Add Thomas function needed to make isohybrid bootable images.
This commit is contained in:
Vreixo Formoso
parent
1a4c5ba679
commit
186c2f2ff7
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@ -52,6 +52,7 @@ libisofs_libisofs_la_SOURCES = \
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libisofs/joliet.c \
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libisofs/eltorito.h \
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libisofs/eltorito.c \
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libisofs/make_isohybrid_mbr.c \
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libisofs/iso1999.h \
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libisofs/iso1999.c \
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libisofs/data_source.c
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@ -1,8 +1,8 @@
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/*
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* Copyright (c) 2007 Vreixo Formoso
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*
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* This file is part of the libisofs project; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License version 2 as
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*
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* This file is part of the libisofs project; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation. See COPYING file for details.
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*/
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@ -100,4 +100,21 @@ int el_torito_catalog_file_src_create(Ecma119Image *target, IsoFileSrc **src);
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*/
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int eltorito_writer_create(Ecma119Image *target);
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/*
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* Create a MBR for an isohybrid enabled ISOLINUX boot image.
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*
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* It is assumed that the caller has verified the readiness of the boot image
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* by checking for 0xfb 0xc0 0x78 0x70 at bytes 0x40 to 0x43 of isolinux.bin.
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*
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* @param bin_lba The predicted LBA of isolinux.bin within the emerging ISO.
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* @param img_blocks The predicted number of 2048 byte blocks in the ISO.
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* It will get rounded up to full MBs and that many blocks
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* must really be written as ISO 9660 image.
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* @param mbr A buffer of at least 512 bytes to take the result which is
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* to be written as the very beginning of the ISO.
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* @param flag unused yet, submit 0
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* @return <0 = fatal, 0 = failed , 1 = ok , 2 = ok with size warning
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*/
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int make_isohybrid_mbr(int bin_lba, int *img_blocks, char *mbr, int flag);
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#endif /* LIBISO_ELTORITO_H */
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@ -0,0 +1,198 @@
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#include <ctype.h>
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#include <stdint.h>
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#include <sys/types.h>
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#include <stdlib.h>
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#include <stdio.h>
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#include <unistd.h>
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#include <string.h>
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#include <errno.h>
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/* for gettimeofday() */
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#include <sys/time.h>
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/* This code stems from syslinux-3.72/utils/isohybrid, a perl script
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under GPL which is Copyright 2002-2008 H. Peter Anvin.
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Line numbers in comments refer to the lines of that script.
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It has been analyzed and re-written in C language 2008 by Thomas Schmitt.
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As soon as it is part of a libisofs test version, H. Peter Anvin will
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be asked about his own copyright claims and/or license tolerance in
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respect to this C code.
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*/
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/* A helper function. One could replace it by one or two macros. */
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static int lsb_to_buf(char **wpt, int value, int bits, int flag)
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{
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int b;
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for (b = 0; b < bits; b += 8)
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*((unsigned char *) ((*wpt)++)) = (value >> b) & 0xff;
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return (1);
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}
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/*
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* Create a MBR for an isohybrid enabled ISOLINUX boot image.
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*
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* It is assumed that the caller has verified the readiness of the boot image
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* by checking for 0xfb 0xc0 0x78 0x70 at bytes 0x40 to 0x43 of isolinux.bin.
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*
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* @param bin_lba The predicted LBA of isolinux.bin within the emerging ISO.
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* @param img_blocks The predicted number of 2048 byte blocks in the ISO.
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* It will get rounded up to full MBs and that many blocks
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* must really be written as ISO 9660 image.
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* @param mbr A buffer of at least 512 bytes to take the result which is
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* to be written as the very beginning of the ISO.
