java-llvm/classfile.c

#include "classfile.h"
#include <assert.h>
#include <memory.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define SWAP_ENDIANNESS

void read_u2(void* ptr, size_t n, FILE* file) {
  u2 buffer[n];
  fread(&buffer, sizeof(u2), n, file);
#ifdef SWAP_ENDIANNESS
  for (size_t i = 0; i < n; i++) {
    buffer[i] = (buffer[i] >> 8) | (buffer[i] << 8);
  }
#endif
  memcpy(ptr, &buffer, n * sizeof(u2));
}

void read_u4(void* ptr, size_t n, FILE* file) {
  u4 buffer[n];
  fread(&buffer, sizeof(u4), n, file);
#ifdef SWAP_ENDIANNESS
  for (size_t i = 0; i < n; i++) {
    buffer[i] = ((buffer[i] >> 24) & 0xff) | // move byte 3 to byte 0
                ((buffer[i] << 8) & 0xff0000) | // move byte 1 to byte 2
                ((buffer[i] >> 8) & 0xff00) | // move byte 2 to byte 1
                ((buffer[i] << 24) & 0xff000000);
  }
#endif
  memcpy(ptr, &buffer, n * sizeof(u4));
}

stack_frame_type stack_frame_type_enum(u2 frame_type) {
  if (0 <= frame_type && frame_type <= 63) {
    return SAME;
  } else if (64 <= frame_type && frame_type <= 127) {
    return SAME_LOCALS_1_STACK_ITEM_FRAME;
  } else if (frame_type == 247) {
    return SAME_LOCALS_1_STACK_ITEM_FRAME_EXTENDED;
  } else if (248 <= frame_type && frame_type <= 250) {
    return CHOP;
  } else if (frame_type == 251) {
    return SAME_FRAME_EXTENDED;
  } else if (252 <= frame_type && frame_type <= 254) {
    return APPEND;
  } else if (frame_type == 255) {
    return FULL_FRAME;
  } else {
    printf("unknown stack frame type: %hu\n", frame_type);
    assert(0);
  }
}

