Add reinterpretPtr.nim

README.md

@@ -27,3 +27,6 @@ This is similar to std/deques, but has fixed size storage that can be allocated
 
 ### [staticSeq](https://demotomohiro.github.io/littlesugar/staticSeq.html)
 This is similar to seq, but internal storage size is fixed to `N` and it can be allocated on stack.
+
+### [reinterpretPtr](https://demotomohiro.github.io/littlesugar/reinterpretPtr.html)
+Reinterpret the given pointer to a different pointer type.

littlesugar.nimble

@@ -30,4 +30,5 @@ task docgen, "Generate html documents":
   selfExec "doc --outdir:htmldocs --index:on src/littlesugar/setLambda.nim"
   selfExec "doc --outdir:htmldocs --index:on src/littlesugar/staticDeque.nim"
   selfExec "doc --outdir:htmldocs --index:on src/littlesugar/staticSeq.nim"
+  selfExec "doc --outdir:htmldocs --index:on src/littlesugar/reinterpretPtr.nim"
   selfExec "buildIndex -o:htmldocs/theindex.html htmldocs"

src/littlesugar/reinterpretPtr.nim

@@ -0,0 +1,25 @@
+func reinterpretPtr*[T: ptr](src: ptr or pointer): T =
+  ## Reinterpret the given pointer to a different pointer type.
+  ##
+  ## This is same to cast, but only accepts a pointer type for safer type convertion.
+  ## But it still can be unsafe.
+  cast[T](src)
+
+when isMainModule:
+  var
+    a = 123
+    pa = a.addr
+    pa2: pointer = pa
+
+  doAssert reinterpretPtr[ptr int](pa2) is ptr int
+  doAssert reinterpretPtr[ptr int](pa2)[] == 123
+  doAssert not compiles(reinterpretPtr[ptr int](a))
+  doAssert reinterpretPtr[ptr int](nil) is ptr int
+  doAssert reinterpretPtr[ptr int](nil) == nil
+
+  var
+    s = "Hello"
+    cs = s.cstring
+    ps: pointer = cs
+  doAssert reinterpretPtr[cstring](ps) is cstring
+  doAssert reinterpretPtr[cstring](ps) == "Hello"