зеркало из https://github.com/mozilla/moz-skia.git
503 строки
12 KiB
C++
503 строки
12 KiB
C++
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/*
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* Copyright 2011 Google Inc.
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*
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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*/
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#include "Forth.h"
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#include "ForthParser.h"
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#include "SkTDArray.h"
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#include "SkString.h"
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#include "SkTDStack.h"
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ForthEngine::ForthEngine(ForthOutput* output) : fOutput(output) {
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size_t size = 32 * sizeof(intptr_t);
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fStackBase = reinterpret_cast<intptr_t*>(sk_malloc_throw(size));
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fStackStop = fStackBase + size/sizeof(intptr_t);
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fStackCurr = fStackStop;
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}
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ForthEngine::~ForthEngine() {
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sk_free(fStackBase);
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}
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void ForthEngine::sendOutput(const char text[]) {
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if (fOutput) {
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fOutput->show(text);
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} else {
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SkDebugf("%s", text);
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}
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}
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void ForthEngine::push(intptr_t value) {
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if (fStackCurr > fStackBase) {
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SkASSERT(fStackCurr <= fStackStop && fStackCurr > fStackBase);
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*--fStackCurr = value;
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} else {
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this->signal_error("overflow");
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}
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}
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intptr_t ForthEngine::peek(size_t index) const {
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SkASSERT(fStackCurr < fStackStop && fStackCurr >= fStackBase);
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if (fStackCurr + index < fStackStop) {
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return fStackCurr[index];
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} else {
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this->signal_error("peek out of range");
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return 0x80000001;
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}
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}
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void ForthEngine::setTop(intptr_t value) {
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if (fStackCurr < fStackStop) {
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SkASSERT(fStackCurr < fStackStop && fStackCurr >= fStackBase);
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*fStackCurr = value;
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} else {
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this->signal_error("underflow");
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}
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}
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intptr_t ForthEngine::pop() {
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if (fStackCurr < fStackStop) {
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SkASSERT(fStackCurr < fStackStop && fStackCurr >= fStackBase);
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return *fStackCurr++;
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} else {
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this->signal_error("underflow");
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return 0x80000001;
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}
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}
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///////////////////////////////////////////////////////////////////////////////
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void ForthWord::call(ForthCallBlock* block) {
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ForthEngine engine(NULL);
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// setup the initial stack with the callers input data
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if (block) {
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// walk the array backwards, so that the top of the stack is data[0]
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for (size_t i = 0; i < block->in_count; i++) {
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engine.push(block->in_data[i]);
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}
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}
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// now invoke the word
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this->exec(&engine);
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// now copy back the stack into the caller's output data
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if (block) {
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size_t n = engine.depth();
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block->out_depth = n;
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if (n > block->out_count) {
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n = block->out_count;
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}
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for (size_t i = 0; i < n; i++) {
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block->out_data[i] = engine.peek(i);
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}
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}
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}
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///////////////////////////////////////////////////////////////////////////////
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/*
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reading an initial 32bit value from the code stream:
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xxxxxxxx xxxxxxxx xxxxxxxx xxxxxx00
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Those last two bits are always 0 for a word, so we set those bits for other
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opcodes
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00 -- execute this word
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01 -- push (value & ~3) on the data stack
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10 -- push value >> 2 on the data stack (sign extended)
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11 -- switch (value >>> 2) for Code
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*/
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class FCode {
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public:
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enum {
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kCodeShift = 2,
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kCodeMask = 7,
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kCodeDataShift = 5
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};
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static unsigned GetCode(intptr_t c) {
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return ((uint32_t)c >> kCodeShift) & kCodeMask;
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}
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static unsigned GetCodeData(intptr_t c) {
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return (uint32_t)c >> kCodeDataShift;
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}
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enum Bits {
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kWord_Bits = 0, // must be zero for function address
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kDataClear2_Bits = 1,
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kDataShift2_Bits = 2,
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kCodeShift2_Bits = 3
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};
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enum Code {
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kPushInt_Code, // for data that needs more than 30 bits
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kIF_Code,
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kELSE_Code,
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kDone_Code
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};
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static unsigned MakeCode(Code code) {
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return (code << kCodeShift) | kCodeShift2_Bits;
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}
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void appendInt(int32_t);
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void appendWord(ForthWord*);
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void appendIF();
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bool appendELSE();
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bool appendTHEN();
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void done();
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intptr_t* detach() {
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this->done();
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return fData.detach();
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}
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intptr_t* begin() {
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this->done();
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return fData.begin();
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}
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static void Exec(const intptr_t*, ForthEngine*);
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private:
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SkTDArray<intptr_t> fData;
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SkTDStack<size_t> fIfStack;
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};
