Clean up and document the generator for qurltld_p.h

This scans the public suffix list and emits suitable content for the
header.  Made some modest efficiency gains while hopefully making the
code easier to understand.  Check for success when opening files.

Change-Id: If6b25c5c85f86209b33d9188743e820690e7dc05
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>

1 files changed, 96 insertions, 67 deletions

diff --git a/util/corelib/qurl-generateTLDs/main.cpp b/util/corelib/qurl-generateTLDs/main.cpp
index 7268fb077a..6fde287049 100644
--- a/util/corelib/qurl-generateTLDs/main.cpp
+++ b/util/corelib/qurl-generateTLDs/main.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2016 The Qt Company Ltd.
+** Copyright (C) 2019 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the utils of the Qt Toolkit.
@@ -28,33 +28,66 @@
 
 #include <QtCore>
 
+const QString quadQuote = QStringLiteral("\"\""); // Closes one string, opens a new one.
+
 static QString utf8encode(const QByteArray &array) // turns e.g. tranøy.no to tran\xc3\xb8y.no
 {
     QString result;
     result.reserve(array.length() + array.length() / 3);
+    bool wasHex = false;
     for (int i = 0; i < array.length(); ++i) {
         char c = array.at(i);
         // if char is non-ascii, escape it
         if (c < 0x20 || uchar(c) >= 0x7f) {
             result += "\\x" + QString::number(uchar(c), 16);
+            wasHex = true;
         } else {
             // if previous char was escaped, we need to make sure the next char is not
             // interpreted as part of the hex value, e.g. "äc.com" -> "\xabc.com"; this
             // should be "\xab""c.com"
-            QRegExp hexEscape("\\\\x[a-fA-F0-9][a-fA-F0-9]$");
             bool isHexChar = ((c >= '0' && c <= '9') ||
-                             (c >= 'a' && c <= 'f') ||
-                             (c >= 'A' && c <= 'F'));
-            if (result.contains(hexEscape) && isHexChar)
-                result += "\"\"";
+                              (c >= 'a' && c <= 'f') ||
+                              (c >= 'A' && c <= 'F'));
+            if (wasHex && isHexChar)
+                result += quadQuote;
             result += c;
+            wasHex = false;
         }
     }
     return result;
 }
 
-int main(int argc, char **argv) {
+/*
+    Digest public suffix data into efficiently-searchable form.
+
+    Takes the public suffix list (see usage message), a list of DNS domains
+    whose child domains should not be presumed to trust one another, and
+    converts it to a form that lets qtbase/src/corelib/io/qtldurl.cpp's query
+    functions find entries efficiently.
+
+    Each line of the suffix file (aside from comments and blanks) gives a suffix
+    (starting with a dot) with an optional prefix of '*' (to include every
+    immediate child) or of '!'  (to exclude the suffix, e.g. from a '*' line for
+    a tail of it).  A line with neither of these prefixes is an exact match.
+
+    Each line is hashed and the hash is reduced modulo the number of lines
+    (tldCount); lines are grouped by reduced hash and separated by '\0' bytes
+    within each group. Conceptually, the groups are then emitted to a single
+    huge string, along with a table (tldIndices[tldCount]) of indices into that
+    string of the starts of the the various groups.
+
+    However, that huge string would exceed the 64k limit at least one compiler
+    imposes on a single string literal, so we actually split up the huge string
+    into an array of chunks, each less than 64k in size. Each group is written
+    to a single chunk (so we start a new chunk if the next group would take the
+    present chunk over the limit). There are tldChunkCount chunks; their lengths
+    are saved in tldChunks[tldChunkCount]; the chunks themselves in
+    tldData[tldChunkCount]. See qtldurl.cpp's containsTLDEntry() for how to
+    search for a string in the resulting data.
+*/
 
+int main(int argc, char **argv)
+{
     QCoreApplication app(argc, argv);
     if (argc < 3) {
         printf("\nusage: %s inputFile outputFile\n\n", argv[0]);
@@ -68,14 +101,20 @@ int main(int argc, char **argv) {
         exit(1);
     }
     QFile file(argv[1]);
-    QFile outFile(argv[2]);
-    file.open(QIODevice::ReadOnly);
-    outFile.open(QIODevice::WriteOnly);
+    if (!file.open(QIODevice::ReadOnly)) {
+        fprintf("Failed to open input file (%s); see %s -usage", argv[1], argv[0]);
+        return 1;
+    }
 
-    QByteArray outIndicesBufferBA;
-    QBuffer outIndicesBuffer(&outIndicesBufferBA);
-    outIndicesBuffer.open(QIODevice::WriteOnly);
+    QFile outFile(argv[2]);
+    if (!outFile.open(QIODevice::WriteOnly)) {
+        file.close()
+        fprintf("Failed to open output file (%s); see %s -usage", argv[2], argv[0]);
+        return 1;
+    }
 
+    // Write tldData[] and tldIndices[] in one scan of the (input) file, but
+    // buffer tldData[] so we don'te interleave them in the outFile.
     QByteArray outDataBufferBA;
     QBuffer outDataBuffer(&outDataBufferBA);
     outDataBuffer.open(QIODevice::WriteOnly);
@@ -85,75 +124,65 @@ int main(int argc, char **argv) {
         file.readLine();
         lineCount++;
     }
+    outFile.write("static const quint16 tldCount = ");
+    outFile.write(QByteArray::number(lineCount));
+    outFile.write(";\n");
+
     file.reset();
     QVector<QString> strings(lineCount);
     while (!file.atEnd()) {
-        QString s = QString::fromUtf8(file.readLine());
-        QString st = s.trimmed();
+        QString st = QString::fromUtf8(file.readLine()).trimmed();
         int num = qt_hash(st) % lineCount;
+        QString &entry = strings[num];
+        st = utf8encode(st.toUtf8());
 