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* @param flag unused yet, submit 0
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* @return <0 = fatal, 0 = failed , 1 = ok , 2 = ok with size warning
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*/
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int make_isohybrid_mbr(int bin_lba, int *img_blocks, char *mbr, int flag)
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{
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/* According to H. Peter Anvin this binary code stems from
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syslinux-3.72/mbr/isohdpfx.S
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*/
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static int mbr_code_size = 271;
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static unsigned char mbr_code[271] = { 0xfa, 0x31, 0xc0, 0x8e, 0xd8, 0x8e,
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0xd0, 0xbc, 0x00, 0x7c, 0x89, 0xe6, 0x06, 0x57, 0x52, 0x8e, 0xc0,
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0xfb, 0xfc, 0xbf, 0x00, 0x06, 0xb9, 0x00, 0x01, 0xf3, 0xa5, 0xea,
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0x20, 0x06, 0x00, 0x00, 0x52, 0xb4, 0x41, 0xbb, 0xaa, 0x55, 0x31,
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0xc9, 0x30, 0xf6, 0xf9, 0xcd, 0x13, 0x72, 0x14, 0x81, 0xfb, 0x55,
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0xaa, 0x75, 0x0e, 0x83, 0xe1, 0x01, 0x74, 0x09, 0x66, 0xc7, 0x06,
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0xb4, 0x06, 0xb4, 0x42, 0xeb, 0x15, 0x5a, 0x51, 0xb4, 0x08, 0xcd,
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0x13, 0x83, 0xe1, 0x3f, 0x51, 0x0f, 0xb6, 0xc6,
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0x40, 0x50, 0xf7, 0xe1, 0x52, 0x50, 0xbb, 0x00, 0x7c, 0xb9, 0x04,
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0x00, 0x66, 0xa1, 0xb0, 0x07, 0xe8, 0x40, 0x00, 0x72, 0x74, 0x66,
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0x40, 0x80, 0xc7, 0x02, 0xe2, 0xf4, 0x66, 0x81, 0x3e, 0x40, 0x7c,
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0xfb, 0xc0, 0x78, 0x70, 0x75, 0x07, 0xfa, 0xbc, 0xf4, 0x7b, 0xe9,
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0xc6, 0x75, 0xe8, 0x79, 0x00, 0x69, 0x73, 0x6f, 0x6c, 0x69, 0x6e,
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0x75, 0x78, 0x2e, 0x62, 0x69, 0x6e, 0x20, 0x6d, 0x69, 0x73, 0x73,
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0x69, 0x6e, 0x67, 0x20, 0x6f, 0x72, 0x20, 0x63, 0x6f, 0x72, 0x72,
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0x75, 0x70, 0x74,
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0x2e, 0x0d, 0x0a, 0x66, 0x60, 0x66, 0x31, 0xd2, 0x66, 0x52, 0x66,
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0x50, 0x06, 0x53, 0x6a, 0x01, 0x6a, 0x10, 0x89, 0xe6, 0x66, 0xf7,
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0x36, 0xf0, 0x7b, 0xc0, 0xe4, 0x06, 0x88, 0xe1, 0x88, 0xc5, 0x92,
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0xf6, 0x36, 0xf6, 0x7b, 0x88, 0xc6, 0x08, 0xe1, 0x41, 0xb8, 0x01,
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0x02, 0x8a, 0x16, 0xfa, 0x7b, 0xcd, 0x13, 0x8d, 0x64, 0x10, 0x66,
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0x61, 0xc3, 0xe8, 0x1e, 0x00, 0x4f, 0x70, 0x65, 0x72, 0x61, 0x74,
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0x69, 0x6e, 0x67, 0x20, 0x73, 0x79, 0x73, 0x74, 0x65, 0x6d, 0x20,
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0x6c, 0x6f, 0x61,
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0x64, 0x20, 0x65, 0x72, 0x72, 0x6f, 0x72, 0x2e, 0x0d, 0x0a, 0x5e,
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0xac, 0xb4, 0x0e, 0x8a, 0x3e, 0x62, 0x04, 0xb3, 0x07, 0xcd, 0x10,
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0x3c, 0x0a, 0x75, 0xf1, 0xcd, 0x18, 0xf4, 0xeb, 0xfd };
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static int h = 64, s = 32;
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int i, warn_size = 0, id;
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char *wpt;
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off_t imgsize, cylsize, frac, padding, c, cc;
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/* For generating a weak random number */
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struct timeval tv;
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struct timezone tz;
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if (bin_lba < 0 || bin_lba >= (1 << 29))
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return (0); /* 1 TB limit of signed 32 bit addressing of 512 byte blocks */
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/*
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84: Gets size of image in bytes.
