Changeset 183988 in webkit

Timestamp:

May 8, 2015, 1:44:23 AM (11 years ago)

Author:

akling@apple.com

Message:

Optimize serialization of quoted JSON strings.
<​https://webkit.org/b/144754>

Reviewed by Darin Adler.

Source/JavaScriptCore:

Optimized the serialization of quoted strings into JSON by moving the logic into
StringBuilder so it can make smarter decisions about buffering.

12% progression on Kraken/json-stringify-tinderbox (on my Mac Pro.)

• bytecompiler/NodesCodegen.cpp:

(JSC::ObjectPatternNode::toString): Use the new StringBuilder API.

• runtime/JSONObject.h:
• runtime/JSONObject.cpp:

(JSC::Stringifier::Holder::appendNextProperty):
(JSC::appendStringToStringBuilder): Deleted.
(JSC::appendQuotedJSONStringToBuilder): Deleted.
(JSC::Stringifier::appendQuotedString): Deleted.
(JSC::Stringifier::appendStringifiedValue): Moved the bulk of this logic
to StringBuilder and call that from here.

Source/WebKit2:

• NetworkProcess/cache/NetworkCacheEntry.cpp:

(WebKit::NetworkCache::Entry::asJSON): Use the new StringBuilder API.

Source/WTF:

Add a StringBuilder API for appending a quoted JSON string. This is used by
JSON.stringify() to implement efficient appending of strings while escaping
quotes, control characters and \uNNNN-style characters.

The main benefit comes from only doing a single buffer expansion up front,
instead of doing it every time we append something. The fudge factor is pretty
large, since the maximum number of output characters per input character is 6.

The first landing of this patch had two bugs in it:

• Made \uNNNN escapes uppercase hexadecimal instead of lowercase.
• Didn't preallocate enough space for 8-bit input strings.

Both were caught by existing tests on our bots, and both were due to last-minute
changes before landing. :/

• wtf/text/StringBuilder.cpp:

(WTF::appendQuotedJSONStringInternal):
(WTF::StringBuilder::appendQuotedJSONString):

• wtf/text/StringBuilder.h:

Location:

trunk/Source

Files:

• JavaScriptCore/ChangeLog (modified) (1 diff)
• JavaScriptCore/bytecompiler/NodesCodegen.cpp (modified) (1 diff)
• JavaScriptCore/runtime/JSONObject.cpp (modified) (4 diffs)
• JavaScriptCore/runtime/JSONObject.h (modified) (1 diff)
• WTF/ChangeLog (modified) (1 diff)
• WTF/wtf/text/StringBuilder.cpp (modified) (2 diffs)
• WTF/wtf/text/StringBuilder.h (modified) (1 diff)
• WebKit2/ChangeLog (modified) (1 diff)
• WebKit2/NetworkProcess/cache/NetworkCacheEntry.cpp (modified) (5 diffs)

trunk/Source/JavaScriptCore/ChangeLog

@@ +1 @@
+2015-05-08  Andreas Kling  <akling@apple.com>
+
+        Optimize serialization of quoted JSON strings.
+        <https://webkit.org/b/144754>
+
+        Reviewed by Darin Adler.
+
+        Optimized the serialization of quoted strings into JSON by moving the logic into
+        StringBuilder so it can make smarter decisions about buffering.
+
+        12% progression on Kraken/json-stringify-tinderbox (on my Mac Pro.)
+
+        * bytecompiler/NodesCodegen.cpp:
+        (JSC::ObjectPatternNode::toString): Use the new StringBuilder API.
+
+        * runtime/JSONObject.h:
+        * runtime/JSONObject.cpp:
+        (JSC::Stringifier::Holder::appendNextProperty):
+        (JSC::appendStringToStringBuilder): Deleted.
+        (JSC::appendQuotedJSONStringToBuilder): Deleted.
+        (JSC::Stringifier::appendQuotedString): Deleted.
+        (JSC::Stringifier::appendStringifiedValue): Moved the bulk of this logic
+        to StringBuilder and call that from here.
+
 2015-05-07  Commit Queue  <commit-queue@webkit.org>
 

