JavaScriptCore-1097.13.tar.gz

[apple/javascriptcore.git] / runtime / UString.cpp

diff --git a/runtime/UString.cpp b/runtime/UString.cpp
index 8fb0dfdd03d3011bf885da7dbb78ba416e9bbc8e..5b1e9a0e0b12a0a7aefc627192562ab43377d4dc 100644 (file)
--- a/runtime/UString.cpp
+++ b/runtime/UString.cpp
@@ -25,24 +25,21 @@
 #include "UString.h"
 
 #include "JSGlobalObjectFunctions.h"
 #include "UString.h"
 
 #include "JSGlobalObjectFunctions.h"

-#include "Collector.h"
-#include "dtoa.h"
+#include "Heap.h"

 #include "Identifier.h"
 #include "Operations.h"
 #include <ctype.h>
 #include <limits.h>
 #include <limits>
 #include "Identifier.h"
 #include "Operations.h"
 #include <ctype.h>
 #include <limits.h>
 #include <limits>

-#include <math.h>

 #include <stdio.h>
 #include <stdlib.h>
 #include <stdio.h>
 #include <stdlib.h>

-#include <string.h>

 #include <wtf/ASCIICType.h>
 #include <wtf/Assertions.h>
 #include <wtf/MathExtras.h>
 #include <wtf/StringExtras.h>
 #include <wtf/Vector.h>
 #include <wtf/ASCIICType.h>
 #include <wtf/Assertions.h>
 #include <wtf/MathExtras.h>
 #include <wtf/StringExtras.h>
 #include <wtf/Vector.h>

+#include <wtf/dtoa.h>

 #include <wtf/unicode/UTF8.h>
 #include <wtf/unicode/UTF8.h>

-#include <wtf/StringExtras.h>

 
 #if HAVE(STRINGS_H)
 #include <strings.h>
 
 #if HAVE(STRINGS_H)
 #include <strings.h>


@@ -54,41 +51,54 @@ using namespace std;
 
 namespace JSC {
 
 
 namespace JSC {
 

-extern const double NaN;
-extern const double Inf;
+COMPILE_ASSERT(sizeof(UString) == sizeof(void*), UString_should_stay_small);

 
 

-// The null string is immutable, except for refCount.
-UString* UString::s_nullUString;
+// Construct a string with UTF-16 data.
+UString::UString(const UChar* characters, unsigned length)
+    : m_impl(characters ? StringImpl::create(characters, length) : 0)
+{
+}

 
 

-void initializeUString()
+// Construct a string with UTF-16 data, from a null-terminated source.
+UString::UString(const UChar* characters)

 {
 {

-    // UStringImpl::empty() does not construct its static string in a threadsafe fashion,
-    // so ensure it has been initialized from here.
-    UStringImpl::empty();
+    if (!characters)
+        return;
+
+    int length = 0;
+    while (characters[length] != UChar(0))
+        ++length;

 
 

-    UString::s_nullUString = new UString;
+    m_impl = StringImpl::create(characters, length);

 }
 
 }
 

-UString::UString(const char* c)
-    : m_rep(Rep::create(c))
+// Construct a string with latin1 data.
+UString::UString(const LChar* characters, unsigned length)
+    : m_impl(characters ? StringImpl::create(characters, length) : 0)

 {
 }
 
 {
 }
 

-UString::UString(const char* c, unsigned length)
-    : m_rep(Rep::create(c, length))
+UString::UString(const char* characters, unsigned length)
+    : m_impl(characters ? StringImpl::create(reinterpret_cast<const LChar*>(characters), length) : 0)

 {
 }
 
 {
 }
 

-UString::UString(const UChar* c, unsigned length)
-    : m_rep(Rep::create(c, length))
+// Construct a string with latin1 data, from a null-terminated source.
+UString::UString(const LChar* characters)
+    : m_impl(characters ? StringImpl::create(characters) : 0)

 {
 }
 
 {
 }
 

-UString UString::from(int i)
+UString::UString(const char* characters)
+    : m_impl(characters ? StringImpl::create(reinterpret_cast<const LChar*>(characters)) : 0)

