| /* |
| * Copyright 2017 Google Inc. |
| * |
| * Use of this source code is governed by a BSD-style license that can be |
| * found in the LICENSE file. |
| */ |
| |
| #ifndef SkJSONWriter_DEFINED |
| #define SkJSONWriter_DEFINED |
| |
| #include "include/core/SkStream.h" |
| #include "include/core/SkString.h" |
| #include "include/core/SkTypes.h" |
| #include "include/private/base/SkNoncopyable.h" |
| #include "include/private/base/SkTArray.h" |
| #include "src/base/SkUTF.h" |
| |
| #include <cstring> |
| #include <cstdint> |
| #include <string> |
| #include <type_traits> |
| |
| /** |
| * Lightweight class for writing properly structured JSON data. No random-access, everything must |
| * be generated in-order. The resulting JSON is written directly to the SkWStream supplied at |
| * construction time. Output is buffered, so writing to disk (via an SkFILEWStream) is ideal. |
| * |
| * There is a basic state machine to ensure that JSON is structured correctly, and to allow for |
| * (optional) pretty formatting. |
| * |
| * This class adheres to the RFC-4627 usage of JSON (not ECMA-404). In other words, all JSON |
| * created with this class must have a top-level object or array. Free-floating values of other |
| * types are not considered valid. |
| * |
| * Note that all error checking is in the form of asserts - invalid usage in a non-debug build |
| * will simply produce invalid JSON. |
| */ |
| class SkJSONWriter : SkNoncopyable { |
| public: |
| enum class Mode { |
| /** |
| * Output the minimal amount of text. No additional whitespace (including newlines) is |
| * generated. The resulting JSON is suitable for fast parsing and machine consumption. |
| */ |
| kFast, |
| |
| /** |
| * Output human-readable JSON, with indented objects and arrays, and one value per line. |
| * Slightly slower than kFast, and produces data that is somewhat larger. |
| */ |
| kPretty |
| }; |
| |
| /** |
| * Construct a JSON writer that will serialize all the generated JSON to 'stream'. |
| */ |
| SkJSONWriter(SkWStream* stream, Mode mode = Mode::kFast) |
| : fBlock(new char[kBlockSize]) |
| , fWrite(fBlock) |
| , fBlockEnd(fBlock + kBlockSize) |
| , fStream(stream) |
| , fMode(mode) |
| , fState(State::kStart) { |
| fScopeStack.push_back(Scope::kNone); |
| fNewlineStack.push_back(true); |
| } |
| |
| ~SkJSONWriter() { |
| this->flush(); |
| delete[] fBlock; |
| SkASSERT(fScopeStack.size() == 1); |
| SkASSERT(fNewlineStack.size() == 1); |
| } |
| |
| /** |
| * Force all buffered output to be flushed to the underlying stream. |
| */ |
| void flush() { |
| if (fWrite != fBlock) { |
| fStream->write(fBlock, fWrite - fBlock); |
| fWrite = fBlock; |
| } |
| } |
| |
| /** |
| * Append the name (key) portion of an object member. Must be called between beginObject() and |
| * endObject(). If you have both the name and value of an object member, you can simply call |
| * the two argument versions of the other append functions. |
| */ |
| void appendName(const char* name) { |
| if (!name) { |
| return; |
| } |
| SkASSERT(Scope::kObject == this->scope()); |
| SkASSERT(State::kObjectBegin == fState || State::kObjectValue == fState); |
| if (State::kObjectValue == fState) { |
| this->write(",", 1); |
| } |
| this->separator(this->multiline()); |
| this->write("\"", 1); |
| this->write(name, strlen(name)); |
| this->write("\":", 2); |
| fState = State::kObjectName; |
| } |
| |
| /** |
| * Adds a new object. A name must be supplied when called between beginObject() and |
| * endObject(). Calls to beginObject() must be balanced by corresponding calls to endObject(). |
| * By default, objects are written out with one named value per line (when in kPretty mode). |
| * This can be overridden for a particular object by passing false for multiline, this will |
| * keep the entire object on a single line. This can help with readability in some situations. |
| * In kFast mode, this parameter is ignored. |
| */ |
| void beginObject(const char* name = nullptr, bool multiline = true) { |
| this->appendName(name); |
| this->beginValue(true); |
| this->write("{", 1); |
| fScopeStack.push_back(Scope::kObject); |
| fNewlineStack.push_back(multiline); |
| fState = State::kObjectBegin; |
| } |
| |
| /** |
| * Ends an object that was previously started with beginObject(). |
| */ |
| void endObject() { |
| SkASSERT(Scope::kObject == this->scope()); |
| SkASSERT(State::kObjectBegin == fState || State::kObjectValue == fState); |
| bool emptyObject = State::kObjectBegin == fState; |
| bool wasMultiline = this->multiline(); |
| this->popScope(); |
