From 52be99d8c0862ff87db9a4f9ccec1ac4b5f7caed Mon Sep 17 00:00:00 2001
From: Andreas Baumann <mail@andreasbaumann.cc>
Date: Fri, 2 Sep 2022 09:18:52 +0200
Subject: added a quite unsorted first version of a floppy boot loader

---
 floppy/lstar.c | 102 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 102 insertions(+)
 create mode 100644 floppy/lstar.c

(limited to 'floppy/lstar.c')

diff --git a/floppy/lstar.c b/floppy/lstar.c
new file mode 100644
index 0000000..2a7d541
--- /dev/null
+++ b/floppy/lstar.c
@@ -0,0 +1,102 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <bsd/string.h>
+#include <string.h>
+
+static int octal_to_int( char *s, int size )
+{
+	int n = 0;
+	char *c = s;
+	while( size > 0 ) {
+		n *= 8;
+		n += *c - '0';
+		c++;
+		size--;
+	}
+	
+	return n;
+}
+
+int main( int argc, char *argv[] )
+{
+	FILE *f = NULL;
+	char buf[512];
+	char filename[100];
+	char size_octal[12];
+	char cksum_octal[8];
+	int size;
+	unsigned int cksum;
+	unsigned int computed_cksum;
+	int i, n;
+	int terminate = 0;
+
+	if( argc != 2 ) {
+		fprintf( stderr, "usage: %s <tarfile>\n", argv[0] );
+		exit( EXIT_FAILURE );
+	}
+	
+	f = fopen( argv[1], "r" );
+	if( f == NULL ) {
+		fprintf( stderr, "ERROR: failed to open file '%s'\n", argv[1] );
+		exit( EXIT_FAILURE );
+	}
+	
+	do {
+		clearerr( f );
+		n = fread( buf, 512, 1, f );
+		if( n == 0 ) {
+			if( ferror( f ) ) {
+				fprintf( stderr, "ERR: read error\n" );
+				terminate = 1;
+			} else if( feof( f ) ) {
+				terminate = 1;
+				break;
+			}
+		}
+		
+		if( memcmp( &buf[257], "ustar", 5 ) == 0 ) {
+			strlcpy( filename, buf, 100 );
+			
+			if( strcmp( filename, "" ) != 0 ) {
+
+				printf( "file: %s\n", filename );
+			
+				strlcpy( size_octal, &buf[124], 12 );
+				printf( "size (octal): %s\n", size_octal );
+
+				size = octal_to_int( size_octal, 11 );
+				printf( "size (decimal): %d\n", size );
+
+				strlcpy( cksum_octal, &buf[148], 8 );
+				printf( "cksum (octal): %s\n", cksum_octal );
+				cksum = octal_to_int( cksum_octal, 6 );
+				printf( "cksum (decimal): %d\n", cksum );
+				
+				for( i = 148; i < 148+8; i++ ) {
+					buf[i] = ' ';
+				}
+				computed_cksum = 0;
+				for( i = 0; i < 512; i++ ) {
+					computed_cksum += (unsigned char)buf[i];
+				}
+				printf( "cksum (computed): %d\n", computed_cksum );
+				if( cksum != computed_cksum ) {
+					fprintf( stderr, "ERR: checksum mismatch in header!\n" );
+				}
+
+				while( size > 0 ) {
+					fread( buf, 512, 1, f );
+					size -= 512;
+				}
+			} else {
+				fprintf( stderr, "INFO: the end\n" );
+			}			
+		} else {
+			fprintf( stderr, "WARN: skipping non TAR header\n" );
+		}
+	} while( !terminate );
+	
+	fclose( f );
+	
+	exit( EXIT_SUCCESS );
+}
-- 
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