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89:
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*/
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imgsize = ((off_t) img_blocks) * (off_t) 2048;
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/*
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90: Computes $padding, size of padded image and number $c of
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pseudo-cylinders ($h and $s are constants set in line 24).
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102: $cc is $c curbed to 1024.
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*/
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cylsize = h * s * 512;
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frac = imgsize % cylsize;
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padding = (frac > 0 ? cylsize - frac : 0);
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imgsize += padding;
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*img_blocks = imgsize / (off_t) 2048;
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c = imgsize / cylsize;
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if (c > 1024) {
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warn_size = 1;
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cc = 1024;
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} else
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cc = c;
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/*
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107: Brings the hex-encoded bytes from the file __END__ into
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113: the MBR buffer. (This function holds them in mbr_code[].)
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*/
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for (i = 0; i < mbr_code_size; i++)
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mbr[i] = mbr_code[i];
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/*
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118: Pads up to 432
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*/
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for (i = mbr_code_size; i < 432; i++)
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mbr[i] = 0;
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/* From here on use write cursor wpt */
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wpt = mbr + 432;
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/*
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120: Converts LBA of isolinux.bin to blocksize 512 and writes
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to buffer. Appends 4 zero bytes.
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*/
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lsb_to_buf(&wpt, bin_lba * 4, 32, 0);
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lsb_to_buf(&wpt, 0, 32, 0);
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/*
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121: I do not understand where $id should eventually come
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from. An environment variable ?
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125: Whatever, i use some 32-bit random value with no crypto strength.
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*/
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gettimeofday(&tv, &tz);
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id = 0xffffffff & (tv.tv_sec ^ (tv.tv_usec * 2000));
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/*
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126: Adds 4 id bytes and 2 zero bytes.
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*/
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lsb_to_buf(&wpt, id, 32, 0);
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lsb_to_buf(&wpt, 0, 16, 0);
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/*
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129: Composes 16 byte record from the parameters determined
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147: so far. Appends it to buffer and add 48 zero bytes.
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*/
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/* There are 4 "partition slots". Only the first is non-zero here.
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In the perl script, the fields are set in variables and then
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written to buffer. I omit the variables.
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*/
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/* 0x80 */
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lsb_to_buf(&wpt, 0x80, 8, 0);
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/* bhead */
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lsb_to_buf(&wpt, 0, 8, 0);
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/* bsect */
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lsb_to_buf(&wpt, 1, 8, 0);
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/* bcyl */
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lsb_to_buf(&wpt, 0, 8, 0);
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/* fstype */
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lsb_to_buf(&wpt, 0x83, 8, 0);
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/* ehead */
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lsb_to_buf(&wpt, h - 1, 8, 0);
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/* esect */
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lsb_to_buf(&wpt, s + (((cc - 1) & 0x300) >> 2), 8, 0);
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/* ecyl */
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lsb_to_buf(&wpt, (cc - 1) & 0xff, 8, 0);
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/* 0 */
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lsb_to_buf(&wpt, 0, 32, 0);
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/* psize */
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lsb_to_buf(&wpt, c * h * s, 32, 0);
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/* Fill the other three slots with zeros */
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for (i = 0; i < 3 * 4; i++)
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lsb_to_buf(&wpt, 0, 32, 0);
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/*
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148: Appends bytes 0x55 , 0xAA.
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*/
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lsb_to_buf(&wpt, 0x55, 8, 0);
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lsb_to_buf(&wpt, 0xaa, 8, 0);
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return (1);
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}
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