| if (!emptyObject) { |
| this->separator(wasMultiline); |
| } |
| this->write("}", 1); |
| } |
| |
| /** |
| * Adds a new array. A name must be supplied when called between beginObject() and |
| * endObject(). Calls to beginArray() must be balanced by corresponding calls to endArray(). |
| * By default, arrays are written out with one value per line (when in kPretty mode). |
| * This can be overridden for a particular array by passing false for multiline, this will |
| * keep the entire array on a single line. This can help with readability in some situations. |
| * In kFast mode, this parameter is ignored. |
| */ |
| void beginArray(const char* name = nullptr, bool multiline = true) { |
| this->appendName(name); |
| this->beginValue(true); |
| this->write("[", 1); |
| fScopeStack.push_back(Scope::kArray); |
| fNewlineStack.push_back(multiline); |
| fState = State::kArrayBegin; |
| } |
| |
| /** |
| * Ends an array that was previous started with beginArray(). |
| */ |
| void endArray() { |
| SkASSERT(Scope::kArray == this->scope()); |
| SkASSERT(State::kArrayBegin == fState || State::kArrayValue == fState); |
| bool emptyArray = State::kArrayBegin == fState; |
| bool wasMultiline = this->multiline(); |
| this->popScope(); |
| if (!emptyArray) { |
| this->separator(wasMultiline); |
| } |
| this->write("]", 1); |
| } |
| |
| /** |
| * Functions for adding values of various types. The single argument versions add un-named |
| * values, so must be called either |
| * - Between beginArray() and endArray() -or- |
| * - Between beginObject() and endObject(), after calling appendName() |
| */ |
| void appendString(const char* value, size_t size) { |
| this->beginValue(); |
| this->write("\"", 1); |
| if (value) { |
| char const * const end = value + size; |
| while (value < end) { |
| char const * next = value; |
| SkUnichar u = SkUTF::NextUTF8(&next, end); |
| switch (u) { |
| case '"': this->write("\\\"", 2); break; |
| case '\\': this->write("\\\\", 2); break; |
| case '\b': this->write("\\b", 2); break; |
| case '\f': this->write("\\f", 2); break; |
| case '\n': this->write("\\n", 2); break; |
| case '\r': this->write("\\r", 2); break; |
| case '\t': this->write("\\t", 2); break; |
| default: { |
| if (u < 0) { |
| next = value + 1; |
| SkString s("\\u"); |
| s.appendHex((unsigned char)*value, 4); |
| this->write(s.c_str(), s.size()); |
| } else if (u < 0x20) { |
| SkString s("\\u"); |
| s.appendHex(u, 4); |
| this->write(s.c_str(), s.size()); |
| } else { |
| this->write(value, next - value); |
| } |
| } break; |
| } |
| value = next; |
| } |
| } |
| this->write("\"", 1); |
| } |
| void appendString(const SkString& value) { |
| this->appendString(value.c_str(), value.size()); |
| } |
| // Avoid the non-explicit converting constructor from char* |
| template <class T, std::enable_if_t<std::is_same_v<T,std::string>,bool> = false> |
| void appendString(const T& value) { |
| this->appendString(value.data(), value.size()); |
| } |
| template <size_t N> inline void appendNString(char const (&value)[N]) { |
| static_assert(N > 0); |
| this->appendString(value, N-1); |
| } |
| void appendCString(const char* value) { |
| this->appendString(value, value ? strlen(value) : 0); |
| } |
| |
| void appendPointer(const void* value) { this->beginValue(); this->appendf("\"%p\"", value); } |
| void appendBool(bool value) { |
| this->beginValue(); |
| if (value) { |
| this->write("true", 4); |
| } else { |
| this->write("false", 5); |
| } |
| } |
| void appendS32(int32_t value) { this->beginValue(); this->appendf("%d", value); } |
| void appendS64(int64_t value); |
| void appendU32(uint32_t value) { this->beginValue(); this->appendf("%u", value); } |
| void appendU64(uint64_t value); |
| void appendFloat(float value) { this->beginValue(); this->appendf("%g", value); } |
| void appendDouble(double value) { this->beginValue(); this->appendf("%g", value); } |
| void appendFloatDigits(float value, int digits) { |
| this->beginValue(); |
| this->appendf("%.*g", digits, value); |
| } |
| void appendDoubleDigits(double value, int digits) { |
| this->beginValue(); |
| this->appendf("%.*g", digits, value); |
| } |
| void appendHexU32(uint32_t value) { this->beginValue(); this->appendf("\"0x%x\"", value); } |
| void appendHexU64(uint64_t value); |
| |
| void appendString(const char* name, const char* value, size_t size) { |
| this->appendName(name); |
| this->appendString(value, size); |
| } |
| void appendString(const char* name, const SkString& value) { |
| this->appendName(name); |
| this->appendString(value.c_str(), value.size()); |
