re-write CLI argument parsing for testability

tools/cliutil.cpp

@@ -0,0 +1,83 @@
+/**
+ * Copyright - See the COPYRIGHT that is included with this distribution.
+ * pvxs is distributed subject to a Software License Agreement found
+ * in file LICENSE that is included with this distribution.
+ */
+
+#include "cliutil.h"
+
+namespace pvxs {
+
+bool operator==(const ArgVal& rhs, const ArgVal& lhs) {
+    return rhs.defined==lhs.defined && rhs.value==lhs.value;
+}
+
+GetOpt::GetOpt(int argc, char *argv[], const char *spec)
+    :argv0("<program name>")
+{
+    if(argc>=1)
+        argv0 = argv[0];
+
+    bool allpos = false; // after "--", treat all remaining as positional
+    for(int i=1; i<argc; i++) {
+        const char * arg = argv[i];
+        if(!allpos && arg[0]=='-') {
+            arg++;
+
+            if(arg[0]=='-') {
+                if(arg[1]=='\0') { // "--"
+                    allpos = true;
+                    continue;
+                }
+                // "--..." not supported
+                arguments.emplace_back(-1, argv[i]);
+                continue;
+            }
+            // process as short args
+
+            for(; *arg; arg++) {
+                for(auto s=spec; *s; s++) {
+                    if(*s==*arg) { // match
+                        if(s[1]==':') { // need arg value
+                            if(arg[1]=='\0') { // "-a", "value"
+                                if(i+1==argc) {
+                                    // oops. no value
+                                    arguments.emplace_back('?', nullptr);
+                                    return;
+                                }
+                                arguments.emplace_back(*arg, argv[i+1]);
+                                i++;
+
+                            } else {
+                                // "-avalue"
+                                arguments.emplace_back(*arg, &arg[1]);
+                            }
+                            goto nextarg;
+
+                        } else { // flag
+                            arguments.emplace_back(*s, nullptr);
+                            // continue scanning for more flags.  eg. "-vv"
+                            goto nextchar;
+                        }
+                    } else {
+                        if(s[1]==':')
+                            s++;
+                    }
+                }
+                // unrecognized
+                arguments.emplace_back(-1, nullptr);
+                break;
+nextchar:
+                (void)0;  // need a statement after label...
+            }
+nextarg:
+            (void)0;
+
+        } else {
+            positional.push_back(arg);
+        }
+        success = true;
+    }
+}
+
+} // namespace pvxs