void parse_attribute(ClassFile* cf, attribute_info* base, FILE* file) {
  char* name = (char*)cf->constant_pool[base->attribute_name_index - 1].info.utf8_info.bytes;
  printf("%s\n", name);
  if (strcmp("ConstantValue", name) == 0) {
    read_u2(&(base->info.constant_value_attribute.constantvalue_index), 1, file);
  } else if (strcmp("Code", name) == 0) {
    read_u2(&(base->info.code_attribute.max_stack), 2, file);
    read_u4(&(base->info.code_attribute.code_length), 1, file);
    base->info.code_attribute.code = (u1*)malloc(base->info.code_attribute.code_length);
    fread(base->info.code_attribute.code, base->info.code_attribute.code_length, 1, file);
    read_u2(&(base->info.code_attribute.exception_table_length), 1, file);
    base->info.code_attribute.exception_table = malloc(sizeof(u2) * 4 * base->info.code_attribute.exception_table_length);
    for (u2 i = 0; i < base->info.code_attribute.exception_table_length; i++) {
      read_u2(&(base->info.code_attribute.exception_table[i].start_pc), 4, file);
    }
    read_u2(&(base->info.code_attribute.attributes_count), 1, file);
    base->info.code_attribute.attributes = malloc(sizeof(attribute_info) * base->info.code_attribute.attributes_count);
    for (u2 i = 0; i < base->info.code_attribute.attributes_count; i++) {
      attribute_info* attr = &(base->info.code_attribute.attributes[i]);
      read_u2(&(attr->attribute_name_index), 1, file);
      read_u4(&(attr->attribute_length), 1, file);
      parse_attribute(cf, attr, file);
    }
  } else if (strcmp("StackMapTable", name) == 0) {
    read_u2(&(base->info.stack_map_table_attribute.number_of_entries), 1, file);
    base->info.stack_map_table_attribute.entries = malloc(sizeof(stack_map_frame) * base->info.stack_map_table_attribute.number_of_entries);
    for (u2 i = 0; i < base->info.stack_map_table_attribute.number_of_entries; i++) {
      stack_map_frame* entry = &(base->info.stack_map_table_attribute.entries[i]);
      fread(&(entry->frame_type), 1, 1, file);
      u1 frame_type = entry->frame_type;
      switch (stack_frame_type_enum(frame_type)) {
        case SAME:
          break;
        case SAME_LOCALS_1_STACK_ITEM_FRAME:
          fread(&(entry->same_locals_1_stack_item_frame.stack[0].tag), 1, 1, file);
          if (entry->same_locals_1_stack_item_frame.stack[0].tag == ITEM_Object) {
            read_u2(&(entry->same_locals_1_stack_item_frame.stack[0].Object_variable_info.cpool_index), 1, file);
          } else if (entry->same_locals_1_stack_item_frame.stack[0].tag == ITEM_Uninitialized) {
            read_u2(&(entry->same_locals_1_stack_item_frame.stack[0].Uninitialized_variable_info.offset), 1, file);
          }
          break;
        case SAME_LOCALS_1_STACK_ITEM_FRAME_EXTENDED:
          read_u2(&(entry->same_locals_1_stack_item_frame_extended.offset_delta), 1, file);
          fread(&(entry->same_locals_1_stack_item_frame_extended.stack[0].tag), 1, 1, file);
          if (entry->same_locals_1_stack_item_frame_extended.stack[0].tag == ITEM_Object) {
            read_u2(&(entry->same_locals_1_stack_item_frame_extended.stack[0].Object_variable_info.cpool_index), 1, file);
          } else if (entry->same_locals_1_stack_item_frame_extended.stack[0].tag == ITEM_Uninitialized) {
            read_u2(&(entry->same_locals_1_stack_item_frame_extended.stack[0].Uninitialized_variable_info.offset), 1, file);
          }
          break;
        case CHOP:
          read_u2(&(entry->chop_frame.offset_delta), 1, file);
          break;
        case SAME_FRAME_EXTENDED:
          read_u2(&(entry->same_frame_extended.offset_delta), 1, file);
          break;
        case APPEND:
          read_u2(&(entry->append_frame.offset_delta), 1, file);
          u2 count = frame_type - 251;
          entry->append_frame.locals = malloc(sizeof(verification_type_info) * count);
          for (u2 j = 0; j < count; j++) {
            fread(&(entry->append_frame.locals[j].tag), 1, 1, file);
            if (entry->append_frame.locals[j].tag == ITEM_Object) {
              read_u2(&(entry->append_frame.locals[j].Object_variable_info.cpool_index), 1, file);
            } else if (entry->append_frame.locals[j].tag == ITEM_Uninitialized) {
              read_u2(&(entry->append_frame.locals[j].Uninitialized_variable_info.offset), 1, file);
            }
          }
          break;
        case FULL_FRAME:
          read_u2(&(entry->full_frame.offset_delta), 1, file);
          read_u2(&(entry->full_frame.number_of_locals), 1, file);
          entry->full_frame.locals = malloc(sizeof(verification_type_info) * entry->full_frame.number_of_locals);
          for (u2 j = 0; j < entry->full_frame.number_of_locals; j++) {
            fread(&(entry->full_frame.locals[j].tag), 1, 1, file);
            if (entry->full_frame.locals[j].tag == ITEM_Object) {
              read_u2(&(entry->full_frame.locals[j].Object_variable_info.cpool_index), 1, file);
            } else if (entry->full_frame.locals[j].tag == ITEM_Uninitialized) {
              read_u2(&(entry->full_frame.locals[j].Uninitialized_variable_info.offset), 1, file);
            }
          }
          read_u2(&(entry->full_frame.number_of_stack_items), 1, file);
          entry->full_frame.stack = malloc(sizeof(verification_type_info) * entry->full_frame.number_of_stack_items);
          for (u2 j = 0; j < entry->full_frame.number_of_stack_items; j++) {
            fread(&(entry->full_frame.stack[j].tag), 1, 1, file);
            if (entry->full_frame.stack[j].tag == ITEM_Object) {
              read_u2(&(entry->full_frame.stack[j].Object_variable_info.cpool_index), 1, file);
            } else if (entry->full_frame.stack[j].tag == ITEM_Uninitialized) {
              read_u2(&(entry->full_frame.stack[j].Uninitialized_variable_info.offset), 1, file);
            }
          }
          break;
      }
    }
  } else if (strcmp("NestHost", name) == 0) {
    printf("NestHost not implemented.\n");
    assert(0);
  } else if (strcmp("NestMembers", name)) {
    printf("NestMembers not implemented.\n");
    assert(0);
  } else if (strcmp("PermittedSubclasses", name) == 0) {
    printf("PermittedSubclasses not implemented.\n");
    assert(0);
  } else {
    printf("unhandled attribute type: %s", name);
  }
}

ClassFile* ClassFile_load(const char* path) {
  FILE* file = fopen(path, "rb");
  if (file == NULL)
    return NULL;

