[ALTERNATE PATCH] Add a simple option parser.

[Pierre Habouzit <madcoder@debian.org>]

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The option parser takes argc, argv, an array of struct option
and a usage string.  Each of the struct option elements in the array
describes a valid option, its type and a pointer to the location where the
value is written.  The entry point is parse_options(), which scans through
the given argv, and matches each option there against the list of valid
options.  During the scan, argv is rewritten to only contain the
non-option command line arguments and the number of these is returned.

Aggregation of single switches is allowed:
  -rC0 is the same as -r -C 0 (supposing that -C wants an arg).

Boolean switches automatically support the option with the same name,
prefixed with 'no-' to disable the switch:
  --no-color / --color only need to have an entry for "color".

Long options are supported either with '=' or without:
  --some-option=foo is the same as --some-option foo

Signed-off-by: Kristian Høgsberg <krh@redhat.com>
Signed-off-by: Pierre Habouzit <madcoder@debian.org>
---

I'm sorry about the "From" I don't intend to "steal" the patch in any
sense, it's just an alternate proposal.

oh and I don't grok what OPTION_LAST is for, so I left it apart, but
it seems unused ?


 Makefile        |    2 +-
 parse-options.c |  154 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 parse-options.h |   29 ++++++++++
 3 files changed, 184 insertions(+), 1 deletions(-)
 create mode 100644 parse-options.c
 create mode 100644 parse-options.h

diff --git a/Makefile b/Makefile
index 62bdac6..d90e959 100644
--- a/Makefile
+++ b/Makefile
@@ -310,7 +310,7 @@ LIB_OBJS = \
 	alloc.o merge-file.o path-list.o help.o unpack-trees.o $(DIFF_OBJS) \
 	color.o wt-status.o archive-zip.o archive-tar.o shallow.o utf8.o \
 	convert.o attr.o decorate.o progress.o mailmap.o symlinks.o remote.o \
-	transport.o bundle.o
+	transport.o bundle.o parse-options.o
 
 BUILTIN_OBJS = \
 	builtin-add.o \
diff --git a/parse-options.c b/parse-options.c
new file mode 100644
index 0000000..eb3ff40
--- /dev/null
+++ b/parse-options.c
@@ -0,0 +1,154 @@
+#include "git-compat-util.h"
+#include "parse-options.h"
+
+struct optparse_t {
+	const char **argv;
+	int argc;
+	const char *opt;
+};
+
+static inline const char *skippfx(const char *str, const char *prefix)
+{
+	size_t len = strlen(prefix);
+	return strncmp(str, prefix, len) ? NULL : str + len;
+}
+
+static int opterror(struct option *opt, const char *reason, int shorterr)
+{
+	if (shorterr) {
+		return error("switch `%c' %s", opt->short_name, reason);
+	} else {
+		return error("option `%s' %s", opt->long_name, reason);
+	}
+}
+
+static int get_value(struct optparse_t *p, struct option *opt,
+					 int boolean, int shorterr)
+{
+	switch (opt->type) {
+		const char *s;
+		int v;
+
+	  case OPTION_BOOLEAN:
+		*(int *)opt->value = boolean;
+		return 0;
+
+	  case OPTION_STRING:
+		if (p->opt && *p->opt) {
+			*(const char **)opt->value = p->opt;
+			p->opt = NULL;
+		} else {
+			if (p->argc < 1)
+				return opterror(opt, "requires a value", shorterr);
+			*(const char **)opt->value = *++p->argv;
+			p->argc--;
+		}
+		return 0;
+
+	  case OPTION_INTEGER:
+		if (p->opt && *p->opt) {
+			v = strtol(p->opt, (char **)&s, 10);
+			p->opt = NULL;
+		} else {
+			if (p->argc < 1)
+				return opterror(opt, "requires a value", shorterr);
+			v = strtol(*++p->argv, (char **)&s, 10);
+			p->argc--;
+		}
+		if (*s)
+			return opterror(opt, "expects a numerical value", shorterr);
+		*(int *)opt->value = v;
+		return 0;
+	}
+
+	abort();
+}
+
+static int parse_short_opt(struct optparse_t *p, struct option *options, int count)
+{
+	int i;
+
+	for (i = 0; i < count; i++) {
+		if (options[i].short_name == *p->opt) {
+			p->opt++;
+			return get_value(p, options + i, 1, 1);
+		}
+	}
+	return error("unknown switch `%c'", *p->opt);
+}
+
+static int parse_long_opt(struct optparse_t *p, const char *arg,
+                          struct option *options, int count)
+{
+	int boolean = 1;
+	int i;
+
+	for (i = 0; i < count; i++) {
+		const char *rest;
+		
+		if (!options[i].long_name)
+			continue;
+
+		rest = skippfx(arg, options[i].long_name);
+		if (!rest && options[i].type == OPTION_BOOLEAN) {
+			if (!rest && skippfx(arg, "no-")) {
+				rest = skippfx(arg + 3, options[i].long_name);
+				boolean = 0;
+			}
+			if (rest && *rest == '=')
+				return opterror(options + i, "takes no value", 0);
+		}
+		if (!rest || (*rest && *rest != '='))
+			continue;
+		if (*rest) {
+			p->opt = rest;
+		}
+		return get_value(p, options + i, boolean, 0);
+	}
+	return error("unknown option `%s'", arg);
+}
+
+int parse_options(int argc, const char **argv,
+		  struct option *options, int count,
+		  const char *usage_string)
+{
+	struct optparse_t optp = { argv + 1, argc - 1, NULL };
+	int j = 0;
+
+	while (optp.argc) {
+		const char *arg = optp.argv[0];
+
+		if (*arg != '-' || !arg[1]) {
+			argv[j++] = *optp.argv++;
+			optp.argc--;
+			continue;
+		}
+
+		if (arg[1] != '-') {
+			optp.opt = arg + 1;
+			while (*optp.opt) {
+				if (parse_short_opt(&optp, options, count) < 0) {
+					usage(usage_string);
+					return -1;
+				}
+			}
+			optp.argc--;
+			optp.argv++;
+			continue;
+		}
+
+		if (!arg[2]) /* "--" */
+			break;
+
+		if (parse_long_opt(&optp, arg + 2, options, count)) {
+			usage(usage_string);
+			return -1;
+		}
+		optp.argc--;
+		optp.argv++;
+	}
+
+	memmove(argv + j, optp.argv, optp.argc * sizeof(argv));
+	argv[j + optp.argc] = NULL;
+	return j + optp.argc;
+}
diff --git a/parse-options.h b/parse-options.h
new file mode 100644
index 0000000..e4749d0
--- /dev/null
+++ b/parse-options.h
@@ -0,0 +1,29 @@
+#ifndef PARSE_OPTIONS_H
+#define PARSE_OPTIONS_H
+
+enum option_type {
+	OPTION_BOOLEAN,
+	OPTION_STRING,
+	OPTION_INTEGER,
+#if 0
+	OPTION_LAST,
+#endif
+};
+
+struct option {
+	enum option_type type;
+	const char *long_name;
+	char short_name;
+	void *value;
+};
+
+/* parse_options() will filter out the processed options and leave the
+ * non-option argments in argv[].  The return value is the number of
+ * arguments left in argv[].
+ */
+
+extern int parse_options(int argc, const char **argv,
+			 struct option *options, int count,
+			 const char *usage_string);
+
+#endif
-- 
1.5.3.4.1156.ga72f9d-dirty


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