 {
 {

-    UChar buf[1 + sizeof(i) * 3];
-    UChar* end = buf + sizeof(buf) / sizeof(UChar);
-    UChar* p = end;
+}
+
+UString UString::number(int i)
+{
+    LChar buf[1 + sizeof(i) * 3];
+    LChar* end = buf + WTF_ARRAY_LENGTH(buf);
+    LChar* p = end;

 
     if (i == 0)
         *--p = '0';
 
     if (i == 0)
         *--p = '0';


@@ -113,17 +123,21 @@ UString UString::from(int i)
     return UString(p, static_cast<unsigned>(end - p));
 }
 
     return UString(p, static_cast<unsigned>(end - p));
 }
 

-UString UString::from(long long i)
+UString UString::number(long long i)

 {
 {

-    UChar buf[1 + sizeof(i) * 3];
-    UChar* end = buf + sizeof(buf) / sizeof(UChar);
-    UChar* p = end;
+    LChar buf[1 + sizeof(i) * 3];
+    LChar* end = buf + WTF_ARRAY_LENGTH(buf);
+    LChar* p = end;

 
     if (i == 0)
         *--p = '0';
     else if (i == std::numeric_limits<long long>::min()) {
         char minBuf[1 + sizeof(i) * 3];
 
     if (i == 0)
         *--p = '0';
     else if (i == std::numeric_limits<long long>::min()) {
         char minBuf[1 + sizeof(i) * 3];

+#if OS(WINDOWS)
+        snprintf(minBuf, sizeof(minBuf), "%I64d", std::numeric_limits<long long>::min());
+#else

         snprintf(minBuf, sizeof(minBuf), "%lld", std::numeric_limits<long long>::min());
         snprintf(minBuf, sizeof(minBuf), "%lld", std::numeric_limits<long long>::min());

+#endif

         return UString(minBuf);
     } else {
         bool negative = false;
         return UString(minBuf);
     } else {
         bool negative = false;


@@ -142,11 +156,11 @@ UString UString::from(long long i)
     return UString(p, static_cast<unsigned>(end - p));
 }
 
     return UString(p, static_cast<unsigned>(end - p));
 }
 

-UString UString::from(unsigned u)
+UString UString::number(unsigned u)

 {
 {

-    UChar buf[sizeof(u) * 3];
-    UChar* end = buf + sizeof(buf) / sizeof(UChar);
-    UChar* p = end;
+    LChar buf[sizeof(u) * 3];
+    LChar* end = buf + WTF_ARRAY_LENGTH(buf);
+    LChar* p = end;

 
     if (u == 0)
         *--p = '0';
 
     if (u == 0)
         *--p = '0';


@@ -160,11 +174,11 @@ UString UString::from(unsigned u)
     return UString(p, static_cast<unsigned>(end - p));
 }
 
     return UString(p, static_cast<unsigned>(end - p));
 }
 

-UString UString::from(long l)
+UString UString::number(long l)

 {
 {

-    UChar buf[1 + sizeof(l) * 3];
-    UChar* end = buf + sizeof(buf) / sizeof(UChar);
-    UChar* p = end;
+    LChar buf[1 + sizeof(l) * 3];
+    LChar* end = buf + WTF_ARRAY_LENGTH(buf);
+    LChar* p = end;

 
     if (l == 0)
         *--p = '0';
 
     if (l == 0)
         *--p = '0';


@@ -189,362 +203,132 @@ UString UString::from(long l)
     return UString(p, end - p);
 }
 
     return UString(p, end - p);
 }
 

-UString UString::from(double d)
+UString UString::number(double d)

 {
 {

-    DtoaBuffer buffer;
-    unsigned length;
-    doubleToStringInJavaScriptFormat(d, buffer, &length);
-    return UString(buffer, length);
+    NumberToStringBuffer buffer;
+    return UString(numberToString(d, buffer));

 }
 
 }
 

-char* UString::ascii() const
+UString UString::substringSharingImpl(unsigned offset, unsigned length) const

 {
 {

-    static char* asciiBuffer = 0;
-
-    unsigned length = size();
-    unsigned neededSize = length + 1;
-    delete[] asciiBuffer;
-    asciiBuffer = new char[neededSize];
-
-    const UChar* p = data();
-    char* q = asciiBuffer;
-    const UChar* limit = p + length;
-    while (p != limit) {
-        *q = static_cast<char>(p[0]);
-        ++p;
-        ++q;
-    }
-    *q = '\0';
+    // FIXME: We used to check against a limit of Heap::minExtraCost / sizeof(UChar).

