add support for long-opts (#332)

Uses [optparse] to add support for long-opts. optparse is posix
compliant with getopt(3) and thus would be backwards compatible.
It does not have any dependency (not even the c standard library!) and
is C89 compatible and thus fits our current code-style.

[optparse]: https://github.com/skeeto/optparse

Note that we're using a couple `pragma`-s to silence some harmless
warnings. This should be portable because these pragma-s don't change the
behavior of the program. Furthermore, C standard mandates that unknown
pragma's should be ignored by the compiler and thus would not result in
build failure on compilers which do not recognize them.

Closes: https://codeberg.org/nsxiv/nsxiv/issues/328
Reviewed-on: https://codeberg.org/nsxiv/nsxiv/pulls/332
Reviewed-by: eylles <eylles@noreply.codeberg.org>

1 files changed, 403 insertions, 0 deletions

diff --git a/optparse.h b/optparse.h
new file mode 100644
index 0000000..8d6c0a9
--- /dev/null
+++ b/optparse.h
@@ -0,0 +1,403 @@
+/* Optparse --- portable, reentrant, embeddable, getopt-like option parser
+ *
+ * This is free and unencumbered software released into the public domain.
+ *
+ * To get the implementation, define OPTPARSE_IMPLEMENTATION.
+ * Optionally define OPTPARSE_API to control the API's visibility
+ * and/or linkage (static, __attribute__, __declspec).
+ *
+ * The POSIX getopt() option parser has three fatal flaws. These flaws
+ * are solved by Optparse.
+ *
+ * 1) Parser state is stored entirely in global variables, some of
+ * which are static and inaccessible. This means only one thread can
+ * use getopt(). It also means it's not possible to recursively parse
+ * nested sub-arguments while in the middle of argument parsing.
+ * Optparse fixes this by storing all state on a local struct.
+ *
+ * 2) The POSIX standard provides no way to properly reset the parser.
+ * This means for portable code that getopt() is only good for one
+ * run, over one argv with one option string. It also means subcommand
+ * options cannot be processed with getopt(). Most implementations
+ * provide a method to reset the parser, but it's not portable.
+ * Optparse provides an optparse_arg() function for stepping over
+ * subcommands and continuing parsing of options with another option
+ * string. The Optparse struct itself can be passed around to
+ * subcommand handlers for additional subcommand option parsing. A
+ * full reset can be achieved by with an additional optparse_init().
+ *
+ * 3) Error messages are printed to stderr. This can be disabled with
+ * opterr, but the messages themselves are still inaccessible.
+ * Optparse solves this by writing an error message in its errmsg
+ * field. The downside to Optparse is that this error message will
+ * always be in English rather than the current locale.
+ *
+ * Optparse should be familiar with anyone accustomed to getopt(), and
+ * it could be a nearly drop-in replacement. The option string is the
+ * same and the fields have the same names as the getopt() global
+ * variables (optarg, optind, optopt).
+ *
+ * Optparse also supports GNU-style long options with optparse_long().
+ * The interface is slightly different and simpler than getopt_long().
+ *
+ * By default, argv is permuted as it is parsed, moving non-option
+ * arguments to the end. This can be disabled by setting the `permute`
+ * field to 0 after initialization.
+ */
+#ifndef OPTPARSE_H
+#define OPTPARSE_H
+
+#ifndef OPTPARSE_API
+#  define OPTPARSE_API
+#endif
+
+struct optparse {
+    char **argv;
+    int permute;
+    int optind;
+    int optopt;
+    char *optarg;
+    char errmsg[64];
+    int subopt;
+};
+
+enum optparse_argtype {
+    OPTPARSE_NONE,
+    OPTPARSE_REQUIRED,
+    OPTPARSE_OPTIONAL
+};
+
+struct optparse_long {
+    const char *longname;
+    int shortname;
+    enum optparse_argtype argtype;
+};
+
+/**
+ * Initializes the parser state.
+ */
+OPTPARSE_API
+void optparse_init(struct optparse *options, char **argv);
+
+/**
+ * Read the next option in the argv array.
+ * @param optstring a getopt()-formatted option string.
+ * @return the next option character, -1 for done, or '?' for error
+ *
+ * Just like getopt(), a character followed by no colons means no
+ * argument. One colon means the option has a required argument. Two
+ * colons means the option takes an optional argument.
+ */
+OPTPARSE_API
+int optparse(struct optparse *options, const char *optstring);
+
+/**
+ * Handles GNU-style long options in addition to getopt() options.
