os: helper for parsing an counting-flag or value-flag option

Parses an option that may either be used for setting an integer value or
given one or multiple times (without argument) to increase an value

Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>

os/cmdline.c

@@ -0,0 +1,32 @@
+/* SPDX-License-Identifier: MIT OR X11
+ *
+ * Copyright © 2024 Enrico Weigelt, metux IT consult <info@metux.net>
+ *
+ * @brief command line helper functions
+ */
+
+#include <dix-config.h>
+
+#include <string.h>
+#include <stdlib.h>
+
+#include "os/cmdline.h"
+
+int ProcessCmdLineMultiInt(int argc, char *argv[], int *idx, const char* name, int *value)
+{
+    if (strcmp(argv[*idx], name))
+        return 0;
+
+    int i2 = *idx+1;
+    if (i2 < argc && argv[i2]) {
+        char *end;
+        long val = strtol(argv[i2], &end, 0);
+        if (*end == '\0') {
+            (*idx)++;
+            (*value) = val;
+            return 1;
+        }
+    }
+    (*value)++;
+    return 1;
+}

os/cmdline.h

@@ -17,4 +17,19 @@ void UseMsg(void);
 void ProcessCommandLine(int argc, char * argv[]);
 void CheckUserParameters(int argc, char **argv, char **envp);
 
+/*
+ * @brief check for and parse an counting-flag or value-flag option
+ *
+ * Parses an option that may either be used for setting an integer value or
+ * given one or multiple times (without argument) to increase an value
+ *
+ * @param argc total number of elements in argv
+ * @param argv array of pointers to cmdline argument strings
+ * @param idx pointer to current index in argv -- eventually will be modified
+ * @param name the command line argument name
+ * @param value pointer to the field holding the setting value
+ * @return non-zero if the flag was found and parsed
+ */
+int ProcessCmdLineMultiInt(int argc, char *argv[], int *idx, const char* name, int *value);
+
 #endif /* _XSERVER_OS_CMELINE_H */

os/meson.build

@@ -5,6 +5,7 @@ srcs_os = [
     'auth.c',
     'backtrace.c',
     'client.c',
+    'cmdline.c',
     'connection.c',
     'fmt.c',
     'inputthread.c',