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void FCode::appendInt(int32_t value) {
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if ((value & 3) == 0) {
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*fData.append() = value | kDataClear2_Bits;
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} else if ((value << 2 >> 2) == value) {
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*fData.append() = (value << 2) | kDataShift2_Bits;
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} else {
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intptr_t* p = fData.append(2);
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*p++ = (kPushInt_Code << 2) | kCodeShift2_Bits;
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*p++ = value;
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}
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}
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void FCode::appendWord(ForthWord* word) {
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SkASSERT((reinterpret_cast<intptr_t>(word) & 3) == 0);
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*fData.append() = reinterpret_cast<intptr_t>(word);
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}
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void FCode::appendIF() {
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size_t ifIndex = fData.count();
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fIfStack.push(ifIndex);
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*fData.append() = MakeCode(kIF_Code);
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}
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bool FCode::appendELSE() {
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if (fIfStack.empty()) {
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return false;
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}
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size_t elseIndex = fData.count();
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*fData.append() = MakeCode(kELSE_Code);
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size_t ifIndex = fIfStack.top();
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// record the offset in the data part of the if-code
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fData[ifIndex] |= (elseIndex - ifIndex) << kCodeDataShift;
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// now reuse this IfStack entry to track the else
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fIfStack.top() = elseIndex;
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return true;
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}
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bool FCode::appendTHEN() {
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if (fIfStack.empty()) {
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return false;
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}
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// this is either an IF or an ELSE
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size_t index = fIfStack.top();
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// record the offset in the data part of the code
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fData[index] |= (fData.count() - index - 1) << kCodeDataShift;
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fIfStack.pop();
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return true;
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}
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void FCode::done() {
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*fData.append() = (kDone_Code << 2) | kCodeShift2_Bits;
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}
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void FCode::Exec(const intptr_t* curr, ForthEngine* engine) {
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for (;;) {
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intptr_t c = *curr++;
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switch (c & 3) {
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case kWord_Bits:
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reinterpret_cast<ForthWord*>(c)->exec(engine);
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break;
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case kDataClear2_Bits:
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engine->push(c & ~3);
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break;
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case kDataShift2_Bits:
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engine->push(c >> 2);
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break;
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case kCodeShift2_Bits:
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switch (GetCode(c)) {
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case kPushInt_Code:
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engine->push(*curr++);
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break;
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case kIF_Code:
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if (!engine->pop()) {
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// takes us past the ELSE or THEN
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curr += GetCodeData(c);
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}
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break;
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case kELSE_Code:
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// takes us past the THEN
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curr += GetCodeData(c);
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break;
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case kDone_Code:
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return;
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}
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break;
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}
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}
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}
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///////////////////////////////////////////////////////////////////////////////
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class CustomWord : public ForthWord {
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public:
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// we assume ownership of code[]
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CustomWord(intptr_t code[]) : fCode(code) {}
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virtual ~CustomWord() { sk_free(fCode); }
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virtual void exec(ForthEngine* engine) {
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FCode::Exec(fCode, engine);
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}
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private:
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intptr_t* fCode;
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};
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///////////////////////////////////////////////////////////////////////////////
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ForthParser::ForthParser() : fDict(4096) {
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this->addStdWords();
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}
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ForthParser::~ForthParser() {
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SkTDict<ForthWord*>::Iter iter(fDict);
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ForthWord* word;
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while (iter.next(&word)) {
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delete word;
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}
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}
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static const char* parse_error(const char msg[]) {
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SkDebugf("-- parser error: %s\n", msg);
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return NULL;
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}
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/** returns true if c is whitespace, including null
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*/
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static bool is_ws(int c) {
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return c <= ' ';
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}
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static const char* parse_token(const char** text, size_t* len) {
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const char* s = *text;
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while (is_ws(*s)) {
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if (0 == *s) {
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return NULL;
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}
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s++;
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}
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const char* token = s++;
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while (!is_ws(*s)) {
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s++;
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}
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*text = s;
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*len = s - token;
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return token;
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}
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static bool is_digit(int c) { return (unsigned)(c - '0') <= 9; }
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static int hex_val(int c) {
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if (is_digit(c)) {
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return c - '0';
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} else {
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if (c <= 'Z') {
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return 10 + c - 'A';
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} else {
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return 10 + c - 'a';
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}
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}
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}
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static bool parse_num(const char str[], size_t len, int32_t* numBits) {
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if (1 == len && !is_digit(*str)) {
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return false;
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}
