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LiveEdit: Optimize compare by stripping common suffix and prefix.

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Review URL: http://codereview.chromium.org/7087031

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8128 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This commit is contained in:
peter.rybin@gmail.com 2011-05-31 20:58:21 +00:00
parent ab00b00a87
commit 8f2274c841
3 changed files with 116 additions and 20 deletions
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124
src/liveedit.cc
View File

@ -66,7 +66,7 @@ void SetElementNonStrict(Handle<JSObject> object,
class Differencer {
public:
explicit Differencer(Comparator::Input* input)
: input_(input), len1_(input->getLength1()), len2_(input->getLength2()) {
: input_(input), len1_(input->GetLength1()), len2_(input->GetLength2()) {
buffer_ = NewArray<int>(len1_ * len2_);
}
~Differencer() {
@ -151,7 +151,7 @@ class Differencer {
if (cached_res == kEmptyCellValue) {
Direction dir;
int res;
if (input_->equals(pos1, pos2)) {
if (input_->Equals(pos1, pos2)) {
res = CompareUpToTail(pos1 + 1, pos2 + 1);
dir = EQ;
} else {
@ -279,6 +279,70 @@ static bool CompareSubstrings(Handle<String> s1, int pos1,
}
// Additional to Input interface. Lets switch Input range to subrange.
// More elegant way would be to wrap one Input as another Input object
// and translate positions there, but that would cost us additional virtual
// call per comparison.
class SubrangableInput : public Comparator::Input {
public:
virtual void SetSubrange1(int offset, int len) = 0;
virtual void SetSubrange2(int offset, int len) = 0;
};
class SubrangableOutput : public Comparator::Output {
public:
virtual void SetSubrange1(int offset, int len) = 0;
virtual void SetSubrange2(int offset, int len) = 0;
};
static int min(int a, int b) {
return a < b ? a : b;
}
// Finds common prefix and suffix in input. This parts shouldn't take space in
// linear programming table. Enable subranging in input and output.
static void NarrowDownInput(SubrangableInput* input,
SubrangableOutput* output) {
const int len1 = input->GetLength1();
const int len2 = input->GetLength2();
int common_prefix_len;
int common_suffix_len;
{
common_prefix_len = 0;
int prefix_limit = min(len1, len2);
while (common_prefix_len < prefix_limit &&
input->Equals(common_prefix_len, common_prefix_len)) {
common_prefix_len++;
}
common_suffix_len = 0;
int suffix_limit = min(len1 - common_prefix_len, len2 - common_prefix_len);
while (common_suffix_len < suffix_limit &&
input->Equals(len1 - common_suffix_len - 1,
len2 - common_suffix_len - 1)) {
common_suffix_len++;
}
}
if (common_prefix_len > 0 || common_suffix_len > 0) {
int new_len1 = len1 - common_suffix_len - common_prefix_len;
int new_len2 = len2 - common_suffix_len - common_prefix_len;
input->SetSubrange1(common_prefix_len, new_len1);
input->SetSubrange2(common_prefix_len, new_len2);
output->SetSubrange1(common_prefix_len, new_len1);
output->SetSubrange2(common_prefix_len, new_len2);
}
}
// A helper class that writes chunk numbers into JSArray.
// Each chunk is stored as 3 array elements: (pos1_begin, pos1_end, pos2_end).
class CompareOutputArrayWriter {
@ -319,13 +383,13 @@ class TokensCompareInput : public Comparator::Input {
: s1_(s1), offset1_(offset1), len1_(len1),
s2_(s2), offset2_(offset2), len2_(len2) {
}
virtual int getLength1() {
virtual int GetLength1() {
return len1_;
}
virtual int getLength2() {
virtual int GetLength2() {
return len2_;
}
bool equals(int index1, int index2) {
bool Equals(int index1, int index2) {
return s1_->Get(offset1_ + index1) == s2_->Get(offset2_ + index2);
}
@ -401,20 +465,26 @@ class LineEndsWrapper {
// Represents 2 strings as 2 arrays of lines.
class LineArrayCompareInput : public Comparator::Input {
class LineArrayCompareInput : public SubrangableInput {
public:
LineArrayCompareInput(Handle<String> s1, Handle<String> s2,