+ * This works a lot like GNU's getopt_long(). The last option in
+ * longopts must be all zeros, marking the end of the array. The
+ * longindex argument may be NULL.
+ */
+OPTPARSE_API
+int optparse_long(struct optparse *options,
+                  const struct optparse_long *longopts,
+                  int *longindex);
+
+/**
+ * Used for stepping over non-option arguments.
+ * @return the next non-option argument, or NULL for no more arguments
+ *
+ * Argument parsing can continue with optparse() after using this
+ * function. That would be used to parse the options for the
+ * subcommand returned by optparse_arg(). This function allows you to
+ * ignore the value of optind.
+ */
+OPTPARSE_API
+char *optparse_arg(struct optparse *options);
+
+/* Implementation */
+#ifdef OPTPARSE_IMPLEMENTATION
+
+#define OPTPARSE_MSG_INVALID "invalid option"
+#define OPTPARSE_MSG_MISSING "option requires an argument"
+#define OPTPARSE_MSG_TOOMANY "option takes no arguments"
+
+static int
+optparse_error(struct optparse *options, const char *msg, const char *data)
+{
+    unsigned p = 0;
+    const char *sep = " -- '";
+    while (*msg)
+        options->errmsg[p++] = *msg++;
+    while (*sep)
+        options->errmsg[p++] = *sep++;
+    while (p < sizeof(options->errmsg) - 2 && *data)
+        options->errmsg[p++] = *data++;
+    options->errmsg[p++] = '\'';
+    options->errmsg[p++] = '\0';
+    return '?';
+}
+
+OPTPARSE_API
+void
+optparse_init(struct optparse *options, char **argv)
+{
+    options->argv = argv;
+    options->permute = 1;
+    options->optind = argv[0] != 0;
+    options->subopt = 0;
+    options->optarg = 0;
+    options->errmsg[0] = '\0';
+}
+
+static int
+optparse_is_dashdash(const char *arg)
+{
+    return arg != 0 && arg[0] == '-' && arg[1] == '-' && arg[2] == '\0';
+}
+
+static int
+optparse_is_shortopt(const char *arg)
+{
+    return arg != 0 && arg[0] == '-' && arg[1] != '-' && arg[1] != '\0';
+}
+
+static int
+optparse_is_longopt(const char *arg)
+{
+    return arg != 0 && arg[0] == '-' && arg[1] == '-' && arg[2] != '\0';
+}
+
+static void
+optparse_permute(struct optparse *options, int index)
+{
+    char *nonoption = options->argv[index];
+    int i;
+    for (i = index; i < options->optind - 1; i++)
+        options->argv[i] = options->argv[i + 1];
+    options->argv[options->optind - 1] = nonoption;
+}
+
+static int
+optparse_argtype(const char *optstring, char c)
+{
+    int count = OPTPARSE_NONE;
+    if (c == ':')
+        return -1;
+    for (; *optstring && c != *optstring; optstring++);
+    if (!*optstring)
+        return -1;
+    if (optstring[1] == ':')
+        count += optstring[2] == ':' ? 2 : 1;
+    return count;
+}
+
+OPTPARSE_API
+int
+optparse(struct optparse *options, const char *optstring)
+{
+    int type;
+    char *next;
+    char *option = options->argv[options->optind];
+    options->errmsg[0] = '\0';
+    options->optopt = 0;
+    options->optarg = 0;
+    if (option == 0) {
+        return -1;
+    } else if (optparse_is_dashdash(option)) {
+        options->optind++; /* consume "--" */
+        return -1;
+    } else if (!optparse_is_shortopt(option)) {
+        if (options->permute) {
+            int index = options->optind++;
+            int r = optparse(options, optstring);
+            optparse_permute(options, index);
+            options->optind--;
+            return r;
+        } else {
+            return -1;
+        }
+    }
+    option += options->subopt + 1;
+    options->optopt = option[0];
+    type = optparse_argtype(optstring, option[0]);
+    next = options->argv[options->optind + 1];
+    switch (type) {
+    case -1: {
+        char str[2] = {0, 0};
+        str[0] = option[0];
+        options->optind++;
+        return optparse_error(options, OPTPARSE_MSG_INVALID, str);
+    }
+    case OPTPARSE_NONE:
+        if (option[1]) {
+            options->subopt++;
+        } else {
+            options->subopt = 0;
+            options->optind++;
+        }
+        return option[0];
+    case OPTPARSE_REQUIRED:
+        options->subopt = 0;
+        options->optind++;
+        if (option[1]) {
+            options->optarg = option + 1;
+        } else if (next != 0) {
+            options->optarg = next;
+            options->optind++;
+        } else {
+            char str[2] = {0, 0};
+            str[0] = option[0];
+            options->optarg = 0;
+            return optparse_error(options, OPTPARSE_MSG_MISSING, str);