trunk/Source/JavaScriptCore/bytecompiler/NodesCodegen.cpp

@@ -3088 +3088 @@
     for (size_t i = 0; i < m_targetPatterns.size(); i++) {
         if (m_targetPatterns[i].wasString)
-            appendQuotedJSONStringToBuilder(builder, m_targetPatterns[i].propertyName.string());
+            builder.appendQuotedJSONString(m_targetPatterns[i].propertyName.string());
         else
             builder.append(m_targetPatterns[i].propertyName.string());

trunk/Source/JavaScriptCore/runtime/JSONObject.cpp

@@ -108 +108 @@
     friend class Holder;
 
-    static void appendQuotedString(StringBuilder&, const String&);
-
     JSValue toJSON(JSValue, const PropertyNameForFunctionCall&);
 
@@ -256 +254 @@
 }
 
-template <typename CharType>
-static void appendStringToStringBuilder(StringBuilder& builder, const CharType* data, int length)
-{
-    for (int i = 0; i < length; ++i) {
-        int start = i;
-        while (i < length && (data[i] > 0x1F && data[i] != '"' && data[i] != '\\'))
-            ++i;
-        builder.append(data + start, i - start);
-        if (i >= length)
-            break;
-        switch (data[i]) {
-        case '\t':
-            builder.append('\\');
-            builder.append('t');
-            break;
-        case '\r':
-            builder.append('\\');
-            builder.append('r');
-            break;
-        case '\n':
-            builder.append('\\');
-            builder.append('n');
-            break;
-        case '\f':
-            builder.append('\\');
-            builder.append('f');
-            break;
-        case '\b':
-            builder.append('\\');
-            builder.append('b');
-            break;
-        case '"':
-            builder.append('\\');
-            builder.append('"');
-            break;
-        case '\\':
-            builder.append('\\');
-            builder.append('\\');
-            break;
-        default:
-            static const char hexDigits[] = "0123456789abcdef";
-            UChar ch = data[i];
-            LChar hex[] = { '\\', 'u', static_cast<LChar>(hexDigits[(ch >> 12) & 0xF]), static_cast<LChar>(hexDigits[(ch >> 8) & 0xF]), static_cast<LChar>(hexDigits[(ch >> 4) & 0xF]), static_cast<LChar>(hexDigits[ch & 0xF]) };
-            builder.append(hex, WTF_ARRAY_LENGTH(hex));
-            break;
-        }
-    }
-}
-
-void appendQuotedJSONStringToBuilder(StringBuilder& builder, const String& message)
-{
-    builder.append('"');
-
-    if (message.is8Bit())
-        appendStringToStringBuilder(builder, message.characters8(), message.length());
-    else
-        appendStringToStringBuilder(builder, message.characters16(), message.length());
-
-    builder.append('"');
-}
-
-void Stringifier::appendQuotedString(StringBuilder& builder, const String& value)
-{
-    appendQuotedJSONStringToBuilder(builder, value);
-}
-
 inline JSValue Stringifier::toJSON(JSValue value, const PropertyNameForFunctionCall& propertyName)
 {
@@ -386 +318 @@
     String stringValue;
     if (value.getString(m_exec, stringValue)) {
-        appendQuotedString(builder, stringValue);
+        builder.appendQuotedJSONString(stringValue);
         return StringifySucceeded;
     }
@@ -557 +489 @@
 
         // Append the property name.
-        appendQuotedString(builder, propertyName.string());
+        builder.appendQuotedJSONString(propertyName.string());
         builder.append(':');
         if (stringifier.willIndent())

trunk/Source/JavaScriptCore/runtime/JSONObject.h

@@ -63 +63 @@
 JS_EXPORT_PRIVATE String JSONStringify(ExecState*, JSValue, unsigned indent);
 
