From a7fe1af609e905f6e5fbf291ec43261a41d9541f Mon Sep 17 00:00:00 2001
From: Lars Knoll <lars.knoll@qt.io>
Date: Sun, 15 Mar 2020 18:45:43 +0100
Subject: Remove QRegExp usage from the XBM handler

Change-Id: Ie7141c2a04c233bc1298195aebfc0437e43df0d1
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>
---
 src/gui/image/qxbmhandler.cpp | 51 ++++++++++++++++++++++++-------------------
 1 file changed, 28 insertions(+), 23 deletions(-)

diff --git a/src/gui/image/qxbmhandler.cpp b/src/gui/image/qxbmhandler.cpp
index f06561690c..c422826035 100644
--- a/src/gui/image/qxbmhandler.cpp
+++ b/src/gui/image/qxbmhandler.cpp
@@ -44,7 +44,6 @@
 
 #include <qimage.h>
 #include <qiodevice.h>
-#include <qregexp.h>
 #include <qvariant.h>
 
 #include <stdio.h>
@@ -67,8 +66,6 @@ static bool read_xbm_header(QIODevice *device, int& w, int& h)
     const int buflen = 300;
     const int maxlen = 4096;
     char buf[buflen + 1];
-    QRegExp r1(QLatin1String("^#define[ \t]+[a-zA-Z0-9._]+[ \t]+"));
-    QRegExp r2(QLatin1String("[0-9]+"));
 
     qint64 readBytes = 0;
     qint64 totalReadBytes = 0;
@@ -90,30 +87,38 @@ static bool read_xbm_header(QIODevice *device, int& w, int& h)
             return false;
     }
 
-    buf[readBytes - 1] = '\0';
-    QString sbuf;
-    sbuf = QString::fromLatin1(buf);
+    auto parseDefine = [] (const char *buf, int len) -> int {
+        auto isAsciiLetterOrNumber = [] (char ch) -> bool {
+            return (ch >= '0' && ch <= '9') ||
+                    (ch >= 'A' && ch <= 'Z') ||
+                    (ch >= 'a' && ch <= 'z') ||
+                    ch == '_' || ch == '.';
+        };
+        auto isAsciiSpace = [] (char ch) -> bool {
+            return ch == ' ' || ch == '\t';
+        };
+        const char define[] = "#define";
+        constexpr size_t defineLen = sizeof(define) - 1;
+        if (strncmp(buf, define, defineLen) != 0)
+            return 0;
+        int index = defineLen;
+        while (buf[index] && isAsciiSpace(buf[index]))
+            ++index;
+        while (buf[index] && isAsciiLetterOrNumber(buf[index]))
+            ++index;
+        while (buf[index] && isAsciiSpace(buf[index]))
+            ++index;
+
+        return QByteArray(buf + index, len - index).toInt();
+    };
+
 
     // "#define .._width <num>"
-    if (r1.indexIn(sbuf) == 0 &&
-         r2.indexIn(sbuf, r1.matchedLength()) == r1.matchedLength())
-        w = QByteArray(&buf[r1.matchedLength()]).trimmed().toInt();
-    else
-        return false;
+    w = parseDefine(buf, readBytes - 1);
 
-    // "#define .._height <num>"
     readBytes = device->readLine(buf, buflen);
-    if (readBytes <= 0)
-        return false;
-    buf[readBytes - 1] = '\0';
-
-    sbuf = QString::fromLatin1(buf);
-
-    if (r1.indexIn(sbuf) == 0 &&
-         r2.indexIn(sbuf, r1.matchedLength()) == r1.matchedLength())
-        h = QByteArray(&buf[r1.matchedLength()]).trimmed().toInt();
-    else
-        return false;
+    // "#define .._height <num>"
+    h = parseDefine(buf, readBytes - 1);
 
     // format error
     if (w <= 0 || w > 32767 || h <= 0 || h > 32767)
-- 
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