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const char* start = str;
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int32_t num = 0;
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bool neg = false;
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if (*str == '-') {
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neg = true;
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str += 1;
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} else if (*str == '#') {
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str++;
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while (str - start < len) {
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num = num*16 + hex_val(*str);
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str += 1;
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}
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*numBits = num;
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return true;
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}
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while (is_digit(*str)) {
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num = 10*num + *str - '0';
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str += 1;
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}
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SkASSERT(str - start <= len);
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if (str - start == len) {
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if (neg) {
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num = -num;
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}
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*numBits = num;
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return true;
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}
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// if we're not done with the token then the next char must be a decimal
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if (*str != '.') {
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return false;
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}
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str += 1;
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float x = num;
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float denom = 1;
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while (str - start < len && is_digit(*str)) {
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x = 10*x + *str - '0';
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denom *= 10;
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str += 1;
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}
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x /= denom;
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if (str - start == len) {
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if (neg) {
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x = -x;
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}
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*numBits = f2i_bits(x);
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return true;
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}
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return false;
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}
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static const char* parse_comment(const char text[]) {
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SkASSERT(*text == '(');
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while (')' != *++text) {
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if (0 == *text) {
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return NULL;
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}
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}
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return text + 1; // skip past the closing ')'
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}
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const char* ForthParser::parse(const char text[], FCode* code) {
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for (;;) {
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size_t len;
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const char* token = parse_token(&text, &len);
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if (NULL == token) {
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break;
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}
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if (1 == len) {
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if ('(' == *token) {
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text = parse_comment(token);
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if (NULL == text) {
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return NULL;
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}
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continue;
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}
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if (';' == *token) {
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break;
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}
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if (':' == *token) {
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token = parse_token(&text, &len);
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if (NULL == token) {
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return parse_error("missing name after ':'");
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}
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FCode subCode;
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text = this->parse(text, &subCode);
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if (NULL == text) {
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return NULL;
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}
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this->add(token, len, new CustomWord(subCode.detach()));
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continue;
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}
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}
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int32_t num;
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if (parse_num(token, len, &num)) {
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// note that num is just the bit representation of the float
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code->appendInt(num);
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} else if (2 == len && memcmp(token, "IF", 2) == 0) {
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code->appendIF();
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} else if (4 == len && memcmp(token, "ELSE", 4) == 0) {
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if (!code->appendELSE()) {
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return parse_error("ELSE with no matching IF");
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}
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} else if (4 == len && memcmp(token, "THEN", 4) == 0) {
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if (!code->appendTHEN()) {
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return parse_error("THEN with no matching IF");
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}
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} else{
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ForthWord* word = this->find(token, len);
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if (NULL == word) {
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SkString str(token, len);
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str.prepend("unknown word ");
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return parse_error(str.c_str());
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}
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code->appendWord(word);
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}
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}
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return text;
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}
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///////////////////////////////////////////////////////////////////////////////
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class ForthEnv::Impl {
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public:
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ForthParser fParser;
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FCode fBuilder;
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};
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ForthEnv::ForthEnv() {
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fImpl = new Impl;
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}
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ForthEnv::~ForthEnv() {
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delete fImpl;
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}
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void ForthEnv::addWord(const char name[], ForthWord* word) {
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fImpl->fParser.addWord(name, word);
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}
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void ForthEnv::parse(const char text[]) {
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fImpl->fParser.parse(text, &fImpl->fBuilder);
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}
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ForthWord* ForthEnv::findWord(const char name[]) {
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return fImpl->fParser.find(name, strlen(name));
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}
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void ForthEnv::run(ForthOutput* output) {
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ForthEngine engine(output);
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FCode::Exec(fImpl->fBuilder.begin(), &engine);
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}
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#if 0
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void ForthEnv::run(const char text[], ForthOutput* output) {
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FCode builder;
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if (fImpl->fParser.parse(text, &builder)) {
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ForthEngine engine(output);
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FCode::Exec(builder.begin(), &engine);
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}
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}
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#endif
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