nar

commit 329695dd70ab47175849cd9b4c662e92ec3be982
parent 02253f088516cd0129fdb00a94108bdc4eef43f7
Author: kocotian <kocotian@kocotian.pl>
Date:   Thu, 28 Jan 2021 19:38:30 +0100

archive creating

Diffstat:
A
STRUCTURE.wiki
 | 
25
+++++++++++++++++++++++++
M
nar.c
 | 
90
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

2 files changed, 115 insertions(+), 0 deletions(-)
diff --git a/STRUCTURE.wiki b/STRUCTURE.wiki
@@ -0,0 +1,25 @@
+= NAR Structure =
+
+Typical NAR archive contains:
+- Archive header
+- File array (just files)
+
+== NAR Archive header ==
+
+| Bytes | Description                  |
+|-------|------------------------------|
+| 4     | *NAR[Line Feed]* magic value |
+
+== NAR File array ==
+
+File array structure:
+
+| Bytes        | Description                   |
+|--------------|-------------------------------|
+| 8            | File size                     |
+| 2            | File mode                     |
+| 4            | Owner ID                      |
+| 4            | Owner's Group ID              |
+| *Length* + 1 | File name (NULL terminated)   |
+| *File size*  | File content                  |
+| 1            | End of file confirmation byte |
diff --git a/nar.c b/nar.c
@@ -3,18 +3,108 @@
 
 #define _XOPEN_SOURCE 700
 
+#include <fcntl.h>
 #include <stdio.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
 
 #include "arg.h"
 #include "util.h"
 
+static void create(char *fn, int fc, char *farr[]);
+static void usage(void);
+
+const char eofbyte = 'k';
 char *argv0;
+int verbose;
+
+void
+create(char *fn, int fc, char *farr[])
+{
+	int fd, fdl;
+	struct stat sb;
+	int i = -1;
+	void *membuf;
+
+	u_int64_t b64;
+	u_int32_t b32;
+	u_int16_t b16;
+
+	/* opening a file */
+	if (fn != NULL) {
+		if ((fd = open(fn, O_CREAT | O_WRONLY, 0644)) < 0)
+			die("error while opening %s:", fn);
+	}
+	else
+		fd = 1; /* if no filename, default will be stdout */
+
+	/* write magic value */
+	write(fd, "NAR\n", 4);
+
+	/* main creation loop */
+	while (++i < fc) {
+		if (verbose)
+			fprintf(stderr, "adding file %s\n", farr[i]);
+		if (stat(farr[i], &sb) < 0)
+			die("stat: %s:", farr[i]);
+		b64 = sb.st_size; write(fd, &b64, 8);
+		b16 = sb.st_mode; write(fd, &b16, 2);
+		b32 = sb.st_uid;  write(fd, &b32, 4);
+		b32 = sb.st_gid;  write(fd, &b32, 4);
+		write(fd, farr[i], strlen(farr[i]) + 1);
+		if ((fdl = open(farr[i], O_RDONLY)) < 0)
+			die("open: %s:", farr[i]);
+		membuf = mmap(NULL, sb.st_size, PROT_READ, MAP_PRIVATE, fdl, 0);
+		write(fd, membuf, sb.st_size);
+		munmap(membuf, sb.st_size);
+		write(fd, &eofbyte, 1);
+		close(fdl);
+	}
+
+	/* closing a file */
+	if (fn != NULL)
+		close(fd);
+}
+
+void
+usage(void)
+{
+	die("usage: %s [-cx] [-v] [-f filename]", argv0);
+}
 
 int
 main(int argc, char *argv[])
 {
+	char *filename = NULL;
+	char flag = 0;
+
+	verbose = 0;
+
 	ARGBEGIN {
+	case 'c': case 'x': /* FALLTHROUGH */
+		if (!flag)
+			flag = ARGC();
+		else
+			die("you can't specify more than one operation on the same time");
+		break;
+	case 'v':
+		verbose = 1;
+		break;
+	case 'f':
+		filename = ARGF();
+		break;
 	default:
+		usage();
 		break;
 	} ARGEND;
+
+	switch (flag) {
+	case 'c': create(filename, argc, argv); break;
+	default: usage(); break;
+	}
+
+	return 0;
 }