func computeMmapSize()

in file.go [657:694]

• 26 lines of code
• 7 McCabe index (conditional complexity)

func computeMmapSize(minSize, maxSize, pageSize uint) (uint, reason) {
	if maxSize != 0 {
		// return maxSize as multiple of pages. Round downwards in case maxSize
		// is not multiple of pages

		if minSize > maxSize {
			maxSize = minSize
		}

		sz := ((maxSize + pageSize - 1) / pageSize) * pageSize
		if sz < initSize {
			return 0, raiseInvalidParamf("max size of %v bytes is too small", maxSize)
		}

		return sz, nil
	}

	if minSize < doubleLimit {
		// grow by next power of 2, starting at 64KB
		initBits := uint(16) // 64KB min
		power2Bits := uint(64 - bits.LeadingZeros64(uint64(minSize)))
		if power2Bits < initBits {
			power2Bits = initBits
		}
		return 1 << power2Bits, nil
	}

	// allocate number of 1GB blocks to fulfill minSize
	sz := ((minSize + (sz1GB - 1)) / sz1GB) * sz1GB
	if sz > maxMmapSize {
		return 0, raiseInvalidParamf("mmap size of %v bytes is too large", sz)
	}

	// ensure we have a multiple of pageSize
	sz = ((sz + pageSize - 1) / pageSize) * pageSize

	return sz, nil
}