 
 

-    return asciiBuffer;
-}
+    unsigned stringLength = this->length();
+    offset = min(offset, stringLength);
+    length = min(length, stringLength - offset);

 
 

-bool UString::is8Bit() const
-{
-    const UChar* u = data();
-    const UChar* limit = u + size();
-    while (u < limit) {
-        if (u[0] > 0xFF)
-            return false;
-        ++u;
-    }
-
-    return true;
+    if (!offset && length == stringLength)
+        return *this;
+    return UString(StringImpl::create(m_impl, offset, length));

 }
 
 }
 

-UChar UString::operator[](unsigned pos) const
+bool operator==(const UString& s1, const char *s2)

 {
 {

-    if (pos >= size())
-        return '\0';
-    return data()[pos];
+    if (s1.isEmpty())
+        return !s2;
+
+    return equal(s1.impl(), s2);

 }
 
 }
 

-double UString::toDouble(bool tolerateTrailingJunk, bool tolerateEmptyString) const
+// This method assumes that all simple checks have been performed by
+// the inlined operator==() in the header file.
+bool equalSlowCase(const UString& s1, const UString& s2)

 {
 {

-    if (size() == 1) {
-        UChar c = data()[0];
-        if (isASCIIDigit(c))
-            return c - '0';
-        if (isASCIISpace(c) && tolerateEmptyString)
-            return 0;
-        return NaN;
-    }
-
-    // FIXME: If tolerateTrailingJunk is true, then we want to tolerate junk 
-    // after the number, even if it contains invalid UTF-16 sequences. So we
-    // shouldn't use the UTF8String function, which returns null when it
-    // encounters invalid UTF-16. Further, we have no need to convert the
-    // non-ASCII characters to UTF-8, so the UTF8String does quite a bit of
-    // unnecessary work.
-    CString s = UTF8String();
-    if (s.isNull())
-        return NaN;
-    const char* c = s.data();
-
-    // skip leading white space
-    while (isASCIISpace(*c))
-        c++;
-
-    // empty string ?
-    if (*c == '\0')
-        return tolerateEmptyString ? 0.0 : NaN;
-
-    double d;
-
-    // hex number ?
-    if (*c == '0' && (*(c + 1) == 'x' || *(c + 1) == 'X')) {
-        const char* firstDigitPosition = c + 2;
-        c++;
-        d = 0.0;
-        while (*(++c)) {
-            if (*c >= '0' && *c <= '9')
-                d = d * 16.0 + *c - '0';
-            else if ((*c >= 'A' && *c <= 'F') || (*c >= 'a' && *c <= 'f'))
-                d = d * 16.0 + (*c & 0xdf) - 'A' + 10.0;
-            else
-                break;
-        }
-
-        if (d >= mantissaOverflowLowerBound)
-            d = parseIntOverflow(firstDigitPosition, c - firstDigitPosition, 16);
-    } else {
-        // regular number ?
-        char* end;
-        d = WTF::strtod(c, &end);
-        if ((d != 0.0 || end != c) && d != Inf && d != -Inf) {
-            c = end;
-        } else {
-            double sign = 1.0;
-
-            if (*c == '+')
-                c++;
-            else if (*c == '-') {
-                sign = -1.0;
-                c++;
+    StringImpl* rep1 = s1.impl();
+    StringImpl* rep2 = s2.impl();
+    unsigned size1 = rep1->length();
+
+    // At this point we know 
+    //   (a) that the strings are the same length and
+    //   (b) that they are greater than zero length.
+    bool s1Is8Bit = rep1->is8Bit();
+    bool s2Is8Bit = rep2->is8Bit();
+    
+    if (s1Is8Bit) {
+        const LChar* d1 = rep1->characters8();
+        if (s2Is8Bit) {
+            const LChar* d2 = rep2->characters8();
+            
+            if (d1 == d2) // Check to see if the data pointers are the same.
+                return true;
+            
+            // Do quick checks for sizes 1 and 2.
+            switch (size1) {
+            case 1:
+                return d1[0] == d2[0];
+            case 2:
+                return (d1[0] == d2[0]) & (d1[1] == d2[1]);
+            default:
+                return (!memcmp(d1, d2, size1 * sizeof(LChar)));

