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Commit e2444edd authored by yangguo@chromium.org's avatar yangguo@chromium.org
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Refactor out assumption that one byte strings are ascii in utf8 processing. 

R=yangguo@chromium.org
BUG=

Review URL: https://chromiumcodereview.appspot.com/11725006
Patch from Dan Carney <dcarney@google.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@13302 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
parent 252fbddc
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Showing with 226 additions and 366 deletions
src/api.cc
View file @ e2444edd
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src/handles.cc
View file @ e2444edd
......@@ -883,165 +883,6 @@ Handle<ObjectHashTable> PutIntoObjectHashTable(Handle<ObjectHashTable> table,
}
// This method determines the type of string involved and then gets the UTF8
// length of the string. It doesn't flatten the string and has log(n) recursion
// for a string of length n. If the failure flag gets set, then we have to
// flatten the string and retry. Failures are caused by surrogate pairs in deep
// cons strings.
// Single surrogate characters that are encountered in the UTF-16 character
// sequence of the input string get counted as 3 UTF-8 bytes, because that
// is the way that WriteUtf8 will encode them. Surrogate pairs are counted and
// encoded as one 4-byte UTF-8 sequence.
// This function conceptually uses recursion on the two halves of cons strings.
// However, in order to avoid the recursion going too deep it recurses on the
// second string of the cons, but iterates on the first substring (by manually
// eliminating it as a tail recursion). This means it counts the UTF-8 length
// from the end to the start, which makes no difference to the total.
// Surrogate pairs are recognized even if they are split across two sides of a
// cons, which complicates the implementation somewhat. Therefore, too deep
// recursion cannot always be avoided. This case is detected, and the failure
// flag is set, a signal to the caller that the string should be flattened and
// the operation retried.
int Utf8LengthHelper(String* input,
int from,
int to,
bool followed_by_surrogate,
int max_recursion,
bool* failure,
bool* starts_with_surrogate) {
if (from == to) return 0;
int total = 0;
bool dummy;
while (true) {
if (input->IsOneByteRepresentation()) {
*starts_with_surrogate = false;
return total + to - from;
}
switch (StringShape(input).representation_tag()) {
case kConsStringTag: {
ConsString* str = ConsString::cast(input);
String* first = str->first();
String* second = str->second();
int first_length = first->length();
if (first_length - from > to - first_length) {
if (first_length < to) {
// Right hand side is shorter. No need to check the recursion depth
// since this can only happen log(n) times.
bool right_starts_with_surrogate = false;
total += Utf8LengthHelper(second,
0,
to - first_length,
followed_by_surrogate,
max_recursion - 1,
failure,
&right_starts_with_surrogate);
if (*failure) return 0;
followed_by_surrogate = right_starts_with_surrogate;
input = first;
to = first_length;
} else {
// We only need the left hand side.
input = first;
}
} else {
if (first_length > from) {
// Left hand side is shorter.
if (first->IsOneByteRepresentation()) {
total += first_length - from;
*starts_with_surrogate = false;
starts_with_surrogate = &dummy;
input = second;
from = 0;
to -= first_length;
} else if (second->IsOneByteRepresentation()) {
followed_by_surrogate = false;
total += to - first_length;
input = first;
to = first_length;
} else if (max_recursion > 0) {
bool right_starts_with_surrogate = false;
// Recursing on the long one. This may fail.
total += Utf8LengthHelper(second,
0,
to - first_length,
followed_by_surrogate,
max_recursion - 1,
failure,
&right_starts_with_surrogate);
if (*failure) return 0;
input = first;
to = first_length;
followed_by_surrogate = right_starts_with_surrogate;
} else {
*failure = true;
return 0;
}
} else {
// We only need the right hand side.
input = second;
from = 0;
to -= first_length;
}
}
continue;
}
case kExternalStringTag:
case kSeqStringTag: {
Vector<const uc16> vector = input->GetFlatContent().ToUC16Vector();
const uc16* p = vector.start();
int previous = unibrow::Utf16::kNoPreviousCharacter;
for (int i = from; i < to; i++) {
uc16 c = p[i];
total += unibrow::Utf8::Length(c, previous);
previous = c;
}
if (to - from > 0) {
if (unibrow::Utf16::IsLeadSurrogate(previous) &&
followed_by_surrogate) {
total -= unibrow::Utf8::kBytesSavedByCombiningSurrogates;
}
if (unibrow::Utf16::IsTrailSurrogate(p[from])) {
*starts_with_surrogate = true;
}
}
return total;
}
case kSlicedStringTag: {
SlicedString* str = SlicedString::cast(input);
int offset = str->offset();
input = str->parent();
from += offset;
to += offset;
continue;
}
default:
break;
}
UNREACHABLE();
return 0;
}
return 0;
}
int Utf8Length(Handle<String> str) {
bool dummy;
bool failure;
int len;
const int kRecursionBudget = 100;
do {
failure = false;
len = Utf8LengthHelper(
*str, 0, str->length(), false, kRecursionBudget, &failure, &dummy);
if (failure) FlattenString(str);
} while (failure);
return len;
}
DeferredHandleScope::DeferredHandleScope(Isolate* isolate)
: impl_(isolate->handle_scope_implementer()) {
ASSERT(impl_->isolate() == Isolate::Current());
......
src/handles.h
View file @ e2444edd
......@@ -214,8 +214,6 @@ void FlattenString(Handle<String> str);
// string.
Handle<String> FlattenGetString(Handle<String> str);
int Utf8Length(Handle<String> str);
Handle<Object> SetProperty(Isolate* isolate,
Handle<Object> object,
Handle<Object> key,
......
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