QDecompressHelper: use the new readPointer function in QByteDataBuffer

Gets rid of moving strings back and forth, which was extra expensive
without QList's prepend optimization (which is returning, but getting
rid of the moves is even better).

Change-Id: I520fc140310a0e1f096dda97f2e999d0e7993e77
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 29 insertions, 43 deletions

diff --git a/src/network/access/qdecompresshelper.cpp b/src/network/access/qdecompresshelper.cpp
index 981153a852..2e44a58cf4 100644
--- a/src/network/access/qdecompresshelper.cpp
+++ b/src/network/access/qdecompresshelper.cpp
@@ -510,16 +510,12 @@ qsizetype QDecompressHelper::readZLib(char *data, const qsizetype maxSize)
     static const size_t zlibMaxSize =
             size_t(std::numeric_limits<decltype(inflateStream->avail_in)>::max());
 
-    QByteArray input;
-    if (!compressedDataBuffer.isEmpty()) {
-        if (zlibMaxSize < size_t(compressedDataBuffer.sizeNextBlock()))
-            input = compressedDataBuffer.read(zlibMaxSize);
-        else
-            input = compressedDataBuffer.read();
-    }
+    QByteArrayView input = compressedDataBuffer.readPointer();
+    if (size_t(input.size()) > zlibMaxSize)
+        input = input.sliced(zlibMaxSize);
 
     inflateStream->avail_in = input.size();
-    inflateStream->next_in = reinterpret_cast<Bytef *>(input.data());
+    inflateStream->next_in = reinterpret_cast<Bytef *>(const_cast<char *>(input.data()));
 
     bool bigMaxSize = (zlibMaxSize < size_t(maxSize));
     qsizetype adjustedAvailableOut = bigMaxSize ? qsizetype(zlibMaxSize) : maxSize;
@@ -547,7 +543,8 @@ qsizetype QDecompressHelper::readZLib(char *data, const qsizetype maxSize)
                 return -1;
             } else {
                 inflateStream->avail_in = input.size();
-                inflateStream->next_in = reinterpret_cast<Bytef *>(input.data());
+                inflateStream->next_in =
+                        reinterpret_cast<Bytef *>(const_cast<char *>(input.data()));
                 continue;
             }
         } else if (ret < 0 || ret == Z_NEED_DICT) {
@@ -569,6 +566,7 @@ qsizetype QDecompressHelper::readZLib(char *data, const qsizetype maxSize)
                     delete inflateStream;
                     decoderPointer = nullptr;
                     // Failed to reinitialize, so we'll just return what we have
+                    compressedDataBuffer.advanceReadPointer(input.size() - avail_in);
                     return bytesDecoded;
                 } else {
                     inflateStream->next_in = next_in;
@@ -577,6 +575,7 @@ qsizetype QDecompressHelper::readZLib(char *data, const qsizetype maxSize)
                 }
             } else {
                 // No extra data, stream is at the end. We're done.
+                compressedDataBuffer.advanceReadPointer(input.size());
                 return bytesDecoded;
             }
         }
@@ -589,23 +588,19 @@ qsizetype QDecompressHelper::readZLib(char *data, const qsizetype maxSize)
             inflateStream->next_out = reinterpret_cast<Bytef *>(data + bytesDecoded);
         }
 
-        if (inflateStream->avail_in == 0 && inflateStream->avail_out > 0
-            && !compressedDataBuffer.isEmpty()) {
+        if (inflateStream->avail_in == 0 && inflateStream->avail_out > 0) {
             // Grab the next input!
-            if (zlibMaxSize < size_t(compressedDataBuffer.sizeNextBlock()))
-                input = compressedDataBuffer.read(zlibMaxSize);
-            else
-                input = compressedDataBuffer.read();
+            compressedDataBuffer.advanceReadPointer(input.size());
+            input = compressedDataBuffer.readPointer();
+            if (size_t(input.size()) > zlibMaxSize)
+                input = input.sliced(zlibMaxSize);
             inflateStream->avail_in = input.size();
-            inflateStream->next_in = reinterpret_cast<Bytef *>(input.data());
+            inflateStream->next_in =
+                    reinterpret_cast<Bytef *>(const_cast<char *>(input.data()));
         }
     } while (inflateStream->avail_out > 0 && inflateStream->avail_in > 0);
 