             }
             }

-
-            // We used strtod() to do the conversion. However, strtod() handles
-            // infinite values slightly differently than JavaScript in that it
-            // converts the string "inf" with any capitalization to infinity,
-            // whereas the ECMA spec requires that it be converted to NaN.
-
-            if (c[0] == 'I' && c[1] == 'n' && c[2] == 'f' && c[3] == 'i' && c[4] == 'n' && c[5] == 'i' && c[6] == 't' && c[7] == 'y') {
-                d = sign * Inf;
-                c += 8;
-            } else if ((d == Inf || d == -Inf) && *c != 'I' && *c != 'i')
-                c = end;
-            else
-                return NaN;

         }
         }

-    }
-
-    // allow trailing white space
-    while (isASCIISpace(*c))
-        c++;
-    // don't allow anything after - unless tolerant=true
-    // FIXME: If string contains a U+0000 character, then this check is incorrect.
-    if (!tolerateTrailingJunk && *c != '\0')
-        d = NaN;
-
-    return d;
-}
-
-double UString::toDouble(bool tolerateTrailingJunk) const
-{
-    return toDouble(tolerateTrailingJunk, true);
-}
-
-double UString::toDouble() const
-{
-    return toDouble(false, true);
-}
-
-uint32_t UString::toUInt32(bool* ok) const
-{
-    double d = toDouble();
-    bool b = true;
-
-    if (d != static_cast<uint32_t>(d)) {
-        b = false;
-        d = 0;
-    }
-
-    if (ok)
-        *ok = b;
-
-    return static_cast<uint32_t>(d);
-}
-
-uint32_t UString::toUInt32(bool* ok, bool tolerateEmptyString) const
-{
-    double d = toDouble(false, tolerateEmptyString);
-    bool b = true;
-
-    if (d != static_cast<uint32_t>(d)) {
-        b = false;
-        d = 0;
-    }
-
-    if (ok)
-        *ok = b;
-
-    return static_cast<uint32_t>(d);
-}
-
-uint32_t UString::toStrictUInt32(bool* ok) const
-{
-    if (ok)
-        *ok = false;
-
-    // Empty string is not OK.
-    unsigned len = m_rep->length();
-    if (len == 0)
-        return 0;
-    const UChar* p = m_rep->characters();
-    unsigned short c = p[0];
-
-    // If the first digit is 0, only 0 itself is OK.
-    if (c == '0') {
-        if (len == 1 && ok)
-            *ok = true;
-        return 0;
-    }
-
-    // Convert to UInt32, checking for overflow.
-    uint32_t i = 0;
-    while (1) {
-        // Process character, turning it into a digit.
-        if (c < '0' || c > '9')
-            return 0;
-        const unsigned d = c - '0';
-
-        // Multiply by 10, checking for overflow out of 32 bits.
-        if (i > 0xFFFFFFFFU / 10)
-            return 0;
-        i *= 10;
-
-        // Add in the digit, checking for overflow out of 32 bits.
-        const unsigned max = 0xFFFFFFFFU - d;
-        if (i > max)
-            return 0;
-        i += d;
-
-        // Handle end of string.
-        if (--len == 0) {
-            if (ok)
-                *ok = true;
-            return i;
+        
+        const UChar* d2 = rep2->characters16();
+        
+        for (unsigned i = 0; i < size1; i++) {
+            if (d1[i] != d2[i])
+                return false;

         }
         }

-
-        // Get next character.
-        c = *(++p);
+        return true;