| } |
| // Avoid the non-explicit converting constructor from char* |
| template <class T, std::enable_if_t<std::is_same_v<T,std::string>,bool> = false> |
| void appendString(const char* name, const T& value) { |
| this->appendName(name); |
| this->appendString(value.data(), value.size()); |
| } |
| template <size_t N> inline void appendNString(const char* name, char const (&value)[N]) { |
| static_assert(N > 0); |
| this->appendName(name); |
| this->appendString(value, N-1); |
| } |
| void appendCString(const char* name, const char* value) { |
| this->appendName(name); |
| this->appendString(value, value ? strlen(value) : 0); |
| } |
| #define DEFINE_NAMED_APPEND(function, type) \ |
| void function(const char* name, type value) { this->appendName(name); this->function(value); } |
| |
| /** |
| * Functions for adding named values of various types. These add a name field, so must be |
| * called between beginObject() and endObject(). |
| */ |
| DEFINE_NAMED_APPEND(appendPointer, const void *) |
| DEFINE_NAMED_APPEND(appendBool, bool) |
| DEFINE_NAMED_APPEND(appendS32, int32_t) |
| DEFINE_NAMED_APPEND(appendS64, int64_t) |
| DEFINE_NAMED_APPEND(appendU32, uint32_t) |
| DEFINE_NAMED_APPEND(appendU64, uint64_t) |
| DEFINE_NAMED_APPEND(appendFloat, float) |
| DEFINE_NAMED_APPEND(appendDouble, double) |
| DEFINE_NAMED_APPEND(appendHexU32, uint32_t) |
| DEFINE_NAMED_APPEND(appendHexU64, uint64_t) |
| |
| #undef DEFINE_NAMED_APPEND |
| |
| void appendFloatDigits(const char* name, float value, int digits) { |
| this->appendName(name); |
| this->appendFloatDigits(value, digits); |
| } |
| void appendDoubleDigits(const char* name, double value, int digits) { |
| this->appendName(name); |
| this->appendDoubleDigits(value, digits); |
| } |
| |
| private: |
| enum { |
| // Using a 32k scratch block gives big performance wins, but we diminishing returns going |
| // any larger. Even with a 1MB block, time to write a large (~300 MB) JSON file only drops |
| // another ~10%. |
| kBlockSize = 32 * 1024, |
| }; |
| |
| enum class Scope { |
| kNone, |
| kObject, |
| kArray |
| }; |
| |
| enum class State { |
| kStart, |
| kEnd, |
| kObjectBegin, |
| kObjectName, |
| kObjectValue, |
| kArrayBegin, |
| kArrayValue, |
| }; |
| |
| void appendf(const char* fmt, ...) SK_PRINTF_LIKE(2, 3); |
| |
| void beginValue(bool structure = false) { |
| SkASSERT(State::kObjectName == fState || |
| State::kArrayBegin == fState || |
| State::kArrayValue == fState || |
| (structure && State::kStart == fState)); |
| if (State::kArrayValue == fState) { |
| this->write(",", 1); |
| } |
| if (Scope::kArray == this->scope()) { |
| this->separator(this->multiline()); |
| } else if (Scope::kObject == this->scope() && Mode::kPretty == fMode) { |
| this->write(" ", 1); |
| } |
| // We haven't added the value yet, but all (non-structure) callers emit something |
| // immediately, so transition state, to simplify the calling code. |
| if (!structure) { |
| fState = Scope::kArray == this->scope() ? State::kArrayValue : State::kObjectValue; |
| } |
| } |
| |
| void separator(bool multiline) { |
| if (Mode::kPretty == fMode) { |
| if (multiline) { |
| this->write("\n", 1); |
| for (int i = 0; i < fScopeStack.size() - 1; ++i) { |
| this->write(" ", 3); |
| } |
| } else { |
| this->write(" ", 1); |
| } |
| } |
| } |
| |
| void write(const char* buf, size_t length) { |
| if (static_cast<size_t>(fBlockEnd - fWrite) < length) { |
| // Don't worry about splitting writes that overflow our block. |
| this->flush(); |
| } |
| if (length > kBlockSize) { |
| // Send particularly large writes straight through to the stream (unbuffered). |
| fStream->write(buf, length); |
| } else { |
| memcpy(fWrite, buf, length); |
| fWrite += length; |
| } |
| } |
| |
| Scope scope() const { |
| SkASSERT(!fScopeStack.empty()); |
| return fScopeStack.back(); |
| } |
| |
| bool multiline() const { |
| SkASSERT(!fNewlineStack.empty()); |
| return fNewlineStack.back(); |
| } |
| |
| void popScope() { |
| fScopeStack.pop_back(); |
| fNewlineStack.pop_back(); |
| switch (this->scope()) { |
| case Scope::kNone: |
| fState = State::kEnd; |
| break; |
| case Scope::kObject: |
| fState = State::kObjectValue; |
| break; |
| case Scope::kArray: |
| fState = State::kArrayValue; |
| break; |
| default: |
| SkDEBUGFAIL("Invalid scope"); |
| break; |
| } |
| } |
| |
| char* fBlock; |
| char* fWrite; |
| char* fBlockEnd; |
| |
| SkWStream* fStream; |
| Mode fMode; |
| State fState; |
| SkSTArray<16, Scope, true> fScopeStack; |
| SkSTArray<16, bool, true> fNewlineStack; |
| }; |
| |
| #endif |