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pretty_printer.c
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/**
* A program to output the contents of constant_pool
* by parsing java .class files as that's made in javap tool.
*
* This code is written as an assignment to understand
* the structure of the class files.
*
* Author: Aleksandr Ushaev
* Created: 14.02.2020
*
*/
#include "pretty_printer.h"
/**
* Converts .class double representation to C double as it specified
* oracle specification.
*
* @param bits from .class file
* @return converted double
*/
double long_bits_to_double(long bits)
{
int s = ((bits >> 63) == 0) ? 2 : 1;
int e = (int)((bits >> 52) & 0x7ffL);
long m = (e == 0)
? (bits & 0xfffffffffffffL) << 1
: (bits & 0xfffffffffffffL) | 0x10000000000000L;
double_cast d_cast; // Create double via struct + union
d_cast.parts.sign = s;
d_cast.parts.exponent = e;
d_cast.parts.mantisa = m;
return d_cast.d;
}
/**
* Check .class double representation for positive/negative infinity and NaN
*
* @param bits from .class file
* @return inf_nan field
*/
inf_nan check_long_bits_for_inf_nan(long bits)
{
if (bits == 0x7ff0000000000000L)
return POSITIVE_INFINITY;
else if (bits == 0xfff0000000000000L)
return NEGATIVE_INFINITY;
else if ((bits > 0x7ff0000000000000L && bits < 0x7fffffffffffffffL) || (bits > 0xfff0000000000001L && bits < 0xffffffffffffffffL))
return NAN;
else
return NORMAL;
}
/**
* Get utf string from constant_pool
*
* @param class struct where to seatch
* @param id of constant_pool info
* @return utf8 string
*/
char *get_utf(class *cls, int id)
{
constant_info *cur_constant_info = cls->constant_pool + id;
char *utf;
while (cur_constant_info->class_i.tag != CONSTANT_Utf8)
{
cur_constant_info = cls->constant_pool + (cur_constant_info->class_i.name_index - 1);
}
cur_constant_info->utf_i.bytes[strcspn(cur_constant_info->utf_i.bytes, "\n")] = 0;
return cur_constant_info->utf_i.bytes;
}
/**
* Print .class minor and major versions
* @param stream to write for
* @param class struct with specified versions
*/
void print_version_info(FILE *stream, class *cls)
{
fprintf(stream, "minor version: %d\n", cls->minor_version);
fprintf(stream, "major version: %d\n\n", cls->major_version);
}
/**
* Print constant_pool info as it prints in javap tool
*
* @param stream to write for
* @param class struct
*/
void print_constant_pool(FILE *stream, class *cls)
{
const uint16_t total_constants_count = cls->constant_pool_count - 1;
for (int i = 0; i < total_constants_count; i++)
{
constant_info *cur_constant_info = cls->constant_pool + i;
switch (cur_constant_info->class_i.tag)
{
case CONSTANT_Class: // done
fprintf(stream, "#%d = Class\t\t#%d\t\t// %s\n", i + 1,
cur_constant_info->class_i.name_index, get_utf(cls, i));
break;
case CONSTANT_Fieldref: // done 1-st, done 2-nd
fprintf(stream, "#%d = Fieldref\t\t#%d.#%d\t\t// %s.%s:%s\n", i + 1,
cur_constant_info->ref_i.class_index, cur_constant_info->ref_i.name_and_type_index,
get_utf(cls, cur_constant_info->ref_i.class_index - 1),
get_utf(cls, (cls->constant_pool + (cur_constant_info->ref_i.name_and_type_index - 1))->ref_i.class_index - 1),
get_utf(cls, (cls->constant_pool + (cur_constant_info->ref_i.name_and_type_index - 1))->ref_i.name_and_type_index - 1));
break;
case CONSTANT_InterfaceMethodref: // done 1-st, done 2-nd
fprintf(stream, "#%d = InterfaceMethodRef\t#%d.#%d\t\t// %s.%s:%s\n", i + 1,
cur_constant_info->ref_i.class_index, cur_constant_info->ref_i.name_and_type_index,
get_utf(cls, cur_constant_info->ref_i.class_index - 1),
get_utf(cls, (cls->constant_pool + (cur_constant_info->ref_i.name_and_type_index - 1))->ref_i.class_index - 1),
get_utf(cls, (cls->constant_pool + (cur_constant_info->ref_i.name_and_type_index - 1))->ref_i.name_and_type_index - 1));