     }
     }

-}
-
-unsigned UString::find(const UString& f, unsigned pos) const
-{
-    unsigned fsz = f.size();
-
-    if (fsz == 1) {
-        UChar ch = f[0];
-        const UChar* end = data() + size();
-        for (const UChar* c = data() + pos; c < end; c++) {
-            if (*c == ch)
-                return static_cast<unsigned>(c - data());
+    
+    if (s2Is8Bit) {
+        const UChar* d1 = rep1->characters16();
+        const LChar* d2 = rep2->characters8();
+        
+        for (unsigned i = 0; i < size1; i++) {
+            if (d1[i] != d2[i])
+                return false;

         }
         }

-        return NotFound;
-    }
-
-    unsigned sz = size();
-    if (sz < fsz)
-        return NotFound;
-    if (fsz == 0)
-        return pos;
-    const UChar* end = data() + sz - fsz;
-    unsigned fsizeminusone = (fsz - 1) * sizeof(UChar);
-    const UChar* fdata = f.data();
-    unsigned short fchar = fdata[0];
-    ++fdata;
-    for (const UChar* c = data() + pos; c <= end; c++) {
-        if (c[0] == fchar && !memcmp(c + 1, fdata, fsizeminusone))
-            return static_cast<unsigned>(c - data());
-    }
-
-    return NotFound;
-}
-
-unsigned UString::find(UChar ch, unsigned pos) const
-{
-    const UChar* end = data() + size();
-    for (const UChar* c = data() + pos; c < end; c++) {
-        if (*c == ch)
-            return static_cast<unsigned>(c - data());
-    }
-
-    return NotFound;
-}
-
-unsigned UString::rfind(const UString& f, unsigned pos) const
-{
-    unsigned sz = size();
-    unsigned fsz = f.size();
-    if (sz < fsz)
-        return NotFound;
-    if (pos > sz - fsz)
-        pos = sz - fsz;
-    if (fsz == 0)
-        return pos;
-    unsigned fsizeminusone = (fsz - 1) * sizeof(UChar);
-    const UChar* fdata = f.data();
-    for (const UChar* c = data() + pos; c >= data(); c--) {
-        if (*c == *fdata && !memcmp(c + 1, fdata + 1, fsizeminusone))
-            return static_cast<unsigned>(c - data());
+        return true;
+        

     }
     }

-
-    return NotFound;
-}
-
-unsigned UString::rfind(UChar ch, unsigned pos) const
-{
-    if (isEmpty())
-        return NotFound;
-    if (pos + 1 >= size())
-        pos = size() - 1;
-    for (const UChar* c = data() + pos; c >= data(); c--) {
-        if (*c == ch)
-            return static_cast<unsigned>(c - data());
-    }
-
-    return NotFound;
-}
-
-UString UString::substr(unsigned pos, unsigned len) const
-{
-    unsigned s = size();
-
-    if (pos >= s)
-        pos = s;
-    unsigned limit = s - pos;
-    if (len > limit)
-        len = limit;
-
-    if (pos == 0 && len == s)
-        return *this;
-
-    return UString(Rep::create(m_rep, pos, len));
-}
-
-bool operator==(const UString& s1, const char *s2)
-{
-    if (s2 == 0)
-        return s1.isEmpty();
-
-    const UChar* u = s1.data();
-    const UChar* uend = u + s1.size();
-    while (u != uend && *s2) {
-        if (u[0] != (unsigned char)*s2)
-            return false;
-        s2++;
-        u++;
+    
+    const UChar* d1 = rep1->characters16();
+    const UChar* d2 = rep2->characters16();
+    
+    if (d1 == d2) // Check to see if the data pointers are the same.
+        return true;
+    
+    // Do quick checks for sizes 1 and 2.
+    switch (size1) {
+    case 1:
+        return d1[0] == d2[0];
+    case 2:
+        return (d1[0] == d2[0]) & (d1[1] == d2[1]);
+    default:
+        return (!memcmp(d1, d2, size1 * sizeof(UChar)));

     }
     }

-
-    return u == uend && *s2 == 0;

 }
 
 bool operator<(const UString& s1, const UString& s2)
 {
 }
 
 bool operator<(const UString& s1, const UString& s2)
 {

-    const unsigned l1 = s1.size();
-    const unsigned l2 = s2.size();
+    const unsigned l1 = s1.length();
+    const unsigned l2 = s2.length();

     const unsigned lmin = l1 < l2 ? l1 : l2;
     const unsigned lmin = l1 < l2 ? l1 : l2;

