, need to const-cast so we can call + // the non-const Visitor::VisitFields. NOTE: C is not modified except the + // `all_default` field by CanEncodeVisitor. + Status VisitConst(const Fields& t) { return Visit(const_cast<Fields*>(&t)); } + + // Derived types (overridden by InitVisitor because it is unsafe to read + // from *value there) + + Status Bool(bool default_value, bool* JXL_RESTRICT value) override { + uint32_t bits = *value ? 1 : 0; + JXL_RETURN_IF_ERROR(Bits(1, static_cast<uint32_t>(default_value), &bits)); + JXL_DASSERT(bits <= 1); + *value = bits == 1; + return true; + } + + // Overridden by ReadVisitor and WriteVisitor. + // Called before any conditional visit based on "extensions". + // Overridden by ReadVisitor, CanEncodeVisitor and WriteVisitor. + Status BeginExtensions(uint64_t* JXL_RESTRICT extensions) override { + JXL_RETURN_IF_ERROR(U64(0, extensions)); + + extension_states_.Begin(); + return true; + } + + // Called after all extension fields (if any). Although non-extension + // fields could be visited afterward, we prefer the convention that + // extension fields are always the last to be visited. Overridden by + // ReadVisitor. + Status EndExtensions() override { + extension_states_.End(); + return true; + } + + private: + size_t depth_ = 0; // to check nesting + ExtensionStates extension_states_; +}; +} // namespace fields_internal + +} // namespace jxl + +#endif // LIB_JXL_FIELDS_H_ |