-JS_EXPORT_PRIVATE void appendQuotedJSONStringToBuilder(StringBuilder&, const String&);
-
     
 } // namespace JSC

trunk/Source/WTF/ChangeLog

@@ +1 @@
+2015-05-08  Andreas Kling  <akling@apple.com>
+
+        Optimize serialization of quoted JSON strings.
+        <https://webkit.org/b/144754>
+
+        Reviewed by Darin Adler.
+
+        Add a StringBuilder API for appending a quoted JSON string. This is used by
+        JSON.stringify() to implement efficient appending of strings while escaping
+        quotes, control characters and \uNNNN-style characters.
+
+        The main benefit comes from only doing a single buffer expansion up front,
+        instead of doing it every time we append something. The fudge factor is pretty
+        large, since the maximum number of output characters per input character is 6.
+
+        The first landing of this patch had two bugs in it:
+
+        - Made \uNNNN escapes uppercase hexadecimal instead of lowercase.
+        - Didn't preallocate enough space for 8-bit input strings.
+
+        Both were caught by existing tests on our bots, and both were due to last-minute
+        changes before landing. :/
+
+        * wtf/text/StringBuilder.cpp:
+        (WTF::appendQuotedJSONStringInternal):
+        (WTF::StringBuilder::appendQuotedJSONString):
+        * wtf/text/StringBuilder.h:
+
 2015-05-07  Commit Queue  <commit-queue@webkit.org>
 

trunk/Source/WTF/wtf/text/StringBuilder.cpp

@@ -29 +29 @@
 
 #include "IntegerToStringConversion.h"
+#include "MathExtras.h"
 #include "WTFString.h"
 #include <wtf/dtoa.h>
@@ -361 +362 @@
 }
 
+template <typename OutputCharacterType, typename InputCharacterType>
+static void appendQuotedJSONStringInternal(OutputCharacterType*& output, const InputCharacterType* input, unsigned length)
+{
+    for (const InputCharacterType* end = input + length; input != end; ++input) {
+        if (*input > 0x1F && *input != '"' && *input != '\\') {
+            *output++ = *input;
+            continue;
+        }
+        switch (*input) {
+        case '\t':
+            *output++ = '\\';
+            *output++ = 't';
+            break;
+        case '\r':
+            *output++ = '\\';
+            *output++ = 'r';
+            break;
+        case '\n':
+            *output++ = '\\';
+            *output++ = 'n';
+            break;
+        case '\f':
+            *output++ = '\\';
+            *output++ = 'f';
+            break;
+        case '\b':
+            *output++ = '\\';
+            *output++ = 'b';
+            break;
+        case '"':
+            *output++ = '\\';
+            *output++ = '"';
+            break;
+        case '\\':
+            *output++ = '\\';
+            *output++ = '\\';
+            break;
+        default:
+            ASSERT((*input & 0xFF00) == 0);
+            static const char hexDigits[] = "0123456789abcdef";
+            *output++ = '\\';
+            *output++ = 'u';
+            *output++ = '0';
+            *output++ = '0';
+            *output++ = static_cast<LChar>(hexDigits[(*input >> 4) & 0xF]);
+            *output++ = static_cast<LChar>(hexDigits[*input & 0xF]);
+            break;
+        }
+    }
+}
+
+void StringBuilder::appendQuotedJSONString(const String& string)
+{
+    // Make sure we have enough buffer space to append this string without having
+    // to worry about reallocating in the middle.
+    // The 2 is for the '"' quotes on each end.
+    // The 6 is for characters that need to be \uNNNN encoded.
+    size_t maximumCapacityRequired = length() + 2 + string.length() * 6;
+    RELEASE_ASSERT(maximumCapacityRequired < std::numeric_limits<unsigned>::max());
+
+    if (is8Bit() && !string.is8Bit())
+        allocateBufferUpConvert(m_bufferCharacters8, roundUpToPowerOfTwo(maximumCapacityRequired));
+    else
+        reserveCapacity(roundUpToPowerOfTwo(maximumCapacityRequired));
+
+    if (is8Bit()) {
+        ASSERT(string.is8Bit());
+        LChar* output = m_bufferCharacters8 + m_length;
+        *output++ = '"';
+        appendQuotedJSONStringInternal(output, string.characters8(), string.length());
+        *output++ = '"';
+        m_length = output - m_bufferCharacters8;
+    } else {
+        UChar* output = m_bufferCharacters16 + m_length;
+        *output++ = '"';
+        if (string.is8Bit())
+            appendQuotedJSONStringInternal(output, string.characters8(), string.length());
+        else
+            appendQuotedJSONStringInternal(output, string.characters16(), string.length());
+        *output++ = '"';
+        m_length = output - m_bufferCharacters16;
+    }
+}
+
 } // namespace WTF