-    const UChar* c1 = s1.data();
-    const UChar* c2 = s2.data();
-    unsigned l = 0;
-    while (l < lmin && *c1 == *c2) {
+    if (s1.is8Bit() && s2.is8Bit()) {
+        const LChar* c1 = s1.characters8();
+        const LChar* c2 = s2.characters8();
+        unsigned length = 0;
+        while (length < lmin && *c1 == *c2) {
+            c1++;
+            c2++;
+            length++;
+        }
+        if (length < lmin)
+            return (c1[0] < c2[0]);
+
+        return (l1 < l2);        
+    }
+    const UChar* c1 = s1.characters();
+    const UChar* c2 = s2.characters();
+    unsigned length = 0;
+    while (length < lmin && *c1 == *c2) {

         c1++;
         c2++;
         c1++;
         c2++;

-        l++;
+        length++;

     }
     }

-    if (l < lmin)
+    if (length < lmin)

         return (c1[0] < c2[0]);
 
     return (l1 < l2);
         return (c1[0] < c2[0]);
 
     return (l1 < l2);


@@ -552,11 +336,11 @@ bool operator<(const UString& s1, const UString& s2)
 
 bool operator>(const UString& s1, const UString& s2)
 {
 
 bool operator>(const UString& s1, const UString& s2)
 {

-    const unsigned l1 = s1.size();
-    const unsigned l2 = s2.size();
+    const unsigned l1 = s1.length();
+    const unsigned l2 = s2.length();

     const unsigned lmin = l1 < l2 ? l1 : l2;
     const unsigned lmin = l1 < l2 ? l1 : l2;

-    const UChar* c1 = s1.data();
-    const UChar* c2 = s2.data();
+    const UChar* c1 = s1.characters();
+    const UChar* c2 = s2.characters();

     unsigned l = 0;
     while (l < lmin && *c1 == *c2) {
         c1++;
     unsigned l = 0;
     while (l < lmin && *c1 == *c2) {
         c1++;


@@ -569,45 +353,123 @@ bool operator>(const UString& s1, const UString& s2)
     return (l1 > l2);
 }
 
     return (l1 > l2);
 }
 

-int compare(const UString& s1, const UString& s2)
+CString UString::ascii() const

 {
 {

-    const unsigned l1 = s1.size();
-    const unsigned l2 = s2.size();
-    const unsigned lmin = l1 < l2 ? l1 : l2;
-    const UChar* c1 = s1.data();
-    const UChar* c2 = s2.data();
-    unsigned l = 0;
-    while (l < lmin && *c1 == *c2) {
-        c1++;
-        c2++;
-        l++;
+    // Basic Latin1 (ISO) encoding - Unicode characters 0..255 are
+    // preserved, characters outside of this range are converted to '?'.
+
+    unsigned length = this->length();
+
+    if (this->is8Bit()) {
+        const LChar* characters = this->characters8();
+        
+        char* characterBuffer;
+        CString result = CString::newUninitialized(length, characterBuffer);
+        
+        for (unsigned i = 0; i < length; ++i) {
+            LChar ch = characters[i];
+            characterBuffer[i] = ch && (ch < 0x20 || ch > 0x7f) ? '?' : ch;
+        }
+        
+        return result;        

     }
 
     }
 

-    if (l < lmin)
-        return (c1[0] > c2[0]) ? 1 : -1;
+    const UChar* characters = this->characters16();

 
 

-    if (l1 == l2)
-        return 0;
+    char* characterBuffer;
+    CString result = CString::newUninitialized(length, characterBuffer);
+
+    for (unsigned i = 0; i < length; ++i) {
+        UChar ch = characters[i];
+        characterBuffer[i] = ch && (ch < 0x20 || ch >= 0x7f) ? '?' : ch;
+    }

 
 

-    return (l1 > l2) ? 1 : -1;
+    return result;