-    if (inflateStream->avail_in) {
-        // Some input was left unused; move back to the buffer
-        input = input.right(inflateStream->avail_in);
-        compressedDataBuffer.prepend(input);
-    }
+    compressedDataBuffer.advanceReadPointer(input.size() - inflateStream->avail_in);
 
     return bytesDecoded;
 }
@@ -645,10 +640,8 @@ qsizetype QDecompressHelper::readBrotli(char *data, const qsizetype maxSize)
         return bytesDecoded;
     Q_ASSERT(bytesDecoded < maxSize);
 
-    QByteArray input;
-    if (!compressedDataBuffer.isEmpty())
-        input = compressedDataBuffer.read();
-    const uint8_t *encodedPtr = reinterpret_cast<const uint8_t *>(input.constData());
+    QByteArrayView input = compressedDataBuffer.readPointer();
+    const uint8_t *encodedPtr = reinterpret_cast<const uint8_t *>(input.data());
     size_t encodedBytesRemaining = input.size();
 
     uint8_t *decodedPtr = reinterpret_cast<uint8_t *>(data + bytesDecoded);
@@ -668,10 +661,12 @@ qsizetype QDecompressHelper::readBrotli(char *data, const qsizetype maxSize)
         case BROTLI_DECODER_RESULT_SUCCESS:
             BrotliDecoderDestroyInstance(brotliDecoderState);
             decoderPointer = nullptr;
+            compressedDataBuffer.clear();
             return bytesDecoded;
         case BROTLI_DECODER_RESULT_NEEDS_MORE_INPUT:
-            if (!compressedDataBuffer.isEmpty()) {
-                input = compressedDataBuffer.read();
+            compressedDataBuffer.advanceReadPointer(input.size());
+            input = compressedDataBuffer.readPointer();
+            if (!input.isEmpty()) {
                 encodedPtr = reinterpret_cast<const uint8_t *>(input.constData());
                 encodedBytesRemaining = input.size();
                 break;
@@ -684,11 +679,7 @@ qsizetype QDecompressHelper::readBrotli(char *data, const qsizetype maxSize)
             break;
         }
     }
-    if (encodedBytesRemaining) {
-        // Some input was left unused; move back to the buffer
-        input = input.right(QByteArray::size_type(encodedBytesRemaining));
-        compressedDataBuffer.prepend(input);
-    }
+    compressedDataBuffer.advanceReadPointer(input.size() - encodedBytesRemaining);
     return bytesDecoded;
 #endif
 }
@@ -702,10 +693,8 @@ qsizetype QDecompressHelper::readZstandard(char *data, const qsizetype maxSize)
 #else
     ZSTD_DStream *zstdStream = toZstandardPointer(decoderPointer);
 
-    QByteArray input;
-    if (!compressedDataBuffer.isEmpty())
-        input = compressedDataBuffer.read();
-    ZSTD_inBuffer inBuf { input.constData(), size_t(input.size()), 0 };
+    QByteArrayView input = compressedDataBuffer.readPointer();
+    ZSTD_inBuffer inBuf { input.data(), size_t(input.size()), 0 };
 
     ZSTD_outBuffer outBuf { data, size_t(maxSize), 0 };
 
@@ -721,17 +710,14 @@ qsizetype QDecompressHelper::readZstandard(char *data, const qsizetype maxSize)
             // if pos == size then there may be data left over in internal buffers
             if (outBuf.pos == outBuf.size) {
                 decoderHasData = true;
-            } else if (inBuf.pos == inBuf.size && !compressedDataBuffer.isEmpty()) {
-                input = compressedDataBuffer.read();
+            } else if (inBuf.pos == inBuf.size) {
+                compressedDataBuffer.advanceReadPointer(input.size());
+                input = compressedDataBuffer.readPointer();
                 inBuf = { input.constData(), size_t(input.size()), 0 };
             }
         }
     }
-    if (inBuf.pos < inBuf.size) {
-        // Some input was left unused; move back to the buffer
-        input = input.mid(QByteArray::size_type(inBuf.pos));
-        compressedDataBuffer.prepend(std::move(input));
-    }
+    compressedDataBuffer.advanceReadPointer(inBuf.pos);
     return bytesDecoded;
 #endif
 }