trunk/Source/WTF/wtf/text/StringBuilder.h

@@ -160 +160 @@
     }
 
+    WTF_EXPORT_PRIVATE void appendQuotedJSONString(const String&);
+
     template<unsigned charactersCount>
     ALWAYS_INLINE void appendLiteral(const char (&characters)[charactersCount]) { append(characters, charactersCount - 1); }

trunk/Source/WebKit2/ChangeLog

@@ +1 @@
+2015-05-08  Andreas Kling  <akling@apple.com>
+
+        Optimize serialization of quoted JSON strings.
+        <https://webkit.org/b/144754>
+
+        Reviewed by Darin Adler.
+
+        * NetworkProcess/cache/NetworkCacheEntry.cpp:
+        (WebKit::NetworkCache::Entry::asJSON): Use the new StringBuilder API.
+
 2015-05-08  Commit Queue  <commit-queue@webkit.org>
 

trunk/Source/WebKit2/NetworkProcess/cache/NetworkCacheEntry.cpp

@@ -31 +31 @@
 #include "NetworkCacheDecoder.h"
 #include "NetworkCacheEncoder.h"
-#include <JavaScriptCore/JSONObject.h>
 #include <WebCore/ResourceRequest.h>
 #include <WebCore/SharedBuffer.h>
@@ -160 +159 @@
     json.appendLiteral("{\n");
     json.appendLiteral("\"hash\": ");
-    JSC::appendQuotedJSONStringToBuilder(json, m_key.hashAsString());
+    json.appendQuotedJSONString(m_key.hashAsString());
     json.appendLiteral(",\n");
     json.appendLiteral("\"bodySize\": ");
@@ -169 +168 @@
     json.appendLiteral(",\n");
     json.appendLiteral("\"partition\": ");
-    JSC::appendQuotedJSONStringToBuilder(json, m_key.partition());
+    json.appendQuotedJSONString(m_key.partition());
     json.appendLiteral(",\n");
     json.appendLiteral("\"timestamp\": ");
@@ -175 +174 @@
     json.appendLiteral(",\n");
     json.appendLiteral("\"URL\": ");
-    JSC::appendQuotedJSONStringToBuilder(json, m_response.url().string());
+    json.appendQuotedJSONString(m_response.url().string());
     json.appendLiteral(",\n");
     json.appendLiteral("\"bodyHash\": ");
-    JSC::appendQuotedJSONStringToBuilder(json, info.bodyHash);
+    json.appendQuotedJSONString(info.bodyHash);
     json.appendLiteral(",\n");
     json.appendLiteral("\"bodyShareCount\": ");
@@ -190 +189 @@
         firstHeader = false;
         json.appendLiteral("    ");
-        JSC::appendQuotedJSONStringToBuilder(json, header.key);
+        json.appendQuotedJSONString(header.key);
         json.appendLiteral(": ");
-        JSC::appendQuotedJSONStringToBuilder(json, header.value);
+        json.appendQuotedJSONString(header.value);
     }
     json.appendLiteral("\n}\n");