  ClassFile* cf = (ClassFile*)malloc(sizeof(ClassFile));

  // magic 4bytes, minor_version 2bytes, major_version 2bytes,
  // constant_pool_count 2bytes
  read_u4(&(cf->magic), 1, file);
  read_u2(&(cf->minor_version), 3, file);

  // constant_pool
  cf->constant_pool = (cp_info*)malloc(sizeof(cp_info) * (cf->constant_pool_count - 1));
  for (u2 i = 0; i < (cf->constant_pool_count - 1); i++) {
    // cp_info.tag 2bytes
    fread(&(cf->constant_pool[i].tag), 1, 1, file);
    size_t size;
    switch (cf->constant_pool[i].tag) {
      case CONSTANT_Class:
        read_u2(&(cf->constant_pool[i].info.class_info.name_index), 1, file);
        break;
      case CONSTANT_Fieldref:
        read_u2(&(cf->constant_pool[i].info.fieldref_info.class_index), 1, file);
        read_u2(&(cf->constant_pool[i].info.fieldref_info.name_and_type_index), 1, file);
        break;
      case CONSTANT_Methodref:
        read_u2(&(cf->constant_pool[i].info.methodref_info.class_index), 1, file);
        read_u2(&(cf->constant_pool[i].info.methodref_info.name_and_type_index), 1, file);
        break;
      case CONSTANT_InterfaceMethodref:
        read_u2(&(cf->constant_pool[i].info.interface_methodred_info.class_index), 1, file);
        read_u2(&(cf->constant_pool[i].info.interface_methodred_info.name_and_type_index), 1, file);
        break;
      case CONSTANT_String:
        read_u2(&(cf->constant_pool[i].info.string_info.string_index), 1, file);
        break;
      case CONSTANT_Integer:
        read_u4(&(cf->constant_pool[i].info.integer_info.bytes), 1, file);
        break;
      case CONSTANT_Float:
        read_u4(&(cf->constant_pool[i].info.float_info.bytes), 1, file);
        break;
      case CONSTANT_Long:
        read_u4(&(cf->constant_pool[i].info.long_info.high_bytes), 1, file);
        read_u4(&(cf->constant_pool[i].info.long_info.low_bytes), 1, file);
        break;
      case CONSTANT_Double:
        read_u4(&(cf->constant_pool[i].info.double_info.high_bytes), 1, file);
        read_u4(&(cf->constant_pool[i].info.double_info.low_bytes), 1, file);
        break;
      case CONSTANT_NameAndType:
        read_u2(&(cf->constant_pool[i].info.name_and_type_info.name_index), 1, file);
        read_u2(&(cf->constant_pool[i].info.name_and_type_info.descriptor_index), 1, file);
        break;
      case CONSTANT_Utf8:
        read_u2(&(cf->constant_pool[i].info.utf8_info.length), 1, file);
        cf->constant_pool[i].info.utf8_info.bytes = (u1*)malloc(cf->constant_pool[i].info.utf8_info.length);
        fread(cf->constant_pool[i].info.utf8_info.bytes, cf->constant_pool[i].info.utf8_info.length, 1, file);
        break;
      case CONSTANT_MethodHandle:
        fread(&(cf->constant_pool[i].info.method_handle_info.reference_kind), 1, 1, file);
        read_u2(&(cf->constant_pool[i].info.method_handle_info.reference_index), 1, file);
        break;
      case CONSTANT_MethodType:
        read_u2(&(cf->constant_pool[i].info.method_type_info.descriptor_index), 1, file);
        break;
      case CONSTANT_Dynamic:
        read_u2(&(cf->constant_pool[i].info.dynamic_info.bootstrap_method_attr_index), 1, file);
        read_u2(&(cf->constant_pool[i].info.dynamic_info.name_and_type_index), 1, file);
        break;
      case CONSTANT_InvokeDynamic:
        read_u2(&(cf->constant_pool[i].info.invoke_dynamic_info.bootstrap_method_attr_index), 1, file);
        read_u2(&(cf->constant_pool[i].info.invoke_dynamic_info.name_and_type_index), 1, file);
        break;
      case CONSTANT_Module:
        read_u2(&(cf->constant_pool[i].info.module_info.name_index), 1, file);
        break;
      case CONSTANT_Package:
        read_u2(&(cf->constant_pool[i].info.package_info.name_index), 1, file);
        break;
      default:
        printf("unknown constant tag: %hhu\n", cf->constant_pool[i].tag);
        // assert(0);
    }
  }

