From 7bd361665890f5cb3a1d3325ad7e6be333609716 Mon Sep 17 00:00:00 2001
From: Ivailo Monev <xakepa10@laimg.moc>
Date: Sat, 23 Nov 2019 21:52:42 +0000
Subject: [PATCH] rework ICU codec to avoid relocations during conversion

---
 src/core/codecs/qicucodec.cpp | 108 +++++++++++++++---------------------------
 1 file changed, 39 insertions(+), 69 deletions(-)

diff --git a/src/core/codecs/qicucodec.cpp b/src/core/codecs/qicucodec.cpp
index ed3e57e10..c56ea633e 100644
--- a/src/core/codecs/qicucodec.cpp
+++ b/src/core/codecs/qicucodec.cpp
@@ -419,93 +419,63 @@ UConverter *QIcuCodec::getConverter(QTextCodec::ConverterState *state) const
     return conv;
 }
 
-QString QIcuCodec::convertToUnicode(const char *chars, int length, QTextCodec::ConverterState *state) const
+// enough space to hold BOM, each char as surrogate pair and terminator
+#define QMAXSTRLEN(X) 1 + (X * 2) + 2
+
+QString QIcuCodec::convertToUnicode(const char *src, int length, QTextCodec::ConverterState *state) const
 {
     UConverter *conv = getConverter(state);
 
-    // for small strings pre-allocate 2x the length, else increment by 2 to be
-    // able to hold atleast one more surrogate pair
-    const bool small = (length < 100);
-    QString string(small ? (length * 2) : (length + 2), Qt::Uninitialized);
-
-    bool failed = false;
-    const char *end = chars + length;
-    int convertedChars = 0;
+    QString string(QMAXSTRLEN(length), Qt::Uninitialized);
+    UChar *dest = reinterpret_cast<UChar *>(string.data());
     UErrorCode error = U_ZERO_ERROR;
-    while (chars != end) {
-        UChar *uc = reinterpret_cast<UChar *>(string.data());
-        const UChar *ucEnd = uc + string.length();
-        uc += convertedChars;
-        ucnv_toUnicode(conv,
-                       &uc, ucEnd,
-                       &chars, end,
-                       0, false, &error);
-        if (Q_UNLIKELY(U_FAILURE(error))) {
-            qWarning("QIcuCodec::convertToUnicode: failed %s", u_errorName(error));
-            failed = true;
-            break;
+    const int convresult = ucnv_toUChars(conv, dest, string.length(), src, length, &error);
+    if (Q_UNLIKELY(U_FAILURE(error))) {
+        qWarning("QIcuCodec::convertToUnicode: failed %s", u_errorName(error));
+        if (state) {
+            error = U_ZERO_ERROR;
+            char errorbytes[10];
+            int8_t invalidlen = 0;
+            ucnv_getInvalidChars(conv,
+                            errorbytes,
+                            &invalidlen,
+                            &error);
+            state->invalidChars = invalidlen;
         }
-
-        convertedChars = uc - reinterpret_cast<const UChar *>(string.constData());
-        if (!small)
-            string.resize(string.length() + 2);
-    }
-    string.resize(convertedChars);
-
-    if (failed && state) {
-        error = U_ZERO_ERROR;
-        char errorbytes[10];
-        int8_t invalidlen = 0;
-        ucnv_getInvalidChars(conv,
-                        errorbytes,
-                        &invalidlen,
-                        &error);
-        state->invalidChars = invalidlen;
+    } else {
+        string.resize(convresult);
     }
 
     if (!state)
         ucnv_close(conv);
     return string;
 }
+#undef QMAXSTRLEN
 
 QByteArray QIcuCodec::convertFromUnicode(const QChar *unicode, int length, QTextCodec::ConverterState *state) const
 {
     UConverter *conv = getConverter(state);
 
-    int requiredLength = UCNV_GET_MAX_BYTES_FOR_STRING(length, ucnv_getMaxCharSize(conv));
-    QByteArray string(requiredLength, Qt::Uninitialized);
-
-    bool failed = false;
+    int maxbytes = UCNV_GET_MAX_BYTES_FOR_STRING(length, ucnv_getMaxCharSize(conv));
+    QByteArray string(maxbytes, Qt::Uninitialized);
+    const UChar *src = reinterpret_cast<const UChar *>(unicode);
+    char *dest = reinterpret_cast<char *>(string.data());
     UErrorCode error = U_ZERO_ERROR;
-    const UChar *uc = reinterpret_cast<const UChar *>(unicode);
-    const UChar *end = uc + length;
-    int convertedChars = 0;
-    while (uc != end) {
-        char *ch = (char *)string.data();
-        char *chEnd = ch + string.length();
-        ch += convertedChars;
-        ucnv_fromUnicode(conv,
-                         &ch, chEnd,
-                         &uc, end,
-                         0, false, &error);
-        if (Q_UNLIKELY(U_FAILURE(error))) {
-            qWarning("QIcuCodec::convertFromUnicode: failed %s", u_errorName(error));
-            failed = true;
-            break;
+    const int convresult = ucnv_fromUChars(conv, dest, string.length(), src, length, &error);
+    if (Q_UNLIKELY(U_FAILURE(error))) {
+        qWarning("QIcuCodec::convertFromUnicode: failed %s", u_errorName(error));
+        if (state) {
+            error = U_ZERO_ERROR;
+            char errorbytes[10];
+            int8_t invalidlen = 0;
+            ucnv_getInvalidChars(conv,
+                            errorbytes,
+                            &invalidlen,
+                            &error);
+            state->invalidChars = invalidlen;
         }
-        convertedChars = ch - string.data();
-    }
-    string.resize(convertedChars);
-
-    if (failed && state) {
-        error = U_ZERO_ERROR;
-        char errorbytes[10];
-        int8_t invalidlen = 0;
-        ucnv_getInvalidChars(conv,
-                        errorbytes,
-                        &invalidlen,
-                        &error);
-        state->invalidChars = invalidlen;
+    } else {
+        string.resize(convresult);
     }
 
     if (!state)
-- 
2.11.0