logic cleanup

stdlib/Mmap/src/Mmap.jl

@@ -208,23 +208,37 @@ function mmap(io::IO,
  mmaplen = (offset - offset_page) + len
 
  file_desc = gethandle(io)
+ szfile = convert(Csize_t, len + offset)
+ requestedSizeLarger = szfile > filesize(io)
  # platform-specific mmapping
  @static if Sys.isunix()
  prot, flags, iswrite = settings(file_desc, shared)
- szfile = convert(Csize_t, len + offset)
- if iswrite && grow
- grow!(io, offset, len)
- elseif szfile > filesize(io)
- throw(ArgumentError("unable to increase file size to $szfile due to read-only permissions"))
+ if requestedSizeLarger
+ if iswrite
+ if grow
+ grow!(io, offset, len)
+ else
+ throw(ArgumentError("requested size $szfile larger than file size $(filesize(io)), but requested not to grow"))
+ end
+ end
+ if !iswrite
+ throw(ArgumentError("unable to increase file size to $szfile due to read-only permissions"))
+ end
  end
  # mmap the file
  ptr = ccall(:jl_mmap, Ptr{Cvoid}, (Ptr{Cvoid}, Csize_t, Cint, Cint, RawFD, Int64),
  C_NULL, mmaplen, prot, flags, file_desc, offset_page)
  systemerror("memory mapping failed", reinterpret(Int, ptr) == -1)
  else
  name, readonly, create = settings(io)
- szfile = convert(Csize_t, len + offset)
- readonly && szfile > filesize(io) && throw(ArgumentError("unable to increase file size to $szfile due to read-only permissions"))
+ if requestedSizeLarger
+ if readonly
+ throw(ArgumentError("unable to increase file size to $szfile due to read-only permissions"))
+ end
+ if !readonly && !grow
+ throw(ArgumentError("requested size $szfile larger than file size $(filesize(io)), but requested not to grow"))
+ end
+ end
  handle = create ? ccall(:CreateFileMappingW, stdcall, Ptr{Cvoid}, (OS_HANDLE, Ptr{Cvoid}, DWORD, DWORD, DWORD, Cwstring),
  file_desc, C_NULL, readonly ? PAGE_READONLY : PAGE_READWRITE, szfile >> 32, szfile & typemax(UInt32), name) :
  ccall(:OpenFileMappingW, stdcall, Ptr{Cvoid}, (DWORD, Cint, Cwstring),