// Copyright 2015 the V8 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 V8_WASM_MODULE_DECODER_H_
#define V8_WASM_MODULE_DECODER_H_

#if !V8_ENABLE_WEBASSEMBLY
#error This header should only be included if WebAssembly is enabled.
#endif  // !V8_ENABLE_WEBASSEMBLY

#include <memory>

#include "src/common/globals.h"
#include "src/logging/metrics.h"
#include "src/wasm/function-body-decoder.h"
#include "src/wasm/wasm-constants.h"
#include "src/wasm/wasm-features.h"
#include "src/wasm/wasm-module.h"
#include "src/wasm/wasm-result.h"

namespace v8 {
namespace internal {

class DelayedCounterUpdates;

namespace wasm {

struct CompilationEnv;

inline bool IsValidSectionCode(uint8_t byte) {
  // Allow everything within [kUnknownSectionCode, kLastKnownModuleSection].
  static_assert(kUnknownSectionCode == 0);
  return byte <= kLastKnownModuleSection;
}

V8_EXPORT_PRIVATE const char* SectionName(SectionCode code);

using ModuleResult = Result<std::shared_ptr<WasmModule>>;

class DecodedNameSection {
 public:
  explicit DecodedNameSection(base::Vector<const uint8_t> wire_bytes,
                              WireBytesRef name_section);

 private:
  friend class NamesProvider;

  IndirectNameMap local_names_;
  IndirectNameMap label_names_;
  NameMap type_names_;
  NameMap table_names_;
  NameMap memory_names_;
  NameMap global_names_;
  NameMap element_segment_names_;
  NameMap data_segment_names_;
  IndirectNameMap field_names_;
  NameMap tag_names_;
};

enum class DecodingMethod {
  kSync,
  kAsync,
  kSyncStream,
  kAsyncStream,
  kDeserialize
};

// Validation strategy:
// Everything except for the code section is validated as part of decoding.
// The code section (aka the function bodies) is validated as early as possible
// for the respective scenario. Code running later can then assume that all
// functions have been validated. As of this writing, the bottlenecks are the
// following:
// - {WasmEngine::SyncCompile} for sync or sync streaming compilation.
// - {AsyncCompileJob::DecodeModule} for async compilation.
// - {WasmCompilationUnit::ExecuteCompilation} (orchestrated by
//   {AsyncStreamingProcessor::ProcessFunctionBody}) for async streaming
//   compilation.
// - {AsyncCompileJob::PrepareNativeModule} for the fallback from streaming
//   to non-streaming compilation after a bad prefix cache hit.

// Decodes the bytes of a wasm module in {wire_bytes} while recording events and
// updating counters in the given isolate.
V8_EXPORT_PRIVATE ModuleResult DecodeWasmModule(
    Isolate*, WasmEnabledFeatures, base::Vector<const uint8_t> wire_bytes,
    bool validate_functions, DecodingMethod decoding_method,
    WasmDetectedFeatures* detected_features);

// Decodes the bytes of a wasm module in {wire_bytes} and returns delayed
// counter updates and the metrics event to the caller.
V8_EXPORT_PRIVATE ModuleResult DecodeWasmModule(
    WasmEnabledFeatures enabled_features,
    base::Vector<const uint8_t> wire_bytes, bool validate_functions,
    DelayedCounterUpdates* delayed_counters,
    std::optional<v8::metrics::WasmModuleDecoded>* metrics_event,
    DecodingMethod decoding_method, WasmDetectedFeatures* detected_features);

// Decodes the bytes of a wasm module in {wire_bytes} without recording events
// or updating counters.
V8_EXPORT_PRIVATE ModuleResult DecodeWasmModule(
    WasmEnabledFeatures enabled_features,
    base::Vector<const uint8_t> wire_bytes, bool validate_functions,
    WasmDetectedFeatures* detected_features);

// Stripped down version for disassembler needs.
V8_EXPORT_PRIVATE ModuleResult DecodeWasmModuleForDisassembler(
    base::Vector<const uint8_t> wire_bytes, ITracer* tracer);

// Exposed for testing. Decodes a single function signature, allocating it
// in the given zone.
V8_EXPORT_PRIVATE
Result<std::pair<WasmModuleSignatureStorage, const FunctionSig*>>
DecodeWasmSignatureForTesting(WasmEnabledFeatures enabled_features,
                              base::Vector<const uint8_t> bytes);

struct CustomSectionOffset {
  WireBytesRef section;
  WireBytesRef name;
  WireBytesRef payload;
};

V8_EXPORT_PRIVATE std::vector<CustomSectionOffset> DecodeCustomSections(
    base::Vector<const uint8_t> wire_bytes);

// Decode the function names from the name section. Returns the result as an
// unordered map. Only names with valid utf8 encoding are stored and conflicts
// are resolved by choosing the last name read.
void DecodeFunctionNames(base::Vector<const uint8_t> wire_bytes,
                         NameMap& names);
// Decode the type names from the type section, store them in the provided
// vector/map indexed by *canonical* index.
// The vector {typenames} must have sufficient size.
// Existing non-empty names won't be overwritten.
// The number of allocated characters will be added to {total_allocated_size}.
void DecodeCanonicalTypeNames(
    base::Vector<const uint8_t> wire_bytes, const WasmModule* module,
    std::vector<base::OwnedVector<char>>& typenames,
    std::map<uint32_t, std::vector<base::OwnedVector<char>>>& fieldnames,
    size_t* total_allocated_size);

// Validate all functions in the module. Return the first validation error
// (deterministically), or an empty {WasmError} if all functions are
// valid.
V8_EXPORT_PRIVATE WasmError
ValidateFunctions(const WasmModule*, WasmEnabledFeatures enabled_features,
                  base::Vector<const uint8_t> wire_bytes,
                  WasmDetectedFeatures* detected_features);

WasmError GetWasmErrorWithName(base::Vector<const uint8_t> wire_bytes,
                               int func_index, const WasmModule* module,
                               WasmError error);

class ModuleDecoderImpl;

class ModuleDecoder {
 public:
  explicit ModuleDecoder(WasmEnabledFeatures enabled_features,
                         WasmDetectedFeatures* detected_features);
  ~ModuleDecoder();

  void DecodeModuleHeader(base::Vector<const uint8_t> bytes);

  void DecodeSection(SectionCode section_code,
                     base::Vector<const uint8_t> bytes, uint32_t offset);

  void StartCodeSection(WireBytesRef section_bytes);

  bool CheckFunctionsCount(uint32_t functions_count, uint32_t error_offset);

  void DecodeFunctionBody(uint32_t index, uint32_t size, uint32_t offset);

  ModuleResult FinishDecoding();

  const std::shared_ptr<WasmModule>& shared_module() const;

  WasmModule* module() const { return shared_module().get(); }

  bool ok() const;

  // Translates the unknown section that decoder is pointing to to an extended
  // SectionCode if the unknown section is known to decoder.
  // The decoder is expected to point after the section length and just before
  // the identifier string of the unknown section.
  // The return value is the number of bytes that were consumed.
  static size_t IdentifyUnknownSection(ModuleDecoder* decoder,
                                       base::Vector<const uint8_t> bytes,
                                       uint32_t offset, SectionCode* result);

 private:
  std::unique_ptr<ModuleDecoderImpl> impl_;
};

}  // namespace wasm
}  // namespace internal
}  // namespace v8

#endif  // V8_WASM_MODULE_DECODER_H_