initial publication

examples/extractversion.go

@@ -0,0 +1,64 @@
+package main
+
+import (
+	"encoding/binary"
+	"fmt"
+)
+
+const (
+	posMajor int = 1 + iota
+	posMinor
+	posPatch
+	posRelFlag
+)
+
+var (
+	singleValVer      uint32
+	singleValVerBytes []byte = []byte{
+		0x01, 0x02, 0x03, 0x01, // A version of 1.2.3 with the PreRelease release flag enabled
+	}
+	ord binary.ByteOrder = binary.BigEndian
+)
+
+func main() {
+
+	var verVal uint8
+
+	singleValVer = ord.Uint32(singleValVerBytes)
+
+	// fmt's Printf, for some silly reason, strips leading 0's from hex formatting unless you explicitly pad or align precision.
+	fmt.Printf("%d\n%#.8x\n", singleValVer, singleValVer)
+	// Prints:
+	/*
+		16909057
+		0x01020301
+	*/
+
+	/*
+		The individual versions can be fetched by the following. This comment is an explanation of the condensed form below in code.
+
+		1. n = 8 * i // i is the version component you want. See the pos* constants at the top. 8 to align to a byte (8 bits).
+		2. offset = 32 - n // 32 because singleValVar is a uint32 (and thus 4 bytes, or 32 bits, in memory).
+		3. cmp = singleValVer >> offset // Shift to the bit offset we're interested in.
+		4. val32 = cmp & 0xff // It's then AND'd with 0xff (256) to get the set bits -- but still a uint32, so
+		5. verVal = uint8(val32)
+	*/
+
+	// For example:
+	for i, verNm := range map[int]string{
+		posMajor:   "Major",
+		posMinor:   "Minor",
+		posPatch:   "Patch",
+		posRelFlag: "Release Flag(s)",
+	} {
+		verVal = uint8((singleValVer >> (32 - (8 * i))) & 0xff)
+		fmt.Printf("%s: %d (%#02x)\n", verNm, verVal, verVal)
+	}
+	// Prints:
+	/*
+		Major: 1 (0x01)
+		Minor: 2 (0x02)
+		Patch: 3 (0x03)
+		Release Flag(s): 1 (0x01)
+	*/
+}