From 9fad209177414598f40241f1b2f2c4034b587e2d Mon Sep 17 00:00:00 2001
From: Andrew Chambers <ac@acha.ninja>
Date: Thu, 14 Oct 2021 21:02:47 +1300
Subject: Add arg parsing.

---
 main.c   | 49 +++++++++++++++++++++++++++++++++++++++----------
 minias.h | 21 +++++++++++++++++++++
 2 files changed, 60 insertions(+), 10 deletions(-)

diff --git a/main.c b/main.c
index 5851844..64101d2 100644
--- a/main.c
+++ b/main.c
@@ -1,7 +1,6 @@
 #include "minias.h"
+#include <getopt.h>
 
-/* Output file. */
-static FILE *outf = NULL;
 /* Parsed assembly */
 static AsmLine *allasm = NULL;
 
@@ -27,12 +26,12 @@ static Section *data = NULL;
 static Section *textrel = NULL;
 static Section *datarel = NULL;
 
-char *filename = "<stdin>";
-size_t curlineno = 0;
+static char *infilename = "<stdin>";
+static size_t curlineno = 0;
 
 void lfatal(const char *fmt, ...) {
   va_list ap;
-  fprintf(stderr, "%s:%ld: ", filename, curlineno);
+  fprintf(stderr, "%s:%ld: ", infilename, curlineno);
   va_start(ap, fmt);
   vwarn(fmt, ap);
   va_end(ap);
@@ -1156,8 +1155,8 @@ static void handlerelocs(void) {
 }
 
 static void out(const void *buf, size_t n) {
-  fwrite(buf, 1, n, outf);
-  if (ferror(outf))
+  fwrite(buf, 1, n, stdout);
+  if (ferror(stdout))
     fatal("fwrite:");
 }
 
@@ -1197,18 +1196,48 @@ static void outelf(void) {
       continue;
     out(sections[i].data, sections[i].hdr.sh_size);
   }
-  if (fflush(outf) != 0)
+  if (fflush(stdout) != 0)
     fatal("fflush:");
 }
 
-int main(void) {
+static void usage(char *argv0) {
+  fprintf(stderr, "usage: %s [-o OUT] [input]\n", argv0);
+  exit(2);
+}
+
+int main(int argc, char *argv[]) {
+
+  char *argv0, *outfname;
+
+  argv0 = argv[0];
+
+  ARGBEGIN {
+  case 'o':
+    outfname = EARGF(usage(argv0));
+    if (!freopen(outfname, "w", stdout))
+      fatal("unable to open %s:", outfname);
+    break;
+  default:
+    usage(argv[0]);
+  }
+  ARGEND
+
+  if (argc >= 2)
+    usage(argv0);
+
+  if (argc == 1) {
+    infilename = argv[argc - 1];
+    if (!freopen(infilename, "r", stdin))
+      fatal("unable to open %s:", infilename);
+  }
+
   symbols = mkhtab(256);
-  outf = stdout;
   allasm = parse();
   initsections();
   assemble();
   fillsymtab();
   handlerelocs();
   outelf();
+
   return 0;
 }
\ No newline at end of file
diff --git a/minias.h b/minias.h
index c16caf0..de6f2c8 100644
--- a/minias.h
+++ b/minias.h
@@ -342,6 +342,27 @@ AsmLine *parse(void);
 
 /* util.c */
 
+#define ARGBEGIN                                                               \
+  for (;;) {                                                                   \
+    if (argc > 0)                                                              \
+      ++argv, --argc;                                                          \
+    if (argc == 0 || (*argv)[0] != '-')                                        \
+      break;                                                                   \
+    if ((*argv)[1] == '-' && !(*argv)[2]) {                                    \
+      ++argv, --argc;                                                          \
+      break;                                                                   \
+    }                                                                          \
+    for (char *opt_ = &(*argv)[1], done_ = 0; !done_ && *opt_; ++opt_) {       \
+      switch (*opt_)
+
+#define ARGEND                                                                 \
+  }                                                                            \
+  }
+
+#define EARGF(x)                                                               \
+  (done_ = 1, opt_[1] ? ++opt_ : argv[1] ? --argc,                             \
+   *++argv : ((x), abort(), (char *)0))
+
 void vwarn(const char *fmt, va_list ap);
 void fatal(const char *fmt, ...);
 void unreachable(void);
-- 
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