LineEndsWrapper line_ends1, LineEndsWrapper line_ends2)
: s1_(s1), s2_(s2), line_ends1_(line_ends1),
line_ends2_(line_ends2) {
line_ends2_(line_ends2),
subrange_offset1_(0), subrange_offset2_(0),
subrange_len1_(line_ends1_.length()),
subrange_len2_(line_ends2_.length()) {
}
int getLength1() {
return line_ends1_.length();
int GetLength1() {
return subrange_len1_;
}
int getLength2() {
return line_ends2_.length();
int GetLength2() {
return subrange_len2_;
}
bool equals(int index1, int index2) {
bool Equals(int index1, int index2) {
index1 += subrange_offset1_;
index2 += subrange_offset2_;
int line_start1 = line_ends1_.GetLineStart(index1);
int line_start2 = line_ends2_.GetLineStart(index2);
int line_end1 = line_ends1_.GetLineEnd(index1);
@ -427,26 +497,42 @@ class LineArrayCompareInput : public Comparator::Input {
return CompareSubstrings(s1_, line_start1, s2_, line_start2,
len1);
}
void SetSubrange1(int offset, int len) {
subrange_offset1_ = offset;
subrange_len1_ = len;
}
void SetSubrange2(int offset, int len) {
subrange_offset2_ = offset;
subrange_len2_ = len;
}
private:
Handle<String> s1_;
Handle<String> s2_;
LineEndsWrapper line_ends1_;
LineEndsWrapper line_ends2_;
int subrange_offset1_;
int subrange_offset2_;
int subrange_len1_;
int subrange_len2_;
};
// Stores compare result in JSArray. For each chunk tries to conduct
// a fine-grained nested diff token-wise.
class TokenizingLineArrayCompareOutput : public Comparator::Output {
class TokenizingLineArrayCompareOutput : public SubrangableOutput {
public:
TokenizingLineArrayCompareOutput(LineEndsWrapper line_ends1,
LineEndsWrapper line_ends2,
Handle<String> s1, Handle<String> s2)
: line_ends1_(line_ends1), line_ends2_(line_ends2), s1_(s1), s2_(s2) {
: line_ends1_(line_ends1), line_ends2_(line_ends2), s1_(s1), s2_(s2),
subrange_offset1_(0), subrange_offset2_(0) {
}
void AddChunk(int line_pos1, int line_pos2, int line_len1, int line_len2) {
line_pos1 += subrange_offset1_;
line_pos2 += subrange_offset2_;
int char_pos1 = line_ends1_.GetLineStart(line_pos1);
int char_pos2 = line_ends2_.GetLineStart(line_pos2);
int char_len1 = line_ends1_.GetLineStart(line_pos1 + line_len1) - char_pos1;
@ -466,6 +552,12 @@ class TokenizingLineArrayCompareOutput : public Comparator::Output {
array_writer_.WriteChunk(char_pos1, char_pos2, char_len1, char_len2);
}
}
void SetSubrange1(int offset, int len) {
subrange_offset1_ = offset;
}
void SetSubrange2(int offset, int len) {
subrange_offset2_ = offset;
}
Handle<JSArray> GetResult() {
return array_writer_.GetResult();
@ -479,6 +571,8 @@ class TokenizingLineArrayCompareOutput : public Comparator::Output {
LineEndsWrapper line_ends2_;
Handle<String> s1_;
Handle<String> s2_;
int subrange_offset1_;
int subrange_offset2_;
};
@ -493,6 +587,8 @@ Handle<JSArray> LiveEdit::CompareStrings(Handle<String> s1,
LineArrayCompareInput input(s1, s2, line_ends1, line_ends2);
TokenizingLineArrayCompareOutput output(line_ends1, line_ends2, s1, s2);
NarrowDownInput(&input, &output);
Comparator::CalculateDifference(&input, &output);
return output.GetResult();

6
src/liveedit.h
View File

@ -148,9 +148,9 @@ class Comparator {
// element from the first array and element from the second array.
class Input {
public:
virtual int getLength1() = 0;
virtual int getLength2() = 0;
virtual bool equals(int index1, int index2) = 0;
virtual int GetLength1() = 0;
virtual int GetLength2() = 0;
virtual bool Equals(int index1, int index2) = 0;
protected:
virtual ~Input() {}

6
test/cctest/test-liveedit.cc
View File

@ -44,13 +44,13 @@ class StringCompareInput : public Comparator::Input {
public:
StringCompareInput(const char* s1, const char* s2) : s1_(s1), s2_(s2) {
}
int getLength1() {
int GetLength1() {
return StrLength(s1_);
}
int getLength2() {
int GetLength2() {
return StrLength(s2_);
}
bool equals(int index1, int index2) {
bool Equals(int index1, int index2) {
return s1_[index1] == s2_[index2];
}