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authorThomas Voss <mail@thomasvoss.com> 2021-10-08 23:46:05 +0200
committerThomas Voss <mail@thomasvoss.com> 2021-10-08 23:46:05 +0200
commitd4a272edf46ad64b5bb9f1d1305f471d1f15ecfa (patch)
tree8fe297cbb9091eecac286833a375bfcd88850b5d /getgopt.go
[Meta] Initial commit
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+/*
+ * BSD Zero Clause License
+ *
+ * Copyright (c) 2021 Thomas Voss
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+ * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+ * AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+ * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+ * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+ * OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+ * PERFORMANCE OF THIS SOFTWARE.
+ */
+
+package getgopt
+
+import (
+ "fmt"
+ "os"
+)
+
+const (
+ errNoArg = "option requires an argument -- %c\n"
+ errBadArg = "unknown option -- %c\n"
+)
+
+var (
+ opt = 1
+ optlen int
+ parsed bool
+ opts [255]option
+)
+
+var (
+ /* The argument to the matched flag */
+ Optarg string
+ /* If true, print error messages */
+ Opterr = true
+ /* During parsing this is the current index into os.Args being parsed. After parsing this is
+ * the index to the first non-option element of os.Args.
+ */
+ Optind = 1
+ /* The flag that caused the last parsing error */
+ Optopt byte
+)
+
+type option struct {
+ arg bool
+ used bool
+}
+
+func parseArgs(optstring string) {
+ length := len(optstring)
+
+ if (length > 0) && (optstring[0] == ':') {
+ Opterr = false
+ }
+
+ for i, c := range optstring {
+ if c != ':' {
+ opts[c].used = true
+ opts[c].arg = ((i < length-1) && (optstring[i+1] == ':'))
+ }
+ }
+}
+
+/* A function to parse command line flags. This function takes as it's arguments from first to last,
+ * the count of command line arguments, the array of command line arguments (os.Args), an option
+ * string, and a pointer to a byte where the current flag can be stored. When called the current
+ * flag will be stored in `optptr` and the global variables `Optarg`, `Opterr`, `Optind`, and
+ * `Optopt` may be set.
+ *
+ * If there are still more arguments to be parsed, the function will return true. Otherwise false is
+ * returned. This makes it very easy to incorperate into a for/while loop.
+ */
+func Getopt(argc int, argv []string, optstring string, optptr *byte) bool {
+ /* If we havem't parsed the optstring yet, parse it */
+ if !parsed {
+ parseArgs(optstring)
+ parsed = true
+ }
+
+ /* Instantly return false if the follow cases are met */
+ if Optind >= argc || argv[Optind] == "" || argv[Optind][0] != '-' ||
+ argv[Optind] == "-" || optstring == "" {
+ return false
+ } else if argv[Optind] == "--" {
+ Optind++
+ return false
+ }
+
+ /* For each element of argv we calculate its length */
+ if opt == 1 {
+ optlen = len(argv[Optind])
+ }
+
+ /* The current flag */
+ currFlag := argv[Optind][opt]
+
+ if opts[currFlag].used {
+ if opts[currFlag].arg {
+ if opt == optlen-1 {
+ Optind += 2
+ if Optind > argc {
+ Optopt = currFlag
+ if Opterr {
+ *optptr = '?'
+ fmt.Fprintf(os.Stderr, errNoArg, Optopt)
+ } else {
+ *optptr = ':'
+ }
+ } else {
+ Optarg = argv[Optind-1]
+ *optptr = currFlag
+ }
+ opt = 1
+ return true
+ }
+
+ /* If the opt takes an argument but it's not the last character in the
+ * string
+ */
+ *optptr = currFlag
+ Optarg = string(argv[Optind][opt+1:])
+ Optind++
+ opt = 1
+ } else { /* If the opt doesn't take an argument */
+ if opt == optlen-1 {
+ opt = 1
+ Optind++
+ } else {
+ opt++
+ }
+
+ *optptr = currFlag
+ }
+ } else { /* If the arg isn't in optstring */
+ if Opterr {
+ fmt.Fprintf(os.Stderr, errBadArg, argv[Optind][opt])
+ }
+ Optopt = currFlag
+ *optptr = '?'
+
+ if opt == optlen-1 {
+ Optind++
+ opt = 1
+ } else {
+ opt++
+ }
+ }
+
+ return true
+}