PDF: Add (low-memory) SkPDFBitmap class

src/pdf/SkDeflateWStream.cpp

+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkDeflateWStream.h"
+
+#ifndef SK_HAS_ZLIB
+
+SkDeflateWStream::SkDeflateWStream(SkWStream*) { SkDEBUGFAIL("!SK_HAS_ZLIB"); }
+SkDeflateWStream::~SkDeflateWStream() {}
+bool SkDeflateWStream::write(const void*, size_t) { return false; }
+void SkDeflateWStream::flush() {}
+size_t SkDeflateWStream::bytesWritten() { return 0; }
+

[mtklein, 2015/02/12 00:21:45]

Don't we need to 
  struct SkDeflateWStream::Impl{};

You might just guard the whole header by SK_HAS_ZLIB if it's not going to work
without it.

[hal.canary, 2015/02/12 21:28:03]

Done.

+#else  // SK_HAS_ZLIB
+
+#  ifdef SK_SYSTEM_ZLIB
+#    include <zlib.h>
+#  else
+#    include SK_ZLIB_INCLUDE
+#  endif
+
+#define SKDEFLATEWSTREAM_INPUT_BUFFER_SIZE 4096
+#define SKDEFLATEWSTREAM_OUTPUT_BUFFER_SIZE 4024  // 4096 + 128, usually big

[mtklein, 2015/02/12 00:21:45]

Um, 4024 != 4096 + 128.

[hal.canary, 2015/02/12 21:28:03]

Done.

I was testing out big and small values for this constant (to make sure the code
worked regardless) and made a type when returning it to 4224.)

+                                                  // enough to always do a
+                                                  // single loop.
+
+// called by both write() and ~SkDeflateWStream()
+static void do_deflate(int flush,
+                       z_stream* zStream,
+                       SkWStream* out,
+                       unsigned char* inBuffer,
+                       size_t inBufferSize) {
+    zStream->next_in = inBuffer;
+    zStream->avail_in = inBufferSize;
+    unsigned char outBuffer[SKDEFLATEWSTREAM_OUTPUT_BUFFER_SIZE];
+    SkDEBUGCODE(int returnValue;)
+    do {
+        zStream->next_out = outBuffer;
+        zStream->avail_out = sizeof(outBuffer);
+        SkDEBUGCODE(returnValue =) deflate(zStream, flush);
+        SkASSERT(!zStream->msg);
+
+        out->write(outBuffer, sizeof(outBuffer) - zStream->avail_out);
+    } while (zStream->avail_in || !zStream->avail_out);
+    SkASSERT(flush == Z_FINISH
+                 ? returnValue == Z_STREAM_END
+                 : returnValue == Z_OK);
+}
+
+// Hide all zlib impl details.
+struct SkDeflateWStream::Impl {
+    SkWStream* fOut;
+    unsigned char fInBuffer[SKDEFLATEWSTREAM_INPUT_BUFFER_SIZE];
+    size_t fInBufferIndex;
+    z_stream fZStream;
+};
+
+SkDeflateWStream::SkDeflateWStream(SkWStream* out)
+    : fImpl(new SkDeflateWStream::Impl) {
+    fImpl->fOut = out;
+    fImpl->fInBufferIndex = 0;
+    fImpl->fZStream.zalloc = Z_NULL;
+    fImpl->fZStream.zfree = Z_NULL;
+    fImpl->fZStream.opaque = Z_NULL;
+    fImpl->fZStream.data_type = Z_BINARY;
+    SkDEBUGCODE(int r =) deflateInit(&fImpl->fZStream, Z_DEFAULT_COMPRESSION);
+    SkASSERT(Z_OK == r);
+}
+
+SkDeflateWStream::~SkDeflateWStream() {
+    do_deflate(Z_FINISH, &fImpl->fZStream, fImpl->fOut, fImpl->fInBuffer,
+               fImpl->fInBufferIndex);
+    (void)deflateEnd(&fImpl->fZStream);
+    delete fImpl;
+}
+
+bool SkDeflateWStream::write(const void* void_buffer, size_t len) {
+    const char* buffer = (const char*)void_buffer;
+    while (len > 0) {
+        size_t tocopy =
+                SkTMin(len, sizeof(fImpl->fInBuffer) - fImpl->fInBufferIndex);
+        memcpy(fImpl->fInBuffer + fImpl->fInBufferIndex, buffer, tocopy);
+        len -= tocopy;
+        buffer += tocopy;
+        fImpl->fInBufferIndex += tocopy;
+        SkASSERT(fImpl->fInBufferIndex <= sizeof(fImpl->fInBuffer));
+
+        // if the buffer isn't filled, don't call intp zlib yet.

[mtklein, 2015/02/12 00:21:45]

into

[hal.canary, 2015/02/12 21:28:03]

Done.

+        if (sizeof(fImpl->fInBuffer) == fImpl->fInBufferIndex) {
+            do_deflate(Z_SYNC_FLUSH, &fImpl->fZStream, fImpl->fOut,
+                       fImpl->fInBuffer, fImpl->fInBufferIndex);
+            fImpl->fInBufferIndex = 0;
+        }
+    }
+    return true;
+}
+
+void SkDeflateWStream::flush() {
+    do_deflate(Z_FULL_FLUSH, &fImpl->fZStream, fImpl->fOut, fImpl->fInBuffer,
+               fImpl->fInBufferIndex);
+    fImpl->fInBufferIndex = 0;
+}
+
+size_t SkDeflateWStream::bytesWritten() const {
+    return fImpl->fZStream.total_in + fImpl->fInBufferIndex;
+}
+
+#endif  // SK_HAS_ZLIB