 }
 
 }
 

-CString UString::UTF8String(bool strict) const
+CString UString::latin1() const

 {
 {

-    // Allocate a buffer big enough to hold all the characters.
-    const unsigned length = size();
+    // Basic Latin1 (ISO) encoding - Unicode characters 0..255 are
+    // preserved, characters outside of this range are converted to '?'.
+
+    unsigned length = this->length();
+    const UChar* characters = this->characters();
+
+    char* characterBuffer;
+    CString result = CString::newUninitialized(length, characterBuffer);
+
+    for (unsigned i = 0; i < length; ++i) {
+        UChar ch = characters[i];
+        characterBuffer[i] = ch > 0xff ? '?' : ch;
+    }
+
+    return result;
+}
+
+// Helper to write a three-byte UTF-8 code point to the buffer, caller must check room is available.
+static inline void putUTF8Triple(char*& buffer, UChar ch)
+{
+    ASSERT(ch >= 0x0800);
+    *buffer++ = static_cast<char>(((ch >> 12) & 0x0F) | 0xE0);
+    *buffer++ = static_cast<char>(((ch >> 6) & 0x3F) | 0x80);
+    *buffer++ = static_cast<char>((ch & 0x3F) | 0x80);
+}
+
+CString UString::utf8(bool strict) const
+{
+    unsigned length = this->length();
+
+    if (!length)
+        return CString("", 0);
+
+    // Allocate a buffer big enough to hold all the characters
+    // (an individual UTF-16 UChar can only expand to 3 UTF-8 bytes).
+    // Optimization ideas, if we find this function is hot:
+    //  * We could speculatively create a CStringBuffer to contain 'length' 
+    //    characters, and resize if necessary (i.e. if the buffer contains
+    //    non-ascii characters). (Alternatively, scan the buffer first for
+    //    ascii characters, so we know this will be sufficient).
+    //  * We could allocate a CStringBuffer with an appropriate size to
+    //    have a good chance of being able to write the string into the
+    //    buffer without reallocing (say, 1.5 x length).

     if (length > numeric_limits<unsigned>::max() / 3)
     if (length > numeric_limits<unsigned>::max() / 3)

-        return CString(); 
-    Vector<char, 1024> buffer(length * 3);
-
-    // Convert to runs of 8-bit characters.
-    char* p = buffer.data();
-    const UChar* d = reinterpret_cast<const UChar*>(&data()[0]);
-    ConversionResult result = convertUTF16ToUTF8(&d, d + length, &p, p + buffer.size(), strict);
-    if (result != conversionOK)

         return CString();
 
         return CString();
 

-    return CString(buffer.data(), p - buffer.data());
+    Vector<char, 1024> bufferVector(length * 3);
+    char* buffer = bufferVector.data();
+
+    if (is8Bit()) {
+        const LChar* characters = this->characters8();
+
+        ConversionResult result = convertLatin1ToUTF8(&characters, characters + length, &buffer, buffer + bufferVector.size());
+        ASSERT_UNUSED(result, result != targetExhausted); // (length * 3) should be sufficient for any conversion
+    } else {
+        const UChar* characters = this->characters16();
+
+        ConversionResult result = convertUTF16ToUTF8(&characters, characters + length, &buffer, buffer + bufferVector.size(), strict);
+        ASSERT(result != targetExhausted); // (length * 3) should be sufficient for any conversion
+
+        // Only produced from strict conversion.
+        if (result == sourceIllegal)
+            return CString();
+
+        // Check for an unconverted high surrogate.
+        if (result == sourceExhausted) {
+            if (strict)
+                return CString();
+            // This should be one unpaired high surrogate. Treat it the same
+            // was as an unpaired high surrogate would have been handled in
+            // the middle of a string with non-strict conversion - which is
+            // to say, simply encode it to UTF-8.
+            ASSERT((characters + 1) == (this->characters() + length));
+            ASSERT((*characters >= 0xD800) && (*characters <= 0xDBFF));
+            // There should be room left, since one UChar hasn't been converted.
+            ASSERT((buffer + 3) <= (buffer + bufferVector.size()));
+            putUTF8Triple(buffer, *characters);
+        }
+    }
+
+    return CString(bufferVector.data(), buffer - bufferVector.data());

 }
 
 } // namespace JSC
 }
 
 } // namespace JSC