break;
case CONSTANT_Methodref: // done 1-st, done 2-nd
fprintf(stream, "#%d = MethodRef\t\t#%d.#%d\t\t// %s.%s:%s\n", i + 1,
cur_constant_info->ref_i.class_index, cur_constant_info->ref_i.name_and_type_index,
get_utf(cls, cur_constant_info->ref_i.class_index - 1),
get_utf(cls, (cls->constant_pool + (cur_constant_info->ref_i.name_and_type_index - 1))->ref_i.class_index - 1),
get_utf(cls, (cls->constant_pool + (cur_constant_info->ref_i.name_and_type_index - 1))->ref_i.name_and_type_index - 1));
break;
case CONSTANT_NameAndType: // done 1-st, done 2-nd
fprintf(stream, "#%d = NameAndType\t#%d:#%d\t\t// %s:%s\n", i + 1,
cur_constant_info->ref_i.class_index, cur_constant_info->ref_i.name_and_type_index,
get_utf(cls, cur_constant_info->ref_i.class_index - 1),
get_utf(cls, cur_constant_info->ref_i.name_and_type_index - 1));
break;
case CONSTANT_String: // done
fprintf(stream, "#%d = String\t\t#%d\t\t// %s\n", i + 1,
cur_constant_info->string_i.string_index, get_utf(cls, i));
break;
case CONSTANT_Integer: // done
fprintf(stream, "#%d = Integer\t\t%d\n", i + 1,
cur_constant_info->int_float_i.bytes);
break;
case CONSTANT_Float: // done
fprintf(stream, "#%d = Float\t\t%f\n", i + 1,
(float)cur_constant_info->int_float_i.bytes);
break;
case CONSTANT_Long: // done
fprintf(stream, "#%d = Long\t\t%ldl\n", i + 1,
((long)cur_constant_info->long_double_i.high_bytes << 32) + cur_constant_info->long_double_i.low_bytes);
i++;
break;
case CONSTANT_Double: // done
switch (check_long_bits_for_inf_nan(((long)cur_constant_info->long_double_i.high_bytes << 32) + cur_constant_info->long_double_i.low_bytes))
{
case POSITIVE_INFINITY:
fprintf(stream, "#%d = Double\t\tInfinityd\n", i + 1);
break;
case NEGATIVE_INFINITY:
fprintf(stream, "#%d = Double\t\t-Infinityd\n", i + 1);
break;
case NAN:
fprintf(stream, "#%d = Double\t\tNaNd\n", i + 1);
break;
case NORMAL:
fprintf(stream, "#%d = Double\t\t%lfd\n", i + 1,
long_bits_to_double(((long)cur_constant_info->long_double_i.high_bytes << 32) + cur_constant_info->long_double_i.low_bytes));
break;
}
i++;
break;
case CONSTANT_Utf8: // done
fprintf(stream, "#%d = Utf8\t\t%s\n", i + 1, cur_constant_info->utf_i.bytes);
break;
case CONSTANT_MethodHandle: // done
fprintf(stream, "#%d = MethodHandle\t%d:#%d\t\t// %s %s.%s:%s\n", i + 1,
cur_constant_info->method_handle_i.reference_kind, cur_constant_info->method_handle_i.reference_index,
reference_kind[cur_constant_info->method_handle_i.reference_kind - 1],
get_utf(cls, (cls->constant_pool + (cur_constant_info->method_handle_i.reference_index - 1))->ref_i.class_index - 1),
get_utf(cls, (cls->constant_pool + (cls->constant_pool + (cur_constant_info->method_handle_i.reference_index - 1))->ref_i.name_and_type_index - 1)->ref_i.class_index - 1),
get_utf(cls, (cls->constant_pool + (cls->constant_pool + (cur_constant_info->method_handle_i.reference_index - 1))->ref_i.name_and_type_index - 1)->ref_i.name_and_type_index - 1));
break;
case CONSTANT_MethodType: // done
fprintf(stream, "#%d = MethodType\t\t%d\t\t// %s\n", i + 1,
cur_constant_info->method_type_i.descriptor_index,
get_utf(cls, cur_constant_info->method_type_i.descriptor_index - 1));
break;
case CONSTANT_InvokeDynamic: // done
fprintf(stream, "#%d = InvokeDynamic\t#%d:#%d\t\t// #%d:%s:%s\n", i + 1,
cur_constant_info->invoke_dynamic_i.bootstrap_method_attr_index,
cur_constant_info->invoke_dynamic_i.name_and_type_index,
cur_constant_info->invoke_dynamic_i.bootstrap_method_attr_index,
get_utf(cls, (cls->constant_pool + (cur_constant_info->invoke_dynamic_i.name_and_type_index - 1))->ref_i.class_index - 1),
get_utf(cls, (cls->constant_pool + (cur_constant_info->invoke_dynamic_i.name_and_type_index - 1))->ref_i.name_and_type_index - 1));
break;
default:
break;
}
}
}