QRingBuffer: allow to search from any position

Change-Id: I348cd9da88fc81c3dd0789ce8cce9d80c4524e24
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@theqtcompany.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

3 files changed, 28 insertions, 14 deletions

diff --git a/src/corelib/tools/qringbuffer.cpp b/src/corelib/tools/qringbuffer.cpp
index 85cfdaf129..5345b44204 100644
--- a/src/corelib/tools/qringbuffer.cpp
+++ b/src/corelib/tools/qringbuffer.cpp
@@ -193,20 +193,33 @@ void QRingBuffer::clear()
     bufferSize = 0;
 }
 
-qint64 QRingBuffer::indexOf(char c, qint64 maxLength) const
+qint64 QRingBuffer::indexOf(char c, qint64 maxLength, qint64 pos) const
 {
-    qint64 index = 0;
-    qint64 j = head;
-    for (int i = 0; index < maxLength && i < buffers.size(); ++i) {
-        const char *ptr = buffers[i].constData() + j;
-        j = qMin(index + (i == tailBuffer ? tail : buffers[i].size()) - j, maxLength);
-
-        while (index < j) {
-            if (*ptr++ == c)
-                return index;
-            ++index;
+    if (maxLength <= 0 || pos < 0)
+        return -1;
+
+    qint64 index = -(pos + head);
+    for (int i = 0; i < buffers.size(); ++i) {
+        const qint64 nextBlockIndex = qMin(index + (i == tailBuffer ? tail : buffers[i].size()),
+                                           maxLength);
+
+        if (nextBlockIndex > 0) {
+            const char *ptr = buffers[i].constData();
+            if (index < 0) {
+                ptr -= index;
+                index = 0;
+            }
+
+            do {
+                if (*ptr++ == c)
+                    return index + pos;
+            } while (++index < nextBlockIndex);
+
+            if (index == maxLength)
+                return -1;
+        } else {
+            index = nextBlockIndex;
         }
-        j = 0;
     }
     return -1;
 }
diff --git a/src/corelib/tools/qringbuffer_p.h b/src/corelib/tools/qringbuffer_p.h
index 68509a6a80..e7e80bc02c 100644
--- a/src/corelib/tools/qringbuffer_p.h
+++ b/src/corelib/tools/qringbuffer_p.h
@@ -114,7 +114,7 @@ public:
 
     Q_CORE_EXPORT void clear();
     inline qint64 indexOf(char c) const { return indexOf(c, size()); }
-    Q_CORE_EXPORT qint64 indexOf(char c, qint64 maxLength) const;
+    Q_CORE_EXPORT qint64 indexOf(char c, qint64 maxLength, qint64 pos = 0) const;
     Q_CORE_EXPORT qint64 read(char *data, qint64 maxLength);
     Q_CORE_EXPORT QByteArray read();
     Q_CORE_EXPORT qint64 peek(char *data, qint64 maxLength, qint64 pos = 0) const;
diff --git a/tests/auto/corelib/tools/qringbuffer/tst_qringbuffer.cpp b/tests/auto/corelib/tools/qringbuffer/tst_qringbuffer.cpp
index 77fc6ad6ae..74b6edf11f 100644
--- a/tests/auto/corelib/tools/qringbuffer/tst_qringbuffer.cpp
+++ b/tests/auto/corelib/tools/qringbuffer/tst_qringbuffer.cpp
@@ -284,7 +284,8 @@ void tst_QRingBuffer::indexOf()
     for (int i = 1; i < 256; ++i) {
         qint64 index = ringBuffer.indexOf(char(i));
         QCOMPARE(index, qint64(i - 1));
-        QCOMPARE(ringBuffer.indexOf(char(i), i), index);
+        QCOMPARE(ringBuffer.indexOf(char(i), i, i >> 1), index);
+        QCOMPARE(ringBuffer.indexOf(char(i), 256, i), Q_INT64_C(-1));
         QCOMPARE(ringBuffer.indexOf(char(i), i - 1), -1); // test for absent char
     }
 }