-        QString utf8String = utf8encode(st.toUtf8());
+        // For domain 1.com, we could get something like a.com\01.com, which
+        // would be misinterpreted as octal 01, so we need to separate such
+        // strings with quotes:
+        if (!entry.isEmpty() && st.at(0).isDigit())
+            entry.append(quadQuote);
 
-        // for domain 1.com, we could get something like
-        // a.com\01.com, which would be interpreted as octal 01,
-        // so we need to separate those strings with quotes
-        QRegExp regexpOctalEscape(QLatin1String("^[0-9]"));
-        if (!strings.at(num).isEmpty() && st.contains(regexpOctalEscape))
-            strings[num].append("\"\"");
-
-        strings[num].append(utf8String);
-        strings[num].append("\\0");
+        entry.append(st);
+        entry.append("\\0");
     }
-
-    outIndicesBuffer.write("static const quint16 tldCount = ");
-    outIndicesBuffer.write(QByteArray::number(lineCount));
-    outIndicesBuffer.write(";\n");
-    outIndicesBuffer.write("static const quint32 tldIndices[");
-//    outIndicesBuffer.write(QByteArray::number(lineCount+1)); // not needed
-    outIndicesBuffer.write("] = {\n");
+    outFile.write("static const quint32 tldIndices[] = {\n");
+    outDataBuffer.write("\nstatic const char *tldData[] = {\n");
 
     int totalUtf8Size = 0;
     int chunkSize = 0; // strlen of the current chunk (sizeof is bigger by 1)
-    int stringUtf8Size = 0;
     QStringList chunks;
     for (int a = 0; a < lineCount; a++) {
-        bool lineIsEmpty = strings.at(a).isEmpty();
-        if (!lineIsEmpty) {
-            strings[a].prepend("\"");
-            strings[a].append("\"");
-        }
-        int zeroCount = strings.at(a).count(QLatin1String("\\0"));
-        int utf8CharsCount = strings.at(a).count(QLatin1String("\\x"));
-        int quoteCount = strings.at(a).count('"');
-        stringUtf8Size = strings.at(a).count() - (zeroCount + quoteCount + utf8CharsCount * 3);
-        chunkSize += stringUtf8Size;
-        // MSVC 2015 chokes if sizeof(a single string) > 0xffff
-        if (chunkSize >= 0xffff) {
-            static int chunkCount = 0;
-            qWarning() << "chunk" << ++chunkCount << "has length" << chunkSize - stringUtf8Size;
-            outDataBuffer.write(",\n\n");
-            chunks.append(QByteArray::number(totalUtf8Size));
-            chunkSize = 0;
+        outFile.write(QByteArray::number(totalUtf8Size));
+        outFile.write(",\n");
+        const QString &entry = strings.at(a);
+        if (!entry.isEmpty()) {
+            const int zeroCount = entry.count(QLatin1String("\\0"));
+            const int utf8CharsCount = entry.count(QLatin1String("\\x"));
+            const int quoteCount = entry.count('"');
+            const int stringUtf8Size = entry.count() - (zeroCount + quoteCount + utf8CharsCount * 3);
+            chunkSize += stringUtf8Size;
+            // MSVC 2015 chokes if sizeof(a single string) > 0xffff
+            if (chunkSize >= 0xffff) {
+                static int chunkCount = 0;
+                qWarning() << "chunk" << ++chunkCount << "has length" << chunkSize - stringUtf8Size;
+                outDataBuffer.write(",\n\n");
+                chunks.append(QString::number(totalUtf8Size));
+                chunkSize = 0;
+            }
+            totalUtf8Size += stringUtf8Size;
+
+            outDataBuffer.write("\"");
+            outDataBuffer.write(entry.toUtf8());
+            outDataBuffer.write("\"\n");
         }
-        outDataBuffer.write(strings.at(a).toUtf8());
-        if (!lineIsEmpty)
-            outDataBuffer.write("\n");
-        outIndicesBuffer.write(QByteArray::number(totalUtf8Size));
-        outIndicesBuffer.write(",\n");
-        totalUtf8Size += stringUtf8Size;
     }
-    chunks.append(QByteArray::number(totalUtf8Size));
-    outIndicesBuffer.write(QByteArray::number(totalUtf8Size));
-    outIndicesBuffer.write("};\n");
-    outIndicesBuffer.close();
-    outFile.write(outIndicesBufferBA);
+    chunks.append(QString::number(totalUtf8Size));
+    outFile.write(QByteArray::number(totalUtf8Size));
+    outFile.write("};\n");
 
+    outDataBuffer.write("};\n");
     outDataBuffer.close();
-    outFile.write("\nstatic const char *tldData[");
-//    outFile.write(QByteArray::number(charSize)); // not needed
-    outFile.write("] = {\n");
     outFile.write(outDataBufferBA);
-    outFile.write("};\n");
 
     // write chunk information
     outFile.write("\nstatic const quint16 tldChunkCount = ");
@@ -162,6 +191,6 @@ int main(int argc, char **argv) {
     outFile.write(chunks.join(", ").toLatin1());
     outFile.write("};\n");
     outFile.close();
-    printf("data generated to %s . Now copy the data from this file to src/corelib/io/qurltlds_p.h in your Qt repo\n", argv[2]);
-    exit(0);
+    printf("Data generated to %s - now revise qtbase/src/corelib/io/qurltlds_p.h to use this data.\n", argv[2]);
+    return 0;
 }