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/* javaclassname.c
*
* Extracts the class name from a Java class file; intended for use in a Java
* wrapper of the type supported by the binfmt_misc option in the Linux kernel.
*
* Copyright (C) 1999 Colin J. Watson <cjw44@cam.ac.uk>.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include <stdlib.h>
#include <stdio.h>
#include <stdarg.h>
#include <sys/types.h>
/* From Sun's Java VM Specification, as tag entries in the constant pool. */
#define CP_UTF8 1
#define CP_INTEGER 3
#define CP_FLOAT 4
#define CP_LONG 5
#define CP_DOUBLE 6
#define CP_CLASS 7
#define CP_STRING 8
#define CP_FIELDREF 9
#define CP_METHODREF 10
#define CP_INTERFACEMETHODREF 11
#define CP_NAMEANDTYPE 12
/* Define some commonly used error messages */
#define seek_error() error("%s: Cannot seek\n", program)
#define corrupt_error() error("%s: Class file corrupt\n", program)
#define eof_error() error("%s: Unexpected end of file\n", program)
#define utf8_error() error("%s: Only ASCII 1-255 supported\n", program);
char *program;
long *pool;
u_int8_t read_8(FILE *classfile);
u_int16_t read_16(FILE *classfile);
void skip_constant(FILE *classfile, u_int16_t *cur);
void error(const char *format, ...);
int main(int argc, char **argv);
/* Reads in an unsigned 8-bit integer. */
u_int8_t read_8(FILE *classfile)
{
int b = fgetc(classfile);
if(b == EOF)
eof_error();
return (u_int8_t)b;
}
/* Reads in an unsigned 16-bit integer. */
u_int16_t read_16(FILE *classfile)
{
int b1, b2;
b1 = fgetc(classfile);
if(b1 == EOF)
eof_error();
b2 = fgetc(classfile);
if(b2 == EOF)
eof_error();
return (u_int16_t)((b1 << 8) | b2);
}
/* Reads in a value from the constant pool. */
void skip_constant(FILE *classfile, u_int16_t *cur)
{
u_int16_t len;
int seekerr = 1;
pool[*cur] = ftell(classfile);
switch(read_8(classfile))
{
case CP_UTF8:
len = read_16(classfile);
seekerr = fseek(classfile, len, SEEK_CUR);
break;
case CP_CLASS:
case CP_STRING:
seekerr = fseek(classfile, 2, SEEK_CUR);
break;
case CP_INTEGER:
case CP_FLOAT:
case CP_FIELDREF:
case CP_METHODREF:
case CP_INTERFACEMETHODREF:
case CP_NAMEANDTYPE:
seekerr = fseek(classfile, 4, SEEK_CUR);
break;
case CP_LONG:
case CP_DOUBLE:
seekerr = fseek(classfile, 8, SEEK_CUR);
++(*cur);
break;
default:
corrupt_error();
}
if(seekerr)
seek_error();
}
void error(const char *format, ...)
{
va_list ap;
va_start(ap, format);
vfprintf(stderr, format, ap);
va_end(ap);
exit(1);
}
int main(int argc, char **argv)
{
FILE *classfile;
u_int16_t cp_count, i, this_class, classinfo_ptr;
u_int8_t length;
program = argv[0];
if(!argv[1])
error("%s: Missing input file\n", program);
classfile = fopen(argv[1], "rb");
if(!classfile)
error("%s: Error opening %s\n", program, argv[1]);
if(fseek(classfile, 8, SEEK_SET)) /* skip magic and version numbers */
seek_error();
cp_count = read_16(classfile);
pool = calloc(cp_count, sizeof(long));
if(!pool)
error("%s: Out of memory for constant pool\n", program);
for(i = 1; i < cp_count; ++i)
skip_constant(classfile, &i);
if(fseek(classfile, 2, SEEK_CUR)) /* skip access flags */
seek_error();
this_class = read_16(classfile);
if(this_class < 1 || this_class >= cp_count)
corrupt_error();
if(!pool[this_class] || pool[this_class] == -1)
corrupt_error();
if(fseek(classfile, pool[this_class] + 1, SEEK_SET))
seek_error();
classinfo_ptr = read_16(classfile);
if(classinfo_ptr < 1 || classinfo_ptr >= cp_count)
corrupt_error();
if(!pool[classinfo_ptr] || pool[classinfo_ptr] == -1)
corrupt_error();
if(fseek(classfile, pool[classinfo_ptr] + 1, SEEK_SET))
seek_error();
length = read_16(classfile);
for(i = 0; i < length; ++i)
{
u_int8_t x = read_8(classfile);
if((x & 0x80) || !x)
{
if((x & 0xE0) == 0xC0)
{
u_int8_t y = read_8(classfile);
if((y & 0xC0) == 0x80)
{
int c = ((x & 0x1f) << 6) + (y & 0x3f);
if(c) putchar(c);
else utf8_error();
}
else utf8_error();
}
else utf8_error();
}
else if(x == '/') putchar('.');
else putchar(x);
}
putchar('\n');
free(pool);
fclose(classfile);
return 0;
}
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