  // access_flags 2bytes, this_class 2bytes, super_class 2bytes, interface_count
  // 2byte
  read_u2(&(cf->access_flags), 4, file);

  // interfaces
  cf->interfaces = (u2*)malloc(2 * cf->interfaces_count);
  read_u2(cf->interfaces, cf->interfaces_count, file);

  // fields_count 2bytes
  read_u2(&(cf->fields_count), 1, file);

  // fields
  cf->fields = (field_info*)malloc(sizeof(field_info) * cf->fields_count);
  for (u2 i = 0; i < cf->fields_count; i++) {
    // access_flags 2bytes, name_index 2bytes, descriptor_index 2bytes,
    // attributes_count 2bytes
    read_u2(&(cf->fields[i].access_flags), 4, file);
    cf->fields[i].attributes = (attribute_info*)malloc(sizeof(attribute_info) * cf->fields[i].attributes_count);
    for (u2 j = 0; j < cf->fields[i].attributes_count; j++) {
      // attribute_name_index 2bytes, attribute_length 4bytes
      read_u2(&(cf->fields[i].attributes[j].attribute_name_index), 1, file);
      read_u4(&(cf->fields[i].attributes[j].attribute_length), 1, file);
      // TODO: parse attributes by tag
      // this has an unknown amount of layers, should be moved out to a function
      // cf->fields[i].attributes[j].info =
      //     (u1 *)malloc(cf->fields[i].attributes[j].attribute_length);
      // fread(cf->fields[i].attributes[j].info,
      //       cf->fields[i].attributes[j].attribute_length, 1, file);

      parse_attribute(cf, &(cf->fields[i].attributes[j]), file);
    }
  }

  // methods_count 2bytes
  read_u2(&(cf->methods_count), 1, file);

  // methods
  cf->methods = (method_info*)malloc(sizeof(method_info) * cf->methods_count);
  for (u2 i = 0; i < cf->methods_count; i++) {
    // access_flags 2bytes, name_index 2bytes, descriptor_index 2bytes,
    // attributes_count 2bytes
    read_u2(&(cf->methods[i].access_flags), 4, file);
    cf->methods[i].attributes = (attribute_info*)malloc(sizeof(attribute_info) * cf->methods[i].attributes_count);
    for (u2 j = 0; j < cf->methods[i].attributes_count; j++) {
      // attribute_name_index 2bytes, attribute_length 4bytes
      read_u2(&(cf->methods[i].attributes[j].attribute_name_index), 1, file);
      read_u4(&(cf->methods[i].attributes[j].attribute_length), 1, file);
      // TODO: parse attributes by tag
      // this has an unknown amount of layers, should be moved out to a function
      // cf->methods[i].attributes[j].info =
      //     (u1 *)malloc(cf->methods[i].attributes[j].attribute_length);
      // fread(cf->methods[i].attributes[j].info,
      //       cf->methods[i].attributes[j].attribute_length, 1, file);
      parse_attribute(cf, &(cf->methods[i].attributes[j]), file);
    }
  }

  // attributes_count 2bytes
  read_u2(&(cf->attributes_count), 1, file);

  // attributes
  cf->attributes = (attribute_info*)malloc(sizeof(attribute_info) * cf->attributes_count);
  for (u2 i = 0; i < cf->attributes_count; i++) {
    // attribute_name_index 2bytes, attribute_length 4bytes
    read_u2(&(cf->attributes[i].attribute_name_index), 1, file);
    read_u4(&(cf->attributes[i].attribute_length), 1, file);
    // cf->attributes[i].info = (u1
    // *)malloc(cf->attributes[i].attribute_length);
    //  TODO: parse attributes by tag
    //  this has an unknown amount of layers, should be moved out to a function
    //  fread(cf->attributes[i].info, cf->attributes[i].attribute_length, 1,
    //  file);
    parse_attribute(cf, &(cf->attributes[i]), file);
  }

  fclose(file);

  return cf;
}

void ClassFile_info(const ClassFile* cf) {
  printf(
      "magic=%X\n"
      "minor_version=%hu\n"
      "major_version=%hu\n"
      "constant_pool_count=%hu\n"
      "access_flags=%hx\n"
      "this_class=%hu\n"
      "super_class=%hu\n"
      "interfaces_count=%hu\n"
      "fields_count=%hu\n"
      "methods_count=%hu\n"
      "attributes_count=%hu\n",
      cf->magic, cf->minor_version, cf->major_version, cf->constant_pool_count, cf->access_flags, cf->this_class, cf->super_class, cf->interfaces_count,
      cf->fields_count, cf->methods_count, cf->attributes_count);
}