/* * Copyright (c) 1997, 2010, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. * * This code 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 * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. * */#ifndef SHARE_VM_CODE_COMPRESSEDSTREAM_HPP#define SHARE_VM_CODE_COMPRESSEDSTREAM_HPP#include "memory/allocation.hpp"// Simple interface for filing out and filing in basic types// Used for writing out and reading in debugging information.class CompressedStream : public ResourceObj { friend class VMStructs; protected: u_char* _buffer; int _position; enum { // Constants for UNSIGNED5 coding of Pack200 lg_H = 6, H = 1<<lg_H, // number of high codes (64) L = (1<<BitsPerByte)-H, // number of low codes (192) MAX_i = 4 // bytes are numbered in (0..4), max 5 bytes }; // these inlines are defined only in compressedStream.cpp static inline juint encode_sign(jint value); // for Pack200 SIGNED5 static inline jint decode_sign(juint value); // for Pack200 SIGNED5 static inline juint reverse_int(juint bits); // to trim trailing float 0's public: CompressedStream(u_char* buffer, int position = 0) { _buffer = buffer; _position = position; } u_char* buffer() const { return _buffer; } // Positioning int position() const { return _position; } void set_position(int position) { _position = position; }};class CompressedReadStream : public CompressedStream { private: inline u_char read() { return _buffer[_position++]; } // This encoding, called UNSIGNED5, is taken from J2SE Pack200. // It assumes that most values have lots of leading zeroes. // Very small values, in the range [0..191], code in one byte. // Any 32-bit value (including negatives) can be coded, in // up to five bytes. The grammar is: // low_byte = [0..191] // high_byte = [192..255] // any_byte = low_byte | high_byte // coding = low_byte // | high_byte low_byte // | high_byte high_byte low_byte // | high_byte high_byte high_byte low_byte // | high_byte high_byte high_byte high_byte any_byte // Each high_byte contributes six bits of payload. // The encoding is one-to-one (except for integer overflow) // and easy to parse and unparse. jint read_int_mb(jint b0) { int pos = position() - 1; u_char* buf = buffer() + pos; assert(buf[0] == b0 && b0 >= L, "correctly called"); jint sum = b0; // must collect more bytes: b[1]...b[4] int lg_H_i = lg_H; for (int i = 0; ; ) { jint b_i = buf[++i]; // b_i = read(); ++i; sum += b_i << lg_H_i; // sum += b[i]*(64**i) if (b_i < L || i == MAX_i) { set_position(pos+i+1); return sum; } lg_H_i += lg_H; } } public: CompressedReadStream(u_char* buffer, int position = 0) : CompressedStream(buffer, position) {} jboolean read_bool() { return (jboolean) read(); } jbyte read_byte() { return (jbyte ) read(); } jchar read_char() { return (jchar ) read_int(); } jshort read_short() { return (jshort ) read_signed_int(); } jint read_int() { jint b0 = read(); if (b0 < L) return b0; else return read_int_mb(b0); } jint read_signed_int(); jfloat read_float(); // jfloat_cast(reverse_int(read_int())) jdouble read_double(); // jdouble_cast(2*reverse_int(read_int)) jlong read_long(); // jlong_from(2*read_signed_int())};class CompressedWriteStream : public CompressedStream { private: bool full() { return _position >= _size; } void store(u_char b) { _buffer[_position++] = b; } void write(u_char b) { if (full()) grow(); store(b); } void grow(); void write_int_mb(jint value); // UNSIGNED5 coding, 1-5 byte cases protected: int _size; public: CompressedWriteStream(int initial_size); CompressedWriteStream(u_char* buffer, int initial_size, int position = 0) : CompressedStream(buffer, position) { _size = initial_size; } void write_bool(jboolean value) { write(value); } void write_byte(jbyte value) { write(value); } void write_char(jchar value) { write_int(value); } void write_short(jshort value) { write_signed_int(value); } void write_int(jint value) { if ((juint)value < L && !full()) store((u_char)value); else write_int_mb(value); } void write_signed_int(jint value); // write_int(encode_sign(value)) void write_float(jfloat value); // write_int(reverse_int(jint_cast(v))) void write_double(jdouble value); // write_int(reverse_int(<low,high>)) void write_long(jlong value); // write_signed_int(<low,high>)};#endif // SHARE_VM_CODE_COMPRESSEDSTREAM_HPP