transform_reduce

This is a parallelizable version of accumulate. These look like they can
go out of order.

Signed-off-by: Rosen Penev <[email protected]>

Author: neheb

src/tiffcomposite_int.cpp

@@ -15,8 +15,10 @@
 #include "value.hpp"
 
 #include <algorithm>
+#include <functional>
 #include <iostream>
 #include <memory>
+#include <numeric>
 
 // *****************************************************************************
 namespace {
@@ -1363,11 +1365,7 @@ size_t TiffDataEntry::doSizeData() const {
 }
 
 size_t TiffSubIfd::doSizeData() const {
-  size_t len = 0;
-  for (auto&& ifd : ifds_) {
-    len += ifd->size();
-  }
-  return len;
+  return std::transform_reduce(ifds_.begin(), ifds_.end(), size_t{0}, std::plus<>(), std::mem_fn(&TiffSubIfd::size));
 }
 
 size_t TiffIfdMakernote::doSizeData() const {
@@ -1379,22 +1377,14 @@ size_t TiffComponent::sizeImage() const {
 }
 
 size_t TiffDirectory::doSizeImage() const {
-  size_t len = 0;
-  for (auto&& component : components_) {
-    len += component->sizeImage();
-  }
-  if (pNext_) {
-    len += pNext_->sizeImage();
-  }
-  return len;
+  size_t len = pNext_ ? pNext_->sizeImage() : 0;
+  return std::transform_reduce(components_.begin(), components_.end(), len, std::plus<>(),
+                               std::mem_fn(&TiffDirectory::sizeImage));
 }
 
 size_t TiffSubIfd::doSizeImage() const {
-  size_t len = 0;
-  for (auto&& ifd : ifds_) {
-    len += ifd->sizeImage();
-  }
-  return len;
+  return std::transform_reduce(ifds_.begin(), ifds_.end(), size_t{0}, std::plus<>(),
+                               std::mem_fn(&TiffSubIfd::sizeImage));
 }  // TiffSubIfd::doSizeImage
 
 size_t TiffIfdMakernote::doSizeImage() const {
@@ -1409,11 +1399,9 @@ size_t TiffImageEntry::doSizeImage() const {
   if (!pValue())
     return 0;
   auto len = pValue()->sizeDataArea();
-  if (len == 0) {
-    for (const auto& [_, off] : strips_) {
-      len += off;
-    }
-  }
+  if (len == 0)
+    return std::transform_reduce(strips_.begin(), strips_.end(), len, std::plus<>(),
+                                 [](const auto& s) { return s.second; });
   return len;
 }  // TiffImageEntry::doSizeImage