+        }
+        return option[0];
+    case OPTPARSE_OPTIONAL:
+        options->subopt = 0;
+        options->optind++;
+        if (option[1])
+            options->optarg = option + 1;
+        else
+            options->optarg = 0;
+        return option[0];
+    }
+    return 0;
+}
+
+OPTPARSE_API
+char *
+optparse_arg(struct optparse *options)
+{
+    char *option = options->argv[options->optind];
+    options->subopt = 0;
+    if (option != 0)
+        options->optind++;
+    return option;
+}
+
+static int
+optparse_longopts_end(const struct optparse_long *longopts, int i)
+{
+    return !longopts[i].longname && !longopts[i].shortname;
+}
+
+static void
+optparse_from_long(const struct optparse_long *longopts, char *optstring)
+{
+    char *p = optstring;
+    int i;
+    for (i = 0; !optparse_longopts_end(longopts, i); i++) {
+        if (longopts[i].shortname && longopts[i].shortname < 127) {
+            int a;
+            *p++ = longopts[i].shortname;
+            for (a = 0; a < (int)longopts[i].argtype; a++)
+                *p++ = ':';
+        }
+    }
+    *p = '\0';
+}
+
+/* Unlike strcmp(), handles options containing "=". */
+static int
+optparse_longopts_match(const char *longname, const char *option)
+{
+    const char *a = option, *n = longname;
+    if (longname == 0)
+        return 0;
+    for (; *a && *n && *a != '='; a++, n++)
+        if (*a != *n)
+            return 0;
+    return *n == '\0' && (*a == '\0' || *a == '=');
+}
+
+/* Return the part after "=", or NULL. */
+static char *
+optparse_longopts_arg(char *option)
+{
+    for (; *option && *option != '='; option++);
+    if (*option == '=')
+        return option + 1;
+    else
+        return 0;
+}
+
+static int
+optparse_long_fallback(struct optparse *options,
+                       const struct optparse_long *longopts,
+                       int *longindex)
+{
+    int result;
+    char optstring[96 * 3 + 1]; /* 96 ASCII printable characters */
+    optparse_from_long(longopts, optstring);
+    result = optparse(options, optstring);
+    if (longindex != 0) {
+        *longindex = -1;
+        if (result != -1) {
+            int i;
+            for (i = 0; !optparse_longopts_end(longopts, i); i++)
+                if (longopts[i].shortname == options->optopt)
+                    *longindex = i;
+        }
+    }
+    return result;
+}
+
+OPTPARSE_API
+int
+optparse_long(struct optparse *options,
+              const struct optparse_long *longopts,
+              int *longindex)
+{
+    int i;
+    char *option = options->argv[options->optind];
+    if (option == 0) {
+        return -1;
+    } else if (optparse_is_dashdash(option)) {
+        options->optind++; /* consume "--" */
+        return -1;
+    } else if (optparse_is_shortopt(option)) {
+        return optparse_long_fallback(options, longopts, longindex);
+    } else if (!optparse_is_longopt(option)) {
+        if (options->permute) {
+            int index = options->optind++;
+            int r = optparse_long(options, longopts, longindex);
+            optparse_permute(options, index);
+            options->optind--;
+            return r;
+        } else {
+            return -1;
+        }
+    }
+
+    /* Parse as long option. */
+    options->errmsg[0] = '\0';
+    options->optopt = 0;
+    options->optarg = 0;
+    option += 2; /* skip "--" */
+    options->optind++;
+    for (i = 0; !optparse_longopts_end(longopts, i); i++) {
+        const char *name = longopts[i].longname;
+        if (optparse_longopts_match(name, option)) {
+            char *arg;
+            if (longindex)
+                *longindex = i;
+            options->optopt = longopts[i].shortname;
+            arg = optparse_longopts_arg(option);
+            if (longopts[i].argtype == OPTPARSE_NONE && arg != 0) {
+                return optparse_error(options, OPTPARSE_MSG_TOOMANY, name);
+            } if (arg != 0) {
+                options->optarg = arg;
+            } else if (longopts[i].argtype == OPTPARSE_REQUIRED) {
+                options->optarg = options->argv[options->optind];
+                if (options->optarg == 0)
+                    return optparse_error(options, OPTPARSE_MSG_MISSING, name);
+                else
+                    options->optind++;
+            }
+            return options->optopt;
+        }
+    }
+    return optparse_error(options, OPTPARSE_MSG_INVALID, option);
+}
+
+#endif /* OPTPARSE_IMPLEMENTATION */
+#endif /* OPTPARSE_H */