From d5309bf4cf9e36e161027cf7ad1775eb355433f1 Mon Sep 17 00:00:00 2001
From: Jacques Lucke <jacques@blender.org>
Date: Wed, 21 Apr 2021 16:59:22 +0200
Subject: Functions: add slice method for generic spans

---
 source/blender/functions/FN_generic_span.hh | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/source/blender/functions/FN_generic_span.hh b/source/blender/functions/FN_generic_span.hh
index ea2bd49fa09..e2c49697ba9 100644
--- a/source/blender/functions/FN_generic_span.hh
+++ b/source/blender/functions/FN_generic_span.hh
@@ -85,6 +85,14 @@ class GSpan {
     BLI_assert(type_->is<T>());
     return Span<T>(static_cast<const T *>(data_), size_);
   }
+
+  GSpan slice(const int64_t start, int64_t size) const
+  {
+    BLI_assert(start >= 0);
+    BLI_assert(size >= 0);
+    const int64_t new_size = std::max<int64_t>(0, std::min(size, size_ - start));
+    return GSpan(*type_, POINTER_OFFSET(data_, type_->size() * start), new_size);
+  }
 };
 
 /**
@@ -153,6 +161,14 @@ class GMutableSpan {
     BLI_assert(type_->is<T>());
     return MutableSpan<T>(static_cast<T *>(data_), size_);
   }
+
+  GMutableSpan slice(const int64_t start, int64_t size) const
+  {
+    BLI_assert(start >= 0);
+    BLI_assert(size >= 0);
+    const int64_t new_size = std::max<int64_t>(0, std::min(size, size_ - start));
+    return GMutableSpan(*type_, POINTER_OFFSET(data_, type_->size() * start), new_size);
+  }
 };
 
 }  // namespace blender::fn
-- 
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