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Land patch by Oleg Eterevsky (oleg@chromium.org).

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Original review: http://codereview.chromium.org/646010/show

Change the implementation of lastIndexOf method of String. Convert the
strings in question to Vector<char> or Vector<uc16> and execute simple
search algorithm on them.

The difference in speed on 500k character string is about 10x.

TBR=ager@chromium.org

Review URL: http://codereview.chromium.org/650036

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@3922 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This commit is contained in:
vitalyr@chromium.org 2010-02-19 17:11:47 +00:00
parent d931c9b70a
commit 91a2fb7ace
1 changed files with 79 additions and 23 deletions
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102
src/runtime.cc
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@ -2366,7 +2366,7 @@ static int StringMatchStrategy(Vector<const schar> sub,
// We have an ASCII haystack and a non-ASCII needle. Check if there
// really is a non-ASCII character in the needle and bail out if there
// is.
if (sizeof(pchar) > 1 && sizeof(schar) == 1) {
if (sizeof(schar) == 1 && sizeof(pchar) > 1) {
for (int i = 0; i < pat.length(); i++) {
uc16 c = pat[i];
if (c > String::kMaxAsciiCharCode) {
@ -2469,29 +2469,66 @@ static Object* Runtime_StringIndexOf(Arguments args) {
}
template <typename schar, typename pchar>
static int StringMatchBackwards(Vector<const schar> sub,
Vector<const pchar> pat,
int idx) {
ASSERT(pat.length() >= 1);
ASSERT(idx + pat.length() <= sub.length());
if (sizeof(schar) == 1 && sizeof(pchar) > 1) {
for (int i = 0; i < pat.length(); i++) {
uc16 c = pat[i];
if (c > String::kMaxAsciiCharCode) {
return -1;
}
}
}
pchar pattern_first_char = pat[0];
for (int i = idx; i >= 0; i--) {
if (sub[i] != pattern_first_char) continue;
int j = 1;
while (j < pat.length()) {
if (pat[j] != sub[i+j]) {
break;
}
j++;
}
if (j == pat.length()) {
return i;
}
}
return -1;
}
static Object* Runtime_StringLastIndexOf(Arguments args) {
NoHandleAllocation ha;
HandleScope scope; // create a new handle scope
ASSERT(args.length() == 3);
CONVERT_ARG_CHECKED(String, sub, 0);
CONVERT_ARG_CHECKED(String, pat, 1);
Object* index = args[2];
Object* index = args[2];
uint32_t start_index;
if (!Array::IndexFromObject(index, &start_index)) return Smi::FromInt(-1);
uint32_t pat_length = pat->length();
uint32_t sub_length = sub->length();
if (start_index + pat_length > sub_length) {
start_index = sub_length - pat_length;
}
if (pat_length == 0) {
return Smi::FromInt(start_index);
}
if (!sub->IsFlat()) {
FlattenString(sub);
}
uint32_t pattern_length = pat->length();
uint32_t sub_length = sub->length();
if (start_index + pattern_length > sub_length) {
start_index = sub_length - pattern_length;
}
if (pattern_length == 1) {
if (pat_length == 1) {
AssertNoAllocation no_heap_allocation; // ensure vectors stay valid
if (sub->IsAsciiRepresentation()) {
uc16 pchar = pat->Get(0);
@ -2508,20 +2545,39 @@ static Object* Runtime_StringLastIndexOf(Arguments args) {
}
}
pat->TryFlattenIfNotFlat();
for (int i = start_index; i >= 0; i--) {
bool found = true;
for (uint32_t j = 0; j < pattern_length; j++) {
if (sub->Get(i + j) != pat->Get(j)) {
found = false;
break;
}
}
if (found) return Smi::FromInt(i);
if (!pat->IsFlat()) {
FlattenString(pat);
}
return Smi::FromInt(-1);
AssertNoAllocation no_heap_allocation; // ensure vectors stay valid
int position = -1;
if (pat->IsAsciiRepresentation()) {
Vector<const char> pat_vector = pat->ToAsciiVector();
if (sub->IsAsciiRepresentation()) {
position = StringMatchBackwards(sub->ToAsciiVector(),
pat_vector,
start_index);
} else {
position = StringMatchBackwards(sub->ToUC16Vector(),
pat_vector,
start_index);
}
} else {
Vector<const uc16> pat_vector = pat->ToUC16Vector();
if (sub->IsAsciiRepresentation()) {
position = StringMatchBackwards(sub->ToAsciiVector(),
pat_vector,
start_index);
} else {
position = StringMatchBackwards(sub->ToUC16Vector(),
pat_vector,
start_index);
}
}
return Smi::FromInt(position);
}