1 files changed, 76 insertions, 0 deletions
diff --git a/src/util/option.h b/src/util/option.h
new file mode 100644
index 0000000..780a6e9
--- /dev/null
+++ b/src/util/option.h
@@ -0,0 +1,76 @@
+#pragma once
+
+#include <stdbool.h>
+
+
+enum option_spec_kind {
+  OPTSPECKIND_SETBOOL,
+  OPTSPECKIND_CALL,
+  OPTSPECKIND_CALLP,
+
+  OPTSPECKIND_HELPUSAGE,
+  OPTSPECKIND_VERSION,
+
+  OPTSPECKIND_END,  // end of spec list (rest of spec entry ignored)
+};
+
+// For usage info, see option_parse() below.
+struct option_spec {
+  char optc;  // short option character
+  // TODO: long options?
+
+  // From here, the fields should be filled in using the OPTION_* macros.
+  enum option_spec_kind kind;
+  union {
+    struct { bool *ptr; } setbool;
+    struct { void (*fun)(void); } call;
+    struct { void (*fun)(void*); void *data; } callp;
+    struct { const char *usagestr; } helpusage;
+    struct {} version;
+  } spec_sub;
+};
+
+// Takes a bool* and stores 'true' there if the flag is found.
+#define OPTION_SETBOOL(boolptr) \
+  OPTSPECKIND_SETBOOL, {.setbool={.ptr=(boolptr)}}
+
+// Takes a void(*)(void) and calls it every time the flag is found.
+#define OPTION_CALL(funptr) \
+  OPTSPECKIND_CALL, {.call={.fun=(funptr)}}
+
+// Takes a void(*)(void*) and a 'void *data', and calls the function with 'data'
+// every time the flag is found.
+#define OPTION_CALLP(funptr, dataptr) \
+  OPTSPECKIND_CALLP, {.callp={.fun=(funptr), .data=(dataptr)}}
+
+// Takes a printf format string with a single %s, which is substituted (by
+// printf) for argv[0]. Prints the formatted string and exits with code 0.
+#define OPTION_HELPUSAGE(usagestring) \
+  OPTSPECKIND_HELPUSAGE, {.helpusage={.usagestr=(usagestring)}}
+
+// Prints version of the tool and exits with code 0.
+#define OPTION_VERSION() \
+  OPTSPECKIND_VERSION, {.version={}}
+
+// This must be the final entry in the list of option specs; contrary to the
+// other OPTION_* macros, it is an _entire_ 'struct option_spec'.
+#define OPTION_SPEC_END {'\0', OPTSPECKIND_END, {}}
+
+// The spec must not contain duplicate entries for the same short option
+// character.
+// Reshuffles positional arguments to the end of the argument list; returns a
+// pointer to the first positional argument after reshuffling.
+//
+// The specs array is most conveniently declared as a C array:
+//
+//   const struct option_spec[] = {
+//     {'h', OPTION_HELPUSAGE("Gebruik: %s <args>\n")},
+//     {'V', OPTION_VERSION()},
+//     OPTION_SPEC_END
+//   }
+//
+// The individual option specs should be initialised with a brace-initialiser
+// containing the short option character followed by one of the OPTION_* macros,
+// as shown in the example above. See the comments above the macros for their
+// meaning. End the list with OPTION_SPEC_END.
+char** option_parse(int argc, char **argv, const struct option_spec *specs);